Endothelium-derived Hyperpolarizing Factor Research Articles

P716Role of EDRFs in aortic and mesenteric arterial function of the UC Davis Type 2 Diabetic Mellitus (UCD-T2DM) male rats

Abstract Several studies have shown vascular dysfunction in diabetic rats, however, there is no data on the vascular function of UC Davis type 2 diabetes Mellitus (UCD-T2DM) rats. UCD-T2DM is a novel but validated model of type 2 diabetes (T2D) which more closely resembles the pathophysiology of diabetes in humans. The aim of this study was to determine whether aortic or mesenteric arterial function were altered in UCD-T2DM male rats. Specifically, we determined the responses to endothelium-dependent vasodilator and vasoconstrictor in this model. We also studied the relative contribution of endothelium-derived relaxing factors (EDRFs) in modulating vascular reactivity of aorta or mesenteric artery (MA) in UCD-T2DM male rats. Endothelium-dependent vasodilation (EDV) to acetylcholine (ACh) was measured in rat aorta or MA pre-contracted with phenylephrine (PE). Particularly, EDV to ACh were measured before and after pretreatment with indomethacin (indo, cyclooxygenase inhibitor), ODQ (soluble guanylate cyclase inhibitor), L-NNA (nitric oxide synthase (NOS) inhibitor), TRAM-34 (IKca blocker), or Apamin (SKca blocker). Constrictor response curves to PE were also generated in both aorta and MA. Furthermore, the protein expression of IK channels were determined using Western blotting. We demonstrated that EDV to ACh was impaired in MA, while potentiated in the aortic rings of UCD-T2DM rats. In diabetic MA, the importance of endothelium-derived hyperpolarizing factor (EDHF) in ACh-induced relaxation was decreased, while the contribution of nitric oxide (NO) was enhanced. On the other hand, in diabetic aorta, the relative contribution of EDHF in relaxation responses to ACh was significantly enhanced (as measured by ACh response which was insensitive to indo, ODQ and L-NNA). The incubation of aorta or MA with TRAM-34 blunted the relaxation responses to ACh in both control and diabetic groups. However, the inhibitory effects of TRAM 34 on ACh responses were more prominent in arteries taken from UCD-T2DM groups compared to those in controls. By contrast, ACh responses were not affected following incubation of aorta or MA with Apamin in either control or diabetic groups suggesting that SKca channels plays no role in EDHF-mediated relaxation in either vascular beds. Accordingly, the IKca expression level was significantly higher in aortic rings of diabetic group than in the controls. The responsiveness to PE was significantly enhanced in the aortic rings of diabetic group, whereas in MA, diabetes did not alter the contractile responses to PE. These data suggest that in MA of UCD-T2DM rats, the predisposition to vascular injury may be due to a shift away from EDHF, initially the major vasodilatory factor, toward a greater reliance on NO. However, in aorta, despite elevated contractile responses, ACh responses were enhanced. Increased contribution of NO-independent factors specifically IKca channel plays a role in potentiated responses to ACh in this model. Acknowledgement/Funding NIHLBI

Exercise restores impaired endothelium-derived hyperpolarizing factor-mediated vasodilation in aged rat aortic arteries via the TRPV4-KCa2.3 signaling complex.

BackgroundAging leads to structural and functional changes in the vasculature characterized by arterial endothelial dysfunction and stiffening of large elastic arteries and is a predominant risk factor for cardiovascular disease, the leading cause of morbidity and mortality in modern societies. Although exercise reduces the risk of many age-related diseases, including cardiovascular disease, the mechanisms underlying the beneficial effects of exercise on age-related endothelial function fully elucidated.PurposeThe present study explored the effects of exercise on the impaired endothelium-derived hyperpolarizing factor (EDHF)–mediated vasodilation in aged arteries and on the involvement of the transient receptor potential vanilloid 4 (TRPV4) channel and the small-conductance calcium-activated potassium (KCa2.3) channel signaling in this process.MethodsMale Sprague-Dawley rats aged 19–21 months were randomly assigned to a sedentary group or to an exercise group. Two-month-old rats were used as young controls.ResultsWe found that TRPV4 and KCa2.3 isolated from primary cultured rat aortic endothelial cells pulled each other down in co-immunoprecipitation assays, indicating that the two channels could physically interact. Using ex vivo functional arterial tension assays, we found that EDHF-mediated relaxation induced by acetylcholine or by the TRPV4 activator GSK1016790A was markedly decreased in aged rats compared with that in young rats and was significantly inhibited by TRPV4 or KCa2.3 blockers in both young and aged rats. However, exercise restored both the age-related and the TRPV4-mediated and KCa2.3-mediated EDHF responses.ConclusionThese results suggest an important role for the TRPV4-KCa2.3 signaling undergirding the beneficial effect of exercise to ameliorate age-related arterial dysfunction.

Effects of Prosopis farcta Root Extract in the Vascular Reactivity of Isolated Goat Coronary Artery

Prosopis species is a medicinal plant, well-known for its beneficial effects in treating various smooth muscles disorders, and its phytochemical analysis revealed the presence of different bioactive compounds in different parts of the plant, most of which show a great role in reducing cardiovascular risks. In the present study, the cardiovascular effect of Prosopis farcta Root Extract (PFRE) was investigated in vitro for possible mechanisms of the extract effect in the vascular reactivity of isolated goat coronary artery (CA) using Organ bath and PowerLab Data Acquisition system. The results of the recording and analyzing of the effect of the PFRE in isolated CA, showed the negative inotropic activity of the extract in CA rings with intact-endothelium, while in CA ring with hyperglycemic-induced endothelium dysfunction the extract tended to vasodilate the CA ring non-significantly, and the extract induced dose-dependent vasodilation in CA rings pre-constricted with high concentration of (30 mM)KCl and showed no effects on contractions induced by (1X10-3-1X10-5) Phenylephrine PE, which is an indicator for its blockade activity on L-type voltage-dependent Ca+2 channel and non-interfering of the extract with the receptor-operated Ca+2 channel. The mechanical recording of the CA ring activities, revealed different potassium (K+) channels including selective calcium-activated potassium channel, ATP-sensitive potassium channel, and different endothelium-derived relaxing factors (EDRF) including nitric oxide and Prostacyclin (PGI2 ) seems to have no role in the relaxation effects of the extract, while the endothelium derived-hyperpolarizing factor (EDHF); epoxy eicosatrienoic acid (EET) showed significant participation in the vasodilation effects of the extract. On the other hand, the extract tended to relax the CA rings through its antagonizing of Ca+2, reducing and inhibiting Ca+2 influx and release from internal stores and interfering with the voltage-operated Ca+2 channels through its alkaloid and flavonoid active compounds which suggested to be the most predicted mechanisms for the maintenance of vasodilating tone and coronary circulation of the PFRE in coronary artery.

Paraoxonase-1 (Pon1) A Potential Endothelial-Derived-Relaxing-Factors (Edrfs) Regulating Enzyme

Background and Aims: Paraoxonase 1 (PON1) is an antiatherogenic high density lipoprotein (HDL)-associated lactonase. Previous findings revealed that PON1 knockout (PON1KO) mice have low blood pressure, which is inversely correlated with their levels of 5,6-epoxyeicosatrienoic acid (5,6-EET), a cytochrome P450 (CYP)-derived arachidonic acid (AA) metabolite. Our previous studies revealed that 5,6-EET is unstable, transforming to the δ-lactone isomer 5,6-δ-DHTL, which is a potential endothelium-derived hyperpolarizing factor (EDHF) that mediates vasodilation, and it is also a potential substrate for PON1.

Direct Impairment of the Endothelial Function by Acute Indoxyl Sulfate through Declined Nitric Oxide and Not Endothelium-Derived Hyperpolarizing Factor or Vasodilator Prostaglandins in the Rat Superior Mesenteric Artery.

Upon stimulation, endothelial cells release various factors to regulate the vascular tone. In particular, vasorelaxing factors, called endothelium-derived relaxing factors (EDRFs), are altered in the production and/or release, as well as their signaling every vessel and under pathophysiological states, including cardiovascular, kidney, and metabolic diseases. Although indoxyl sulfate is known as a protein-bound uremic toxin and circulating levels are elevated in the impaired kidney functions, direct impact on the vascular function, especially EDRF's signaling, remains unclear. In this study, we hypothesize that acute exposure to indoxyl sulfate could alter vascular relaxation in the rat superior mesenteric artery. Accordingly, we measured acetylcholine (ACh)-induced endothelium-dependent relaxation in the absence and presence of several inhibitors to divide into each EDRF, including nitric oxide (NO), vasodilator prostaglandins (PGs), and endothelium-derived hyperpolarizing factor (EDHF). Indoxyl sulfate reduced the sensitivity to ACh but not sodium nitroprusside. Under cyclooxygenase (COX) inhibition or inhibitions of COX plus source of EDHF, such as small (SKCa)- and intermediate (IKCa)-conductance calcium-activated K+ channels, the decreased sensitivity to ACh in indoxyl sulfate exposed vessel was still preserved. However, under inhibition of NO synthase (NOS) or inhibitions of NOS and COX, the difference of sensitivity to ACh between vehicle and indoxyl sulfate was eliminated. These findings indicated that acute exposure of indoxyl sulfate in the rat superior mesenteric artery specifically explicitly impaired NO signaling but not EDHF or vasodilator PGs.

THE EFFECT OF PARAOXONASE 1 ON ENDOTHELIAL CELL HYPERPOLARIZATION MEDIATED BY EICOSAPENTAENOIC ACID AND DOCOSAHEXAENOIC ACID DERIVATIVES

Objective: It has been claimed that Paraoxonase 1 (PON1), an antiatherogenic high-density lipoprotein (HDL)-associated enzyme, protects against cardiovascular disease (CVD), for which hypertension is a major risk factor. On the other hand, an increasing number of studies associate heightened PON1 activity with increased risk of hypertension and CVD. Our previous findings revealed that 5,6-EET, a cytochrome P450 (CYP)-derived arachidonic acid (AA) metabolite is unstable, transforming into a new derivative, which is a potential endothelium-derived hyperpolarizing factor (EDHF). This derivative mediates calcium influx, leading to endothelial hyperpolarization and vasodilation and has also been shown to be hydrolyzed by PON1. Based on the similarity between the chemical structure of CYP-derived metabolites of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to those of AA, we hypothesized that the analogous EPA and DHA derivatives could potentially induce endothelial hyperpolarization and elicit vascular dilation. The aim of this study is to explore hyperpolarization of endothelial cells induced by derivatives of EPA and DHA and PON1's role in hypertension via its effect on this process. Design and method: Human umbilical vein endothelial cells pre-incubated with recombinant PON1 (re-PON1) or human PON1-HDL purified from serum of hypertensive and normotensive patients before the experiment. The endothelial hyperpolarization was monitored by measuring calcium influx via confocal microscopy analysis. Results: Confocal microscopy experiments revealed that endothelial cells incubated with re-PON1 exhibited impaired calcium influx as mediated by EPA and DHA derivatives. Further experiments demonstrated that incubation with human PON1-HDL also reduced calcium influx. However, 1-hour incubation with re-PON1 followed by 3-hour incubation without re-PON1 did not interfere with calcium influx mediated by the EPA derivative. Conclusions: This data suggests that specific EPA and DHA derivatives are potential EDHFs, by regulating calcium influx in the endothelium and that PON1 activity interferes with this process. Therefore, PON1 and those derivatives represent novel targets for future treatment for hypertension.

Figures of the Heart Failure Association: Professor Dr. med. Johann Bauersachs, Chair of the Clinical Science Section.

Figures of the Heart Failure Association: Professor Dr. med. Johann Bauersachs, Chair of the Clinical Science Section.

Placental growth factor blunts uterine artery responses to angiotensin II.

Changes in maternal serum concentration of placental growth factor (PlGF) and vascular response to intravascular infusion of Angiotensin II (Ang II) follow a bell-shaped curve pattern during gestation. This study evaluates the effects of PlGF and soluble vascular endothelial growth factor receptor-1 (sFlt-1) on responses of human uterine arteries (UA) to Ang II. Experimental. Baylor College of Medicine and Texas Children's Hospital-Pavilion for Women. Uterine arteries samples (n=14) were obtained from normotensive women undergoing caesarean hysterectomy at≥32weeks. Uterine arteries rings were incubated with (1) Krebs solution; (2) PlGF at 1.45, 14.5, and 500pg/ml; (3) sFlt-1 at 2ng/ml; and (4) a combination of sFlt-1, and PlGF. Dose-contraction responses to Ang II were determined in UA rings incubated in the above-mentioned conditions. Responses were also measured in presence of L-NAME or inhibitors of endothelium-derived hyperpolarising factor: apamine and charybdotoxin. The t-test was used for comparisons. Changes in vascular reactivity of UA rings. PlGF blunted (P=0.03) and sFlt-1 increased (P<0.01) the UA maximum responses to Ang II. A combination of sFlt-1 and PlGF blunted UA responses to Ang II (P<0.05). l-NAME, apamine, and charybdotoxin reversed the relaxation effects of PlGF on UA responses to Ang II (P<0.05). PlGF contributes to the blunted vascular response to Angiotensin II during normotensive pregnancies and sFlt-1 appears to attenuate this effect. PlGF and sFlt-1 may contribute to the regulation of vascular tone during pregnancy by altering the vascular response to Angiotensin II. Baylor College of Medicine. Placental growth factor and soluble vascular endothelial growth factor receptor-1 modulate the uterine artery response to Angiotensin II in normotensive pregnant women.

Potassium channels contribute to the increased sensitivity of the rabbit carotid artery to hydrogen sulfide in diabetes

Hydrogen sulfide (H2S) is a potential endothelium-derived hyperpolarizing factor (EDHF) and adventitium- or adipocyte-derived relaxing factor (ADRF) which vasorelaxant action is mediated by potassium channels. H2S could also play an important role in the pathophysiology of diabetic cardiovascular complications. The present study has investigated the influence of alloxan-induced diabetes on the role of potassium channels mediating the relaxant response of the rabbit carotid artery to NaHS, a donor of H2S. NaHS (10−8-3 × 10−5 M) relaxed phenylephrine-precontracted carotid arteries, with higher potency in diabetic than in control rabbits. The selective blockers of potassium channels charybdotoxin, 4-amynopiridine and glibenclamide significantly inhibited the relaxant action of NaHS in diabetic rabbits, but not in control rabbits. When compared to control rabbits, carotid arteries from diabetic rabbits showed significantly reduced expression of big conductance Ca+2-activated potassium channels (BKCa), significantly enhanced expression of intermediate conductance Ca+2-activated potassium channels (IKCa) and not significant different expression of voltage-sensitive potassium channels (KV) and ATP-sensitive potassium channels (KATP). These results suggest that an enhanced role of IKCa, KV and KATP potassium channels could be involved in the increased sensitivity of the rabbit carotid artery to H2S in diabetes.

Paying the Toll for Inflammation

Paying the Toll for Inflammation

Abstract WP543: Apelin Impairs Endothelium-Derived Hyperpolarizing Factor (EDHF)-Induced Relaxation of Cerebral Arteries by Inhibiting Activation of Large Conductance, Calcium-Activated K (BK Ca ) Channels in Vascular Smooth Muscle

Introduction: Apelin is a peptide found in fat cells, endothelial cells and CNS neurons. Apelin levels are increased in conditions linked to cardiovascular disease (e.g. obesity, diabetes). Apelin inhibits NO-induced relaxation of cerebral arteries (CA) but its effect on relaxation to EDHF, which often compensates for impaired NO responses in diseased arteries, is unknown. Methods and Results: Immunoblot analysis identified apelin receptor expression in human and rat CA. In isolated rat CA, A23187 (10 -9 – 10 -6 M) caused endothelium-dependent relaxation that was unaffected by inhibitors of eNOS (nitro-l-arginine (3 x 10 -5 M), guanylyl cyclase (ODQ (10 -5 M), cyclooxygenase (indomethacin (10 -5 M) and the H 2 O 2 -scavenger, PEG-catalase (500 U/ml) (n=6). A23187-induced relaxation was attenuated by MS-PPOH (10 -5 M), a selective inhibitor of cyp450-catalyzed synthesis of epoxyeicosatrienoic acids (EETs) (pD 2 =6.86 ± 0.3 vs 5.90 ± 0.1, without and with MS-PPOH; n=6; p&lt;0.05), and abolished by 14,15-EE(Z)E (10 -5 M), a selective EET-receptor antagonist (n=7; p&lt;0.05). Apelin (10 -7 M) inhibited A23187-induced relaxation (pD 2 =7.08 ± 0.2 vs 6.44 ± 0.1, without and with apelin; n=7; p&lt;0.05) as well as relaxation to 11,12-EET, 14,15-EET and NS1619 (BK Ca channel opener), but had no effect on relaxation evoked by levcromakalim (K ATP channel opener). In whole cell patch clamp studies (10mv steps from -60mv to +80mv, 200ms duration) in CA smooth muscle cells, 11,12-EET (10 -5 M), 14,15-EET (10 -5 M), and NS1619 (10 -5 M) each caused an approximately 2-fold increase in BK Ca peak current density (at +80 mV; n=6; p&lt;0.05), which was completely abrogated in the presence of apelin (10 -7 M). The effects of apelin on EET-induced relaxation and activation of BK Ca currents were mimicked by iberiotoxin (10 -7 M) (selective BK Ca channel blocker) and abolished by F13A (10 -7 M), an apelin receptor antagonist. Conclusion: Apelin regulates CA vascular tone by inhibiting endothelium-dependent relaxation evoked by an EDHF-like mediator (possibly an EET) through a mechanism involving activation of apelin receptors and inhibition of BK Ca channels in CA smooth muscle cells. These effects could increase the risk of cerebrovascular dysfunction under conditions where apelin levels are elevated.

The Vasorelaxatory Effect of Nelumbo nucifera Spornioderm on Porcine Coronary Artery.

Endothelium dysfunction is a hallmark of cardiovascular disease (CVD) and is characterized by loss of homeostasis. Nitric oxide deprivation, unbalanced production of vasoactive factors such as thromboxane, endothelium-derived hyperpolarizing factor (EDHF) and production of reactive oxygen species are known as early indicators of CVD. Bioavailability of nitric oxide, antioxidative activity, and regulation of ionic homeostasis are the key targets for prevention of CVD. In this study, we investigated the vasorelaxant action of Nelumbo nucifera extract as well as the underlying mechanism using porcine coronary artery. Vasorelaxant effect of extracts from four different parts of Nelumbo nucifera (flower, leaf, seed, and spornioderm) was tested. Among them, extracts from Nelumbo nucifera spornioderm (NNS) showed the strongest endothelium-dependent vasorelaxation. Vasorelaxation effect of NNS was markedly reduced by inhibitor of endothelial nitric oxide synthase (eNOS), inhibitor of Phosphoinositide 3 kinase (PI3K) and inhibitor of soluble guanylyl cyclase (sGC), but unaffected by inhibitor of cyclooxygenase and EDHF. NNS induced concentration-dependent phosphorylation of eNOS in endothelial cells. Altogether, our study demonstrated that NNS is a potent endothelium-dependent vasodilator, mediated by PI3K-eNOS-sGC pathway. Our present findings showed NNS as a potential herbal candidate for the therapy of cardiovascular diseases associated with endothelial dysfunction and atherosclerosis.

Curcumin vasorelaxation in uterine artery of goat (Capra hircus) is mediated by differential activation of nitric oxide, prostaglandin I2, soluble guanylyl cyclase, and gap junction communication

Background: Curcumin is a principal active constituent of Curcuma longa and has potential therapeutic application in various disease states. In this study, we investigated the mechanism of vasorelaxatory effects of curcumin in middle uterine artery (MUA) of both pregnant (P) and nonpregnant (NP) Capra hircus (Ch). Materials and Methods: The middle uterine arterial rings (MUA) were mounted in an automatic organ bath attached to a PowerLab data acquisition system. We analyzed the effect of curcumin on signaling mediators of endothelium-derived hyperpolarizing factor: nitric oxide (NO), soluble guanylyl cyclase (sGC), prostaglandin I2(PGI2), and myoendothelial gap junctions (MEGJs). Results:The maximal vasorelaxation response to curcumin (1 ρM–100 μM) induced in phenylephrine- precontracted endothelium intact and denuded MUA rings were 42.58%, 25.12% in NP and 55.49%, 12.66%, in P Ch. In the presence of 1H-(1,2,4) oxadiazolo (4,3,-a) quinoxalin-1-one, the maximal curcumin-induced vasorelaxation (CVR) was inhibited to 20.65%, and 15.81% in MUA of NP and P Ch. In the presence of N.-nitro-L-arginine methyl, indomethacin and combination of both CVR were decreased to 20.49%, 12.47%, 12.82% in MUA ring of NP and to 40.60%, 52.55%, 46.53% in MUA ring of P Ch, respectively. The sensitivity of curcumin to MEGJ blockers carbenoxolone, 18β-glycyrrhetinic acid in causing vasorelaxation was 33.18%, 22.61% in MUA rings of NP, and to 15.76%, 18.54% in P Ch. Conclusion: In P Ch, endothelium-dependent vasorelaxation to curcumin is augmented by two-fold as that of MUA of NP. Endothelial vasorelaxation in MUA of NP is mediated through the activation of cyclooxygenase-PGI2-cyclic adenosine monophosphate and endothelial NO synthase (eNOS)-sGC-cyclic guanosine monophosphate (cGMP) signaling with low activation of sGC and MEGJ. In contrast, vasorelaxation to curcumin is mediated through increased activity of sGC and MEGJ with major involvement of eNOS-NO-sGC-cGMP in MUA of P Ch. These studies have strong implications in the therapeutic targeting for hypertensive disorders.

Paraoxonase 1 in endothelial cells impairs vasodilation induced by arachidonic acid lactone metabolite

IntroductionParaoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated lactonase, which is known for its antiatherogenic properties. Previous studies in PON1 knockout (PON1KO) mice revealed that PON1KO mice have low blood pressure, which is inversely correlated with the renal levels of the cytochrome P450 -derived arachidonic acid metabolite 5,6-epoxyeicosatrienoic acid (5,6-EET). Our previous studies revealed that 5,6-EET is unstable, transforming to the δ-lactone isomer 5,6-δ-DHTL, an endothelium-derived hyperpolarizing factor (EDHF) that mediates vasodilation, and it is a potential substrate for PON1. AimTo elucidate the role of PON1 in the modulation of vascular resistance via the regulation of the lactone-containing metabolite 5,6-δ-DHTL. ResultsIn mouse resistance arteries, PON1 was found to be present and active in the endothelial layer. Vascular reactivity experiments revealed that 5,6-δ-DHTL dose-dependently dilates PON1KO mouse mesenteric arteries significantly more than wild type (w.t.) resistance arteries. Pre-incubation with HDL or rePON1 reduced 5,6-δ-DHTL-dependent vasodilation. FACS analyses and confocal microscopy experiments revealed that fluorescence-tagged rePON1 penetrates into human endothelial cells' (ECs') in both dose- and time- dependent manner, accumulate in the perinuclear compartment, and retains its lactonase activity in the cells. The presence of rePON1, but not the presence of PON1 loss-of-lactonase-activity mutant, reduced the Ca2+ influx in the ECs mediated by 5,6-δ-DHTL. ConclusionPON1 lactonase activity in the endothelium affects vascular dilation by regulating Ca2+ influx mediated by the lactone-containing EDHF 5,6-δ-DHTL.

The role of vascular endothelium in nitroglycerin-mediated vasodilation.

Nitroglycerin (or glyceryl trinitrate, GTN) has been long considered an endothelium-independent vasodilator because GTN vasodilation is intact in the absence of the endothelium and in the presence of endothelial dysfunction. However, in animal and in vitro models, GTN has been shown to stimulate the release of certain endothelium-derived vasodilators such as nitric oxide (NO) and prostacyclin (PGI2 ). In addition, chronic GTN therapy leads to endothelial dysfunction. In this series of experiments, we explored how GTN might interact with the vascular endothelium in normal humans, without cardiovascular disease or risk factors associated with abnormalities in vascular function. We examined the effect of inhibition of NO, PGI2 , and epoxyeicosatrienoic acids (EETs, a class of endothelium-derived hyperpolarizing factor) on GTN-mediated vasodilation. We measured arterial blood flow responses to brachial artery infusions of GTN in the absence and presence of L-NMMA (n=13), ketorolac (n=14) and fluconazole (n=16), which are inhibitors of endothelium-derived NO, PGI2 and EETs, respectively, in healthy volunteers. Our results demonstrate that inhibition of endothelium-dependent vasodilator mechanisms does not alter forearm resistance vessel responses to GTN. We conclude that GTN-mediated dilation of forearm resistance vessels is largely independent of vascular endothelium.

Progress of Research on Mechanisms of Moxibustion Intervention Underlying Improvement of Blood Circulation

Moxibustion is one of the commonly used therapy of traditional Chinese medicine by applying burning dried mugwort on particular acupoints of the body surface. In the present paper，we reviewed progress of researches about the mechanisms of moxibustion treatment undering imporvement of blood circulation in recent 15 years. Research results displayed that moxibustion can dilate blood vessels to increase blood flow and improve microcirculation, not only in the local superficial vessels of body, but also in the deep tissues as the brain, stomach and mesentery, kidney, heart, etc., as well as in the distal blood vessels. The vasodilator action of moxibustion stimulation is related to nerve regulation, endothelium derived relaxing factors and vasodilator mediator, etc. through 1) interaction of acetylcholine (Ach)/muscarinic receptor (MR) and noradrenaline (NE)/α- or β-receptor; 2) nitric oxide synthase (NOS)/NO/arachidonic acid/prostacyclin (PGI2)/endothelium-derived hyperpolarizing factor (EDHF) pathway; 3) EDHF/TRPV 4/KCa channel, cytochrome P 450 oxidase/epoxyeicosatrienoicacid (EET); 4) EET/TRPV 4/big conductance calcium-activated potassium channel (BKCa); 5) sulfuretted hydrogen (H2S)/ATP-sensitive potassium channel (KATP) or voltage-gated potassium channels (Kv 7); 6) NO/substance P (SP) or CGRP and adrenergic β 2 receptor(R)/TRPV 1/adenosin A 1 R and A 2 R/NK 1 R pathway; 7) PGI2/adenylyl cyclase (cAMP)/PKA and vasoactive intestinal peptide (VIP), etc. in the vascular endothelium and smooth muscle. These research results may help us understand the effects and mechanisms of moxibustion in the treatment of different clinical conditions by improving microcirculation.

Chronic Intermittent Hypoxia Alters Rat Ophthalmic Artery Reactivity Through Oxidative Stress, Endothelin and Endothelium-Derived Hyperpolarizing Pathways.

Obstructive sleep apnea recently has been associated with a higher frequency of ischemic optic neuropathies. Intermittent hypoxia (IH) has been proposed as a major component of obstructive sleep apnea cardiovascular consequences. However, there currently are no pathophysiologic data regarding the effect of IH on the ocular vascular system. Thus, we assessed the impact of chronic IH exposure on the morphology and vascular reactivity of the rat ophthalmic artery (OA). Rats were exposed to 14 days of IH or normoxia (NX). Ophthalmic artery reactivity was studied using wire myography in rats treated or not with tempol (1 mM/day). Expression of endothelin-1 (ET-1) and its receptors, and of the three nitric oxide synthase (NOS) isoform genes was quantified using quantitative polymerase chain reaction (qPCR) in the retina and optic nerve. Structural alterations (optical and electron microscopy) and superoxide anion production were studied in OA sections. Superoxide ion expression in the OA wall was increased by 23% after IH exposure. Ophthalmic artery contractile response to 3.10-8 M ET-1 was increased by 18.6% and nitric oxide-mediated relaxation was significantly delayed in IH compared to NX rats. In the absence of nitric oxide, cytochrome P450 blockade increased relaxation to acetylcholine in IH rats and delayed it in NX rats. Tempol treatment abolished the IH-induced changes in OA reactivity. These results strongly suggest that chronic IH induces oxidative stress in the rat OA, associated with endothelial dysfunction through alterations of nitric oxide and endothelium-derived hyperpolarising factors (EDHF) pathways.

Correction: Endothelial dysfunction in renal arcuate arteries of obese Zucker rats: The roles of nitric oxide, endothelium-derived hyperpolarizing factors, and calcium-activated K+ channels.

[This corrects the article DOI: 10.1371/journal.pone.0183124.].

Defining the optimal duration for normothermic regional perfusion in the kidney donor: A porcine preclinical study.

Kidneys from donation after circulatory death (DCD) are highly sensitive to ischemia-reperfusion injury and thus require careful reconditioning, such as normothermic regional perfusion (NRP). However, the optimal NRP protocol remains to be characterized. NRP was modeled in a DCD porcine model (30minutes of cardiac arrest) for 2, 4, or 6hours compared to a control group (No-NRP); kidneys were machine-preserved and allotransplanted. NRP appeared to permit recovery from warm ischemia, possibly due to an increased expression of HIF1α-dependent survival pathway. At 2hours, blood levels of ischemic injury biomarkers increased: creatinine, lactate/pyruvate ratio, LDH, AST, NGAL, KIM-1, CD40 ligand, and soluble-tissue-factor. All these markers then decreased with time; however, AST, NGAL, and KIM-1 increased again at 6hours. Hemoglobin and platelets decreased at 6hours, after which the procedure became difficult to maintain. Regarding inflammation, active tissue-factor, cleaved PAR-2 and MCP-1 increased by 4-6hours, but not TNF-α and iNOS. Compared to No-NRP, NRP kidneys showed lower resistance during hypothermic machine perfusion (HMP), likely associated with pe-NRP eNOS activation. Kidneys transplanted after 4 and 6hours of NRP showed better function and outcome, compared to No-NRP. In conclusion, our results confirm the mechanistic benefits of NRP and highlight 4hours as its optimal duration, after which injury markers appear.

Hiroaki Shimokawa.

Hiroaki Shimokawa.