Mechanisms of Rho kinase regulation of vascular reactivity following hemorrhagic shock in rats

Action and therapeutic targets of myosin light chain kinase, an important cardiovascular signaling mechanism

The global incidence of cardiac diseases is increasing, imposing a substantial socioeconomic burden on healthcare systems. The pathogenesis of cardiovascular disease is complex and not fully understood, and the physiological function of the heart is inextricably linked to well-regulated cardiac muscle movement. Myosin light chain kinase (MLCK) is essential for myocardial contraction and diastole, cardiac electrophysiological homeostasis, vasoconstriction of vascular nerves and blood pressure regulation. In this sense, MLCK appears to be an attractive therapeutic target for cardiac diseases. MLCK participates in myocardial cell movement and migration through diverse pathways, including regulation of calcium homeostasis, activation of myosin light chain phosphorylation, and stimulation of vascular smooth muscle cell contraction or relaxation. Recently, phosphorylation of myosin light chains has been shown to be closely associated with the activation of myocardial exercise signaling, and MLCK mediates systolic and diastolic functions of the heart through the interaction of myosin thick filaments and actin thin filaments. It works by upholding the integrity of the cytoskeleton, modifying the conformation of the myosin head, and modulating innervation. MLCK governs vasoconstriction and diastolic function and is associated with the activation of adrenergic and sympathetic nervous systems, extracellular transport, endothelial permeability, and the regulation of nitric oxide and angiotensin II. Additionally, MLCK plays a crucial role in the process of cardiac aging. Multiple natural products/phytochemicals and chemical compounds, such as quercetin, cyclosporin, and ML-7 hydrochloride, have been shown to regulate cardiomyocyte MLCK. The MLCK-modifying capacity of these compounds should be considered in designing novel therapeutic agents. This review summarizes the mechanism of action of MLCK in the cardiovascular system and the therapeutic potential of reported chemical compounds in cardiac diseases by modifying MLCK processes.

Myosin light chain phosphatase is a downstream target of Rho-kinase in endothelin-1-induced transactivation of the TGF-β receptor

BACKGROUND

Rho-kinase (ROCK) regulates actomyosin contraction, coronary vasospasm, and cytoskeleton dynamics. ROCK and of NADPH oxidase (NOX) play an essential role in cardiovascular disease and proteoglycan synthesis, which promotes atherosclerosis by trapping low density lipoprotein. ROCK is activated by endothelin-1 (ET1) and transactivates the transforming growth factor beta receptor (TGFβR1), intensifying Smad signaling and proteoglycan production. This study aimed to identify the role of myosin light chain phosphatase (MLCP) as a downstream target of ROCK in TβR1 transactivation.

METHODS

Vascular smooth muscle cells were treated with ET1 and inhibitors of ROCK and MLCP were added. The phosphorylation levels of Smad2C, myosin light chain (MLC), and MLCP were monitored by western blot, and the mRNA expression of chondroitin 4-O-sulfotransferase 1 (C4ST1) was assessed by quantitative real-time PCR.

RESULTS

We examined ROCK's role in ET1-induced TGFβR1 activation. ROCK phosphorylated MLCP at the MYPT1 T853 residue, blocked by the ROCK inhibitor Y27632. ROCK also increased MLC phosphorylation and actomyosin contraction in response to ET1, enhanced by the phosphatase inhibitor Calyculin A. Calyculin A also increased C4ST1 expression, GAG-chain synthesizing enzymes.

CONCLUSIONS

This work suggests that ROCK is involved in ET1-mediated TβR1 activation through increased MLCP phosphorylation, which leads to Smad2C phosphorylation and stimulates C4ST1 expression.

Autophagy Is Involved in Stellate Ganglion Block Reversing Posthemorrhagic Shock Mesenteric Lymph-Mediated Vascular Hyporeactivity

Objective: The aim of this study was to clarify the role of autophagy in stellate ganglion block (SGB) reversing posthemorrhagic shock mesenteric lymph (PHSML)-mediated vascular hyporeactivity.

Methods: Hemorrhagic shock model in conscious rats was employed to observe the effects of SGB (0.2 ml of 0.25% ropivacaine hydrochloride hydrate) and autophagy inhibitor 3-methyladenine (3-MA; 30 mg/kg) on the vascular reactivity of second-order rat mesenteric arteries in vitro, while the effects of PHSML (1 ml/kg) and autophagy agonist rapamycin (Rapa, 10 mg/kg) on the beneficial effect of SGB were investigated. The cellular viability, contractility, and autophagy-related protein expressions in vascular smooth muscle cells (VSMCs) were detected following treatments of PHSML, PHSML obtained from the rats that underwent hemorrhagic shock plus SGB (PHSML-SGB), and PHSML plus 3-MA (5 mM), respectively.

Results: Hemorrhagic shock significantly decreased the vascular reactivity to gradient norepinephrine (NE), which is reversed by the SGB treatment and 3-MA administration. On the contrary, PHSML intravenous infusion and Rapa administration inhibited the vascular contractile responses in rats that underwent hemorrhagic shock plus SGB treatment. PHSML treatment significantly inhibited the cellular viability and contractility in VSMCs, increased the expressions of LC3-II and Beclin 1, and decreased the expression of p62, along with opposite appearances in these indices following PHSML-SGB treatment. In addition, 3-MA counteracted the adverse roles of PHSML in these indices in VSMCs.

Conclusion: SGB inhibits PHSML-mediated vascular hyporeactivity by reducing the excessive autophagy in VSMCs.

Estrogen Enhances The Microvascular Reactivity Through Rhoa-Rock Pathway In Female Mice During Hemorrhagic Shock

ABSTRACT

Vascular hypo-reactivity plays a critical role inducing organ injury during hemorrhagic shock. 17β-estradiol (E2) can induce vasodilation to increase blood flow in various vascular beds. This study observed whether E2 can restore vascular hypo-reactivity induced by hemorrhagic shock, and whether E2 effects are associated with RhoA - Rho kinase (ROCK)- myosin light chain kinase phosphatase (MLCP) pathway. The hemorrhagic shock model (40 ± 2 mmHg for 1 h, resuscitation for 4 h) was established in ovary intact sham operation (OVI), ovariectomized (OVX) and OVX plus E2 supplement female mice. Intestinal microvascular loop was used to assess blood flow in vivo, mRNA expression and vascular reactivity in vitro. Hemorrhagic shock significantly reduced norepinephrine microvascular reactivity. Decreased microvascular reactivity was exacerbated by OVX and reversed by E2 supplement. U-46619 (RhoA agonist) increased microvascular reactivity, and C3 transferase (an ADP ribosyl transferase that selectively induces RhoA ribosylation) or Y-27632 (ROCK inhibitor) inhibited sham mice microvascular reactivity. Similarly, U-46619 increased microvascular reactivity in OVI and OVX mice following hemorrhagic shock, which was abolished by Y-27632 or concomitant incubation of okadaic acid (OA) (MLCP inhibitor) and Y-27632. In OVX plus E2 supplement mice with hemorrhagic shock, Y-27632 inhibited microvascular reactivity, which was abolished by concomitant U-46619 application. Lastly, hemorrhagic shock remarkably decreased intestinal loop blood flow, RhoA and ROCK mRNA expressions in vascular tissues in OVX females, but not in OVI females, which were reversed by E2 supplement. These results indicate that estrogen improves microvascular reactivity during hemorrhagic shock, and RhoA-ROCK signaling pathway may mediate E2 effects.

Selenium Deficiency Affects Uterine Smooth Muscle Contraction Through Regulation of the RhoA/ROCK Signalling Pathway in Mice

Selenium (Se) is considered one of the essential micronutrients for humans and animals, and its effects on physiological functions are multifaceted. In the present study, we investigated the effects of Se deficiency on uterine smooth muscle contraction in mice by studying G protein Rho (RhoA)/Rho kinase (ROCK) signalling pathway-related molecules. The α-sma in smooth muscle tissue of mice was determined. The extracorporeal contraction curve for uterine smooth muscle in mice was determined. Both of these results indicate that Se deficiency impairs the contractile ability of uterine smooth muscle in mice. The expression of mRNA was measured by real-time quantitative PCR. The results showed that there was no significant change in mRNA expression of RhoA, ROCK, myosin light chain phosphatase (MLCP), or myosin light chain (MLC) in tissues. The protein levels were detected by Western blot. The results showed that there were no significant differences in RhoA, ROCK, MLCP, or MLC expression. However, compared with the CG, the concentration of phosphorylated MLC (P-MLC) increased in the SG and the concentration of P-MLC decreased in the DG. The activity of ROCK and MLCP was tested by liquid scintillation. The results suggest that the lack of Se may affect the regulation of MLCP by ROCK. Cellular experiments were performed to compare with results from tissues. There was no significant difference between the two models. The results indicated that Se deficiency affects uterine smooth muscle contraction by regulating the RhoA/ROCK signalling pathway. As the concentration of Se decreases, the activity of MLCP increases, which promotes the dephosphorylation of P-MLC, causing a decrease in contraction.

Protein markers related to vascular responsiveness after hemorrhagic shock in rats

BACKGROUND

Vascular hyporesponsiveness is an important pathophysiological feature of some critical conditions such as hemorrhagic shock. Many proteins and molecules are involved in the regulation of the pathologic process, however the mechanism has still remained unclear. Our study was intended to look for the related protein markers involved in the regulation of vascular reactivity after hemorrhagic shock.

METHODS

Differential in-gel electrophoresis and tandem mass spectrometry were applied to quantify the differences of protein expression in the superior mesenteric arteries from hemorrhagic shock and normal rats.

RESULTS

A total of 2317 differentially expressed protein spots in the superior mesenteric arteries of rats before and after hemorrhagic shock were found, and 146 protein spots were selected for tandem mass spectrometry identification. Thirty-seven differentially expressed proteins were obtained, including 3 uncharacterized proteins and 34 known proteins. Among them, heat shock protein beta-1 and calmodulin were the known proteins involved in the occurrence of vascular hyporesponsiveness. Bioinformatics analysis results showed that 18 proteins were related to vasoconstriction, 11 proteins may be involved in other vascular functions such as regulation of angiogenesis and endothelial cell proliferation.

CONCLUSIONS

The changes of vascular responsiveness after hemorrhagic shock in rats may be associated with the upregulation or downregulation of previously mentioned protein expressions. These findings may provide the basis for understanding and further study of the mechanism and treatment targets of vascular hyporeactivity after shock.

Diabetes and hyperlipidemia induce dysfunction of VSMCs: contribution of the metabolic inflammation/miRNA pathway

Vascular endothelial cell injury is considered to be the major factor inducing vascular complications in metabolic diseases and plays an important role in other organ damage. With diabetic and hyperlipidemic rats and cultured VSMCs, the present study was aimed at investigating whether the early damage of VSMCs during metabolic diseases plays a critical role in vascular dysfunction and the underlying mechanisms and would be a promising treatment target. With diabetic and hyperlipidemic rats and cultured VSMCs, the changes and relationships of vascular relaxation and contractile function to the vital organ damage and the underlying mechanisms were investigated; meanwhile, the protective and preventive effects of lowering blood lipid and glucose and inhibition of diabetes and hyperlipidemia-induced vascular hyperreactivity were observed. Diabetic and hyperlipidemic rats presented hyperreactivity in vascular contractile response in the early stages. Hyperglycemia and hyperlipidemia directly affected the contractile function of VSMCs. Early application of fasudil, a specific antagonist of Rho kinase, significantly alleviated diabetes and hyperlipidemia-induced organ damage by inhibiting vascular hyperreactivity. Diabetes and hyperlipidemia-induced inflammatory response could upregulate the expression of connexins and Rho kinase by selective downregulation of the expression of miR-10a, miR-139b, miR-206, and miR-222. These findings suggest that hyperglucose and lipid may directly impair VSMCs and induce vascular hyperreactivity in the early stages. Metabolic inflammation-induced changes in the miRNA-connexin/Rho kinase regulatory pathway are the main mechanism for vascular hyperreactivity and organ damage. Measures inhibiting vascular hyperreactivity are promising for the prevention of organ damage induced by metabolic diseases.

Beneficial effects of platelet-derived growth factor on hemorrhagic shock in rats and the underlying mechanisms

Studies have shown that local application of platelet-derived growth factor (PDGF) can be used for the treatment of acute and chronic wounds. We investigated if systemic application of PDGF has a protective effect on acute hemorrhagic shock in rats in the present study. Using hemorrhagic shock rats and isolated superior mesenteric arteries, the effects of PDGF-BB on hemodynamics, animal survival, and vascular reactivity as well as the roles of the gap junction proteins connexin (Cx)40 and Cx43, PKC, and Rho kinase were observed. PDGF-BB (1–15 μg/kg iv) significantly improved the hemodynamics and blood perfusion to vital organs (liver and kidney) as well as vascular reactivity and improved the animal survival in hemorrhagic shock rats. PDGF recovering shock-induced vascular hyporeactivity depended on the integrity of the endothelium and myoendothelial gap junction. Cx43 antisense oligodeoxynucleotide abolished these improving effects of PDGF, whereas Cx40 oligodeoxynucleotide did not. Further study indicated that PDGF increased the activity of Rho kinase and PKC as well as vascular Ca2+ sensitivity, whereas it did not interfere with the intracellular Ca2+ concentration in hypoxia-treated vascular smooth muscle cells. In conclusion, systemic application of PDGF-BB may exert beneficial effects on hemorrhagic shock, which are closely related to the improvement of vascular reactivity and hemodynamics. The improvement of PDGF-BB in vascular reactivity is vascular endothelium and myoendothelial gap junction dependent. Cx43, Rho kinase, and PKC play very important role in this process. These findings suggest that PDGF may be a potential measure to treat acute clinical critical diseases such as severe trauma, shock, and sepsis.

Bradykinin induces vascular contraction after hemorrhagic shock in rats

BACKGROUND

Bradykinin (BK) has many biological effects in inflammation, allergy, and septic shock. Studies have shown that low doses of BK can induce vascular relaxation and high doses can induce vascular contraction in many pathophysiological conditions, but the role and mechanisms that high doses of BK have on vascular contraction in hemorrhagic shock are not clear.

METHODS

With hemorrhagic-shock rats and hypoxia-treated superior mesenteric artery (SMA), we investigated the role and mechanisms of high doses of BK-induced vascular contraction in hemorrhagic shock.

RESULTS

High doses of BK (500-50,000 ng/kg in vivo or 10(-10) to 10(-5) mol/L in vitro) dose dependently induced vascular contraction of SMA and increased the vascular calcium sensitivity in normal and hemorrhagic-shock rats. Less than 10(-10) mol/L of BK induced vascular dilation BK-induced increase of vascular contractile response and calcium sensitivity was reduced by denudation of the endothelium, 18α-glycyrrhetic acid (an inhibitor of myoendothelial gap junction) and connexin 43 antisense oligodeoxynucleotide. Further studies found that high concentrations of BK-induced vascular contraction in hemorrhagic shock was closely related to the activation of Rho A-Rho kinase pathway and Protein Kinase C (PKC) α and ε.

CONCLUSIONS

High doses of BK can induce vascular contraction in hemorrhagic shock condition, which is endothelium and myoendothelial gap junction dependent. Cx43-mediated activation of Rho A-Rho kinase and Protein Kinase C (PKC) pathway plays a very important role in this process. This finding provided a new angle of view to the biological role of BK in other pathophysiological conditions such as hemorrhagic shock or hypoxia.

Rho kinase acts as a downstream molecule to participate in protein kinase Cε regulation of vascular reactivity after hemorrhagic shock in rats

Our previous study demonstrated that Rho kinase and protein kinase C (PKC) played important parts in the regulation of vascular reactivity after shock. Using superior mesenteric arteries (SMAs) from hemorrhagic shock rats and hypoxia-treated vascular smooth muscle cells (VSMCs), relationship of PKCε regulation of vascular reactivity to Rho kinase, as well as the signal transduction after shock, was investigated. The results showed that inhibition of Rho kinase with the Rho kinase-specific inhibitor Y-27632 antagonized the PKCε-specific agonist carbachol and highly expressed PKCε-induced increase of vascular reactivity in SMAs and VSMCs, whereas inhibition of PKCε with its specific inhibitory peptide did not antagonize the Rho kinase agonist (U-46619)-induced increase of vascular reactivity in SMAs and VSMCs. Activation of PKCε or highly expressed PKCε upregulated the activity of Rho kinase and the phosphorylation of PKC-dependent phosphatase inhibitor 17 (CPI-17), zipper interacting protein kinase (ZIPK), and integrin-linked kinase (ILK), whereas activation of Rho kinase increased only CPI-17 phosphorylation. The specific neutralization antibodies of ZIPK and ILK antagonized PKCε-induced increases in the activity of Rho kinase, but CPI-17 neutralization antibody did not antagonize this effect. These results suggested that Rho kinase takes part in the regulation of PKCε on vascular reactivity after shock. Rho kinase is downstream of PKCε. Protein kinase Cε activates Rho kinase via ZIPK and ILK; CPI-17 is downstream of Rho kinase.

Age and sex differences in vascular responsiveness in healthy and trauma patients: contribution of estrogen receptor-mediated Rho kinase and PKC pathways

Several medical conditions exhibit age- and sex-based differences. Whether or not traumatic shock exhibits such differences with regard to vascular responsiveness is not clear. In a cohort of 177 healthy subjects and 842 trauma patients (21–82 years) as well as different ages (4, 8, 10, 14, 18, and 24 wk; 1 and 1.5 years) and sexes of Sprague-Dawley normal and traumatic shock rats, the age- and sex-based differences of vascular responsiveness and the underlying mechanisms were investigated. Middle-aged and young women as well as female rats of reproductive age had higher vascular responsiveness in the normal condition and a lower decrease in vascular responsiveness after traumatic shock than older men and male rats of identical age. Exogenous supplementation of 17β-estrdiol increased vascular reactivity in both male and femal rats of 8–24 wk and preserved vascular responsiveness in rats following traumatic shock. No effect was observed in rats 1 to 1.5 years. These protective effects of estrogen were closely related to G protein-coupled receptor (GPR)30, estrogen receptor-mediated Rho kinase, and PKC pathway activation. Vascular responsiveness exhibits age- and sex-based differences in healthy subjects and trauma patients. Estrogen and its receptor (GPR30) mediated activation of Rho kinase and PKC using genomic and nongenomic mechanisms to elicit protective effects in vascular responsiveness. This finding is important for the personalized treatment for several age- and sex-related diseases involving estrogen.

Effects of interleukin-1β on vascular reactivity after lipopolysaccharide-induced endotoxic shock in rabbits and its relationship with PKC and Rho kinase

Calcium desensitization plays a critical role in the occurrence of vascular hyporeactivity after shock. Interleukin (IL)-1β participates in the regulation of vascular reactivity via both nitric oxide (NO)-dependent and NO-independent mechanisms. However, the specific NO-independent pathway remains to be established. The issue of whether IL-1β modulates vascular reactivity via regulation of calcium sensitivity in the NO-independent mechanism is unclear. In the current study, effects of IL-1β on vascular calcium sensitivity and its relationship with PKC and Rho kinase were investigated in vivo and in vitro using a rabbit model of lipopolysaccharide (LPS)-induced endotoxic shock and superior mesenteric arteries (SMAs), respectively. The calcium sensitivity profile of SMAs displayed a biphasic change after LPS-induced endotoxic shock (significant increase at 0.5 hour and 1 hour after LPS administration and marked decrease after 2 hours) and was negatively related to changes in serum IL-1β. The IL-1 receptor antagonist, IL-1ra (4 μg/mL), partly reversed LPS-induced calcium desensitization. In vitro incubation with IL-1β (50-200 ng/mL) reduced the calcium sensitivity of SMAs and suppressed the activities of Rho kinase and PKC and the phosphorylation of 20-kDa myosin light chain. These effects of IL-1β were shown to be regulated by the PKC agonist, phorbol 12-myristate 13-acetate, and Rho kinase agonist and antagonist, angiotensin II, and Y-27632, respectively. Our results collectively suggest that IL-1β participates in vascular hyporeactivity after endotoxic shock via regulation of vascular calcium sensitivity. Moreover, this regulatory effect of IL-1β seems closely related to downregulation of the activities of PKC and Rho kinase.

Myosin light chain kinase is necessary for post-shock mesenteric lymph drainage enhancement of vascular reactivity and calcium sensitivity in hemorrhagic-shocked rats

Vascular hyporeactivity is an important factor in irreversible shock, and post-shock mesenteric lymph (PSML) blockade improves vascular reactivity after hemorrhagic shock. This study explored the possible involvement of myosin light chain kinase (MLCK) in PSML-mediated vascular hyporeactivity and calcium desensitization. Rats were divided into sham (n=12), shock (n=18), and shock+drainage (n=18) groups. A hemorrhagic shock model (40±2 mmHg, 3 h) was established in the shock and shock+drainage groups. PSML drainage was performed from 1 to 3 h from start of hypotension in shock+drainage rats. Levels of phospho-MLCK (p-MLCK) were determined in superior mesenteric artery (SMA) tissue, and the vascular reactivity to norepinephrine (NE) and sensitivity to Ca²⁺ were observed in SMA rings in an isolated organ perfusion system. p-MLCK was significantly decreased in the shock group compared with the sham group, but increased in the shock+drainage group compared with the shock group. Substance P (1 nM), an agonist of MLCK, significantly elevated the decreased contractile response of SMA rings to both NE and Ca²⁺ at various concentrations. Maximum contractility (E_max) in the shock group increased with NE (from 0.179±0.038 to 0.440±0.177 g/mg, P<0.05) and Ca²⁺ (from 0.515±0.043 to 0.646±0.096 g/mg, P<0.05). ML-7 (0.1 nM), an inhibitor of MLCK, reduced the increased vascular response to NE and Ca²⁺ at various concentrations in the shock+drainage group (from 0.744±0.187 to 0.570±0.143 g/mg in E_max for NE and from 0.729±0.037 to 0.645±0.056 g/mg in E_max for Ca²⁺, P<0.05). We conclude that MLCK is an important contributor to PSML drainage, enhancing vascular reactivity and calcium sensitivity in rats with hemorrhagic shock.

Role of adenosine A2A receptor in organ-specific vascular reactivity following hemorrhagic shock in rats

BACKGROUND

Previous studies have demonstrated differences among organs in terms of shock-induced vascular reactivity and a role for adenosine A2A receptors (A2ARs) in protection against ischemia/reperfusion injury. However, the contributions of A2ARs to organ-specific vascular reactivity and the protection of vascular responsiveness following shock are currently unknown.

METHODS

We investigated the role of A2ARs in different arteries, including the left femoral artery (LFA), thoracic aorta (TA), superior mesenteric artery (SMA), right renal artery (RRA), pulmonary artery (PA), and middle cerebral artery (MCA), in hemorrhagic-shock rats.

RESULTS

The vascular reactivities of the LFA, SMA, RRA, and MCA increased slightly during early shock and then gradually decreased, whereas those of the PA and TA decreased from the start of shock. Different blood vessels lost vascular reactivity at different rates compared with controls; the LFA had the highest rate of loss (64.51%), followed by the SMA (44.69%), TA (36.06%), PA (37.83%), and RRA (32.33%), whereas the MCA had the lowest rate (18.45%). The rate of loss of vascular reactivity in the different vessels was negatively correlated with A2AR expression levels in normal and shock conditions. The highly selective A2AR agonist CGS 21680 significantly improved vascular reactivity, hemodynamic parameters, and animal survival, whereas the specific antagonist SCH58261 further decreased the shock-induced reduction in vascular reactivity and hemodynamic parameters.

CONCLUSIONS

A2ARs are involved in the regulation and protection of vascular reactivity following shock. A2AR activation may have a beneficial effect on hemorrhagic shock by improving vascular reactivity and hemodynamic parameters.

Dexamethasone induces rapid promotion of norepinephrine‑mediated vascular smooth muscle cell contraction

The aim of the present study was to identify the rapid effect of dexamethasone (Dex) on norepinephrine (NE)‑mediated contraction of vascular smooth muscle cells (VSMCs) and to establish the underlying mechanism(s). Rat VSMCs were preincubated with lipopolysaccharide to simulate acute septic shock. Myosin light chain (MLC20) phosphorylation of VSMCs was detected by western blot analysis to observe the effects of Dex on NE‑mediated contraction. Activation of the RhoA/ RhoA kinase (ROCK), extracellular signal‑regulated kinase (ERK) and p38 signaling pathways was detected by western blot analysis to explore the mechanism. It was identified that Dex rapidly promoted NE‑induced phosphorylation of MLC20 in VSMCs and this effect may be non‑genomic. The RhoA/ROCK, ERK and p38 pathways were demonstrated to be important for the rapid effect of Dex‑induced promotion of NE‑mediated contraction in VSMCs. The present results indicate that Dex may rapidly reverse the hyporeactivity of vasoconstriction to NE in vitro and this effect may be mediated by specific non‑genomic mechanisms through increased activation of the RhoA/ROCK, ERK and p38 signaling pathways.

Inhibition of Rho-kinase attenuates endothelial-leukocyte interaction during ischemia-reperfusion injury

Resuscitation from hemorrhagic shock induces endothelial dysfunction and activates inflammatory cascades leading to organ damage. Following restoration of blood flow to ischemic vascular beds, leukocyte-endothelium interactions leading to leukocyte infiltration into the vascular wall occur very early due, in part, to the loss of endothelium-derived nitric oxide (NO). The mechanism by which ischemia-reperfusion injury impairs endothelium-derived NO is not completely understood. We hypothesized that inhibition of Rho-kinase could exert beneficial effects following hemorrhagic shock by preserving endothelial function and attenuating leukocyte trafficking in the microcirculation. Using intravital microscopy, we found that resuscitation from hemorrhage acutely increased the number of rolling and adherent leukocytes in the mouse splanchnic microcirculation. Treatment of mice with the Rho-kinase inhibitor fasudil, markedly attenuated leukocyte-endothelium interaction in response to hemorrhage/reinfusion. The beneficial effect of fasudil was not observed in endothelial nitric oxide synthase (eNOS)(-/-) mice. In conclusion, inhibition of Rho-kinase prevents inflammatory leukocyte trafficking in the microcirculation via an eNOS-dependent mechanism. Our data support a role for Rho-kinase inhibitors in the treatment of ischemia-reperfusion injury.

Regulatory effect of Rac1 on vascular reactivity after hemorrhagic shock in rats

We used isolated superior mesenteric arteries (SMAs) from hemorrhagic-shock rats and hypoxia-treated vascular smooth muscle cells (VSMCs; mimicking the shock state) to observe the effects of platelet-derived growth factor (PDGF; Rac1 stimulator) and NSC23766 (Rac1 antagonist) on vascular reactivity and the relationship with the Rho kinase-myosin light-chain phosphatase (MLCP) and p21-activated kinase (PAK)-myosin light-chain kinase (MLCK) signal pathway. The results indicated that the contractile responses of the SMAs and VSMCs were significantly increased at early shock or after transient hypoxia. NSC23766 (Rac1 antagonist) further increased, whereas PDGF (Rac1 stimulator) decreased the contractile responses of SMAs and VSMCs. In the late period of shock or prolonged hypoxia, the contractile responses of SMAs and VSMCs were significantly decreased; NSC23766 increased (whereas PDGF further decreased) the contractile response of the SMAs and VSMCs. Activation of Rac1 with PDGF significantly increased the activity of PAK and MLCP, and decreased Rho kinase and MLCK activity and 20-kDa myosin light-chain phosphorylation in VSMCs. The PAK inhibitor PAK-18 significantly antagonized the PDGF-induced decrease in MLCK activity, whereas the Rho kinase antagonist Y-27632 further enforced the PDGF-induced increase in MLCP activity. Simple fluid resuscitation did not improve but in combination with NSC23766 significantly improved vascular reactivity and animal survival at 24 hours. This suggested that Rac1 has an inhibitory effect on vasoreactivity after shock. Rac1-mediated regulation of vascular reactivity is mainly through activation of PAK, inhibition of MLCK and inhibition of Rho kinase, unpack the inhibition of Rho kinase to MLCP. Rac1 may be a potential target to treat vascular hyporeactivity in many critical conditions.

Neonatal asphyxia induces the nitration of cardiac myosin light chain 2 that is associated with cardiac systolic dysfunction

Hypoxia followed by reoxygenation (H-R) observed during perinatal asphyxia is a serious complication with high mortality and morbidity rates that may cause adverse cardiovascular effects in neonates. Our aim was to determine if oxidative stress related to H-R induces peroxynitrite-dependent modifications of the cardiac contractile protein, myosin regulatory light chain 2 (MLC2), and whether this is associated with development of cardiac systolic dysfunction. Twelve newborn piglets were acutely instrumented for hemodynamic monitoring and randomized to a control group ventilated with only atmospheric air or to the H-R study group exposed to alveolar normocapnic hypoxia followed by reoxygenation. Afterward, animals were euthanized, and the hearts were harvested for biochemical analyses. Systolic function as well as cardiac MLC2 levels decreased in H-R animals, whereas nitrates and nitrotyrosine levels increased. Negative correlations between nitrates, nitrotyrosine, and MLC2 levels were observed. Moreover, H-R induced nitration of two tyrosine residues within the MLC2 protein. Similarly, in vitro exposure of MLC2 to peroxynitrite resulted in the nitration of tyrosine, which increased the susceptibility of MLC2 to subsequent degradation by matrix metalloproteinase 2. Substitution of this tyrosine with phenylalanine prevented the matrix metalloproteinase 2-dependent degradation of MLC2. In addition, a large decrease in MLC2 phosphorylation caused by H-R was observed. Oxidative stress related to asphyxia induces nitration of cardiac MLC2 protein and thus increases its degradation. This and a large decrease in MLC2 phosphorylation contribute to the development of systolic dysfunction. Inhibition of MLC2 nitration and/or direct inhibition of its degradation by MMP-2 could be potential therapeutic targets aiming at reduction of myocardial damage during resuscitation of asphyxiated newborns.

The mechanism by which RhoA regulates vascular reactivity after hemorrhagic shock in rats

RhoA, an important member of the Rho family of GTPases, has been implicated in many cellular processes. Our pilot study found that RhoA participated in the regulation of vascular reactivity after shock, but the mechanism was incompletely understood. Whether RhoA regulates vascular reactivity through the Rho kinase-myosin light-chain phosphatase (MLCP) and Rac1-p21-activated kinase (PAK)-myosin light-chain kinase (MLCK) signaling pathway needs investigation. With isolated, superior mesenteric arteries from hemorrhagic-shock rats and hypoxia-treated vascular smooth muscle cells (VSMCs), the effects of U-46619 (RhoA agonist) and C3 transferase (RhoA antagonist) on vascular reactivity, and the relationship to the Rho kinase-MLCP and Rac1-PAK-MLCK signaling pathways were observed. The vascular reactivity of the superior mesenteric artery and the contractile response of VSMCs to norepinephrine after prolonged hemorrhagic shock and hypoxia (2 h) were significantly decreased. Activation of RhoA with U-46619 significantly increased shock or hypoxia-induced decreased vascular reactivity. These effects of U-46619 were abolished by Y-27632 (Rho kinase inhibitor) and PDGF (Rac1 stimulator). Y-27632 had a stronger antagonistic effect than PDGF. U-46619 increased the activity of Rho kinase and MLCK, enhanced the phosphorylation of 20-kDa myosin light chain, and decreased the activity of Rac1, PAK, and MLCP in VSMCs after hypoxia. Y-27632-antagonized U-46619 induced the decrease of MLCP activity and the increase of 20-kDa myosin light chain phosphorylation. PDGF-antagonized U-46619 induced decrease of PAK activity and increase of MLCK activity. RhoA has an important role in the regulation of vascular reactivity after hemorrhagic shock. The Rho kinase-MLCP and Rac1-PAK-MLCK signal pathways participate in the regulatory process of RhoA. Rho kinase-MLCP may be the main signaling pathway by which RhoA regulates vascular reactivity.

Stimulation of the adenosine A3 receptor reverses vascular hyporeactivity after hemorrhagic shock in rats

AIM

To investigate whether adenosine A(3) receptors (A(3)AR) stimulation restore vascular reactivity after hemorrhagic shock through a ryanodine receptor (RyR)-mediated and large conductance calcium-activated potassium (BK(Ca)) channel-dependent pathway.

METHODS

Rat hemorrhagic shock model (40 mmHg) and vascular smooth muscle cell (VSMC) hypoxic model were used. The expression of A(3)AR was determined by Western blot and RT-PCR. The effect of A(3)AR stimulation on RyR-mediated Ca(2+) release in VSMCs was analyzed by the Fura-3/AM loading Ca(2+) imaging. The modulation of vascular reactivity to norepinephrine (NE) by A(3)AR stimulation was monitored by an isolated organ tension instrument.

RESULTS

Decrease of A(3)AR expression is consistent with the loss of vasoreactivity to NE in hemorrhagic shock rats. The stimulation of A(3)AR with a selective agonist, IB-MECA, could partly but significantly restore the vasoreactivity in the rats, and this restorative effect could be counteracted by MRS1523, a selective A(3)AR antagonist. In hypoxic VSMCs, RyR activation by caffeine significantly evoked the rise of [Ca(2+)] compared with the control cells, a phenomenon closely associated with the development of vascular hyporeactivity in hemorrhagic shock rats. The stimulation of A(3)AR with IB-MECA significantly blocked this over activation of RyR-mediated Ca(2+) release. RyR activation by caffeine and BK(Ca) channel activation by NS1619 attenuated the restoration of vasoreactivity to NE resulting from A(3)AR stimulation by IB-MECA after hemorrhagic shock; this attenuation effect could be antagonized by a selective BK(Ca) channel blocker.

CONCLUSION

These findings suggest that A(3)AR is involved in the modulation of vasoreactivity after hemorrhagic shock and that stimulation of A(3)AR can restore the decreased vasoreactivity to NE through a RyR-mediated, BK(Ca) channel-dependent signal pathway.

Alcohol does not modulate the augmented acetylcholine-induced vasodilatory response in hemorrhaged rodents

Our previous studies have shown that acute alcohol intoxication (AAI) decreases blood pressure, exacerbates hypotension after hemorrhagic shock, impairs the pressor response to fluid resuscitation, and blunts neuroendocrine activation. We hypothesized that impaired hemodynamic compensation during and after hemorrhagic shock in the acute alcohol-intoxicated host is the result of blunted neuroendocrine activation or, alternatively, of an impaired vascular responsiveness to vasoactive agents. The aim of this study was to examine the effects of AAI, AAI and hemorrhagic shock, and AAI and hemorrhagic shock and resuscitation on reactivity of isolated blood vessel rings to phenylephrine and acetylcholine. Chronically instrumented, conscious male Sprague-Dawley rats (300-350 g) received a primed continuous 15-h intragastric alcohol infusion (2.5 g x kg(-1) + 300 mg x kg(-1) x h(-1)), and time-matched controls received an isocaloric-isovolumic dextrose infusion. At completion of infusions, animals were randomized to sham, 60-min fixed-pressure hemorrhage, or hemorrhagic shock followed by resuscitation with lactated Ringer's solution. At the completion of the experimental protocols, animals were killed, and thoracic aorta and mesenteric artery ring segments (1-2 mm) were prepared and studied in myograph baths. Acute alcohol intoxication did not produce significant alterations in either pressor or dilator responses in aortic or mesenteric rings. These findings suggest that impaired hemodynamic counterregulation during hemorrhagic shock in AAI is not due to decreased vasopressor responsiveness. However, our results suggest a role for accentuated vasodilatory responses that may be central in progression to decompensatory shock.

PKC plays an important mediated effect in arginine vasopressin induced restoration of vascular responsiveness and calcium sensitization following hemorrhagic shock in rats

The present study investigated the mediated effect of protein kinase C (PKC) in arginine vasopressin (AVP)-induced restoration of vascular responsiveness and calcium sensitization following hemorrhagic shock. Using both isolated superior mesenteric artery from hemorrhagic shock rats and hypoxia-treated vascular smooth muscle cell (VSMC), we investigated the roles of PKC-alpha, delta and epsilon isoforms in AVP-induced restoration of vascular reactivity and calcium sensitivity. Meanwhile, effects of their specific inhibitors on the activity of myosin light chain phosphatase (MLCP), myosin light chain kinase (MLCK), and the phosphorylation of myosin light chain (MLC(20)) in VSMC were observed. The results indicated that AVP improved the reactivity of superior mesenteric artery and VSMC to norepinephrine and calcium following hemorrhagic shock and hypoxia. PKC-alpha inhibitor and PKC-epsilon inhibitory peptide antagonized these effects of AVP, while PKC-delta inhibitor only partially antagonized these effects of AVP. AVP up-regulated the expression of PKC-alpha and epsilon in the particulate fractions of hypoxia-treated VSMC with the decrease of the activity of MLCP and the increase of the phosphorylation of MLC(20). These effects of AVP were inhibited by PKC-alpha inhibitor and PKC-epsilon inhibitory peptide, but not by the PKC-delta inhibitor. The results suggested that PKC plays an important role in AVP-induced restoration of vascular reactivity and calcium sensitivity following hemorrhagic shock. PKC-alpha and epsilon may be the main isoforms involved in this process and play effect via MLC(20) phosphorylation dependent mechanism, while PKC-delta may be partially involved in AVP action by other mechanisms.

Regulatory effects of myoendothelial gap junction on vascular reactivity after hemorrhagic shock in rats

Myoendothelial gap junction (MEGJ), one kind of gap junction between vascular endothelial cell and vascular smooth muscle cell, can transmit electrical and chemical signals to keep the electric and machinery activity synchronism of vasculature. After severe trauma or shock, vascular reactivity to vasoconstrictors or vasodilators is greatly reduced. However, whether MEGJ participates in the regulation of vascular reactivity after hemorrhagic shock, what type of MEGJ is involved, and what is the possible mechanism are unknown. With the hemorrhagic shock Sprague-Dawley rats and their superior mesenteric arteries (SMAs), the effects of 18alpha-glycyrrhetic acid, a lipophilic aglycone that disrupts gap junction plaques, on vascular contractile response to norepinephrine (endothelium-independent vascular constrictor), myricetin (endothelium-dependent vasoconstrictor) and relaxation reactivity to sodium nitroprusside (endothelium-independent vasodilator), and acetylcholine (Ach; endothelium-dependent vasodilator) were observed. Meanwhile, the relationship of the mRNA/protein expression of connexins 37, 40, and 43(Cx40 and Cx43) to the changes of vascular reactivity after hemorrhagic shock and the effect of antisense oligodeoxynucleotide of Cx40 or Cx43 on vascular calcium sensitivity and vascular reactivity were investigated. The results indicated that 18alpha-glycyrrhetic acid antagonized myricetin and Ach-induced SMA reactivity, but had no effect on norepinephrine- and sodium nitroprusside-induced vascular response. The mRNA and protein expression of Cx37 and Cx40 of SMA were negatively associated with the vascular reactivity, whereas Cx43 seemed to be a positive relationship to vascular reactivity. Antisense oligodeoxynucleotide of Cx40 significantly increased the calcium sensitivity, myricetin-induced vasoconstriction, and Ach-induced vasodilation, whereas antisense oligodeoxynucleotide of Cx43 depressed them. It was suggested that MEGJ plays an important role in the regulation of endothelium-dependent vascular reactivity after hemorrhagic shock. The involved types were mainly Cx40 and Cx43. The possible mechanism that Cx40/Cx43 regulates the endothelium-dependent vasoconstrictor reactivity may be related to their regulating effects on the calcium sensitivity of vascular smooth muscle cell.