Effects of dexamethasone andl-canavanine on the intracellular calcium-contraction relation of the rat tail artery during septic shock

Diclofenac and dexamethasone modulate the effect of cannabidiol on the rat colon motility ex vivo

Introduction

Due to the growing interest in the use of cannabinoids in supportive therapies, they are increasingly used together with anti-inflammatory drugs. Cannabinoids inhibit gastrointestinal motility, while steroidal and nonsteroidal anti-inflammatory drugs influence motility in other ways. The aim of the research was to study the interactions between cannabidiol (CBD) and these two classes of anti-inflammatory drugs in the context of gastrointestinal motility. Dexamethasone (DEX) was selected as a steroidal drug and diclofenac (DCF) as a nonsteroidal counterpart.

Material and Methods

The experiments were performed on isolated rat colon strips in isometric conditions. The contractile response to acetylcholine (ACh) (1 μM) was measured with no substance applied as a control value and was measured after application of CBD (80 μM), DEX (100 μM), DCF (100 μM), or a combination of these substances.

Results

Cannabidiol strongly inhibited intestinal motility mediated by ACh application, DCF inhibited it non-significantly, while DEX intensified it. When CBD was co-administered with DEX, the combination inhibited intestinal motility non-significantly relative to the ACh-only control. Co-administration of CBD with DCF inhibited motility more than when these substances were administered separately.

Conclusion

Inhibition of the intestinal response to ACh is likely due to the synergistic effect of CBD and endogenous cannabinoids. Dexamethasone lessened the inhibitory effect of CBD, likely because of diminished availability of the arachidonic acid necessary for endogenous cannabinoid synthesis. However, diclofenac may increase endogenous cannabinoid synthesis, because of the greater availability of arachidonic acid caused by DCF blocking the cyclooxygenation pathway.

Steroid use after cardiac arrest is associated with favourable outcomes: a systematic review and meta-analysis

Background

The effect of steroid use on outcomes in patients with cardiac arrest (CA) remains controversial. We systematically reviewed the literature to investigate whether steroid use after CA increased the return of spontaneous circulation (ROSC) rate and survival to discharge in patients with CA.

Methods

PubMed, Embase, CNKI, and the Cochrane Central Register of Controlled Trials were searched for randomized controlled trials (RCTs) and observational studies on the effect of steroid use on outcomes in adults with CA. The outcomes were ROSC and survival to discharge.

Results

Seven studies (four RCTs and three observational studies) were included. Pooled analysis suggested that steroid use was associated with increased ROSC in patients with CA. Steroid use was significantly associated with survival to discharge, which was a consistent finding in RCTs and observational studies. Subgroup analysis based on the time of drug administration (during cardiopulmonary resuscitation [CPR] vs. after CA) showed that steroid use during CPR and after CA were significantly associated with an increased rate of ROSC and survival to discharge.

Conclusion

Current evidence indicates that steroid use after CA could increase ROSC and survival to discharge in patients with CA. However, high-quality and adequately powered RCTs are warranted.

Impaired Ca(2+) Homeostasis and Decreased Orai1 Expression Modulates Arterial Hyporeactivity to Vasoconstrictors During Endotoxemia

We hypothesized that SIRS/endotoxemia-associated hyporesponsiveness to vasoconstrictors is mediated by smaller increases in intracellular Ca(2+) levels due to reduced signaling via the STIM/Orai. Male Wistar rats were injected either with saline or bacterial LPS (i.p.; 10 mg/kg), and experiments were performed 24 h later. LPS-injected rats exhibited decreased systolic blood pressure, increased heart rate, neutrophils' migration into the peritoneal cavity, and elevated alanine aminotransferase levels. Additionally, second-order mesenteric arteries from endotoxemic rats displayed hyporeactivity to contractile agents such as phenylephrine and potassium chloride; decreased contractile responses to Ca(2+); reduced contraction during Ca(2+) loading; and smaller intracellular Ca(2+) stores. Decreased Orai1, but not STIM1, expression was found in resistance mesenteric arteries from LPS-treated rats. Additionally, cultured vascular smooth muscle cell (VSMC) treated with LPS resulted in increased TLR-4 expression, but Myd-88 and STIM-1 expression were not changed. Our data suggest that in endotoxemia, Ca(2+) homeostasis is disrupted in VSMC, with decreased Ca(2+) influx, smaller concentrations of Ca(2+) in the sarcoplasmic reticulum, and decreased activation of Orai1. Abnormal Ca(2+) handling contributes to LPS-associated vascular hyporeactivity.

Corticosteroid therapy in refractory shock following cardiac arrest: a randomized, double-blind, placebo-controlled, trial

Background

The purpose of this study was to determine whether the provision of corticosteroids improves time to shock reversal and outcomes in patients with post-cardiac arrest shock.

Methods

We conducted a randomized, double-blind trial of post-cardiac arrest patients in shock, defined as vasopressor support for a minimum of 1 hour. Patients were randomized to intravenous hydrocortisone 100 mg or placebo every 8 hours for 7 days or until shock reversal. The primary endpoint was time to shock reversal.

Results

Fifty patients were included with 25 in each group. There was no difference in time to shock reversal between groups (hazard ratio: 0.83 [95 % CI: 0.40–1.75], p = 0.63). We found no difference in secondary outcomes including shock reversal (52 % vs. 60 %, p = 0.57), good neurological outcome (24 % vs. 32 %, p = 0.53) or survival to discharge (28 % vs. 36 %, p = 0.54) between the hydrocortisone and placebo groups. Of the patients with a baseline cortisol < 15 ug/dL, 100 % (6/6) in the hydrocortisone group achieved shock reversal compared to 33 % (1/3) in the placebo group (p = 0.08). All patients in the placebo group died (100 %; 3/3) whereas 50 % (3/6) died in the hydrocortisone group (p = 0.43).

Conclusions

In a population of cardiac arrest patients with vasopressor-dependent shock, treatment with hydrocortisone did not improve time to shock reversal, rate of shock reversal, or clinical outcomes when compared to placebo.

Clinical trial registration

Clinicaltrials.gov: NCT00676585, registration date: May 9, 2008.

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.

Effects of L-canavanine and ozone on vascular reactivity in septicemic rats

Septicemia leads to oxidative stress with overproduction of reactive-oxygen species (ROS) and consumption of endogenous antioxidant enzymes. We tested a twofold hypothesis: (1) does oxidative stress (OxS) induced by sepsis acting alone or in concert with augmented inflammatory processes contributes to sepsis-related vascular dysfunction, and, (2) whether ozone (O(3)) and L-canavanine (CAV) mitigate the negative impact of the aforementioned phenomena. We investigated the relative impact of treatment with CAV and/or O(3) on vascular OxS associated vascular functional changes in septicemic rats. For this study, 60 male Sprague-Dawley rats were used and divided into six experimental groups (n = 10): control group (C), sham-operated (Sham), septicemic rats (S), S rats treated with CAV (100 mg/kg. i.p; S + CAV), S rats treated with O(3) (1.2 mg/kg, i.p.; S + O(3)) and S rats treated with both O(3) and CAV (S + O(3) + CAV). After 22 h, the mean arterial blood pressure (MAP), the aortic ring vascular reactivity to phenylephrine, abdominal aortic blood flow (AABF), serum tumor necrosis factor-alpha (TNF-alpha) and plasma nitrite/nitrate (NOx) concentration were measured. In addition, hepatic antioxidant enzyme activities sodium dismutase (SOD) and glutathione peroxidase (GSH-Px) were estimated. Septicemia caused significant elevation of serum TNF-alpha (p < 0.001) and plasma NOx (p < 0.001) and significant (p < 0.001) reduction of AABF (p < 0.001), aortic vascular response to phenylephrine (p < 0.001), MAP (p < 0.001) and hepatic SOD and GSH-Px activity (p < 0.001) compared with the C group, while treatment with O(3) and/or CAV induced significant amelioration of all those increases. Abnormalities were attenuated to a similar extent with treatment with both O(3) and CAV. These results suggested that concomitant administration of O(3) and CAV alleviated the compromised vascular reactivity in septicemic conditions and prevent its progression into septic shock compared with each alone.

beta2- but not beta1-adrenoceptor activation modulates intracellular oxygen availability

beta-Adrenoceptors (beta-ARs) play a critical role in the regulation of cardiovascular function. Intracellular oxygen homeostasis is crucial for the survival of cardiomyocytes. However, it is still unclear whether beta-AR activation can modulate intracellular oxygen. Here we used mitochondrial and cytosolic target Renilla luciferase to detect intracellular oxygen concentration. Pharmacological experiments revealed that beta2-AR activation specifically regulates intracellular oxygen in cardiomyocytes and COS7 cells. This effect was abrogated by inhibitory G protein (Gi) inhibition, endothelial nitric oxide synthase (eNOS) blockade, and NO scavenging, implicating that the beta2-AR-Gi-eNOS pathway is involved in this regulation. beta2-AR activation increased the AMP/ATP ratio, AMPK activity, ROS production and prolyl hydroxylase activity. These effects also contribute to the regulation of beta2-AR signalling, thus providing an additional layer of complexity to enforce the specificity of beta1-AR and beta2-AR signalling. Collectively, the study provides novel insight into the modulation of oxygen homeostasis, broadens the scope of beta2-AR function, and may have crucial implications for beta2-AR signalling regulation.

The Rho-A/Rho-kinase pathway is up-regulated but remains inhibited by cyclic guanosine monophosphate-dependent mechanisms during endotoxemia in small mesenteric arteries

OBJECTIVE

We investigated whether a reduced activity in the Rho-A/Rho-kinase pathway could be involved in the impaired vascular reactivity observed in septic shock.

DESIGN

Ex vivo animal study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Rats received an intraperitoneal injection of lipopolysaccharide (LPS, 10 mg/kg) either 6 or 24 hours before the onset of our experiments. The effects of Y-27632 (a Rho-kinase inhibitor) were assessed in first-order mesenteric rings taken from these animals using wire myograph. The expression of Rho-A, Rho-kinases I and II, and the total and phosphorylated myosin phosphatase targeting subunit 1 (MYPT1) were assessed by Western blotting.

MEASUREMENTS AND MAIN RESULTS

The EC50 to Y-27632 was reduced from 2.10 microM (1.22-3.66 microM) (control) to 0.21 microM (0.09-0.44 microM), and 9.54 (0.82-110.30) nM in LPS-treated groups 6 and 24 hours, respectively. The increased potency of Y-27632 was partially reversed by endothelium removal at both 6 and 24 hours. Incubation of Nomega-nitro-l-arginine methyl ester hydrochloride or 1400W (a nonselective and an inducible nitric oxide synthase inhibitor, respectively) normalized the responses to Y-27632 seen 6 hours after LPS. However, 1400W had no effect, whereas Nomega-nitro-l-arginine methyl ester hydrochloride caused a partial reduction in the enhanced potency of Y-27632 found 24 hours after LPS. The soluble guanylate cyclase inhibitor oxadiazolo[4,3-alpha]quinoxalin-1-one was able to bring the Y-27632 response back to normal both 6 and 24 hours after LPS. Rho-A, Rho-kinase I, Rho-kinase II, and MYPT1 were increased in mesenteric arteries from endotoxemic rats, but the phosphorylated MYPT1 was significantly reduced. However, incubation with oxadiazolo[4,3-alpha]quinoxalin-1-one circumvented the inhibition of MYPT1 phosphorylation found in preparations from LPS-treated animals.

CONCLUSIONS

Our findings revealed an impaired Rho-A/Rho-kinase-mediated phosphorylation of MYPT1 in vessels from endotoxemic animals in a cyclic guanosine monophosphate-dependent manner, suggesting that changes in mechanisms involved in calcium sensitization play a pivotal role in cardiovascular changes observed in septic shock.

Relative adrenal insufficiency in post-cardiac arrest shock is under-recognized

INTRODUCTION

Suppression of the adrenal axis may occur frequently in post-cardiac arrest patients. Physiological doses of corticosteroids have been shown to reverse hypotension and decrease mortality in other forms of shock. We sought to investigate current clinical practice pertaining to the evaluation for relative adrenal insufficiency in post-cardiac arrest shock.

METHODS

We performed a retrospective analysis of post-cardiac arrest patients in an urban emergency department. Inclusion criteria included pre-hospital cardiac arrest patients over the age of 18 with a sustained return of spontaneous circulation that required vasopressor support. Exclusion criteria were traumatic arrest and cardiac arrest in the presence of healthcare personnel. The primary endpoint was the percent of patients in refractory shock that either had their adrenal axis tested or were treated for presumed relative adrenal insufficiency. Data analysis was descriptive in nature.

RESULTS

A total of 79 post-cardiac arrest patients were analyzed. Of the 79 patients, 69 were vasopressor-dependent. Of this group, 13% (9/69) had a cortisol level checked (with or without cosyntropin stimulation). Of those who had a cosyntropin stimulation test performed, 86% met biochemical criteria for relative adrenal insufficiency. Seventeen percent of vasopressor-dependent patients received corticosteroids explicitly for their shock state. Overall, only 32% of patients in refractory shock had testing for relative adrenal insufficiency or received corticosteroids for shock.

CONCLUSIONS

Though vasopressor-dependent shock is common in post-cardiac arrest patients, adrenal insufficiency was not considered in the majority of cases.