Cycles Of Ischemia Reperfusion Research Articles

Acute effect of ischemic preconditioning with different pressures on training volume, work, and fatigue index in an upper limb session

This study aimed to assess the acute effects of ischemic preconditioning at varying pressures on training volume, work, and fatigue index during an upper limb workout session. The sample consisted of 13 participants, comprised of six women and seven men. Each subject was directed to two training sessions that included a bench press and a closed-row exercise. They executed three sets up to concentric failure at 75% of their one-repetition maximum, with two minutes of recovery between sets and exercises. Prior to each experimental session, participants underwent four cycles of five-minute ischemia-reperfusion applied unilaterally and alternately to the arms. In one protocol, the pressure point was set at 50 mmHg above the resting systolic blood pressure, while in the other, a fixed pressure of 220 mmHg was applied. The 50 mmHg protocol led to greater work (p=0.02) and volume (p=0.01) in the closed-row exercise, and additionally, it resulted in a higher overall work (p=0.04). For enhanced upper limb performance, the protocol of 50 mmHg above resting systolic blood pressure proved more effective. Keywords: Ischemic Preconditioning, Strength Training, Upper Limbs, Training Volume, Pressure Occlusion.

Targeting Mitochondrial Dynamics during Lower-Limb Ischemia Reperfusion in Young and Old Mice: Effect of Mitochondrial Fission Inhibitor-1 (mDivi-1).

Peripheral arterial disease (PAD) strikes more than 200 million people worldwide and has a severe prognosis by potentially leading to limb amputation and/or death, particularly in older patients. Skeletal muscle mitochondrial dysfunctions and oxidative stress play major roles in this disease in relation with ischemia-reperfusion (IR) cycles. Mitochondrial dynamics through impairment of fission-fusion balance may contribute to skeletal muscle pathophysiology, but no data were reported in the setting of lower-limb IR despite the need for new therapeutic options. We, therefore, investigated the potential protective effect of mitochondrial division inhibitor-1 (mDivi-1; 50 mg/kg) in young (23 weeks) and old (83 weeks) mice submitted to two-hour ischemia followed by two-hour reperfusion on systemic lactate, muscle mitochondrial respiration and calcium retention capacity, and on transcripts specific for oxidative stress and mitochondrial dynamics. At the systemic levels, an IR-related increase in circulating lactate was still major despite mDivi-1 use (+305.9% p < 0.0001, and +269.4% p < 0.0001 in young and old mice, respectively). Further, IR-induced skeletal muscle mitochondrial dysfunctions (more severely impaired mitochondrial respiration in old mice (OXPHOS CI state, -68.2% p < 0.0001 and -84.9% p < 0.0001 in 23- and 83-week mice) and reduced calcium retention capacity (-46.1% p < 0.001 and -48.2% p = 0.09, respectively) were not corrected by mDivi-1 preconditioning, whatever the age. Further, mDivi-1 treatment did not oppose superoxide anion production (+71.4% p < 0.0001 and +37.5% p < 0.05, respectively). At the transcript level, markers of antioxidant enzymes (SOD 1, SOD 2, catalase, and GPx) and fission markers (Drp1, Fis) remained unchanged or tended to be decreased in the ischemic leg. Fusion markers such as mitofusin 1 or 2 decreased significantly after IR in both groups. In conclusion, aging enhanced the deleterious effects or IR on muscle mitochondrial respiration, and in this setting of lower-limb IR, mDivi-1 failed to protect the skeletal muscle both in young and old mice.

Brain Protection Effects of Mild Hypothermia Combined with Distant Ischemic Postconditioning and Thrombolysis in Patients with Acute Ischemic Stroke.

To assess the effectiveness and molecular mechanisms of mild hypothermia and remote ischemic postconditioning (RIPC) in patients with acute ischemic stroke (AIS) who have undergone thrombolysis therapy. A total of 58 AIS patients who received recombinant tissue plasmin activator (rt-PA) intravenous thrombolysis were included in this prospective study. Participants were randomly allocated to the experimental group (rt-PA intravenous thrombolysis plus mild hypothermic ice cap plus remote ischemic brain protection, n = 30) and the control group (rt-PA intravenous thrombolysis plus 0.9% saline, n = 28). The RIPC was performed for 14 consecutive days on both upper limb arteries spaced 2 minutes apart. Five cycles of ischemia-reperfusion were performed sequentially (2-2, 3-3, 4-4, 5-5, 5-0 minutes, respectively). The outcome measures of the National Institute of Health stroke scale (NIHSS) score, volume of cerebral infarction, serum levels of superoxide dismutase (SOD), malondialdehyde (MDA), interleukin-1β, tumor necrosis factor α, nuclear factors kappa B (NF-κB), and NOD-1ike receptor pyrin 3 (NLRP3) were evaluated at different time points after treatment. Similarly, the 90-day modified Rankin Scale (mRS) scores were compared between the two groups. After treatment, the NIHSS score, MDA, NF-κB, and NLRP3 levels in the experimental group were significantly lower than those in the control group (p < 0.05). While the SOD in the experimental group was significantly higher than in the control group (p < 0.05), the NIHSS scores decreased within groups (all p < 0.05) in both experimental and control groups. The 90-day mRS score (0-2 points) in the experimental group was significantly higher than that in the control group (73.33% vs. 53.57%, p < 0.05) and no significant differences were observed in the safety indices between the two groups (all p > 0.05). Our study shows that combining mild hypothermia and RIPC has a positive effect on brain protection and can significantly reduce the oxidative stress and associated outburst of inflammatory response. The Clinical Trial Registration number is ChiCTR2300073136.

Remote ischemic preconditioning and hypoxia-induced biomarkers in acute myocardial infarction: study on a porcine model

Objectives. Remote ischemic preconditioning (RIPC) mitigates acute myocardial infarction (AMI). We hypothesized that RIPC reduces the size and severity of AMI and explored molecular mechanisms behind this phenomenon. Design. In two series of experiments, piglets underwent 60 min of the circumflex coronary artery occlusion, resulting in AMI. Piglets were randomly assigned into the RIPC groups (n = 7 + 7) and the control groups (n = 7 + 7). The RIPC groups underwent four 5-min hind limb ischemia-reperfusion cycles before AMI. In series I, the protective efficacy of RIPC was investigated by using biomarkers and echocardiography with a follow-up of 24 h. In series II, the heart of each piglet was harvested for TTC-staining to measure infarct size. Muscle biopsies were collected from the hind limb to explore molecular mechanisms of RIPC using qPCR and Western blot analysis. Results. The levels of CK-MBm (p = 0.032) and TnI (p = 0.007) were lower in the RIPC group. Left ventricular ejection fraction in the RIPC group was greater at the end of the follow-up. The myocardial infarct size in the RIPC group was smaller (p = 0.033). Western blot indicated HIF1α stabilization in the skeletal muscle of the RIPC group. PCR analyses showed upregulation of the HIF target mRNAs for glucose transporter (GLUT1), glucose transporter 4 (GLUT4), phosphofructokinase 1 (PFK1), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), enolase 1 (ENO1), lactate dehydrogenase (LDHA) and endothelial nitric oxidate synthase (eNOS). Conclusions. Biochemical, physiologic, and histologic evidence confirms that RIPC decreases the size of AMI. The HIF pathway is likely involved in the mechanism of the RIPC.

Protective effects of limb remote ischemic per-conditioning on the heart injury induced by renal ischemic-reperfusion through the interaction of the apelin with the RAS/iNOS pathway.

Remote ischemic conditioning upregulates endogenous protective pathways in response to ischemia-reperfusion injury. This study tested the hypothesis that limb remote ischemic per- conditioning (RIPerC) exerts cardioprotective effects via the renin-angiotensin system (RAS)/inducible nitric oxide synthase (iNOS)/apelin pathway. Renal ischemia-reperfusion injury (I/R) was induced by bilateral occlusion of the renal pedicles for 60 minutes, followed by 24 hours of reperfusion; sham-operated rats served as controls. RIPerC was induced by four cycles (5 minutes) of limb ischemia-reperfusion along with bilateral renal ischemia. The functional disturbance was evaluated by renal (BUN and creatinine) and cardiac (troponin I and lactate dehydrogenase) injury biomarkers. Renal I/R injury increased renal and cardiac injury biomarkers that were reduced in the RIPerC group. Histopathological findings of the kidney and heart were also suggestive of amelioration injury-induced changes in the RIPerC group. Assessment of cardiac electrophysiology revealed that RIPerC ameliorated the decline in P wave duration without significantly affecting other cardiac electrophysiological changes. Further, renal I/R injury increased the plasma (322.40±34.01 IU/L), renal (8.27±1.10 mIU/mg of Protein), and cardiac (68.28±10.28 mIU/mg of protein) angiotensin-converting enzyme (ACE) activities in association with elevations in the plasma and urine nitrite (25.47±2.01 & 16.62±3.05 μmol/L) and nitrate (15.47±1.33 & 5.01±0.96 μmol/L) levels; these changes were reversed by RIPerC. Further, renal ischemia-reperfusion injury significantly (P=0.047) decreased the renal (but not cardiac) apelin mRNA expression, while renal and cardiac ACE2 (P<0.05) and iNOS (P=0.043) mRNA expressions were significantly increased compared to the sham group; these effects were largely reversed by RIPerC. Our results indicated that RIPerC protects the heart against renal ischemia- reperfusion injury, likely via interaction of the apelin with the RAS/iNOS pathway.

Assessment of remote ischemic conditioning delivery with optical sensor in acute ischemic stroke: Randomised clinical trial protocol.

Remote ischemic conditioning (RIC) is delivered by a blood pressure cuff over the limb, raising pressure 50 mmHg above the systolic blood pressure, to a maximum of 200 mmHg. The cuff is inflated for five minutes and then deflated for five minutes in a sequential ischemia-reperfusion cycle 4-5 times per session. Elevated pressure in the limb may be associated with discomfort and consequently reduced compliance. Continuous assessment of relative blood concentration and oxygenation with a tissue reflectance spectroscopy (a type of optical sensor device) placed over the forearm during the RIC sessions of the arm will allow us to observe the effect of inflation and deflation of the pressure cuff. We hypothesize, in patients with acute ischemic stroke (AIS) and small vessel disease, RIC delivered together with a tissue reflectance sensor will be feasible. The study is a prospective, single-center, randomized control trial testing the feasibility of the device. Patients with AIS within 7 days from symptoms onset; who also have small vessel disease will be randomized 2:1 to intervention or sham control arms. All patients randomized to the intervention arm will receive 5 cycles of ischemia/reperfusion in the non-paralyzed upper limb with a tissue reflectance sensor and patients in the sham control arm will receive pressure by keeping the cuff pressure at 30 mmHg for 5 minutes. A total of 51 patients will be randomized, 17 in the sham control arm and 34 in the intervention arm. The primary outcome measure will be the feasibility of RIC delivered for 7 days or at the time of discharge. The secondary device-related outcome measures are fidelity of RIC delivery and the completion rate of intervention. The secondary clinical outcome includes a modified Rankin scale, recurrent stroke and cognitive assessment at 90 days. RIC delivery together with a tissue reflectance sensor will allow insight into the blood concentration and blood oxygenation changes in the skin. This will allow individualized delivery of the RIC and improve compliance. ClinicalTrials.gov Identifier: NCT05408130, June 7, 2022.

Cytostéatonécrose après reconstruction mammaire par lambeau graisseux avec ou sans préconditionnement ischémique

Cytosteatonecrosis (CTN) is a frequent postoperative complication after breast autologous reconstruction using DIEP (deep inferior epigastric perforator) flap. CTN radiological diagnostic reveals different types of lesions, as nodes or extended fat necrosis, which become in some cases infected, or pass for tumor recurrence after breast cancer treatment. CTN is caused by intraoperative ischemia of the flap, and no current method can prevent postoperative CTN development after DIEP breast reconstruction. Mechanical ischemic preconditioning, consisting in intraoperative briefs consecutive cycles of ischemia reperfusion using vascular clamp upon the graft pedicle, is used in transplantation surgery. This procedure improves the graft tolerance towards ischemic surgical lesions. The aim of this retrospective observational study was to assess PCIM effects on CTN development after DIEP surgery, comparing CTN occurrence after breast reconstruction using DIEP flap with or without intraoperative PCIM. All patients breats reconstructed using DIEP flap between novembre 2020 and may 2022, presenting 6 months postoperative breast echography were retrospectively included. Primary outcome was the ultrasonic existence of CTN, according to the Wagner classification. Clinical data, postoperative outcomes such as infection, hematoma or surgical revision, and length of stay in hospital were also recorded. Twenty nine patients among which 8 PCIM were included. CTN occurrence rate after PCIM (25%) was quite lower than CTN rate without PCIM (71,4%), although the difference was not significant (P=0,088). Other postoperative complications rates were not significantly different with or without PCIM. PCIM seems to improve CTN occurrence after DIEP breast reconstruction, improving fat flap tolerance to ischemic perioperative lesions. Those preliminary results need to be confirmed with clinical prospective study.

788 Baicalin accelerates wound healing in a murine model of ischemic pressure ulcer lesions

Pressure ulcers are a common skin disease that affects the elderly and patients with perceptual or mobility disorders. A pressure ulcer is an ischemic skin necrosis or ulcer that occurs when pressure is applied to a region of the body for an extended period of time, producing poor blood circulation and a lack of oxygen and nutrients. Natural origin pharmaceuticals account for more than half of all modern drugs, and they play an essential role in drug development programs. Baicalin is one of the most important flavonoids in plants, and it is responsible for their pharmacologic effects. This type of natural ingredients provide a wide range of pharmacologic benefits, including anti-inflammatory and anti-tumor properties. The two key processes linked with wound development and effecting the wound healing process with baicalin antioxidant in treating pressure ulcers are oxidative stress and inflammation. However, the effect of baicalin on wound healing in pressure ulcers has not been thoroughly investigated. The wound healing efficacy of baicalin in treating pressure ulcers in a murine pressure ulcer model is investigated in this study. First, the development of 1, 2, 3, 4 stage pressure ulcers after ischemia-reperfusion(I/R) cycle in a murine mouse model. In this model, we investigated the effectiveness of a baicalin in the wound healing of pressure ulcers. We found that baicalin promotes granulation tissue formation, accelerated wound closure, reduced proinflammatory cytokines production and inducing the differentiation of keratinocytes were observed. We expect that this study will contribute to the potential wound therapeutic agent for a pressure ulcer patient.

Recent advances in "sickle and niche" research - Tribute to Dr. Paul S Frenette.

SummaryIn this retrospective, we review the two research topics that formed the basis of the outstanding career of Dr. Paul S. Frenette. In the first part, we focus on sickle cell disease (SCD). The defining feature of SCD is polymerization of the deoxygenated mutant hemoglobin, which leads to a vicious cycle of hemolysis and vaso-occlusion. We survey important discoveries in SCD pathophysiology that have led to recent advances in treatment of SCD. The second part focuses on the hematopoietic stem cell (HSC) niche, the complex microenvironment within the bone marrow that controls HSC function and homeostasis. We detail the cells that constitute this niche, and the factors that these cells use to exert control over hematopoiesis. Here, we trace the scientific paths of Dr. Frenette, highlight key aspects of his research, and identify his most important scientific contributions in both fields.

Remote ischemic preconditioning combined with atorvastatin improves memory after global cerebral ischemia-reperfusion in male rats

Introduction: Damage to hippocampus can occur through ischemia. Memory problems are among the most significant disabilities after stroke. Therefore, improving memory is of great interest in helping post-stroke patients. This study demonstrated that intraperitoneally injection of atorvastatin with a short cycle of ischemia-reperfusion in the left femoral artery improved hippocampal CA1 neurons injury and memory problems after global cerebral ischemia.&#x0D; Materials and methods: In this article survey, we used 64 animals. Rats were divided into 8 groups, (n=8). Group 1: control; group 2: sham; group 3: global cerebral ischemia (GCI) only; group 4: remote ischemic preconditioning (RIP) + GCI; group 5: GCI + atorvastatin (ATO); group 6: GCI + vehicle; group 7: RIP + GCI + ATO; group 8: RIP + GCI + vehicle. We created global cerebral ischemia (GCI) with 20 min occlusion of the Common carotid artery.&#x0D; Results and discussion: Remote ischemic preconditioning could improve rats performance in water maze tests along with a decrease in neuronal death. Also, atorvastatin combined with remote ischemic preconditioning was more effec­tive for memory improvement and reduction of neuronal death. Inconsistent with our result, the function of the animals in the ischemia group was impaired. CA1 hippocampal neurons have an important role in memory and learning, and they can be damaged after cerebral ischemia. Therefore, ischemia can create memory problems. Remote ischemic preconditioning and atorvastatin had a neuroprotective effect and could improve rat performance in water maze test.&#x0D; Conclusion: This study showed that remote ischemic preconditioning with atorvastatin could improve CA1 neuronal injury and memory.

Effects of ischemic conditioning on head and neck free flap oxygenation: a randomized controlled trial

Flap failure after microvascular reconstructive surgery is a rare but devastating complication caused by reperfusion injury and tissue hypoperfusion. Remote ischemic conditioning (RIC) provides protection against ischemia/reperfusion injury and reduces tissue infarction. We hypothesized that RIC would enhance flap oxygenation and exert organ-protective effects during head and neck free flap reconstructive surgery. Adult patients undergoing free flap transfer surgery for head and neck cancer were randomized to receive either RIC or sham-RIC during surgery. RIC consisted of four cycles of 5-min ischemia and 5-min reperfusion applied to the upper or lower extremity. The primary endpoint, tissue oxygen saturation of the flap, was measured by near-infrared spectroscopy on the first postoperative day. Organ-protective effects of RIC were evaluated with infarct size of rat hearts perfused with plasma dialysate from patients received RIC or sham-RIC. Between April 2018 and July 2019, 50 patients were randomized (each n = 25) and 46 were analyzed in the RIC (n = 23) or sham-RIC (n = 23) groups. Tissue oxygen saturation of the flap was similar between the groups (85 ± 12% vs 83 ± 9% in the RIC vs sham-RIC groups; P = 0.471). Myocardial infarct size after treatment of plasma dialysate was significantly reduced in the RIC group (44 ± 7% to 26 ± 6%; P = 0.018) compared to the sham-RIC group (42 ± 6% to 37 ± 7%; P = 0.388). RIC did not improve tissue oxygenation of the transferred free flap in head and neck cancer reconstructive surgery. However, there was evidence of organ-protective effects of RIC in experimental models.Trial registration: Registry number of ClinicalTrials.gov: NCT03474952.

Endothelial cell-derived pro-fibrotic factors increase TGF-β1 expression by smooth muscle cells in response to cycles of hypoxia-hyperoxia

BackgroundThe vascular pathology of peripheral artery disease (PAD) encompasses abnormal microvascular architecture and fibrosis in response to ischemia-reperfusion (I/R) cycles. We aimed to investigate the mechanisms by which pathological changes in the microvasculature direct fibrosis in the context of I/R. MethodsPrimary human aortic endothelial cells (ECs) were cultured under cycles of normoxia-hypoxia (NH) or normoxia-hypoxia-hyperoxia (NHH) to mimic I/R. Primary human aortic smooth muscle cells (SMCs) were cultured and treated with media from the ECs. FindingsThe mRNA and protein expression of the pro-fibrotic factors platelet derived growth factor (PDGF)-BB and connective tissue growth factor (CTGF) were significantly upregulated in ECs undergoing NH or NHH cycles. Treatment of SMCs with media from ECs undergoing NH or NHH cycles led to significant increases in TGF-β1, TGF-β pathway signaling intermediates, and collagen expression. Addition of neutralizing antibodies against PDGF-BB and CTGF to the media blunted the increases in TGF-β1 and collagen expression. Treatment of SMCs with PAD patient-derived serum also led to increased TGF-β1 levels. InterpretationIn an in-vitro model of I/R, which recapitulates the pathophysiology of PAD, increased secretion of PDGF-BB and CTGF by ECs was shown to be predominantly driving TGF-β1-mediated expression by SMCs. These cell culture experiments help elucidate the mechanism and interaction between ECs and SMCs in microvascular fibrosis associated with I/R. Thus, targeting these pro-fibrotic factors may be an effective strategy to combat fibrosis in response to cycles of I/R. FundingNational Institute on Aging at the National Institutes of Health grant number R01AG064420. Research in contextEvidence before this study: Previous studies in gastrocnemius biopsies from peripheral artery disease (PAD) patients showed that transforming growth factor beta 1 (TGF-β1), the most potent inducer of pathological fibrosis, is increased in the vasculature of PAD patients and correlated with collagen deposition. However, the exact cellular source of TGF-β1 remained unclear. Added value of this study: Exposing cells to cycles of normoxia-hypoxia-hyperoxia (NHH) resulted in pathological changes that are consistent with human PAD. This supports the idea that the use of NHH may be a reliable, novel in vitro model of PAD useful for studying associated pathophysiological mechanisms. Furthermore, pro-fibrotic factors (PDGF-BB and CTGF) released from endothelial cells were shown to induce a fibrotic phenotype in smooth muscle cells. This suggests a potential interaction between these cell types in the microvasculature that drives increased TGF-β1 expression and collagen deposition. Thus, targeting these pro-fibrotic factors may be an effective strategy to combat fibrosis in response to cycles of ischemia-reperfusion.

Tackling Ischemic Reperfusion Injury With the Aid of Stem Cells and Tissue Engineering

Ischemia is a severe condition in which blood supply, including oxygen (O), to organs and tissues is interrupted and reduced. This is usually due to a clog or blockage in the arteries that feed the affected organ. Reinstatement of blood flow is essential to salvage ischemic tissues, restoring O, and nutrient supply. However, reperfusion itself may lead to major adverse consequences. Ischemia-reperfusion injury is often prompted by the local and systemic inflammatory reaction, as well as oxidative stress, and contributes to organ and tissue damage. In addition, the duration and consecutive ischemia-reperfusion cycles are related to the severity of the damage and could lead to chronic wounds. Clinical pathophysiological conditions associated with reperfusion events, including stroke, myocardial infarction, wounds, lung, renal, liver, and intestinal damage or failure, are concomitant in due process with a disability, morbidity, and mortality. Consequently, preventive or palliative therapies for this injury are in demand. Tissue engineering offers a promising toolset to tackle ischemia-reperfusion injuries. It devises tissue-mimetics by using the following: (1) the unique therapeutic features of stem cells, i.e., self-renewal, differentiability, anti-inflammatory, and immunosuppressants effects; (2) growth factors to drive cell growth, and development; (3) functional biomaterials, to provide defined microarchitecture for cell-cell interactions; (4) bioprocess design tools to emulate the macroscopic environment that interacts with tissues. This strategy allows the production of cell therapeutics capable of addressing ischemia-reperfusion injury (IRI). In addition, it allows the development of physiological-tissue-mimetics to study this condition or to assess the effect of drugs. Thus, it provides a sound platform for a better understanding of the reperfusion condition. This review article presents a synopsis and discusses tissue engineering applications available to treat various types of ischemia-reperfusions, ultimately aiming to highlight possible therapies and to bring closer the gap between preclinical and clinical settings.

Regular transient limb ischemia protects endothelial function against hypercholesterolemic damage in rabbits.

Regular transient limb ischemia (RTLI) can prevent atherosclerosis in hypercholesterolemic rabbits. As endothelial dysfunction is the initial factor leading to atherosclerosis, we investigated the effect of RTLI on endothelial function in hypercholesterolemic rabbits. We randomly allocated 15 New Zealand white rabbits to three groups, five animals per group: the hypercholesterolemic group (Group H), the sham RTLI group (Group S), and the RTLI group (Group L). All rabbits received hypercholesterolemic fodder daily. No intervention was performed on the rabbits in Group H. Rabbits in Group S were kept in hutches, with a deflated cuff applied to their left hind limb for 60 min every day. For rabbits in Group L, RTLI (six cycles of 5-min ischemia and 5-min reperfusion of the left hind limb) was applied once daily for 12 weeks. At the end of week 12, a segment of the abdominal aorta was isolated from each rabbit for in vitro measurement of the endothelium-dependent vasodilation (EDV) response to different concentrations of acetylcholine and the endothelium-independent vasodilation (EIV) response to sodium nitroprusside. The EDV response was significantly higher in Group L than in Groups S and H (p < 0.05), with no significant difference between Groups S and H (p > 0.05). There was no difference in the EIV response among the three groups. RTLI could improve the EDV response, protecting endothelial function against hypercholesterolemic damage.

Effect of 2-Weeks Ischemic Preconditioning on Exercise Performance: A Pilot Study.

An acute bout of ischemic preconditioning (IPC) has been reported to increase exercise performance. Nevertheless, the ineffectiveness of acute IPC on exercise performance has also been reported. Similarly, the effect of a shot-term intervention of IPC on exercise performance remains controversial in previous studies. In this study, we examined the effects of short-term IPC intervention on whole and local exercise performances and its-related parameters. Ten healthy young males undertook a 2-weeks IPC intervention (6 days/weeks). The IPC applied to both legs with three episodes of a 5-min ischemia and 5-min reperfusion cycle. Whole-body exercise performance was assessed by peak O2 consumption (VO2: VO2 peak) during a ramp-incremental cycling test. Local exercise performance was assessed by time to task failure during a knee extensor sustained endurance test. A repeated moderate-intensity cycling test was performed to evaluate dynamics of pulmonary VO2 and muscle deoxygenation. The knee extensor maximal voluntary contraction and quadriceps femoris cross-sectional area measurements were performed to explore the potentiality for strength gain and muscle hypertrophy. The whole-body exercise performance (i.e., VO2 peak) did not change before and after the intervention (P = 0.147, Power = 0.09, Effect size = 0.21, 95% confidence interval: −0.67, 1.09). Moreover, the local exercise performance (i.e., time to task failure) did not change before and after the intervention (P = 0.923, Power = 0.05, Effect size = 0.02, 95% confidence interval: −0.86, 0.89). Furthermore, no such changes were observed for all parameters measured using a repeated moderate-intensity cycling test and knee extensor strength and quadriceps femoris size measurements. These findings suggest that a 2-weeks IPC intervention cannot increase whole-body and local exercise performances, corresponding with ineffectiveness on its-related parameters in healthy young adults. However, the statistical analyses of changes in the measured parameters in this study showed insufficient statistical power and sensitivity, due to the small sample size. Additionally, this study did not include control group(s) with placebo and/or nocebo. Therefore, further studies with a larger sample size and control group are required to clarify the present findings.

Remote Ischemic Preconditioning Protects Against Endothelial Dysfunction in a Human Model of Systemic Inflammation: A Randomized Clinical Trial.

OBJECTIVE: Inflammation, oxidative stress, and endothelial dysfunction are known to contribute to ischemia-reperfusion injury. Remote ischemic preconditioning (RIPC) protects from endothelial dysfunction and the damage induced by ischemiareperfusion. Using intensive periodontal treatment (IPT), an established human model of acute systemic inflammation, we investigated whether RIPC prevents endothelial dysfunction and modulates systemic levels of inflammation and oxidative stress. APPROACH AND RESULTS: Forty-nine participants with periodontitis were randomly allocated to receive either 3 cycles of ischemia-reperfusion on the upper limb (N=24, RIPC) or a sham procedure (N=25, control) before IPT. Endothelial function assessed by flow-mediated dilatation of the brachial artery, inflammatory cytokines, markers of vascular injury, and oxidative stress were evaluated at baseline, day 1, and day 7 after IPT. Twenty-four hours post-IPT, the RIPC group had lower levels of IL-10 (interleukin-10) and IL-12 (interleukin-12) compared with the control group (P<0.05). RIPC attenuated the IPTinduced increase in IL-1β (interleukin-1β), E-selectin, sICAM-3 (soluble intercellular adhesion molecule 3), and sTM (soluble thrombomodulin) levels between the baseline and day 1 (P for interaction <0.1). Conversely, oxidative stress was differentially increased at day1 in the RIPC group compared with the control group (P for interaction <0.1). This was accompanied by a better flow-mediated dilatation (mean difference 1.75% [95% CI, 0.428–3.07], P=0.011). After 7 days from IPT, most of the inflammatory markers, endothelial-dependent and -independent vasodilation, were similar between groups. CONCLUSIONS: RIPC prevented acute endothelial dysfunction by modulation of inflammation and oxidation processes in patients with periodontitis following exposure to an acute inflammatory stimulus. REGISTRATION: URL: https://clinicaltrials.gov/ct2/show/NCT03072342; Unique identifier: NCT03072342.

Blood flow restriction in the presence or absence of muscle contractions does not preserve vasculature structure and function following 14-days of limb immobilization.

Limb immobilization causes local vasculature to experience detrimental adaptations. Simple strategies to increase blood flow (heating, fidgeting) successfully prevent acute (≤ 1day) impairments; however, none have leveraged the hyperemic response over prolonged periods (weeks) mirroring injury rehabilitation. Throughout a 14-day unilateral limb immobilization, we sought to preserve vascular structure and responsiveness by repeatedly activating a reactive hyperemic response via blood flow restriction (BFR) and amplifying this stimulus by combining BFR with electric muscle stimulation (EMS). Young healthy adults (M:F = 14:17, age = 22.4 ± 3.7years) were randomly assigned to control, BFR, or BFR + EMS groups. BFR and BFR + EMS groups were treated for 30min twice daily (3 × 10min ischemia-reperfusion cycles; 15% maximal voluntary contraction EMS), 5 days/week (20 total sessions). Before and after immobilization, artery diameter, flow-mediated dilation (FMD) and blood flow measures were collected in the superficial femoral artery (SFA). Following immobilization, there was less retrograde blood velocity (+ 1.8 ± 3.6cms-1, P = 0.01), but not retrograde shear (P = 0.097). All groups displayed reduced baseline and peak SFA diameter following immobilization (- 0.46 ± 0.41mm and - 0.43 ± 0.39mm, P < 0.01); however, there were no differences by group or across time for FMD (% diameter change, shear-corrected, or allometrically scaled) nor microvascular function assessed by peak flow capacity. Following immobilization, our results reveal (1) neither BFR nor BFR + EMS mitigate artery structure impairments, (2) intervention-induced shear stress did not affect vascular function assessed by FMD, and (3) retrograde blood velocity is reduced at rest offering potential insight to mechanisms of flow regulation. In conclusion, BFR appears insufficient as a treatment strategy for preventing macrovascular dysfunction during limb immobilization.

Remote Ischemic Conditioning Increases Organ Injury in Murine Sepsis: Experimental Research

Remote ischemic conditioning includes the transfer of information via humoral mediators and/or neurogenic pathways from the initial remote organ exposed to the ischemia to the target organ to be protected. The postulated mechanisms of protection in the target organ involve mitochondrial adaptation to metabolic stress, redox regulation, and downregulation of many key steps leading to cell death. As possible protective mechanisms of remote ischemic conditioning and sepsis pathogenesis have so many common components, in this study, we aimed to investigate the effect of remote ischemic conditioning on survival and organ injury in cecal ligation and perforation induced (CLP) sepsis in mice. After ethical committee approval, ninety Swiss albino mice were divided into 10 groups: control group, control + ischemia group, sham group, sham + ischemia group, sham + 5h ischemia group, sham + 20h ischemia group, CLP group, CLP + ischemia group, CLP + 5h ischemia group, and CLP + 20h ischemia group. In the ischemia groups, for RIC, right hind leg was subjected to 6 cycles of 5-min ischemia and 5-min reperfusion using a surgical clamp. Antibiotics, analgesics, and fluid replacement were applied for 3 days in all groups. The organ damages were scored under light microscopy. Lung injury-related histologically findings were more prominent in CLP + 20h ischemia group than CLP, CLP + ischemia, and CLP + 5h ischemia groups. Spleen injury scores were found higher in CLP + 5h ischemia and CLP + 20h ischemia group than CLP group. Parenchymal cardiac congestion score was higher in CLP + 20h ischemia group than CLP and CLP + 5h ischemia group. The heart necrosis score was highest in CLP + 20h ischemia group. Total organ injury and every single organ injury scores were also highest in the CLP+20h ischemia group. We could not demonstrate any protective effect of remote ischemic conditioning on septic organ injury neither at early nor at late phases of sepsis. In fact, remote ischemic conditioning increased organ injury especially when applied later in cecal ligation and perforation induced sepsis in mice.

The effects of whole-body vibration on wound healing in a mouse pressure ulcer model

BackgroundPressure ulcers are one of the most common complications of immobility resulting from pressure and shear. Whole-body vibration (WBV) has been shown to increase skin blood flow but little information is known about its effect on pressure ulcers. This study investigated the effects of WBV on wound healing in a mouse pressure ulcer model. MethodsTwo cycles of ischemia-reperfusion were performed by external application of two magnetic plates to dorsal skin to induce stage II pressure ulcers characterized by partial-thickness skin loss with exposed dermis. A total of 32 male ICR mice were randomly and equally divided into untreated control and the WBV groups. Immediately after the completion of 2-cycle ischemia-reperfusion injury, mice in the WBV group participated in a WBV program using a vibrator (frequency 45 Hz, peak acceleration 0.4 g, vertical motion) for 30 min/day and 5 consecutive days/week. At days 7 and 14 post-ulceration, wound closure rate was assessed. Wound tissues were harvested for determination of collagen deposition in Masson's trichrome stained sections, neutrophil infiltration and capillary density in hematoxylin and eosin-stained sections, as well as TNF-α and VEGF levels using ELISA. ResultsTNF-α levels and neutrophil infiltration were significantly decreased in wounds on days 7 and 14 of WBV treatment. Moreover, wound closure rate and collagen deposition were remarkably accelerated on day 14. Tissue VEGF and capillary density were unaffected by WBV at either time point. ConclusionsThese findings suggest that WBV has the potential to promote the healing process of stage II pressure ulcers, as evidenced by attenuation of wound inflammation and enhancement collagen deposition.

Abstract 15252: Ischemic-Trained Monocytes Improve Arteriogenesis During Hindlimb Ischemia

Introduction: Recent studies have shown that innate response can build immunological memory. This process called “trained immunity” is an epigenetic reprogramming of the monocytes driven by a metabolism shift towards glycolysis. Hypothesis: Since HIF-1a is a major player in monocytes activation and also targets some epigenetic enzymes, we hypothesize that hypoxia/ischemia can lead to “trained immunity” improving arteriogenesis in a mouse model of hindlimb ischemia. Methods: Mice subjected to a unilateral single ischemia insult for 24hours (24h group: femoral artery ligation for 24 h) or by ischemia reperfusion cycles (Cycle group: ischemia-reperfusion in 4 cycles of 5 minutes) or non-ischemia (sham group), were used as donors in the monocyte transfer experiment. Recipient mice underwent to permanent hindlimb ischemia one day prior the tail vein injection of bone marrow (BM) monocytes from the ischemic leg. Laser Doppler assessed blood flow recovery before and after hindlimb ischemia. Arteriogenesis was quantified on recipient mice by assessing the diameter of gracilis collaterals. A 24h group monocytes from ischemia and non-ischemia leg was used as donors to test the systemic vs. local effect of the ischemic-trained monocytes. Lin- cells were used as a control. Cultured human monocytes were subjected to 24h hypoxia and gene expression for epigenetic enzymes was performed by real time rt-PCR Results: Blood flow recovery in recipients who received ischemic-trained monocytes (24h and cycle) improved overtime compared to sham. Arteriogenesis was significant greater in 24h group compared to sham. Surprisingly, the improvement in blood flow recovery was abolished using combined monocytes from ischemic and non-sichemic, suggesting that ischemia training has a local effect in the monocytes. The Lin- experiment confirmed that the ischemia training is monocyte specific. Moreover, hypoxia regulated epigenetic enzymes responsible for histones methylation in human monocytes. Conclusions: Monocytes can be trained by previous ischemia/hypoxia insult and improve arteriogenesis during hindlimb ischemia. The molecular mechanisms that lead the trained immunity by hypoxia still unknown, however epigenetic modifications might play a role in this process.