Adenosine Pretreatment Research Articles

Adenosine protects cardiomyocytes against acrolein-induced cardiotoxicity by enhancing mitochondrial homeostasis, antioxidant defense, and autophagic flux via ERK-activated FoxO1 upregulation

Acrolein is a ubiquitous gaseous air pollutant and endogenous toxicant, which poses strong risk for oxidative stress-related diseases such as cardiovascular disease. Adenosine has been identified as potential therapeutic agent for age-related cardiovascular disease, while the molecular mechanisms underlying its cardioprotection remain elusive. In the present study, we investigated the myocardial protective effects and the mechanism of adenosine on acrolein-induced toxicity in H9c2 cells and primary neonatal rat cardiomyocytes. We found that acrolein caused apoptosis of cardiomyocytes resulting from oxidative damage, autophagy defect, and mitochondrial dysfunction, as evidenced by loss of mitochondrial membrane potential, impairment of mitochondrial biogenesis, dynamics, and oxidative phosphorylation, decrease of mitochondrial deoxyribonucleic acid (mtDNA) copy number and adenosine 5’-triphosphate (ATP) production. Adenosine pretreatment protected against acrolein-induced cardiotoxicity by maintaining mitochondrial homeostasis, activating the phase II detoxifying enzyme system, promoting autophagic flux, and alleviating mitochondrial-dependent apoptosis. We further demonstrated that the up-regulation of forkhead box protein O1 (FoxO1) mediated by extracellular regulated protein kinases (ERK) activation contributes to the cardioprotection of adenosine. These results expand the application of adenosine in cardioprotection to preventing myocardial damages induced by environmental pollutant acrolein exposure, and uncover the adenosine-ERK-FoxO1 axis as the underlying mechanism mediating the protection of mitochondrial homeostasis, Nrf2-mediated antioxidant defense and autophagic flux, shedding light on the better understanding about the pathological mechanism of cardiovascular disease caused by environmental pollutants and applications of adenosine in cardioprotection.

Effect of Adenosine Receptor Antagonists on Adenosine-Pretreated PC12 Cells Exposed to Paraquat.

Previous studies evaluated the adenosine receptor antagonists alone to determine their effects on oxidative stress, but little is known about adenosine’s protective efficacy when oxidative injury occurs in vivo. Adenosine is a crucial signaling molecule recognized by four distinct G-protein-coupled receptors (GPCRs) (i.e., A1R, A2AR, A2BR, and A3R) and protects cells against pathological conditions. The present study was performed to evaluate the role of antagonist modulation in the setting of paraquat toxicity with adenosine pretreatment. First, PC12 cells were exposed to paraquat (850 μM) and adenosine (30 μM) to develop an in vitro model for the antagonist effect assay. Second, we found that the A1R antagonist DPCPX enhanced the viability of paraquat-induced PC12 cells that underwent adenosine pretreatment. Moreover, the A2AR antagonist ZM241385 decreased the viability of paraquat-induced PC12 cells that underwent adenosine pretreatment. Our findings indicate that adenosine protection requires a dual blockade of A1R and activation of A2AR to work at its full potential, and the A2B and A3 adenosine receptor antagonists increased paraquat-induced oxidative damage. This represents a novel pharmacological strategy based on A1/A2A interactions and can assist in clarifying the role played by AR antagonists in the treatment of neurodegenerative diseases.

Cardioprotection with Adenosine during Coronary Revascularization

Background: Postoperative cardiac dysfunction is a common cause of mortality and morbidity associated with CABG Surgery. Adenosine enhances tolerance of the myocardium to ischemic arrest. Therefore, the study on adenosine pre-treatment as an adjunct to cardioplegia in patients undergoing CABG will definitely help to provide better myocardial protection for better postoperative outcome.
 Methods: Quasi experimental study was done in the Department of Cardiac Surgery, NICVD during July 2012 to June 2014 with patients who underwent conventional CABG surgery. Patients were divided in two groups. Group A: Patients received at regular institutional high-potassium ([K+] = 20 mol/ l) cold (12 °C) blood cardioplegia. and Group B: Patients received 250 μg /kg bolus dose of adenosine pre-treatment, which was immediately followed by high-potassium cold (12 °C) blood cardioplegia after clamp-on. Patients were followed up to evaluate the degree of myocardial damage by measuring perioperative Troponin I, amount of inotropic support, time of assisted ventilation, arrhythmia and mortality.
 Results: Most of the patients in each group belongs to 51-60 years of age range. There was no difference regarding operative parameters in two groups. Time to arrest was significantly shorter in group B compared to group A, indicating that adenosine has the potential to enhance the efficacy of cardioplegic arrest. Plasma level markers of myocardial damage: cardiac Troponin I (cTnI) obtained from serial venous blood samples post-operatively were significantly lower in group B than group A (p<0.05). There was significantly decreased requirement of inotrope in group B during first 24 hrs (p <0.05).
 Conclusion: Decreased level of cardiac enzymes and lower inotropic requirement suggests that an optimal myocardial protection with less cellular damage is obtained with adenosine pre-treatment as adjunct to cold blood cardioplegia.
 Cardiovasc. j. 2021; 13(2): 128-134

Effect of Adenosine on Myocardial Protection as an Adjunct to Cardioplegia during Coronary Artery Bypass Surgery

Background: Adenosine (ADO) has been known to have beneficial effects against tissue injury after myocardial ischemia. So, this study was carried out to investigate the cardio protective effect of exogenous ADO pretreatment as an adjunct to cold blood cardioplegia during coronary artery bypass surgery.Materials and methods: 50 patients (25 in each group) with coronary artery disease undergoing CABG were randomly assigned to both groups: Group A received regular institutional high-potassium ([K+] 20 mol/ 1) cold (12 °C) blood cardioplegia and Group B received 250 ug/ kg adenosine pretreatment followed by antegrade high-potassium cold (12 °C) blood cardioplegia after clamp-on. Clinical outcomes were observed before, during and after the operation.Results: There was no difference regarding operative parameters in two groups. Time to arrest was significantly shorter in group B compared to Group A, indicating that adenosine has the potential to enhance the efficacy of cardioplegic arrest. Plasma level markers of myocardial damage: cardiac Troponin I (cTnl) obtained from serial venous blood samples were significantly lower in group B during cTnl at 10 min after declamping of cross clamp and 12 hours post-operative period than group A. There was significantly decreased requirement of inotrope in group B during 1st 24 hrs. Other postoperative outcomes (mechanical ventilation, ICU stay, postoperative arrhythmia and in hospital mortality were similar in both groups.Conclusion: Decreased level of cardiac enzymes and lower inotropic requirement suggests that a optimal myocardial protection with less cellular damage is obtained with adenosine pretreatment as adjunct to cold blood cardioplegia.University Heart Journal Vol. 14, No. 1, Jan 2018; 21-23

The Effects of Adenosinergic Modulation on Cytokine Levels in a Pentylenetetrazole-Induced Generalized Tonic-Clonic Seizure Model

Objective: It has been suggested that the adenosinergic system and cytokines play a role in the pathogenesis of epilepsy. Although the role of the adenosinergic system in the modulation of seizure activity is well known, the mechanism of this modulation needs to be described in detail. We performed this study to determine the contribution of the proinflammatory cytokines to the generalized seizure activity during adenosine and caffeine treatment. Methods: We induced generalized tonic-clonic seizures with the administration of 60 mg/kg pentylenetetrazole (PTZ) in male Wistar Albino rats. Adenosine (500 mg/kg) or caffeine (5 mg/kg) was administered before PTZ injection. We monitored seizure activity and then determined the TNF-α, IL-1β, and IL-6 levels in the cortical and thalamic brain regions of rats by ELISA. Results: Adenosine pretreatment significantly extended seizure latency (p < 0.05), but did not affect seizure duration and entry time to stage 4 seizure. Caffeine pretreatment did not change seizure latency and seizure duration. PTZ treatment did not change brain cytokine levels significantly (p > 0.05) compared to the control group. Whereas adenosine pretreatment decreased brain TNF-α, IL-1β, and IL-6 levels significantly (p < 0.05), caffeine pretreatment reduced brain cytokine levels slightly but nonsignificantly (p > 0.05). Conclusion: Our results show that there is a clear relation between adenosinergic system and brain tissue cytokine levels. Our findings indicated that TNF-α, IL-1β, and IL-6 participate in the pathogenesis of generalized seizures, and the inhibition of TNF-α, IL-1β, and IL-6 with adenosinergic modulation may decrease seizure severity.

Adenosine as a regulator of NFκB activation

Adenosine as a regulator of NF<i>κ</i>B activation

The Selective A3AR Antagonist LJ-1888 Ameliorates UUO-Induced Tubulointerstitial Fibrosis

Adenosine in the normal kidney significantly elevates in response to cellular damage. The renal A3 adenosine receptor (A3AR) is up-regulated under stress, but the therapeutic effects of A3AR antagonists on chronic kidney disease are not fully understood. The present study examined the effect of LJ-1888 [(2R,3R,4S)-2-[2-chloro-6-(3-iodobenzylamino)-9H-purine-9-yl]-tetrahydrothiophene-3,4-diol], a newly developed potent, selective, species-independent, and orally active A3AR antagonist, on unilateral ureteral obstruction (UUO)-induced renal fibrosis. Pretreatment with LJ-1888 inhibited UUO-induced fibronectin and collagen I up-regulation in a dose-dependent manner. Masson's trichrome staining confirmed that LJ-1888 treatment effectively reduced UUO-induced interstitial collagen accumulation. Furthermore, delayed administration of LJ-1888 showed an equivalent therapeutic effect on tubulointerstitial fibrosis to that of losartan. Small-interfering A3AR transfection effectively inhibited transforming growth factor-β1 (TGF-β1)-induced fibronectin and collagen I up-regulation in proximal tubular cells similar to LJ-1888, confirming that the renoprotective effect of LJ-1888 resulted from A3AR blockade. UUO- or TGF-β1-induced c-Jun N-terminal kinase and extracellular signal-regulated kinase phosphorylation decreased significantly after LJ-1888 administration. A3AR blockade reduced UUO- or TGF-β1-induced up-regulation of lysyl oxidase, which induces cross-linking of extracellular matrix, suggesting that LJ-1888 may also regulate extracellular matrix accumulation via post-translational regulation. In conclusion, the present data demonstrate that the A3AR antagonist, LJ-1888, blocked the development and attenuated the progression of renal fibrosis, and they suggest that LJ-1888 may become a new therapeutic modality for renal interstitial fibrosis.

Adenosine A1 Receptors Promote Vasa Vasorum Endothelial Cell Barrier Integrity via Gi and Akt-Dependent Actin Cytoskeleton Remodeling

BackgroundIn a neonatal model of hypoxic pulmonary hypertension, a dramatic pulmonary artery adventitial thickening, accumulation of inflammatory cells in the adventitial compartment, and angiogenic expansion of the vasa vasorum microcirculatory network are observed. These pathophysiological responses suggest that rapidly proliferating vasa vasorum endothelial cells (VVEC) may exhibit increased permeability for circulating blood cells and macromolecules. However, the molecular mechanisms underlying these observations remain unexplored. Some reports implicated extracellular adenosine in the regulation of vascular permeability under hypoxic and inflammatory conditions. Thus, we aimed to determine the role of adenosine in barrier regulation of VVEC isolated from the pulmonary arteries of normoxic (VVEC-Co) or chronically hypoxic (VVEC-Hyp) neonatal calves.Principal FindingsWe demonstrate via a transendothelial electrical resistance measurement that exogenous adenosine significantly enhanced the barrier function in VVEC-Co and, to a lesser extent, in VVEC-Hyp. Our data from a quantitative reverse transcription polymerase chain reaction show that both VVEC-Co and VVEC-Hyp express all four adenosine receptors (A1, A2A, A2B, and A3), with the highest expression level of A1 receptors (A1Rs). However, A1R expression was significantly lower in VVEC-Hyp compared to VVEC-Co. By using an A1R-specific agonist/antagonist and siRNA, we demonstrate that A1Rs are mostly responsible for adenosine-induced enhancement in barrier function. Adenosine-induced barrier integrity enhancement was attenuated by pretreatment of VVEC with pertussis toxin and GSK690693 or LY294002, suggesting the involvement of Gi proteins and the PI3K-Akt pathway. Moreover, we reveal a critical role of actin cytoskeleton in VVEC barrier regulation by using specific inhibitors of actin and microtubule polymerization. Further, we show that adenosine pretreatment blocked the tumor necrosis factor alpha (TNF-α)-induced permeability in VVEC-Co, validating its anti-inflammatory effects.ConclusionsWe demonstrate for the first time that stimulation of A1Rs enhances the barrier function in VVEC by activation of the Gi/PI3K/Akt pathway and remodeling of actin microfilament.

Protective effects of adenosine on the diabetic myocardium against ischemia–reperfusion injury: Role of calpain

Myocardial ischemia/reperfusion injury (I/RI) is the principal cause of mortality and morbidity in diabetic patients undergoing cardiac surgery. However, there is no specific measure available to protect diabetic hearts in this clinical setting. Our clinical studies showed that adenosine pre-treatment or post-treatment and adding adenosine to cardioplegia solution had significant myocardial protective effects in patients undergoing cardiac surgery. However, the specific protective effects and mechanisms of adenosine in diabetic myocardial I/RI are not clear. Calpain is an important proteolytic enzyme in the myocardium. Studies show that the activation of calpain is an injury factor in not only the diabetic myocardium but also myocardial I/RI progression. We therefore hypothesize that adenosine play a protective role in diabetic myocardial I/RI through the inhibition of calpain.

The myocardial protective effects of adenosine pretreatment in children undergoing cardiac surgery: a randomized controlled clinical trial

Adenosine pretreatment reduces injury caused by ischemia-reperfusion. To investigate the hypothesis that adenosine pretreatment would modulate injury induced by cardiopulmonary bypass (CPB) and myocardial ischemia/reperfusion, we conducted a randomized controlled trial on the effects of adenosine pretreatment in children undergoing surgery to repair congenital heart defects. Children undergoing surgery to repair congenital heart defects were randomized to adenosine pretreatment or control treatment. Adenosine pretreatment was performed by infusing a total of 2.45 mg kg⁻¹ of adenosine over 10 min. Serum troponin I was measured pre- and postoperatively. Multiple clinical parameters, including postoperative use of inotropic medicine and duration in the intensive care unit (ICU), were recorded. A total of 82 patients were enrolled in the study. There were 42 control patients and 40 patients in the adenosine pretreatment group. The mean age and weight of the two groups were not significantly different, nor were cardiopulmonary bypass and cross-clamp times. There were no deaths and severe complications in both groups. The adenosine pretreatment protocol caused significant hypotension but had no significant effect on heart rate. One patient had severe tachycardia shortly after the adenosine pretreatment protocol was completed, and adenosine infusion was continued until CPB was started. Postoperative levels of serum troponin I were greater in the control patients than in the adenosine pretreatment group, indicating that the control group suffered greater myocardial injury. Control group patients required more postoperative inotropic agents than those in the adenosine pretreatment group at 0, 1, and 3 h, indicating that the adenosine pretreatment group had a better cardiac function. The adenosine pretreatment group also required significantly less time in the ICU than the control group (3.2 ± 1.2 days vs 3.9 ± 1.2 days, p = 0.013). This study demonstrates that adenosine pretreatment is protective of the myocardium during open-heart surgery in pediatric patients.

Adenosine pretreatment attenuates angiotensin II-mediated p38 MAPK activation in a protein kinase A dependent manner

AbstractBackground: Adenosine is known as a protective and anti-inflammatory nucleoside. Angiotensin II is the main hormone of the renin-angiotensin system. It is associated with endothelial permeability, recruitment, and activation of the immune cells through induction of inflammatory mediators. Matrix metalloproteinase-9 (MMP-9) plays an important role in inflammatory processes mediated by macrophages. Objectives: Investigate whether adenosine pretreatment modulates angiotensin II-induced MMP-9 expression and activation of signaling molecules. Methods: Human monocytic U-937 cells were treated with either adenosine or angiotensin II alone or angiotensin II following a pretreatment with adenosine. Supernatants were analyzed for MMP-9 activity by zymography method. MMP-9 gene expression was analyzed using real-time PCR. Activation of inflammatory mediators IκB-α, NF-κB, JNK, p38 MAPK, and STAT3 were analyzed by a multi-target ELISA kit. Association of Protein kinase A (PKA) in adenosine effects was studied by pre-incubation with H89, a selective PKA inhibitor. Results: Treatment of the cells with angiotensin II significantly increased MMP-9 production (p &lt;0.05). Adenosine pretreatment did not attenuate this angiotensin II effect. Angiotensin II treatment induced NF-κB, JNK and p38 activation. Pretreatment with adenosine prior to angiotensin II stimulation showed a 40% inhibitory effect on p38 induction (p &lt;0.05). This effect was reversed by PKA inhibition. Conclusion: The present data confirmed that monocytic MMP-9 was a target gene for angiotensin II. Adenosine pretreatment did not inhibit MMP-9 increase in response to angiotensin II. However, it showed a potential inhibitory effect on angiotensin II inflammatory signaling.

Mice that overexpress human heat shock protein 27 have increased renal injury following ischemia reperfusion

We previously showed that activation of the A1 adenosine receptor protected the kidney against ischemia-reperfusion injury by induction and phosphorylation of heat shock protein 27 (HSP27). Here, we used mice that overexpress human HSP27 (huHSP27) to determine if kidneys from these mice were protected against injury. Proximal tubule cells cultured from the transgenic mice had increased resistance to peroxide-induced necrosis compared to cells from wild-type mice. However, after renal ischemic injury, HSP27 transgenic mice had decreased renal function compared to wild-type mice, along with increased renal expression of mRNAs of pro-inflammatory cytokines (TNF-alpha, ICAM-1, MCP-1) and increased plasma and kidney keratinocyte-derived cytokine. Following ischemic injury, neutrophils infiltrated the kidneys earlier in the transgenic mice. Flow cytometric analysis of lymphocyte subsets showed that those isolated from the kidneys of transgenic mice had increased CD3(+), CD4(+), CD8(+), and NK1.1(+) cells 3 h after injury. When splenocytes or NK1.1(+) cells were isolated from transgenic mice and adoptively transferred into wild-type mice there was increased renal injury. Further, depletion of lymphocytes by splenectomy or neutralization of NK1.1(+) cells resulted in improved renal function in the transgenic mice following reperfusion. Our study shows that induction of HSP27 in renal tubular cells protects against necrosis in vitro, but its systemic increase counteracts this protection by exacerbating renal and systemic inflammation in vivo.

Autophagy is required for preconditioning by the adenosine A1 receptor-selective agonist CCPA

We have shown that the cellular process of macroautophagy plays a protective role in HL-1 cardiomyocytes subjected to simulated ischemia/reperfusion (sI/R) (Hamacher-Brady et al. in J Biol Chem 281(40):29776-29787). Since the nucleoside adenosine has been shown to mimic both early and late phase ischemic preconditioning, a potent cardioprotective phenomenon, the purpose of this study was to determine the effect of adenosine on autophagosome formation. Autophagy is a highly regulated intracellular degradation process by which cells remove cytosolic long-lived proteins and damaged organelles, and can be monitored by imaging the incorporation of microtubule-associated light chain 3 (LC3) fused to a fluorescent protein (GFP or mCherry) into nascent autophagosomes. We investigated the effect of adenosine receptor agonists on autophagy and cell survival following sI/R in GFP-LC3 infected HL-1 cells and neonatal rat cardiomyocytes. The A(1) adenosine receptor agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) (100 nM) caused an increase in the number of autophagosomes within 10 min of treatment; the effect persisted for at least 300 min. A significant inhibition of autophagy and loss of protection against sI/R measured by release of lactate dehydrogenase (LDH), was demonstrated in CCPA-pretreated cells treated with an A(1) receptor antagonist, a phospholipase C inhibitor, or an intracellular Ca(+2) chelator. To determine whether autophagy was required for the protective effect of CCPA, autophagy was blocked with a dominant negative inhibitor (Atg5(K130R)) delivered by transient transfection (in HL-1 cells) or protein transduction (in adult rat cardiomyocytes). CCPA attenuated LDH release after sI/R, but protection was lost when autophagy was blocked. To assess autophagy in vivo, transgenic mice expressing the red fluorescent autophagy marker mCherry-LC3 under the control of the alpha myosin heavy chain promoter were treated with CCPA 1 mg/kg i.p. Fluorescence microscopy of cryosections taken from the left ventricle 30 min after CCPA injection revealed a large increase in the number of mCherry-LC3-labeled structures, indicating the induction of autophagy by CCPA in vivo. Taken together, these results indicate that autophagy plays an important role in mediating the cardioprotective effects conferred by adenosine pretreatment.

Adenosine preconditions against ouabain but not against glutamate on CA1‐evoked potentials in rat hippocampal slices

Hypoxic and ischaemic brain damage are believed to involve excessive release of glutamate, and recent work shows that glutamate-induced damage in brain slices can be reduced by preconditioning with hypoxia or glutamate itself. Because adenosine is a powerful preconditioning agent, we have investigated whether adenosine could precondition against glutamate in vitro. In rat hippocampal slices, glutamate depolarization reduced the amplitudes of antidromic- and orthodromic-evoked potentials, with only partial recovery. Applying adenosine before these insults failed to increase that recovery. Ouabain also produced depolarization with partial reversibility, but adenosine pretreatment increased the extent of recovery. The preconditioning effect of adenosine on ouabain responses was prevented by blocking receptors for N-methyl-D-aspartate (NMDA), but not receptors for kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and was blocked by inhibiting nitric oxide synthase. Preconditioning was also abolished by the ATP-dependent potassium channel blockers, glibenclamide (cytoplasmic) or 5-hydroxydecanoate (mitochondrial). We conclude that adenosine does not precondition against glutamate in hippocampal slices, but that it does precondition against ouabain with a pharmacology similar to studies in vivo. Ischaemic neuronal damage is a complex of many factors, and because adenosine can precondition against ischaemic neuronal damage, its failure to protect against glutamate highlights limitations of using glutamate alone as a model for ischaemia. Because damage following ischaemia, trauma or excitotoxicity also involves reduced Na(+),K(+)-ATPase activity, and adenosine can precondition against ouabain, we propose that ouabain-induced damage represents an additional or alternative model for the contribution to cell damage of Na(+),K(+)-ATPase loss, this being more relevant to the mechanisms of preconditioning.

Intravenous adenosine reduces myocardial no-reflow by decreasing endothelin-1 via activation of the ATP-sensitive KM+ channel

It has been verified that adenosine can attenuate myocardial no-reflow. However, the effects of adenosine on adenosine triphosphate-sensitive K+ (KATP) channel and endothelin-1 (ET-1) are unknown.Methods — Forty mini-swines were randomized into 5 study groups: 8 in the control group, 8 in the adenosine pretreatment group, 8 in the glibenclamide (KATP channel blocker)-treated group, 8 in the adenosine and glibenclamide-pretreated group and 8 in the sham-operated group. An acute myocardial infarction and reperfusion model was created with three-hour occlusion of the left anterior descending coronary artery followed by a one-hour reperfusion.Results — Compared with the control group, adenosine significantly decreased the area of no-reflow (myocardial contrast echocardiography: from 78.5 ± 4.5% to 20.7 ± 4.1%, pathological means: from 82.3 ± 1.9% to 21.5 ± 4.3% of ligation area, respectively; all P < 0.01), reduced necrosis size from 98.5 ± 1.3% to 75 ± 4.7% of ligation area, P < 0.05). It also decreased plasma ET-1 and myocardial tissue ET-1. However, glibenclamide abrogated the protective effect of adenosine.Conclusion — The beneficial effect of adenosine on myocardial no-reflow could be due to its effect on ET-1 via the activation of KATP channel.

Effects of ischemic preconditioning and adenosine pretreatment on myocardial function and energetics in a clinically relevant model

Preconditioning (PC) is a potential approach to myocardial protection. We hypothesize that brief ischemia or adenosine given prior to an extended period of warm ischemia may prevent myocardial stunning by altering myocardial metabolism. Using a global ischemia model, 19 dogs were subjected to no PC(control), two episodes of ischemia (2 min of global ischemia followed by 3 min of reperfusion) (IPC), or 30 min of pulmonary artery adenosine infusion (AP), to a maximum of 350 μg/kg/min, followed by 20 min of global warm ischemia on cardiopulmonary bypass. Left ventricular pressure–volume loops and myocardial oxygen consumption (MVO2) were measured at baseline and after 60 min of reperfusion, on right heart bypass. All data were compared between baseline and reperfusion. Load independent left ventricular function, defined as preload recruitable stroke work (PRSW), decreased in control and IPC groups (72±7%, 71±12%, respectively). AP blunted the decrease in PRSW (45±9%, p<.05 compared to control). Myocardial energetic conversion efficiency, defined as the slope of the MVO2–Stroke work relationship was not significantly changed for controls (2.17±0.47 to 1.84±0.68) and IPC (2.99±0.45 to 2.16±0.65), but was for AP (1.16±0.88 to 5.71±1.66, p<0.04). IPC did not prevent ventricular stunning or alter myocardial energetics. AP reduced ventricular stunning but resulted in worsened myocardial energy efficiency. The benefits to ventricular function of the adenosine pretreatment protocol used in this study were only possible at a cost of higher metabolic requirements.

Pretreatment with intracoronary adenosine reduces the incidence of myonecrosis after non-urgent percutaneous coronary intervention: a prospective randomized study

We sought to investigate the effect of adenosine pretreatment on the incidence of myonecrosis after non-urgent percutaneous coronary intervention (PCI). This was a prospective, randomized, open-label study. Patients who were scheduled for non-urgent PCI in de novo native coronary arteries were eligible. All patients were pretreated with aspirin and clopidogrel. Myonecrosis was measured by creatine kinase-myocardial band (CK-MB) elevation after PCI. A total of 62 patients were randomized into the adenosine (n = 31) or standard (n = 31) group. The adenosine group received 50 microg adenosine bolus before wiring of each lesion, whereas the standard group did not. Post-PCI myonecrosis occurred more frequently in the standard group (39 vs. 13%, OR 0.23, 95% CI 0.05-0.95, P = 0.020). After adjustment for drug-eluting stent implantation, multi-vessel stenting, and elevated baseline troponin, the OR was 0.19 (95% CI 0.05-0.72, P = 0.017). The median peak values of CK-MB in the adenosine and standard groups were 2 and 4 microg/L, respectively (P = 0.033). The adjusted difference was 1.95 microg/L (95% CI 0.13-3.77, P = 0.037). The incidences of myocardial infarction (>3 x CK-MB) were 6 and 16% in the adenosine and standard groups, respectively (OR 0.36; 95% CI 0.03-2.46, P = 0.229). Pretreatment with 50 microg of adenosine decreases the incidence of myonecrosis after non-urgent PCI compared with that without pretreatment.

Adenosine is a negative regulator of NF-κB and MAPK signaling in human intestinal epithelial cells

Previous studies suggest that adenosine possesses anti-inflammatory properties, however, the mechanisms by which adenosine affects immune function remain unclear, particularly in the intestine. In this study, we hypothesized that adenosine directly affects pro-inflammatory gene expression in intestinal epithelial cells through modulation of NF-κB signaling. HT-29 cells were treated with adenosine prior to incubation with various stimuli and pro-inflammatory gene expression and signal transduction analyzed. Adenosine pretreatment resulted in a reduction in IL-8 expression and secretion in response to TNF-α, IL-1, LPS, and PMA. This effect was paralleled by inhibition of κB-driven luciferase expression and a reduction in recruitment of NF-κB to the IL-8 promoter. Pretreatment of HT-29 cells also resulted in reduced ERK, p38, and JNK MAPK phosphorylation, following TNF-α treatment. The observed effects in this study occurred independently of known surface adenosine receptors. This study identifies adenosine as a potent negative regulator of pro-inflammatory signaling in intestinal epithelial cells.

Inhibition of the neutrophil NADPH oxidase by adenosine is associated with increased movement of flavocytochrome b between subcellular fractions.

Adenosine is a potent inhibitor of reactive oxygen species (ROS) production by the NADPH oxidase in fMLF-stimulated neutrophils. Although much is known about the pharamacology and signal transduction of this effect, it is not known how adenosine affects assembly and localization of the NADPH oxidase components within the neutrophil. We report here that adenosine pretreatment of fMLF-stimulated neutrophils results in decreased plasma membrane/secretory granule content of the flavocytochrome b components (p22phox and gp91phox) of the NADPH oxidase, which correlates with inhibition of ROS production. Adenosine treatment did not affect upregulation of secretory and specific granule surface markers, confirming that degranulation was not impaired by adenosine. However, adenosine treatment did result in increased movement of cell-surface flavocytochrome b to heavy granule fractions in fMLF-stimulated neutrophils. These data suggest that adenosine-mediated effects on neutrophil ROS production are due, in part to endocytosis and/or redistribution of flavocytochrome b between various subcellular compartments.

Adenosine preconditioning attenuates hepatic reperfusion injury in the rat by preventing the down-regulation of endothelial nitric oxide synthase.

BackgroundPrevious work has suggested that in the liver, adenosine preconditioning is mediated by nitric oxide. Whether the endothelial isoform of nitric oxide synthase plays a part in this mechanism has however not yet been investigated.MethodsWistar rats were used (6 in each group) – Groups: (1) sham, (2) ischemia-reperfusion, (3) adenosine + ischemia-reperfusion, (4) endothelial isoform inhibitor + adenosine + ischemia-reperfusion.ResultsUsing immunohistochemistry, this study has revealed a decrease in the expression of endothelial nitric oxide synthase following hepatic ischemia-reperfusion. This was prevented by adenosine pre-treatment. When an inhibitor of endothelial nitric oxide synthase was administered prior to adenosine pre-treatment, pre-conditioning did not occur despite normal expression of endothelial nitric oxide synthase.ConclusionsThese findings suggest that adenosine attenuates hepatic injury by preventing the downregulation of endothelial nitric oxide synthase that occurs during ischemia-reperfusion.