Hemorrhagic shock-induced vascular hyporeactivity in the rat: relationship to gene expression of nitric oxide synthase, endothelin-1, and select cytokines in corresponding organs

Enteral administration of the protease inhibitor gabexate mesilate preserves vascular function in experimental trauma/hemorrhagic shock

Preserving vascular function is crucial for preventing multiorgan failure and death in ischemic and low-pressure states such as trauma/hemorrhagic shock (T/HS). It has recently been reported that inhibiting circulating proteases released from the bowel to the circulation during T/HS may preserve vascular function and improve outcomes following T/HS. This study aimed to evaluate the role of the serine protease inhibitor gabexate mesilate (GM) in preserving vascular function during T/HS when given enterally. We studied the vascular reactivity of mesenteric arteries from male Wistar rats treated with enteral GM (10 mg/kg) (GM-treated, n = 6) or control (Shock-control, n = 6) following (T/HS) using pressure myography. Concentration-response curves of endothelial-dependent and endothelial-independent agonists (e.g., acetylcholine, sodium nitroprusside) ranging from 10-10 to 10-5 M were performed. In a second set of experiments, ex-vivo arteries from healthy rats were perfused with plasma from shocked animals from both groups and vascular performance was similarly measured. Arteries from the GM-treated group demonstrated a preserved concentration-response curve to the α1 adrenergic agonist phenylephrine compared to arteries from Shock-control animals (- logEC50: - 5.73 ± 0.25 vs. - 6.48 ± 0.2, Shock-control vs. GM-treated, p = 0.04). When perfused with plasma from GM-treated rats, healthy arteries exhibited an even greater constriction and sensitivity to phenylephrine (- logEC50: - 6.62 ± 0.21 vs. - 7.13 ± 0.21, Shock-control vs. GM-treated, p = 0.02). Enteral GM also preserved the endothelium-dependent vascular response to agonists following T/HS and limited syndecan-1 shedding as a marker of glycocalyx compromise (41.84 ± 9 vs. 17.63 ± 3.97 ng/mL, Shock-control vs. GM-treated, p = 0.02). Syndecan-1 cleavage was correlated with plasma trypsin-like activity (r2 = 0.9611). Enteral gabexate mesilate was able to maintain vascular function in experimental T/HS, which was reflected by improved hemodynamics (mean arterial pressure 50.39 ± 7.91 vs. 64.95 ± 3.43 mmHg, Shock-control vs. GM treated, p = 0.0001). Enteral serine protease inhibition may be a potential therapeutic intervention in the treatment of T/HS.

Optimization of a laparoscopic procedure for advanced intrahepatic cholangiocarcinoma based on the concept of "waiting time": a preliminary report

INTRODUCTION

Clinicians increasingly perform laparoscopic surgery for intrahepatic cholangiocarcinoma (ICC). However, this surgery can be difficult in patients with advanced-stage ICC because of the complicated procedures and difficulty in achieving high-quality results. We compared the effects of a three-step optimized procedure with a traditional procedure for patients with advanced-stage ICC.

METHODS

Forty-two patients with advanced-stage ICC who received optimized laparoscopic hemihepatectomy with lymph node dissection (LND, optimized group) and 84 propensity score-matched patients who received traditional laparoscopic hemihepatectomy plus LND (traditional group) were analyzed. Surgical quality, disease-free survival (DFS), and overall survival (OS) were compared.

RESULTS

The optimized group had a lower surgical bleeding score (P = 0.038) and a higher surgeon satisfaction score (P = 0.001). Blood loss during hepatectomy was less in the optimized group (190 vs. 295 mL, P < 0.001). The optimized group had more harvested LNs (12.0 vs. 8.0, P < 0.001) and more positive LNs (8.0 vs. 5.0, P < 0.001), and a similar rate of adequate LND (88.1% vs. 77.4%, P = 0.149). The optimized group had longer median DFS (9.0 vs. 7.0 months, P = 0.018) and median OS (15.0 vs. 13.0 months, P = 0.046). In addition, the optimized group also had a shorter total operation time (P = 0.001), shorter liver resection time (P = 0.001), shorter LND time (P < 0.001), shorter hospital stay (P < 0.001), and lower incidence of total morbidities (14.3% vs. 36.9%, P = 0.009).

CONCLUSIONS

Our optimization of a three-step laparoscopic procedure for advanced ICC was feasible, improved the quality of liver resection and LND, prolonged survival, and led to better intraoperative and postoperative outcomes.

Hemorrhage and saline resuscitation are associated with epigenetic and proteomic reprogramming in the rat lung

BACKGROUND

Epigenetic changes have been described in trauma patients in the form of histone acetylation events, but whether DNA-methylation occurs remains unknown. We hypothesized that the combination of hemorrhage and saline resuscitation would alter DNA-methylation and associated proteomic profiles in the rat lung.

METHODS

Ten rats were subjected to a pressure-controlled hemorrhage and resuscitation model consisting of hemorrhage to a mean arterial pressure (MAP) of 35mmHg for 90 minutes, followed by saline resuscitation to a MAP >70mmHg for 90 minutes (n=5) or sham (only anesthesia and cannulation). Lungs were harvested and subjected to reduced genome wide DNA-methylation analysis through bisulphite sequencing as well as proteomics analysis. Data was analyzed for differentially methylated regions and associated alterations in proteomic networks through a weighted correlation network analysis (WCNA). Pathway analysis was used to establish biological relevance of findings.

RESULTS

Hemorrhage and saline resuscitation were associated with differential methylation of 353 sites across the genome compared to the sham group. Of these, 30 were localized to gene promoter regions, 31 to exon regions and 87 to intron regions. Network analysis identified an association between hemorrhage/resuscitation and DNA-methylation events located to genes involved in areas of endothelial and immune response signaling. The associated proteomic response was characterized by activations of mRNA processing as well as endothelial Nitric Oxide Synthase (eNOS) metabolism.

CONCLUSION

We demonstrated an association between DNA-methylation and hemorrhage/saline resuscitation. These results suggest a potential role of DNA-methylation in the host response to injury.

Activated Drp1-mediated mitochondrial ROS influence the gut microbiome and intestinal barrier after hemorrhagic shock

A role of the mitochondrial dynamin-related protein (Drp1) on gut microbiome composition and intestinal barrier function after hemorrhagic shock has not been identified previously and thus addressed in this study. Here, we used a combination of 16S rRNA gene sequencing and mass spectrometry-based metabolomics profiling in WT and Drp1 KO mouse models to examine the functional impact of activated Drp1 on the gut microbiome as well as mitochondrial metabolic regulation after hemorrhagic shock. Our data showed that changes in mitochondrial Drp1 activity participated in the regulation of intestinal barrier function after hemorrhagic shock. Activated Drp1 significantly perturbed gut microbiome composition in the Bacteroidetes phylum. The abundance of short-chain fatty acid (SCFA) producing microbes, such as Bacteroides, Butyricimonas and Odoribacter, was markedly decreased in mice after shock, and was inversely correlated with both the distribution of the tight junction protein ZO1 and intestinal permeability. Together, these data suggest that Drp1 activation perturbs the gut microbiome community and SCFA production in a ROS-specific manner and thereby substantially disturbs tight junctions and intestinal barrier function after hemorrhagic shock. Our findings provide novel insights for targeting Drp1-mediated mitochondrial function as well as the microbiome in the treatment of intestinal barrier dysfunction after shock.

Modeling trauma in rats: similarities to humans and potential pitfalls to consider

Trauma is the leading cause of mortality in humans below the age of 40. Patients injured by accidents frequently suffer severe multiple trauma, which is life-threatening and leads to death in many cases. In multiply injured patients, thoracic trauma constitutes the third most common cause of mortality after abdominal injury and head trauma. Furthermore, 40-50% of all trauma-related deaths within the first 48 h after hospital admission result from uncontrolled hemorrhage. Physical trauma and hemorrhage are frequently associated with complex pathophysiological and immunological responses. To develop a greater understanding of the mechanisms of single and/or multiple trauma, reliable and reproducible animal models, fulfilling the ethical 3 R's criteria (Replacement, Reduction and Refinement), established by Russell and Burch in 'The Principles of Human Experimental Technique' (published 1959), are required. These should reflect both the complex pathophysiological and the immunological alterations induced by trauma, with the objective to translate the findings to the human situation, providing new clinical treatment approaches for patients affected by severe trauma. Small animal models are the most frequently used in trauma research. Rattus norvegicus was the first mammalian species domesticated for scientific research, dating back to 1830. To date, there exist numerous well-established procedures to mimic different forms of injury patterns in rats, animals that are uncomplicated in handling and housing. Nevertheless, there are some physiological and genetic differences between humans and rats, which should be carefully considered when rats are chosen as a model organism. The aim of this review is to illustrate the advantages as well as the disadvantages of rat models, which should be considered in trauma research when selecting an appropriate in vivo model. Being the most common and important models in trauma research, this review focuses on hemorrhagic shock, blunt chest trauma, bone fracture, skin and soft-tissue trauma, burns, traumatic brain injury and polytrauma.

Effects of mineralocorticoid receptor antagonists on responses to hemorrhagic shock in rats

AIM

To evaluate the effects of mineralocorticoid receptor (MR) antagonists on mortality and inflammatory responses after hemorrhagic shock (HS) in rats.

METHODS

One hundred and two male Sprague–Dawley rats were randomly assigned to one of the following three groups: Control, spironolactone (SPL), and eplerenone (EP) groups. HS was induced by the removal of blood. One half of rats were evaluated to determine mortality, hemodynamics, plasma tumor necrosis factor-alpha (TNF-α) concentrations, and arterial blood gas at 8 h after HS recovery. In the remainder of rats, the expression levels of genes encoding cytokines were evaluated in liver tissue samples at 1 h after HS recovery.

RESULTS

The survival rates 8 h after HS recovery were 71%, 94%, and 82% in the control, SPL, and EP groups, respectively. There were no significant differences in survival rates among the three groups (P = 0.219). Furthermore, there were no significant differences in gene expression levels in the liver or plasma TNF-α concentrations among the three groups (P = 0.888).

CONCLUSION

Pretreatment with MR antagonists did not improve mortality or cytokine responses in the liver after HS recovery in rats.

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.

Propofol attenuates cytokine-mediated upregulation of expression of inducible nitric oxide synthase and apoptosis during regeneration post-partial hepatectomy

Purpose:

To determine the effects of propofol and ketamine anesthesia on liver regeneration in rats after partial hepatectomy (PHT).

Methods:

Male Wistar albino rats were assigned randomly to four groups of 10. Anesthesia was induced and maintained with propofol in groups 1 and 2, and with ketamine in groups 3 and 4. PHT was undertaken in groups 1 and 3. Rats in groups 2 and 4 (control groups) underwent an identical surgical procedure, but without PHT. At postoperative day-5, rats were killed. Regenerated liver was removed, weighed, and evaluated (by immunohistochemical means) for expression of inducible nitric oxide synthase (iNOS), endothelial NOS (eNOS), apoptosis protease-activating factor (APAF)-1, and proliferating cell nuclear antigen (PCNA). Also, blood samples were collected for measurement of levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6.

Results:

Between groups 2 and 4, there were no differences in tissue levels of iNOS, eNOS, and APAF-1 or plasma levels of TNF-α and IL-6. eNOS expression was similar in group 1 and group 3. Expression of iNOS and APAF-1 was mild-to-moderate in group 1, but significantly higher in group 3. Groups 1 and 3 showed an increase in PCNA expression, but expression in both groups was comparable. Plasma levels of TNF-α and IL-6 increased to a lesser degree in group 1 than in group 3.

Conclusion:

Propofol, as an anesthetic agent, may attenuate cytokine-mediated upregulation of iNOS expression and apoptosis in an animal model of liver regeneration after partial hepatectomy.

Involvement of connexin 43 phosphorylation and gap junctional communication between smooth muscle cells in vasopressin-induced ROCK-dependent vasoconstriction after hemorrhagic shock

We examined the roles played by gap junctions (GJs) and the GJ channel protein connexin 43 (Cx43) in arginine vasopressin (AVP)-induced vasoconstriction after hemorrhagic shock and their relationship to Rho kinase (ROCK) and protein kinase C (PKC). The results showed that AVP induced an endothelium-independent contraction in rat superior mesenteric arteries (SMAs). Blocking the GJs significantly decreased the contractile response of SMAs and vascular smooth muscle cells (VSMCs) to AVP after shock and hypoxia. The selective Cx43-mimetic peptide inhibited the vascular contractile effect of AVP after shock and hypoxia. AVP restored hypoxia-induced decrease of Cx43 phosphorylation at Ser²⁶² and gap junctional communication in VSMCs. Activation of RhoA with U-46619 increased the contractile effect of AVP. This effect was antagonized by the ROCK inhibitor Y27632 and the Cx43-mimetic peptide. In contrast, neither an agonist nor an inhibitor of PKC had significant effects on AVP-induced contraction after hemorrhagic shock. In addition, silencing of Cx43 with siRNA blocked the AVP-induced increase of ROCK activity in hypoxic VSMCs. In conclusion, AVP-mediated vascular contractile effects are endothelium and myoendothelial gap junction independent. Gap junctions between VSMCs, gap junctional communication, and Cx43 phosphorylation at Ser²⁶² play important roles in the vascular effects of AVP. RhoA/ROCK, but not PKC, is involved in this process.

Myoendothelial gap junctions mediate regulation of angiopoietin-2-induced vascular hyporeactivity after hypoxia through connexin 43-gated cAMP transfer

Angiopoietin-2 (Ang-2) contributes to vascular hyporeactivity after hemorrhagic shock and hypoxia through upregulation of inducible nitric oxide synthase (iNOS) in a vascular endothelial cell (VEC)-specific and Ang-2/Tie2 receptor-dependent manner. While iNOS is primarily expressed in vascular smooth muscle cells (VSMCs), the mechanisms of signal transfer from VECs to VSMCs are unknown. A double-sided coculture model with VECs and VSMCs from Sprague-Dawley rats was used to investigate the role of myoendothelial gap junctions (MEGJs), the connexin (Cx) isoforms involved, and other relevant mechanisms. After hypoxia, VSMCs treated with exogenous Ang-2 showed increased iNOS expression and hyporeactivity, as well as MEGJ formation and communication. These Ang-2 effects were suppressed by the MEGJ inhibitor 18α-glycyrrhetic acid (18-GA), Tie2 siRNA, or Cx43 siRNA. Reagents antagonizing cAMP or protein kinase A (PKA) in VECs inhibited Cx43 expression in MEGJs, decreasing MEGJ formation and associated communication, after hypoxia following Ang-2 treatment. The increased cAMP levels in VSMCs and transfer of Alexa Fluor 488-labeled cAMP from VECs to VSMCs, after hypoxia following Ang-2 treatment, was antagonized by Cx43 siRNA. A cAMP antagonist added to VECs or VSMCs inhibited both increased iNOS expression and hyporeactivity in VSMCs subjected to hypoxia following Ang-2 treatment. Based on these findings, we propose that Cx43 was the Cx isoform involved in MEGJ-mediated VEC-dependent regulation of Ang-2, which induces iNOS protein expression and vascular hyporeactivity after hypoxia. Cx43 was upregulated by cAMP and PKA, permitting cAMP transfer between cells.

Vascular smooth muscle desensitization in rabbit epigastric and mesenteric arteries during hemorrhagic shock

The decompensatory phase of hemorrhage (shock) is caused by a poorly defined phenomenon termed vascular hyporeactivity (VHR). VHR may reflect an acute in vivo imbalance in levels of contractile and relaxant stimuli favoring net vascular smooth muscle (VSM) relaxation. Alternatively, VHR may be caused by intrinsic VSM desensitization of contraction resulting from prior exposure to high levels of stimuli that temporarily adjusts cell signaling systems. Net relaxation, but not desensitization, would be expected to resolve rapidly in an artery segment removed from the in vivo shock environment and examined in vitro in a fresh solution. Our aim was to 1) induce shock in rabbits and apply an in vitro mechanical analysis on muscular arteries isolated pre- and postshock to determine whether VHR involves intrinsic VSM desensitization, and 2) identify whether net VSM relaxation induced by nitric oxide and cyclic nucleotide-dependent protein kinase activation in vitro can be sustained for some time after relaxant stimulus washout. The potencies of phenylephrine- and histamine-induced contractions in in vitro epigastric artery removed from rabbits posthemorrhage were decreased by ∼0.3 log units compared with the control contralateral epigastric artery removed prehemorrhage. Moreover, a decrease in KCl-induced tonic, relative to phasic, tension of in vitro mesenteric artery correlated with the degree of shock severity as assessed by rates of lactate and K(+) accumulation. VSM desensitization was also caused by tyramine in vivo and PE in vitro, but not by relaxant agents in vitro. Together, these results support the hypothesis that VHR during hemorrhagic decompensation involves contractile stimulus-induced long-lasting, intrinsic VSM desensitization.

Protective role of nuclear factor erythroid 2-related factor 2 in the hemorrhagic shock-induced inflammatory response

Hemorrhagic shock (HS) following trauma or major surgery significantly contributes to mortality. However, the mechanisms through which HS activates the inflammatory response are not yet fully understood. Nuclear factor-erythroid 2 (NF-E2) p45-related factor-2 (Nrf2), a bZIP transcription factor, is a master regulator of robust cytoprotective defenses. The present study investigated the role of Nrf2 in the pathophysiology of HS. Nrf2 expression in peripheral leukocytes obtained from patients with surgery-associated hemorrhage subjected to resuscitation treatment (termed HS patients) or healthy donors was examined by RT-qPCR. A marked increase in Nrf2 expression was detected in the leukocytes obtained from the HS patients, which indicates a correlation between Nrf2 expression and the development of HS. Wild-type (WT; Nrf2^+/+) and Nrf2-deficient [Nrf2^−/− or Nrf2-knockout (KO)] mice were subjected to surgery to induce HS. Systemic inflammation was significantly elevated in the Nrf2-KO mice compared with the WT mice following HS, as assessed by an increase in serum cytokine levels [interleukin (IL)-6, tumor necrosis factor (TNF)-α and IL-1β], as well as high-mobility group box 1 protein (HMGB1) expression. The Nrf2-KO mice exhibited more severe lung and liver injury following HS as evidenced by increased tissue damage, increased myeloperoxidase (MPO) activity and the increased production of pro-inflammatory cytokines. Additionally, Nrf2 deficiency augmented cytokine production induced by the exposure of peritoneal mouse macrophages to lipopolysaccha-ride (LPS) following HS. Taken together, these results suggest that Nrf2 is a critical host factor which limits immune dysregulation and organ injury following HS.

Inhibition of complement C3 might rescue vascular hyporeactivity in a conscious hemorrhagic shock rat model

BACKGROUND

Vascular hyporeactivity in severe hemorrhagic shock could induce refractory hypotension and is an important cause of death. The global acute inflammatory response induced in shock triggers the over-expression of reactive oxygen species, NO, ET1 and TNF-α, which play essential roles in the pathology of vascular hyporeactivity. This leads to a hypothesis that inhibition of the complement system, the mediator of the inflammatory cascade, might be a promising therapeutic exploration for vascular hyporeactivity.

METHODS

We use cobra venom factor (CVF) and the soluble form of CR1 (sCR1) which deplete or inhibit complement C3 respectively to examine its role in vascular hyporeactivity in a conscious hemorrhagic shock rat model.

RESULTS

We first confirmed the over-activation of C3 during shock and the down-regulation effects of CVF and sCR1 on C3. Then, both CVF and sCR1 could significantly mitigate the over-expression of serum NO, ET-1, TNF-α and reactive oxygen species. Finally, the vascular reactivity of superior mesenteric arteries (SMA) was examined in vitro, which confirmed the massive reduction of vascular reactivity in shock, which was significantly rescued by both CVF and sCR1.

CONCLUSIONS

Inhibition of C3 might improve the reactivity of SMA to norepinephrine during hemorrhagic shock possibly through the downregulation of NO, ET1, TNF-α and reactive oxygen radicals.

Vitamin C treatment attenuates hemorrhagic shock related multi-organ injuries through the induction of heme oxygenase-1

BACKGROUND

Vitamin C (VitC) has recently been shown to exert beneficial effects, including protecting organ function and inhibiting inflammation, in various critical care conditions, but the specific mechanism remains unclear. Induction of heme oxygenase (HO)-1, a heat shock protein, has been shown to prevent organ injuries in hemorrhagic shock (HS) but the relationship between VitC and HO-1 are still ill-defined so far. Here we conducted a systemic in vivo study to investigate if VitC promoted HO-1 expression in multiple organs, and then tested if the HO-1 induction property of VitC was related to its organ protection and anti-inflammatory effect.

METHODS

Firstly, to determine the HO-1 induction property of VitC, the HO-1 level were measured in tissues including kidney, liver and lung of the normal and HS model of Sprague-Dawley (SD) rats after VitC treatment (100 mg/kg body weight). Secondly, to testify if VitC prevented HS related organ injuries via inducing HO-1, the HS model of rats were separately pre- and post-treated with VitC, and some of them also received Zinc protoporphyrin (Znpp), a specific HO-1 inhibitor. The HO-1 activity in tissues was tested; the organ injuries (as judged by histological changes in tissues and the biochemical indicators level in serum) and inflammatory response in tissues (as judged by the level of pro-inflammatory cytokines Tumor necrosis factor-α and Interleukin-6 ) were analyzed.

RESULTS

The HO-1 mRNA and protein level in kidney, liver, and lung were highly induced by VitC treatement under normal and HS conditions. The HO-1 activity in tissues was enhanced by both VitC pre- and post-treatment, which was shown to improve the organ injuries and inhibit the inflammatory response in the HS model of rats. Of note, the beneficial effects of VitC were abolished after HO-1 activity was blocked by Znpp.

CONCLUSIONS

VitC led to a profound induction of HO-1 in multiple organs including the kidney, liver and lung, and this property might be responsible for the organ protection and inflammation inhibitory effects of both pre- and post-treatment with VitC in HS.

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.

Bkca opener, NS1619 pretreatment protects against shock-induced vascular hyporeactivity through PDZ-Rho GEF-RhoA-Rho kinase pathway in rats

BACKGROUND

Our previous study showed that the ischemic preconditioning and pretreatment of adenosine triphosphate-sensitive potassium channel (KATP) opener, pinacidil, may induce a good protective effect on shock-induced vascular hyporeactivity. Whether the pretreatment of opener/activator of the large-conductance calcium-activated potassium channel (Bkca), NS1619, can also induce a protective effect on vascular reactivity and play a beneficial effect on subsequent hemorrhagic shock is not clear.

METHODS

With Sprague-Dawley rats subjected to hemorrhagic shock and their isolated superior mesenteric artery, the protective effect of NS1619 (0.5, 1, 2, and 4 mg/kg) pretreatment (30 minutes before hemorrhage shock) on vascular reactivity and the underlying mechanisms were observed.

RESULTS

NS1619 pretreatment significantly improved the 72-hour survival of hemorrhagic shock rats, alleviated shock-induced decrease of vascular reactivity and calcium sensitivity, and increased the cardiac output and oxygen delivery. NS1619 2 mg/kg had the best effect. These protective effects of NS1619 pretreatment on vascular reactivity and calcium sensitivity were antagonized by RhoA inhibitor, C3 transferase, and Rho kinase antagonist, Y-27632. NS1619 pretreatment up-regulated the activities of RhoA, Rho-kinase, and PDZ-Rho GEF (guanine nucleotide exchange factor). These effects of NS1619 pretreatment were eliminated by RhoA inhibitor, C3 transferase.

CONCLUSION

Bkca opener, NS1619 pretreatment has good protective effect on vascular reactivity and calcium sensitivity, which plays a good beneficial effect on hemorrhagic shock. The mechanism may be mainly through PDZ-Rho GEF-RhoA-Rho kinase pathway. Bkca channel may be a potential target for the treatment of shock-induced vascular hyporeactivity.

Adrenal dysfunction in portal hypertensive rats with acute hemorrhage

Nitric oxide (NO) participates in shock and poorer portal hypotensive effect to vasoconstrictors in portal hypertension with hemorrhage, the so-called splanchnic hyposensitivity. Relative adrenal insufficiency accompanies hemorrhagic shock and is found in liver disease, the ‘hepatoadrenal syndrome’, but the relevant interactions remain unsettled. Portal hypertensive rats were induced by partial portal vein ligation (PVL). Experiments were performed on the 14^th day post PVL: (I) ACTH stimulation test for rats without or with hemorrhage; (II) Glypressin response (mean arterial pressure, MAP; portal pressure, PP) in rats (a) without hemorrhage or with hemorrhage, injected with (b) distilled water (DW), (c) dexamethasone 3 mg/kg; (III) To survey the dose-dependent effects of glucocorticoid without being confounded by endogenous adrenal hormone, glypressin response was surveyed in PVL rats with adrenalectomy: (a) without hemorrhage or with hemorrhage, injected with (b) DW; (c) dexamethasone 3 mg/kg; (d) dexamethasone 5 mg/kg. Plasma tumor necrosis factor-α (TNF-α) concentrations and abdominal aorta (AA), superior mesenteric artery (SMA) NO synthases (NOS) mRNA expressions were determined. The results showed that ACTH induced corticosterone release similarly in PVL rats with or without hemorrhage. In bleeding PVL rats, dexamethasone (1) down-regulated AA NOS and enhanced glypressin-induced MAP elevation; (2) did not influence glypressin-induced PP reduction; (3) reduced TNF-α. In bleeding PVL and adrenalectomized rats, high-dose dexamethasone (1) down-regulated AA/SMA NOS; (2) enhanced glypressin-induced MAP elevation and PP reduction; (3) reduced TNF-α. In conclusion, bleeding portal hypertensive rats failed to enhance corticosterone release, suggesting a relative adrenal insufficiency. High-dose dexamethasone reversed systemic hypotension and splanchnic hyporesponsiveness to glypressin in adrenalectomized PVL rats accompanied by TNF-α and NOS down-regulation, suggesting the importance of adequate adrenocorticoid supplement in portal hypertension with hemorrhage and adrenal dysfunction.

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.

BML-111 attenuates hemorrhagic shock-induced acute lung injury through inhibiting activation of mitogen-activated protein kinase pathway in rats

BACKGROUND

Hemorrhagic shock activates cellular stress signals and can lead to systemic inflammatory response, organ injury, and death. Mitogen-activated protein kinase (MAPK) acts as a sensor of tissue injury in models of ischemia-reperfusion injury. Lipoxins are endogenous lipid mediators with potent anti-inflammatory and pro-resolving actions. We hypothesized that BML-111 (a lipoxin A4-receptor agonist) attenuates hemorrhagic shock-induced acute lung injury (ALI) through inhibiting activation of the MAPK pathway.

METHODS

We randomized Sprague-Dawley rats into four groups: sham, hemorrhagic shock-resuscitation (HS), HS plus BML-111 (BML-111), and HS plus BML-111 and BOC-2 (BOC-2). Two hours after resuscitation, we collected samples of lung. We obtained bronchoalveolar lavage fluid for neutrophil count. We performed optical microscopy to examine pathologic changes in lungs. Wet/dry ratios, myeloperoxidase expression, interleukin (IL)-1β and IL-6 levels in lung were measured. We evaluated MAPK activation and the DNA binding activity of activator protein-1 in lung.

RESULTS

Treatment with BML-111 reduced the lung damage and wet/dry ratio, neutrophil count in bronchoalveolar lavage fluid, expression of myeloperoxidase, and production of IL-1β and IL-6 in lung. Phosphorylation of MAPK was also decreased by BML-111 in lung. Furthermore, the DNA binding activity of activator protein-1 was blocked by BML-111. An antagonist of the lipoxin A4-receptor, BOC-2, reversed the protective effect of BML-111 on ALI induced by hemorrhagic shock.

CONCLUSIONS

This study indicates that BML-111 attenuated hemorrhagic shock-induced ALI via the MAPK/activator protein-1 signaling pathway. Therefore, BML-111 may have therapeutic potential for hemorrhagic shock-induced ALI.

Pinacidil pretreatment improves vascular reactivity after shock through PKCα and PKCε in rats

We investigated the beneficial effect of pinacidil pretreatment on vascular reactivity, calcium sensitivity, and animal survival after hemorrhagic shock, its relationship to protein kinase Cα (PKCα), protein kinase Cε (PKCε), and adenosine. Using hemorrhagic shock rats, the protective effects of different extents of pinacidil pretreatment on vascular reactivity and in which the roles of PKCα, PKCε, and adenosine were observed. Pinacidil pretreatment significantly improved shock-induced decrease of vascular reactivity of superior mesenteric artery, which was antagonized by the PKCα antagonist Gö-6976 (5 × 10 mole/L) and PKCε pseudosubstrate inhibitory peptide (1 × 10 mole/L). Pinacidil pretreatment induced the translocation of PKCα and PKCε from the cytoplasm to the membrane. This translocation of PKCα and PKCε was eliminated by adenosine A1 receptor antagonist DPCPX (1 × 10 mole/L). As compared with simple fluid resuscitation, combination with pinacidil pretreatment significantly improved the vascular reactivity and survival rate of hemorrhagic-shocked rats. These results suggested that pinacidil pretreatment could induce good protective effects on vascular reactivity and calcium sensitivity after hemorrhagic shock mainly through the activation of PKCα and PKCε via adenosine A1 receptor, and this protective effect made an important contribution to the overall outcome of shock therapy.

Cannabinoid receptor 2 agonist ameliorates mesenteric angiogenesis and portosystemic collaterals in cirrhotic rats

Angiogenesis in liver cirrhosis leads to splanchnic hyperemia, increased portal inflow, and portosystemic collaterals formation, which may induce lethal complications, such as gastroesophageal variceal hemorrhage and hepatic encephalopathy. Cannabinoids (CBs) inhibit angiogenesis, but the relevant influences in cirrhosis are unknown. In this study, Spraque-Dawley rats received common bile duct ligation (BDL) to induce cirrhosis. BDL rats received vehicle, arachidonyl-2-chloroethylamide (cannabinoid receptor type 1 [CB(1) ] agonist), JWH-015 (cannabinoid receptor type 2 [CB(2) ] agonist), and AM630 (CB(2) antagonist) from days 35 to 42 days after BDL. On the 43rd day, hemodynamics, presence of CB receptors, severity of portosystemic shunting, mesenteric vascular density, vascular endothelial growth factor (VEGF), VEGFR-1, VEGFR-2, phospho-VEGFR-2, cyclooxygenase (COX)-1, COX-2, and endothelial nitric oxide synthase (eNOS) expressions as well as plasma VEGF levels were evaluated. Results showed that CB(1) and CB(2) receptors were present in left adrenal veins of sham rats, splenorenal shunts (the most prominent intra-abdominal shunts) of BDL rats, and mesentery of sham and BDL rats. CB(2) receptor was up-regulated in splenorenal shunts of BDL rats. Both acute and chronic JWH-015 treatment reduced portal pressure and superior mesenteric arterial blood flow. Compared with vehicle, JWH-015 significantly alleviated portosystemic shunting and mesenteric vascular density in BDL rats, but not in sham rats. The concomitant use of JWH-015 and AM630 abolished JWH-015 effects. JWH-133, another CB(2) agonist, mimicked the JWH-015 effects. JWH-015 decreased mesenteric COX-1, COX-2 messenger RNA expressions, and COX-1, COX-2, eNOS protein expressions. Furthermore, JWH-015 decreased intrahepatic angiogenesis and fibrosis.

CONCLUSIONS

CB(2) agonist alleviates portal hypertension (PH), severity of portosystemic collaterals and mesenteric angiogenesis, intrahepatic angiogenesis, and fibrosis in cirrhotic rats. The mechanism is, at least partly, through COX and NOS down-regulation. CBs may be targeted in the control of PH and portosystemic collaterals.

Role of exogenous nitric oxide donor in treatment of decompensated hemorrhagic shock in normotensive and hypertensive rats

INTRODUCTION

In this study, we investigated the role of exogenous NO donor, sodium nitroprusside (SNP), on hemodynamic responses and survival rate during decompensated hemorrhagic shock in normotensive and hypertensive rat.

METHODS

Male wistar rats were divided into normotensive and hypertensive groups (n = 12 each). Then, the animals were subjected to decompensated hemorrhagic shock by withdrawing blood until the mean arterial pressure (MAP) reached to 40 mmHg. After the shock period, the animals were randomly assigned to SNP-treated (0.5 mg/kg) and control groups (n = 6 each). MAP and heart rate (HR) were monitored throughout the experiment and 60 min after the administration of drug. Serum NO concentrations were measured. The survival rate was counted during next 72 h.

RESULTS

Infusion of SNP caused no significant changes in MAP and HR in normotensive and hypertensive animals. Hemorrhagic shock increased serum NO concentration and SNP administration reduced serum NO concentration in either normotensive or hypertensive groups. Survival counts during 72 h after experiment did not improve by SNP administration, and there were no significant differences between normotensive and hypertensive groups.

CONCLUSION

SNP administration cannot improve hemodynamic responses and survival count during decompensated hemorrhagic shock in normotensive and hypertensive animals.

Hemodynamic responses and serum nitrite concentration during uncontrolled hemorrhagic shock in normotensive and hypertensive rats

BACKGROUND

We evaluated the effect of hypertension on hemodynamic responses and serum nitrite concentrations in normotensive (NT) and deoxycorticosteron acetate (DOCA)-Salt hypertensive (HT) rats.

METHODS

Uncontrolled hemorrhagic shock was induced in NT and HT rats (n=7 each) by preliminary bleed of 25 ml/kg followed by a 75% tail amputation. The mean arterial pressure (MAP), heart rate and serum nitrite were measured pre-hemorrhage and during hemorrhage.

RESULTS

Changes in time-averaged MAP after hemorrhage were significantly greater in HT group than NT. After resuscitation, the HT rats failed to restore MAP to baseline level. Serum nitrite level in both groups was significantly increased during shock period. Survival rate of HT animals was lower than NT group, although it was not statistically significant.

CONCLUSIONS

Marked reduction of MAP and less improvement after resuscitation suggested the less adaptation of cardiovascular system in HT animals which may interfere with management of these subjects during uncontrolled hemorrhagic shock.

The roles of angiotensin II receptors in the portosystemic collaterals of portal hypertensive and cirrhotic rats

BACKGROUND/AIMS

In liver cirrhosis/portal hypertension, collaterals as varices may bleed and are influenced by vasoresponsiveness. An angiotensin blockade ameliorates portal hypertension but the influence on collaterals is unknown.

METHODS

Portal hypertension and cirrhosis were induced by portal vein (PVL) and common bile duct ligation (BDL). Hemodynamics, real-time PCR of angiotensin II receptors (AT(1)R, AT(2)R) in the left adrenal vein (LAV, sham) and splenorenal shunt derived from LAV (PVL, BDL) were performed. With an in situcollateral perfusion model, angiotensin II vasoresponsiveness with different preincubations was evaluated: (1) vehicle; (2) AT(1)R blocker losartan; (3) losartan plus nonselective nitric oxide synthase (NOS) inhibitor (N(ω)-nitro-L-arginine); (4) AT(2)R blocker PD123319; (5) PD123319 plus N(ω)-nitro-L-arginine; (6) N(ω)-nitro-L-arginine, and (7) losartan plus inducible NOS inhibitor aminoguanidine.

RESULTS

LAV AT(1)R and AT(2)R expression decreased in PVL and BDL rats. Losartan attenuated angiotensin II-elicited vasoconstriction but PD123319 had no effect. N(ω)-nitro-L-arginine but not aminoguanidine reversed the losartan effect.

CONCLUSIONS

Angiotensin receptors are downregulated in the collateral vessel of portal hypertensive and cirrhotic rats. The AT(1)R blockade attenuates the angiotensin II vasoconstrictive effect, suggesting AT(1)R mediates collateral vasoconstriction and the influence of AT(2)R is negligible. The lack of aminoguanidine influence indicates that endothelial NOS participates in the losartan effect.

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.

Microarray analysis of differentially expressed background genes in rats following hemorrhagic shock

To uncover the contribution of the diversity of the genetic backgrounds to the pathogenesis of hemorrhagic shock, we employed male Sprague-Dawley rats to establish a controlled 2.5 ml/100 g total body weight fixed-volume hemorrhagic shock and left lobular hepatectomy model. RNA was isolated from the liver samples taken from the rats (survival group: rats survived over 24 h after shock; and dead group: rats died within 1 h after shock, n = 3 per group), and subjected to microarray using the illumina(TM) chips for rat cDNA (27,342 genes, >700,000 probes). The results demonstrated that the rats had about 50% survival rate and 100 genes were identified differentially expressed in the two groups. Of these genes, 47 genes were up-regulated and 53 genes down-regulated. Real-time PCR confirmed the differential expression for Aldh1a1, Aldh1a7, Aoc3, Cyp26al, Hdc and Ephx2 genes. Pathway analysis revealed that these genes are involved in circadian rhythm, beta-Alanine metabolism, histidine metabolism, biosynthesis of unsaturated fatty acids, glycine, serine and threonine metabolism, vitamin B6 metabolism, as well as arginine and proline metabolism. Therefore, our study provided a global molecular view on the contribution of genetic backgrounds to the response to hemorrhagic shock.

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.

Beneficial effects of activation of PKC on hemorrhagic shock in rats

BACKGROUND

The reduced vascular reactivity after severe trauma or shock played an important role in the development and outcome of shock. Our previous study showed that protein kinase C (PKC) took part in the regulation of vascular reactivity after hemorrhagic shock. The objective of this study was to investigate the protective effects of activation of PKC on hemorrhagic shock and its related mechanism.

METHODS

Sprague dawley rats were subjected to hemorrhagic shock (40 mm Hg for 2 hours). Effects of the PKC agonist, phorbol-12-myristate-13-acetate (PMA), and its inhibitor, staurosporine, on hemodynamic parameters were observed in vivo or in vitro. The hemodynamic parameters included mean arterial blood pressure, left intraventricular systolic pressure, the maximal change rate of left intraventricular pressure (+/-dp/dtmax), blood gases including pH, Po2, Sao2, and base excess, animal survival time, the vascular reactivity and calcium sensitivity of superior mesenteric artery, and mitochondrial function and blood flow of liver and kidney.

RESULTS

Intravenous administration of PKC agonist, PMA, at the concentration of 1 microg/kg significantly increased the mean arterial blood pressure, left intraventricular systolic pressure, +/-dp/dtmax, the pressor effect, and the contractile response of norepinephrine, it also improved the blood gases, and prolonged the survival time of shocked rats. In addition, the intravenous administration of PMA improved mitochondrial function and liver and kidney blood flow. A total of 10(-7) mol/L of PMA administrated in vitro significantly improved the vascular reactivity and calcium sensitivity of superior mesenteric artery to norepinephrine and Ca2+. These effects of PMA were abolished by the PKC specific inhibitor staurosporine (1 microg/kg in vivo or 10(-7) mol/L in vitro).

CONCLUSION

Activation of PKC has protective effects on hemorrhagic shock. The mechanism is related not only to its hemodynamic stabilization effect via improving vascular reactivity and calcium sensitivity but also to its effect on improving the perfusion and mitochondrial function of vital organs.

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.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Effect of biliary tract external drainage on cytokine expression and histomorphology of intestine, liver, and lung in rats with hemorrhagic shock

OBJECTIVE

To investigate the protective effect of biliary tract external drainage on cytokine expression and pathomorphism of intestine, liver, and lung in rats with hemorrhagic shock.

DESIGN

Randomized, control animal study.

SETTING

This study was conducted at The Institution Digestive Surgery Research Laboratory of Shanghai Jiao Tong University.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Biliary tract external drainage was performed by inserting a cannula into the bile duct. Hemorrhagic shock was induced by drawing blood from the carotid artery.

MEASUREMENTS AND MAIN RESULTS

Twenty-four Sprague-Dawley rats were randomized to three equal groups of eight: sham shock; hemorrhagic shock; and hemorrhagic shock plus bile duct drainage. The messenger RNA expression of tumor necrosis factor-alpha, interleukin-6 in the intestine, liver, and lung tissue from the three groups were analyzed by reverse transcription-polymerase chain reaction. Tumor necrosis factor-alpha was analyzed in the bile of the rats by enzyme-linked immunosorbent assay. Histology of intestine, liver, and lung was performed in all groups by hematoxylin and eosin staining. The messenger RNA expression of tumor necrosis factor-alpha was significantly increased in the hemorrhagic shock group compared with the sham shock group (intestine 0.54 +/- 0.07 vs. 0.37 +/- 0.05, liver 1.01 +/- 0.06 vs. 0.56 +/- 0.07, lung 0.94 +/- 0.07 vs. 0.62 +/- 0.06). The messenger RNA expression of interleukin-6 was also significantly increased in the hemorrhagic shock group compared with the sham shock group (intestine 0.89 +/- 0.12 vs. 0.50 +/- 0.09, liver 1.07 +/- 0.10 vs. 0.57 +/- 0.12, lung 1.09 +/- 0.09 vs. 0.67 +/- 0.06). Biliary tract external drainage reduced significantly the messenger RNA expression of tumor necrosis factor-alpha (intestine 0.43 +/- 0.06 vs. 0.54 +/- 0.07, liver 0.74 +/- 0.18 vs. 1.01 +/- 0.06, lung 0.87 +/- 0.15 vs. 0.94 +/- 0.07) and interleukin-6 (intestine 0.60 +/- 0.11 vs. 0.89 +/- 0.12, liver 0.71 +/- 0.16 vs. 1.07 +/- 0.10, lung 0.88 +/- 0.25 vs. 1.09 +/- 0.09). The concentration of tumor necrosis factor-alpha in bile was significantly higher in the hemorrhagic shock group compared with the sham shock group (31.22 +/- 6.44 ng/mL vs. 15.49 +/- 3.64 ng/mL, p < .01). The histologic observation of the intestine, liver, and lung showed that the biliary tract external drainage significantly attenuate the putrescence and exfoliation of intestinal villi, denaturation and putrescence of hepatocytes, edema, and inflammatory cells infiltration of lung.

CONCLUSIONS

Biliary tract external drainage decreases the messenger RNA expression of tumor necrosis factor-alpha, interleukin-6 and attenuate the tissue injury of the intestine, liver, and lung in rats model of hemorrhagic shock. The gut-liver axis was implicated to play a crucial role in hemorrhagic shock-induced multiple organ dysfunction syndrome.

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.

Effect of Nippostrongylus brasiliensis L3 ES on inflammatory mediator gene transcription in lipopolysaccharide lung inflammation

The anti-inflammatory properties of parasitic helminths have been largely linked to their excretory-secretory (ES) products. Some studies have noted a lack of TNF-alpha production and limited recruitment of neutrophils into the lungs after Nippostrongylus brasiliensis infection. We previously reported that instillation of ES from L3 larvae of N. brasiliensis to the lungs could inhibit the recruitment of neutrophils on a background of LPS-induced inflammation. A similar reduction in neutrophil recruitment was observed in this study. This reduction was associated with the significant inhibition in gene transcription of the adhesion molecule, ICAM-1, and the chemokine, MIP-2 in bronchoalveolar lavage (BAL) cells. The LPS-stimulated gene transcription of the pro-inflammatory cytokines TNF-alpha and IL-1beta was also significantly reduced by L3 ES. Inducible nitric oxide synthase (iNOS) is normally elevated in classically activated macrophages, however, in this case gene transcription of iNOS was inhibited by L3 ES and may suggest a phenotype change to anti-inflammatory. The general inhibition of pro-inflammatory mediators observed in this study suggests that infective stage L3 larvae excrete and/or secrete inhibitory products capable of modifying the normally potent LPS inflammatory response.

Effect of porto-systemic shunting on NOS expression after extended hepatectomy in rats

AIM

Several surgical procedures have been developed for reducing portal vein pressure to prevent postoperative liver injury. Nitric oxide synthase expression (NOS) induced by elevation of portal vein pressure is thought to play an important role in liver regeneration, but the details are not well understood.

METHODS

Rats in the control group and in the subcutaneous splenic transposition (SST) group underwent 90% partial hepatectomy. Survival and portal vein pressure were analyzed. The serum IL-6 and TNF-alpha levels were measured by enzyme-linked immunosorbent assay (ELISA). Hepatocyte proliferation and apoptosis 12 hours after hepatectomy were analyzed immunohistochemically. The protein and messenger RNA expression of inducible and endothelial NOS were analyzed using Western blotting and quantitative reverse transcriptase polymerase chain reaction, respectively.

RESULTS

The survival rate of the SST group was significantly higher. Portal vein pressure, TNF-alpha level and the apoptotic index were significantly lower in the SST group. Twelve hours after surgery, liver inducible NOS (iNOS) protein expression was significantly lower in the SST group. However, protein expression of endothelial NOS was not significantly different between the groups.

CONCLUSION

Inducible NOS expression after extended hepatectomy is related to the effects of porto-systemic shunting on the splanchnic circulation. Also, iNOS induction and concomitant nitric oxide generation appear to participate in the cytotoxicity of excessive portal pressure after extended hepatectomy.

Early organ-specific endothelial activation during hemorrhagic shock and resuscitation

Multiple organ dysfunction syndrome (MODS) is a complication of hemorrhagic shock (HS) and related to high morbidity and mortality. Interaction of activated neutrophils and endothelial cells is considered to play a prominent role in the pathophysiology of MODS. Insight in the nature and molecular basis of endothelial cell activation during HS can assist in identifying new rational targets for early therapeutic intervention. In this study, we examined the kinetics and organ specificity of endothelial cell activation in a mouse model of HS. Anesthetized male mice were subjected to controlled hemorrhage to a MAP of 30 mmHg. Mice were killed after 15, 30, 60, or 90 min of HS. After 90 min of hemorrhagic shock, a group of mice was resuscitated with 6% hydroxyethyl starch 130/0.4. Untreated mice and sham shock mice that underwent instrumentation and 90 min of anesthesia without shock served as controls. Gene expression levels of inflammatory endothelial cell activation (P-selectin, E-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1) and hypoxia-responsive genes (vascular endothelial growth factor and hypoxia-inducible factor 1alpha) were quantified in kidney, liver, lung, brain, and heart tissue by quantitative reverse-transcription-polymerase chain reaction. Furthermore, we examined a selection of these genes with regard to protein expression and localization using immunohistochemical analysis. Induction of inflammatory genes occurred early during HS and already before resuscitation. Expression of adhesion molecules was significantly induced in all organs, albeit to a different extent depending on the organ. Endothelial genes CD31 and VE-cadherin, which function in endothelial cell homeostasis and integrity, were not affected during the shock phase except for VE-cadherin in the liver, which showed increased mRNA levels. The rapid inflammatory activation was not paralleled by induction of hypoxia-responsive genes. This study demonstrated the occurrence of early and organ-specific endothelial cell activation during hemorrhagic shock, as presented by induced expression of inflammatory genes. This implies that early therapeutic intervention at the microvascular level may be a rational strategy to attenuate MODS.