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

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.

Where's the Leak in Vascular Barriers? A Review

Edema is typically presented as a secondary effect from injury, illness, disease, or medication, and its impact on patient wellness is nested within the underlying etiology. Therefore, it is often thought of more as an amplifier to current preexisting conditions. Edema, however, can be an independent risk factor for patient deterioration. Improper management of edema is costly not only to the patient, but also to treatment and care facilities, as mismanagement of edema results in increased lengths of hospital stay. Direct tissue trauma, disease, or inappropriate resuscitation and/or ventilation strategies result in edema formation through physical disruption and chemical messenger-based structural modifications of the microvascular barrier. Derangements in microvascular barrier function limit tissue oxygenation, nutrient flow, and cellular waste removal. Recent studies have sought to elucidate cellular signaling and structural alterations that result in vascular hyperpermeability in a variety of critical care conditions to include hemorrhage, burn trauma, and sepsis. These studies and many others have highlighted how multiple mechanisms alter paracellular and/or transcellular pathways promoting hyperpermeability. Roles for endothelial glycocalyx, extracellular matrix and basement membrane, vesiculo-vacuolar organelles, cellular junction and cytoskeletal proteins, and vascular pericytes have been described, demonstrating the complexity of microvascular barrier regulation. Understanding these basic mechanisms inside and out of microvessels aid in developing better treatment strategies to mitigate the harmful effects of excessive edema formation.

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Role of miR-124 and miR-141 in the regulation of vascular reactivity and the relationship to RhoA and Rac1 after hemorrhage and hypoxia

Recent studies show that hypoxia can alter expression levels of microRNAs (miRNAs). Whether hypoxia or hemorrhage-induced vascular hyporeactivity is related to miRNAs and the underlying mechanisms of this process is not clear. Using hypoxia-treated superior mesenteric arteries (SMAs) and vascular smooth muscle cells (VSMCs) of rats that underwent hemorrhage, we observed the regulatory effects of miR-124/miR-141 on vascular reactivity, the relationship of these miRNAs to RhoA and Rac1, and the mutual regulation of miR-124 and miR-141. The contractile responses of SMAs and VSMCs showed an increase in early stages and a decrease in late stages of hypoxia and hemorrhage. Forty-five miRNAs appeared to have been significantly changed in SMAs after hypoxia, and miR-124 and miR-141 underwent the most change. Overexpressed miR-124 or miR-141 and their antisenses appeared to alter both vascular reactivity and expression of the proteins RhoA and Rac1 after hypoxia. miR-124 inhibited Rac1 by acting at the Rac1 mRNA 3'-untranslated region (UTR), but it led to an increase in RhoA by inhibiting miR-141. miR-141 inhibited RhoA by acting at the RhoA mRNA 3'-UTR, but it led to an increase in Rac1 by inhibiting miR-124. Further study found that miR-124 inhibited miR-141 via transcription factor early growth response gene-1 (Egr-1), whereas miR-141 inhibited miR-124 via transcription of nuclear factor erythroid 2-related factor 2 (Nrf-2). These results suggest that miR-124 and miR-141 participate in the regulation of vascular reactivity after hypoxia and hemorrhage by regulating expression of the RhoA and Rac1 proteins, and in doing so, miR-124 and miR-141 are mutually regulated. These findings provide potential targets for restoring vascular function as part of the treatment protocol for hemorrhagic shock and some other critical illness.

The Ins and Outs of Small GTPase Rac1 in the Vasculature

The Rho family of small GTPases forms a 20-member family within the Ras superfamily of GTP-dependent enzymes that are activated by a variety of extracellular signals. The most well known Rho family members are RhoA (Ras homolog gene family, member A), Cdc42 (cell division control protein 42), and Rac1 (Ras-related C3 botulinum toxin substrate 1), which affect intracellular signaling pathways that regulate a plethora of critical cellular functions, such as oxidative stress, cellular contacts, migration, and proliferation. In this review, we describe the current knowledge on the role of GTPase Rac1 in the vasculature. Whereas most recent reviews focus on the role of vascular Rac1 in endothelial cells, in the present review we also highlight the functional involvement of Rac1 in other vascular cells types, namely, smooth muscle cells present in the media and fibroblasts located in the adventitia of the vessel wall. Collectively, this overview shows that Rac1 activity is involved in various functions within one cell type at distinct locations within the cell, and that there are overlapping but also cell type-specific functions in the vasculature. Chronically enhanced Rac1 activity seems to contribute to vascular pathology; however, Rac1 is essential to vascular homeostasis, which makes Rac1 inhibition as a therapeutic option a delicate balancing act.

Inhibition of prostate smooth muscle contraction and prostate stromal cell growth by the inhibitors of Rac, NSC23766 and EHT1864

BACKGROUND AND PURPOSE

Medical therapy of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) targets smooth muscle contraction in the prostate, or prostate growth. However, current therapeutic options are insufficient. Here, we investigated the role of Rac in the control of smooth muscle tone in human prostates and growth of prostate stromal cells.

EXPERIMENTAL APPROACH

Experiments were performed using human prostate tissues from radical prostatectomy and cultured stromal cells (WPMY-1). Expression of Rac was examined by Western blot and fluorescence staining. Effects of Rac inhibitors (NSC23766 and EHT1864) on contractility were assessed in the organ bath. The effects of Rac inhibitors were assessed by pull-down, cytotoxicity using a cell counting kit, cytoskeletal organization by phalloidin staining and cell growth using an 5-ethynyl-2'-deoxyuridine assay.

KEY RESULTS

Expression of Rac1-3 was observed in prostate samples from each patient. Immunoreactivity for Rac1-3 was observed in the stroma, where it colocalized with the smooth muscle marker, calponin. NSC23766 and EHT1864 significantly reduced contractions of prostate strips induced by noradrenaline, phenylephrine or electrical field stimulation. NSC23766 and EHT1864 inhibited Rac activity in WPMY-1 cells. Survival of WPMY-1 cells ranged between 64 and 81% after incubation with NSC23766 (50 or 100 μM) or EHT1864 (25 μM) for 24 h. NSC23766 and EHT1864 induced cytoskeletal disorganization in WPMY-1 cells. Both inhibitors impaired the growth of WPMY-1 cells.

CONCLUSIONS AND IMPLICATIONS

Rac may be a link connecting the control of prostate smooth muscle tone with proliferation of smooth muscle cells. Improvements in LUTS suggestive of BPH by Rac inhibitors appears possible.

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.

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.

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.