iNOS gene expression modulates microvascular responsiveness in endotoxin-challenged mice

Luteolin improves vasoconstriction function and survival of septic mice via AMPK/NF-κB pathway

Septic shock, the leading cause of death in sepsis, is related to vasoconstriction dysfunction. To investigate the effects of Luteolin (LTL), a flavonoid polyphenol compound, on vasoconstriction dysfunction in septic mice and the underlying mechanism, cecal ligation and puncture (CLP) surgery was performed on wild-type C57BL/6 mice to induce septic shock. Mice were intraperitoneally injected with 0.2 mg/kg LTL within 10 min after CLP surgery with or without 20 mg/kg Compound C (AMPK inhibitor) (CC) 1 h before CLP surgery, and re-administrated every 12 h. The survival rate, systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and mean arterial pressure (MAP) were explored. After the mice were sacrificed, the vasoconstriction function, inflammatory indicators, and possible regulatory signaling pathways were examined. Our data showed that CLP decreased the survival rate, SAP, DAP, MAP, vasoconstriction function, and expression of ADRA1A and p-AMPK/AMPK, as well as increased the mRNA expression of inflammatory cytokines and iNOS, the serum levels of inflammatory cytokines, and the levels of iNOS, p-p65/p65, and p-IκBα/IκBα in aortas (P < 0.05), which could be reversed by LTL treatment (P < 0.05). However, inhibition of AMPK could abolish the protective effects of LTL (P < 0.05). In conclusion, our study manifested that LTL could prevent vasoconstriction dysfunction and increase survival of septic mice via activating AMPK, which suggested that LTL could be a novel therapeutic option for patients with sepsis.

Luteolin alleviates vascular dysfunctions in CLP-induced polymicrobial sepsis in mice

BACKGROUND

Luteolin, a naturally occurring flavonoid, is thought to have health-promoting properties as a part of human diet and has been reported to possess a wide range of pharmacological activities. Therefore, the present study was undertaken to evaluate the effect of luteolin pre-treatment on vascular dysfunctions in sepsis induced by caecal ligation and puncture (CLP) in the mouse model.

METHODS

Mice were divided into four groups: sham, luteolin plus sham, CLP, and luteolin plus CLP. Luteolin was administered (0.2 mg/kg body weight) intraperitoneally one hour (h) before CLP surgery in mice. 20 ± 2 h post CLP surgery, the isolated thoracic aorta of mice was assessed for its vascular reactivity to noradrenaline (NA) and acetylcholine (ACh). To explore the underlying mechanism, aortic mRNA expressions of α_1D adrenoceptors, eNOS and iNOS were investigated.

RESULTS

In mice with CLP-induced sepsis luteolin pre-treatment markedly increased the survival time and attenuated serum lactate level. The CLP group manifested the reduced vascular reactivity to NA and this deficit was restored by luteolin pre-treatment. However, luteolin pre-treatment did not improve α_1D adrenoceptors down-regulation observed in septic mice aorta. In the presence of 1400 W, the NA contractile response was significantly restored in CLP mice aortic tissue in comparison with the respective control of septic mice and further enhanced in the presence of luteolin. Luteolin reduced the iNOS mRNA expression and iNOS-derived nitrite production. Pre-treatment with luteolin restored the endothelial dysfunction in septic mice aorta by improving eNOS mRNA expression and enhanced eNOS-derived nitric oxide (NO) production in septic mice aorta and aortic iNOS gene expression and inducible NO production.

CONCLUSION

The present study suggests that the vasoplegic state to NA in aorta was restored through the iNOS pathway and endothelial dysfunction was reversed via eNOS and NO production pathway.

Prohibitin-1 Is a Dynamically Regulated Blood Protein With Cardioprotective Effects in Sepsis

Background In sepsis, circulating cytokines and lipopolysaccharide elicit mitochondrial dysfunction and cardiomyopathy, a major cause of morbidity and mortality with this condition. Emerging research places the PHB1 (lipid raft protein prohibitin-1) at the nexus of inflammation, metabolism, and oxidative stress. PHB1 has also been reported in circulation, though its function in this compartment is completely unknown. Methods and Results Using a wide-ranging approach across multiple in vitro and in vivo models, we interrogated the functional role of intracellular and circulating PHB1 in the heart during sepsis, and elucidated some of the mechanisms involved. Upon endotoxin challenge or sepsis induction in rodent models, PHB1 translocates from mitochondria to nucleus in cardiomyocytes and is secreted into the circulation from the liver in a manner dependent on nuclear factor (erythroid-derived 2)-like 2, a key transcriptional regulator of the antioxidant response. Overexpression or treatment with recombinant human PHB1 enhances the antioxidant/anti-inflammatory response and protects HL-1 cardiomyocytes from mitochondrial dysfunction and toxicity from cytokine stress. Importantly, administration of recombinant human PHB1 blunted inflammation and restored cardiac contractility and ATP production in mice following lipopolysaccharide challenge. This cardioprotective, anti-inflammatory effect of recombinant human PHB1 was determined to be independent of nuclear factor (erythroid-derived 2)-like 2, but partially dependent on PI3K/AKT  signaling in the heart. Conclusions These findings reveal a previously unknown cardioprotective effect of PHB1 during sepsis, and illustrate a pro-survival, protective role for PHB1 in the circulation. Exploitation of circulating PHB1 as a biomarker and/or therapeutic could have widespread benefit in the clinical management of sepsis and other severe inflammatory disorders.

Mechanistic insights into the protective impact of zinc on sepsis

Sepsis, a systemic inflammation as a response to a bacterial infection, is a huge unmet medical need. Data accumulated over the last decade suggest that the nutritional status of patients as well as composition of their gut microbiome, are strongly linked with the risk to develop sepsis, the severity of the disease and prognosis. In particular, the essential micronutrient zinc is essential in the resistance against sepsis and has shown to be protective in animal models as well as in human patients. The potential mechanisms by which zinc protects in sepsis are discussed in this review paper: we will focus on the inflammatory response, chemotaxis, phagocytosis, immune response, oxidative stress and modulation of the microbiome. A full understanding of the mechanism of action of zinc may open new preventive and therapeutic interventions in sepsis.

Effects of SPAK on vascular reactivity and nitric oxide production in endotoxemic mice

Vasoplegia impedes therapeutic interventions to restore vascular tone, leading to severe hypotension, poor tissue perfusion, and multiple organ failure in septic shock. High levels of circulating nitric oxide (NO) play a crucial role in endotoxin-induced vascular hyporeactivity. Proinflammatory cytokines have been implicated in the induction of inducible NO synthase and overproduction of NO. Anti-inflammatory therapy can diminish NO formation and improve vascular hyporeactivity in septic shock. STE20/SPS1-realted proline/alanine-rich kinase (SPAK) has been reported to activate mitogen-activated protein kinase and contribute to intestinal inflammation. Thus, we evaluated the roles of SPAK in NO production and vascular hyporeactivity in endotoxemic animals. Male wild-type and SPAK deficiency mice were intraperitoneally administered vehicle or Escherichia coli lipopolysaccharide (LPS, 50mg/kg). The changes of systolic blood pressure and plasma nitrate and nitrite levels were measured during the experimental period. Thoracic aortas were exercised to assess vascular reactivity and SPAK expression. In the present study, mice in endotoxin model showed severe hypotension and hyporeactivity to serotonin, phenylephrine (PE), and acetylcholine in the aortic rings. Phosphorylated SPAK expression in the aorta and NO levels in the plasma were also increased in animals with endotoxic shock. However, deletion of SPAK not only reduced the elevation of NO levels but also improved vascular hyporeactivity to serotonin and PE in endotoxemic mice. Taken together, SPAK could be involved in the NO overproduction and vascular hyporesponsiveness to vasoconstrictors in endotoxic shock. Thus, inhibition of SPAK could be useful in the prevention of endotoxin-induced vascular hyporeactivity.

Oxidative stress in sepsis: Pathophysiological implications justifying antioxidant co-therapy

Sepsis is one of the main causes of death among critically ill patients. Sepsis pathogenesis includes infection by gram-negative and gram-positive bacteria, fungi, or both; exacerbated inflammatory response; hypotension, with potential to cause vasodilatory shock; and lesser delivery of oxygen to tissues due to impairment of oxygen utilization by cells. The participation of reactive species and/or free radicals such as nitric oxide (NO), peroxynitrite (ONOO^-), superoxide (O₂^-), hydrogen peroxide (H₂O₂), and hydroxyl radical (OH) has been reported to underlie these effects. Mitochondrial dysfunction is related to loss of inner membrane potential and inhibition of the mitochondrial electron transfer chain and FoF1-adenosine triphosphate-synthase, resulting in cellular energetic failure. In addition, overproduction of NO due to inducible nitric oxide synthase (iNOS) activity has been associated with harmful effects such as general vasodilatation and hypo-responsiveness to therapeutic vasoconstrictor agents. Considering that iNOS expression is regulated by nuclear factor-κB, which may be activated by ROS, antioxidants could inhibit the overexpression of iNOS in sepsis. In line with this, several antioxidants such as vitamins C and E, polyphenols, melatonin, β-glucan, N-acetylcysteine, mitochondrion-targeted antioxidants (MitoQ, MitoE, and peptides associated with dimethyltyrosine), selenium salts, and organoselenium compounds were effective in ameliorating oxidative stress in animal models of sepsis and in a number of clinical trials with septic patients.

Glutathione Supplementation Attenuates Oxidative Stress and Improves Vascular Hyporesponsiveness in Experimental Obstructive Jaundice

We investigated the protective effects and mechanism of glutathione (GSH) on vascular hyporesponsiveness induced by bile duct ligation (BDL) in a rat model. Seventy-two male Sprague-Dawley rats were randomly divided into four groups: a NS group, a GSH group, a BDL + NS group, and a BDL + GSH group. GSH was administrated into rats in the GSH and BDL + GSH groups by gastric gavage. An equal volume of normal saline was, respectively, given in the NS group and BDL + NS group. Blood was gathered for serological determination and thoracic aorta rings were isolated for measurement of isometric tension. Obstructive jaundice led to a significant increase in the serum total bilirubin, AST, and ALT levels. The proinflammatory cytokines levels (TNF-α and IL-1β), concentration of NO, and oxidative stress markers (MDA and 3-NT) were increased as well. All of those were reduced by the treatment of GSH. Meanwhile, contraction of aorta rings to NA and vasorelaxation to ACh or SNP in the BDL group rats were markedly decreased, while GSH administration reversed this change. Our findings suggested that GSH supplementation attenuated overexpressed ONOO(−) from the reaction of excessive NO with O₂^∙- and protected against obstructive jaundice-induced vascular hyporesponsiveness in rats.

Combined treatment with atorvastatin and imipenem improves survival and vascular functions in mouse model of sepsis

We have recently reported that pre-treatment, but not the post-treatment with atorvastatin showed survival benefit and improved hemodynamic functions in cecal ligation and puncture (CLP) model of sepsis in mice. Here we examined whether combined treatment with atorvastatin and imipenem after onset of sepsis can prolong survival and improve vascular functions. At 6 and 18h after sepsis induction, treatment with atorvastatin plus imipenem, atorvastatin or imipenem alone or placebo was initiated. Ex vivo experiments were done on mouse aorta to examine the vascular reactivity to nor-adrenaline and acetylcholine and mRNA expressions of α1D AR, GRK2 and eNOS. Atorvastatin plus imipenem extended the survival time to 56.00±4.62h from 20.00±1.66h observed in CLP mice. The survival time with atorvastatin or imipenem alone was 20.50±1.89h and 27.00±4.09h, respectively. The combined treatment reversed the hyporeactivity to nor-adrenaline through preservation of α1D AR mRNA/protein expression and reversal of α1D AR desensitization mediated by GRK2/Gβγ pathway. The treatment also restored endothelium-dependent relaxation to ACh through restoration of aortic eNOS mRNA expression and NO availability. In conclusion, combined treatment with atorvastatin and imipenem exhibited survival benefit and improved vascular functions in septic mice.

Glycyrrhetinic acid reverses the lipopolysaccharide-induced hypocontractility to noradrenaline in rat aorta: implications to septic shock

Septic shock and associated vascular hyporeactivity to vasoconstrictor agonists remain a major problem of critical care medicine. Here we report that glycyrrhetinic acid (GA), the active component of licorice, effectively restores vascular contractility in the model of lipopolysaccharide (LPS)-treated rat aorta. GA was as effective as the NO synthase inhibitor N(G)-nitroarginine methylester. GA did not affect the vascular NO levels (measured by EPR spin trapping) and relaxations to L-arginine in LPS-treated rings as well as relaxation to S-nitroso-N-acetylpenicillamine in control rings. Thus, GA may represent an interesting alternative to NO synthase inhibitors in sepsis-associated vascular dysfunction.

Methylprednisolone stiffens aortas in lipopolysaccharide-induced chronic inflammation in rats

Introduction

Glucocorticoids are commonly used as therapeutic agents in many acute and chronic inflammatory and auto-immune diseases. The current study investigated the effects of methylprednisolone (a synthetic glucocorticoid) on aortic distensibility and vascular resistance in lipopolysaccharide-induced chronic inflammation in male Wistar rats.

Methods

Chronic inflammation was induced by implanting a subcutaneous slow-release ALZET osmotic pump (1 mg kg⁻¹ day⁻¹ lipopolysaccharide) for either 2 or 4 weeks. Arterial wave transit time (τ) was derived to describe the elastic properties of aortas using the impulse response function of the filtered aortic input impedance spectra.

Results

Long-term lipopolysaccharide challenge enhanced the expression of advanced glycation end products (AGEs) in the aortas. Lipopolysaccharide also upregulated the inducible form of nitric oxide synthase to produce high levels of nitric oxide (NO), which resulted in vasodilation, as evidenced by the fall in total peripheral resistance (R_p). However, lipopolysaccharide challenge did not influence the elastic properties of aortas, as shown by the unaltered τ. The NO-mediated vascular relaxation may counterbalance the AGEs-induced arterial stiffening so that the aortic distensibility remained unaltered. Treating lipopolysaccharide-challenged rats with methylprednisolone prevented peripheral vasodilation because of its ability to increase R_p. However, methylprednisolone produced an increase in aorta stiffness, as manifested by the significant decline in τ. The diminished aortic distensibility by methylprednisolone paralleled a significant reduction in NO plasma levels, in the absence of any significant changes in AGEs content.

Conclusion

Methylprednisolone stiffens aortas and elastic arteries in lipopolysaccharide-induced chronic inflammation in rats, for NO activity may be dominant as a counteraction of AGEs.

Role of active nitrogen molecules in progression of septic shock

INTRODUCTION

Active nitrogen molecules are formed as a result of cell metabolism. They are essential for cell metabolism, but when produced in excess, they contribute to the pathogenesis of several disease processes. These nitrogen molecules play an important role in vascular instability of septic shock. This study was planned to detect the role of active nitrogen molecules in the progression of septic shock.

MATERIALS AND METHODS

Blood samples were collected from 118 critically ill patients admitted in ICU and from 95 healthy relatives accompanying the patients. Patients were categorized into three groups: systemic inflammatory response syndrome (n = 54), sepsis (n = 35) and septic shock (n = 29). Plasma total nitrite (nitrites and nitrates), cytokines like tumour necrosis factor-α (TNF-α) and plasma lactate were measured to assess inflammatory activity and severity of septic shock.

RESULTS

High plasma levels of nitrite and nitrate (No₂-/No₃-) were observed in critically ill patients (mean level 78.92 μmol/l in sepsis and 97.20 μmol/l in septic shock). Mean plasma TNF-α level in sepsis was 213.50 pg/ml and septic shock was 227.38 pg/ml.

CONCLUSION

Plasma No₂-/No₃- and TNF-α levels were high in patients with sepsis and septic shock, which increased with severity of sepsis.

Effects of a selective iNOS inhibitor versus norepinephrine in the treatment of septic shock

Inhibition of NOS is not beneficial in septic shock; selective inhibition of the inducible form (iNOS) may represent a better option. We compared the effects of the selective iNOS inhibitor BYK191023 with those of norepinephrine (NE) in a sheep model of septic shock. Twenty-four anesthetized, mechanically ventilated ewes received 1.5 g/kg body weight of feces into the abdominal cavity to induce sepsis. Animals were randomized into three groups (each n = 8): NE-only, BYK-only, and NE + BYK. The sublingual microcirculation was evaluated with sidestream dark-field videomicroscopy. MAP was higher in the NE + BYK group than in the other groups, but there were no significant differences in cardiac index or systemic vascular resistance. Mean pulmonary arterial pressure was lower in BYK-treated animals than in the NE-only group. PaO2/FiO2 was higher and lactate concentration lower in the BYK groups than in the NE-only group. Mesenteric blood flow was higher in BYK groups than in the NE-only group. Renal blood flow was higher in the NE + BYK group than in the other groups. Functional capillary density and proportion of perfused vessels were higher in the BYK groups than in the NE-only group 18 h after induction of peritonitis. Survival times were similar in the three groups. In this model of peritonitis, selective iNOS inhibition had more beneficial effects than NE on pulmonary artery pressures, gas exchange, mesenteric blood flow, microcirculation, and lactate concentration. Combination of this selective iNOS inhibitor with NE allowed a higher arterial pressure and renal blood flow to be maintained.

Nitric oxide signaling in brain function, dysfunction, and dementia

Nitric oxide (NO) is an important signaling molecule that is widely used in the nervous system. With recognition of its roles in synaptic plasticity (long-term potentiation, LTP; long-term depression, LTD) and elucidation of calcium-dependent, NMDAR-mediated activation of neuronal nitric oxide synthase (nNOS), numerous molecular and pharmacological tools have been used to explore the physiology and pathological consequences for nitrergic signaling. In this review, the authors summarize the current understanding of this subtle signaling pathway, discuss the evidence for nitrergic modulation of ion channels and homeostatic modulation of intrinsic excitability, and speculate about the pathological consequences of spillover between different nitrergic compartments in contributing to aberrant signaling in neurodegenerative disorders. Accumulating evidence points to various ion channels and particularly voltage-gated potassium channels as signaling targets, whereby NO mediates activity-dependent control of intrinsic neuronal excitability; such changes could underlie broader mechanisms of synaptic plasticity across neuronal networks. In addition, the inability to constrain NO diffusion suggests that spillover from endothelium (eNOS) and/or immune compartments (iNOS) into the nervous system provides potential pathological sources of NO and where control failure in these other systems could have broader neurological implications. Abnormal NO signaling could therefore contribute to a variety of neurodegenerative pathologies such as stroke/excitotoxicity, Alzheimer's disease, multiple sclerosis, and Parkinson's disease.

Up-regulation of G-protein-coupled receptors for endothelin and thromboxane by lipid-soluble smoke particles in renal artery of rat

Up-regulation of G-protein-coupled receptors (GPCR) plays key roles in renal hypertension and cardiovascular disease pathogenesis. The present study was designed to examine if lipid-soluble cigarette smoking particles (DSP), nicotine and endotoxin (LPS), induce GPCR up-regulation for thromboxane A(2) (TP), endothelin type A (ET(A) ) and type B (ET(B) ) receptors in renal artery, and if intracellular signal mechanisms are involved. Renal artery segments of rats were exposed to DSP, nicotine or LPS, in organ culture for up to 24 hr. The GPCR-mediated contractions were recorded by using a myograph system. Expression of the GPCR was examined by real-time PCR and immunohistochemistry at mRNA and protein levels. Sarafatoxin 6c (S6c, selective ET(B) receptor agonist), endothelin-1 (ET-1, non-selective ET(A) and ET(B) receptor agonist) and 9,11-Dideoxy-9a,11a-methanoepoxy prostaglandin F(2a) (U46619, a TP receptor agonist) induced contractions were significantly increased after the arterial segments exposed to DSP in a concentration-dependent (0.1-0.4 μl/ml) manner, and S6c also induced a time-dependent contraction, compared to control (dimethyl sulfoxide). This was in parallel with enhanced mRNA expression for ET(B) receptor but not ET(A) and TP receptors, while increased protein expression for ET(A) , ET(B) and TP receptors was seen. The specific nuclear factor-kappa B (NF-κB) signal pathway inhibitor BMS345541 was applied to link DSP effects to the GPCR up-regulation. It totally abolished ET(B) receptor up-regulation, but not ET(A) and TP receptor up-regulations. Our results suggest that DSP transcriptionally up-regulated ET(B) receptor expression in rat renal artery via NF-κB signal pathways, whereas up-regulation of ET(A) and TP receptor-mediated contraction may involve post-transcriptional mechanisms.

Vascular hyporesponsiveness to vasopressors in septic shock: from bench to bedside

PURPOSE

To delineate some of the characteristics of septic vascular hypotension, to assess the most commonly cited and reported underlying mechanisms of vascular hyporesponsiveness to vasoconstrictors in sepsis, and to briefly outline current therapeutic strategies and possible future approaches.

METHODS

Source data were obtained from a PubMed search of the medical literature with the following MeSH terms: Muscle, smooth, vascular/physiopathology; hypotension/etiology; shock/physiopathology; vasodilation/physiology; shock/therapy; vasoconstrictor agents.

RESULTS

Nitric oxide (NO) and peroxynitrite are crucial components implicated in vasoplegia and vascular hyporeactivity. Vascular ATP-sensitive and calcium-activated potassium channels are activated during shock and participate in hypotension. In addition, shock state is characterized by inappropriately low plasma glucocorticoid and vasopressin concentrations, a dysfunction and desensitization of alpha-receptors, and an inactivation of catecholamines by oxidation. Numerous other mechanisms have been individualized in animal models, the great majority of which involve NO: MEK1/2-ERK1/2 pathway, H(2)S, hyperglycemia, and cytoskeleton dysregulation associated with decreased actin expression.

CONCLUSIONS

Many therapeutic approaches have proven their efficiency in animal models, especially therapies directed against one particular compound, but have otherwise failed when used in human shock. Nevertheless, high doses of catecholamines, vasopressin and terlipressin, hydrocortisone, activated protein C, and non-specific shock treatment have demonstrated a partial efficiency in reversing sepsis-induced hypotension.

A pivotal role of endothelial-specific NF-kappaB signaling in the pathogenesis of septic shock and septic vascular dysfunction

Although the role of NF-kappaB in the pathogenesis of sepsis and septic shock has been extensively studied, little is known about the causative contribution of endothelial-intrinsic NF-kappaB to these pathological processes. In this study, we used transgenic (TG) mice (on FVB genetic background) that conditionally overexpress the NF-kappaB inhibitor, mutant I-kappaBalpha, selectively on endothelium and their transgene-negative littermates (wild type (WT)) to define the causative role of endothelial-specific NF-kappaB signaling in septic shock and septic vascular dysfunction. In WT mice, LPS challenge caused systemic hypotension, a significantly blunted vasoconstrictor response to norepinephrine, and an impaired endothelium-dependent vasodilator response to acetylcholine, concomitant with a markedly increased aortic inducible NO synthase expression, significantly elevated plasma and aortic levels of nitrite/nitrate, increased aortic TNF-alpha expression, and decreased aortic endothelial NO synthase (eNOS) expression. In TG mice whose endothelial NF-kappaB was selectively blocked, LPS caused significantly less hypotension and no impairments in vasoconstrictor and endothelium-dependent vasodilator responses, associated with significantly reduced aortic inducible NO synthase expression, decreased plasma and aortic levels of nitrite/nitrate, reduced aortic TNF-alpha expression, and increased aortic eNOS expression. TNF-alpha knockout mice prevented LPS-induced eNOS down-regulation. WT mice subjected to cecal ligation and puncture showed significant systemic hypotension, which was prevented in TG mice. Our data show that selective blockade of endothelial-intrinsic NF-kappaB pathway is sufficient to abrogate the cascades of molecular events that lead to septic shock and septic vascular dysfunction, demonstrating a pivotal role of endothelial-specific NF-kappaB signaling in the pathogenesis of septic shock and septic vascular dysfunction.

Molecular events in the cardiomyopathy of sepsis

Septic cardiomyopathy is a well-described complication of severe sepsis and septic shock. However, the interplay of its underlying mechanisms remains enigmatic. Consequently, we constantly add to our pathophysiological understanding of septic cardiomyopathy. Various cardiosuppressive mediators have been discovered, as have multiple molecular mechanisms (alterations of myocardial calcium homeostasis, mitochondrial dysfunction, and myocardial apoptosis) that may be involved in myocardial dysfunction during sepsis. Finally, the detrimental roles of nitric oxide and peroxynitrite have been unraveled. Here, we describe our present understanding of systemic, supracellular, and cellular molecular mechanisms involved in sepsis-induced myocardial suppression.

Effects of a common human gene variant of extracellular superoxide dismutase on endothelial function after endotoxin in mice

A common gene variant in the heparin-binding domain (HBD) of extracellular superoxide dismutase (ECSOD) may predispose human carriers to ischaemic heart disease. We have demonstrated that the HBD of ECSOD is important for ECSOD to restore vascular dysfunction produced by endotoxin. The purpose of this study was to determine whether the gene variant in the HBD of ECSOD (ECSOD(R213G)) protects against endothelial dysfunction in a model of inflammation. We constructed a recombinant adenovirus that expresses ECSOD(R213G). Adenoviral vectors expressing ECSOD, ECSOD(R213G) or beta-galactosidase (LacZ, a control) were injected i.v. in mice. After 3 days, at which time the plasma SOD activity is maximal, vehicle or endotoxin (lipopolysaccharide or LPS, 40 mg kg(-1)) was injected i.p. Vasomotor function of aorta in vitro was examined 1 day later. Maximal relaxation to sodium nitroprusside was similar in aorta from normal and LPS-treated mice. Maximal relaxation to acetylcholine (10(-5)) was impaired after LPS and LacZ (63 +/- 3%, mean +/- s.e.m.) compared to normal vessels (83 +/- 3%) (P < 0.05). Gene transfer of ECSOD improved (P < 0.05) relaxation in response to acetylcholine (76 +/- 5%) after LPS, whereas gene transfer of ECSOD(R213G) had no effect (65 +/- 4%). Superoxide was increased in aorta (measured using lucigenin and hydroethidine) after LPS, and levels of superoxide were significantly reduced following ECSOD but not ECSOD(R213G). Thus, ECSOD reduces superoxide and improves relaxation to acetylcholine in the aorta after LPS, while the ECSOD variant R213G had minimal effect. These findings suggest that, in contrast to ECSOD, the common human gene variant of ECSOD fails to protect against endothelial dysfunction produced by an inflammatory stimulus.

Decreased intrahepatic response to alpha(1)-adrenergic agonists in lipopolysaccharide-treated rats is located in the sinusoidal area and depends on Kupffer cell function

BACKGROUND AND AIM

Livers from lipopolysaccharide-treated rats have a decreased vascular response to alpha(1)-adrenergic agonists due to an increased production of nitric oxide. Kupffer cells play a central role in the development of intrahepatic microvascular abnormalities during endotoxemia. We investigated the role of Kupffer cells in the intrahepatic vascular tone control in normal and endotoxemic rats.

METHOD

Twenty-four hours after pretreatment with gadolinium chloride (to eliminate/inactivate Kupffer cells) or saline, rats were treated with lipopolysaccharide or a second dose of saline. Six hours later, rats (under deep anesthesia) were submitted to liver perfusion with Krebs-Henseleit solution using a system that allowed the measurement of both perfusion and sinusoidal pressures. Dose-response curves to methoxamine (alpha(1)-adrenergic agonist) were obtained in the absence or the presence of the nitric oxide synthase inhibitor N-monomethyl-L-arginine.

RESULTS

Pretreatment with gadolinium did not change the intrahepatic vascular response to methoxamine in normal livers. Livers from lipopolysaccharide-treated rats showed a decreased sinusoidal vascular response to methoxamine and a 10-fold increase in nitric oxide production during liver perfusion. Either pretreatment with gadolinium or the presence of N-monomethyl-L-arginine in the perfusate restored the response to methoxamine and decreased the nitric oxide overproduction by more than 50%.

CONCLUSIONS

Kupffer cells neither mediate nor modulate the intrahepatic vascular response to alpha(1)-adrenergic agonists in normal livers. Reduction in intrahepatic vascular response to alpha(1)-adrenergic agonists in livers from lipopolysaccharide-treated rats is located in the sinusoidal area and depends on Kupffer cell function.

Live and let die: asymmetric dimethylarginine and septic shock

Nitric oxide (NO) is an important mediator of host defence and of vascular tone. In septic shock, upregulation of inducible NO synthase leads to the production of vast amounts of NO, which contribute to pathogen elimination but also to inappropriate vasodilation and to loss of vascular resistance. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthases shown to contribute to the regulation of vascular tone. ADMA was recently identified as a marker of organ dysfunction and mortality in intensive care patients and as a novel cardiovascular risk factor. In the present issue of Critical Care, a study by O'Dwyer and colleagues identifies ADMA as a potential regulator of NO production in septic shock. Being an inhibitor of NO production, ADMA may at least partly counteract pathological hypotension, but at the same time may impair the NO-dependent host defence. A mechanism is proposed by which the interplay between ADMA and inducible NO synthase activity is mediated. ADMA levels should be determined in future studies evaluating the regulation of NO in the intensive care setting.

Decreased vasopressin responsiveness in vasodilatory septic shock-like conditions

OBJECTIVE

To determine the effect of vasodilatory septic shock-like conditions on vasoconstricting responses to vasopressin and norepinephrine in isolated resistance arteries.

DESIGN

Prospective, randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Male adult Sprague-Dawley rats.

INTERVENTIONS

Small mesenteric arteries (outside diameter, 50-150 microm) were cannulated and studied in vitro under physiologic conditions. A vasodilatory septic shock-like state was produced by treatment with the nitric oxide (NO) donor, S-nitroso-N-acetylpenicillamine (SNAP), and the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX). Vasoconstricting concentration-response relationships were determined for norepinephrine and vasopressin before and after application of SNAP or SNAP+ IBMX. Synergism between low-dose vasopressin and norepinephrine and between low-dose norepinephrine and vasopressin was determined before and after SNAP or SNAP+IBMX.

MAIN RESULTS

Norepinephrine and vasopressin produced concentration-dependent contractions (half-maximal effective concentration [EC(50)] = 2.5 microM and 3.9 nM, respectively) that were significantly inhibited by 1 microM SNAP (EC(50) = 3.6 microM and 8.1 nM, respectively) or 100 microM SNAP + 10 microM IBMX (EC(50) = 10 microM and 8.2 nM, respectively). Low-dose vasopressin significantly increased the responsiveness to norepinephrine (EC50 = 0.5 microM) just as a low-dose norepinephrine significantly enhanced the vasopressin response (EC(50) = 2.3 nM). The synergistic effects of low-dose vasopressin and norepinephrine, or low-dose norepinephrine and vasopressin, were also significantly inhibited by 1 microM SNAP (EC(50) = 2.5 microM and 4.2 nM, respectively) or 100 microM SNAP + 10 microM IBMX (EC(50) = 9 microM and 8.4 nM, respectively).

CONCLUSIONS

Vasoconstriction produced by vasopressin or norepinephrine, and the synergistic vasoconstriction produced by the combinations, was inhibited in vasodilatory septic shock-like conditions. Thus, in addition to the well-described vasopressin deficiency in vasodilatory septic shock, these studies indicate that decreased vasopressin responsiveness further contributes to a state of relative vasopressin insufficiency in this condition.

Role of inducible nitric oxide synthase in the reduced responsiveness of the myocardium to catecholamines in a hyperdynamic, murine model of septic shock*

OBJECTIVES

Excess nitric oxide production is a key mediator of hypotension and catecholamine-resistance in septic shock. Although nitric oxide synthase blockade has been shown to restore hemodynamics, conflicting results on myocardial function were reported. Inducible nitric oxide synthase (iNOS) knockout (iNOS-/-) mice showed improved heart function, but these results were obtained during hypodynamic shock characterized by reduced cardiac output. Therefore, we investigated heart function and catecholamine responsiveness in a clinically relevant, murine model of cecal ligation and puncture (CLP)-induced septic shock.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

University animal research laboratory.

SUBJECTS

Male C57Bl/6 wild-type and iNOS-/- mice.

INTERVENTIONS

Fifteen hours after CLP, three groups of mice (wild-type controls, n = 9; iNOS-/-, n = 12; and wild-type mice receiving 5 mg x kg(-1) intraperitoneally of the selective iNOS inhibitor GW274150 immediately after CLP, n = 8) were anesthetized, mechanically ventilated, and instrumented (central venous and left ventricular pressure-conductance catheter). Measurements were recorded 18, 21, and 24 hrs post-CLP. Hydroxyethylstarch and norepinephrine were infused to achieve normotensive and hyperdynamic hemodynamics.

MEASUREMENTS AND MAIN RESULTS

There was no intergroup difference in mean arterial pressure, stroke volume, and left ventricular ejection fraction. Norepinephrine doses required to achieve the hemodynamic targets were lower in GW274150 (p < .001 vs. controls) and even further reduced in iNOS-/- mice (p < .001 vs. controls, p < .001 vs. GW274150). In the control group, the higher norepinephrine doses resulted in significantly higher heart rates and consequently cardiac output, maximal contraction, and relaxation than in the GW274150 and iNOS-/- animals. Left ventricular end-diastolic volume was also significantly higher in the controls than in the GW274150 and iNOS-/- mice, whereas left ventricular end-diastolic pressure did not differ.

CONCLUSIONS

Our results confirm septic shock-related impaired left ventricular function. Genetic iNOS deletion and pharmacologic iNOS blockade enhanced cardiac norepinephrine responsiveness due to improved systolic function. In contrast, iNOS inhibition seemed to be affiliated with compromised left ventricular relaxation.

The effects of nitric oxide in acute lung injury

Acute lung injury (ALI) is a common clinical problem associated with significant morbidity and mortality. Ongoing clinical and basic research and a greater understanding of the pathophysiology of ALI have not been translated into new anti-inflammatory therapeutic options for patients with ALI, or into a significant improvement in the outcome of ALI. In both animal models and humans with ALI, there is increased endogenous production of nitric oxide (NO) due to enhanced expression and activity of inducible NO synthase (iNOS). This increased presence of iNOS and NO in ALI contributes importantly to the pathophysiology of ALI. However, inhibition of total NO production or selective inhibition of iNOS has not been effective in the treatment of ALI. We have recently suggested that there may be differential effects of NO derived from different cell populations in ALI. This concept of cell-source-specific effects of NO in ALI has potential therapeutic relevance, as targeted iNOS inhibition specifically to key individual cells may be an effective therapeutic approach in patients with ALI. In this paper, we will explore the potential role for endogenous iNOS-derived NO in ALI. We will review the evidence for increased iNOS expression and NO production, the effects of non-selective NOS inhibition, the effects of selective inhibition or deficiency of iNOS, and this concept of cell-source-specific effects of iNOS in both animal models and human ALI.

Vascular interleukin-10 protects against LPS-induced vasomotor dysfunction

We tested the hypotheses that 1) systemic IL-10, after adenoviral gene transfer, protects arteries from impaired relaxation produced by LPS; 2) local expression of IL-10 within the arterial wall protects against vasomotor dysfunction after LPS; and 3) IL-10 protects against vascular dysfunction mediated by inducible NO synthase (iNOS) after LPS. In IL-10-deficient (IL-10−/−) and wild-type (WT, IL-10+/+) mice, LPS in vivo impaired relaxation of arteries to acetylcholine and gene transfer of IL-10 improved responses to acetylcholine. Superoxide levels were elevated in arteries after LPS, and increased levels of superoxide were prevented by gene transfer of IL-10. In arteries incubated with a low concentration of LPS in vitro to eliminate systemic effects of LPS and IL-10 from nonvascular sources, responses to acetylcholine were impaired in IL-10-deficient mice and impairment was largely prevented by gene transfer in vitro of IL-10. In arteries from WT mice in vitro, the low concentration of LPS did not impair responses to acetylcholine. Thus IL-10 within the vessel wall protects against LPS-induced dysfunction. In IL-10-deficient mice, aminoguanidine, which inhibits iNOS, protected against vasomotor dysfunction after LPS. In arteries from iNOS-deficient mice, LPS did not impair responses to acetylcholine. These findings suggest that both systemic and local effects of IL-10 provide important protection of arteries against an inflammatory stimulus and that IL-10 decreases iNOS-mediated impairment of vasorelaxation after LPS.

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

BACKGROUND

Our previous work observed that vascular hyporeactivity to norepinephrine (NE) developed after hemorrhage and the response was not the same in the 4 arteries examined. To evaluate possible mechanisms involved, the present study investigated the gene expression of iNOS, eNOS, IL-1beta, IL-6, TNF-alpha, and endothelin-1 in the corresponding organs, and the roles of nitric oxide (NO) and endothelin (ET).

MATERIALS AND METHODS

LAnesthetized rats (n=7/time point/group) were hemorrhaged to a mean arterial pressure of 50 mmHg for 60 min. The vascular reactivity of the superior mesenteric (SMA), celiac (CA), left renal (LRA), and left femoral arteries (LFA) to NE was measured at baseline, at the end of the hypotensive period (E), and at 1, 2, and 4 h later in the three groups (hemorrhage, hemorrhage+NG-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, or hemorrhage+PD142893, an ET receptor antagonist). Gene expression in ileum, left kidney, liver, and skeletal muscle was determined by quantitative RT-PCR at these times.

RESULTS

Vascular reactivity of SMA, CA, LRA, and LFA to NE decreased as much as 98% over 4 h compared with baseline. This loss of responsiveness in CA and LFA was more severe than in SMA and LRA. Gene expression of iNOS, eNOS, IL-1beta, IL-6, TNF-alpha, and endothelin-1 in the corresponding organs of select vasculatures increased markedly over baseline levels and the fold increase in mRNA levels of these enzymes and mediators in liver and skeletal muscle was higher than in ileum and left kidney. For example, at 4 h, iNOS expression was over 16-fold higher than baseline in liver and skeletal muscle, but 5- and 7-fold higher in ileum and kidney, respectively. L-NAME or PD142893 partially attenuated the decreased vascular reactivity induced by hemorrhagic shock and attenuated the changes in gene expression observed.

CONCLUSION

These findings suggest that the differential expression of NOS, cytokines, and endothelin-1 in different organs are associated with the development of vascular hyporeactivity after hemorrhagic shock and may account, at least in part, for the vascular bed diversity observed.

Signal transduction by the lipopolysaccharide receptor, Toll-like receptor-4

An understanding of lipopolysaccharide (LPS) signal transduction is a key goal in the effort to provide a molecular basis for the lethal effect of LPS during septic shock and point the way to novel therapies. Rapid progress in this field during the last 6 years has resulted in the discovery of not only the receptor for LPS - Toll-like receptor 4 (TLR4) - but also in a better appreciation of the complexity of the signalling pathways activated by LPS. Soon after the discovery of TLR4, the formation of a receptor complex in response to LPS, consisting of dimerized TLR4 and MD-2, was described. Intracellular events following the formation of this receptor complex depend on different sets of adapters. An early response, which is dependent on MyD88 and MyD88-like adapter (Mal), leads to the activation of nuclear factor-kappaB (NF-kappaB). A later response to LPS makes use of TIR-domain-containing adapter-inducing interferon-beta (TRIF) and TRIF-related adapter molecule (TRAM), and leads to the late activation of NF-kappaB and IRF3, and to the induction of cytokines, chemokines, and other transcription factors. As LPS signal transduction is an area of intense research and rapid progress, this review is intended to sum up our present understanding of the events following LPS binding to TLR4, and we also attempt to create a model of the signalling pathways activated by LPS.

Reduction of nitric oxide synthase 2 expression by distamycin A improves survival from endotoxemia

NO synthase 2 (NOS2) plays an important role in endotoxemia through overproduction of NO. Distamycin A (Dist A) belongs to a class of drugs termed minor-groove DNA binders, which can inhibit transcription factor binding to AT-rich regions of DNA. We and others have previously shown that AT-rich regions of DNA surrounding transcription factor binding sites in the NOS2 promoter are critical for NOS2 induction by inflammatory stimuli in vitro. Therefore, we hypothesized that Dist A would attenuate NOS2 up-regulation in vivo during endotoxemia and improve animal survival. C57BL/6 wild-type (WT) mice treated with Dist A and LPS (endotoxin) showed significantly improved survival compared with animals treated with LPS alone. In contrast, LPS-treated C57BL/6 NOS2-deficient (NOS2-/-) mice did not benefit from the protective effect of Dist A on mortality from endotoxemia. Treatment with Dist A resulted in protection from hypotension in LPS-treated WT mice, but not in NOS2-/- mice. Furthermore, LPS-induced NOS2 expression was attenuated in vivo (WT murine tissues) and in vitro (primary peritoneal and RAW 264.7 murine macrophages) with addition of Dist A. Dist A selectively decreased IFN regulatory factor-1 DNA binding in the enhancer region of the NOS2 promoter, and this IFN regulatory factor-1 site is critical for the effect of Dist A in attenuating LPS induction of NOS2. Our data point to a novel approach in modulating NOS2 expression in vivo during endotoxemia and suggest the potential for alternative treatment approaches for critical illness.

Ascorbate protects against impaired arteriolar constriction in sepsis by inhibiting inducible nitric oxide synthase expression

Compromised microvascular responsiveness is one of the key factors associated with mortality of septic patients. The present study addresses the mechanism of protection by ascorbate against impaired vasoconstriction in septic mice. Sepsis (i.e., cecal ligation and puncture (CLP) model) elevated both plasma protein carbonyl (i.e., an index of oxidative stress) and plasma nitrite/nitrate (NOx) levels, reduced baseline mean arterial blood pressure (MABP), and inhibited the MABP pressor response to angiotensin II (Ang II) at 6 h post-CLP. At the microvascular level, sepsis increased the inducible nitric oxide synthase (iNOS) mRNA level in cremaster muscle arterioles (18-25 microm diameter) at 3 h post-CLP, and impaired vasoconstriction to Ang II in these arterioles at 6 h post-CLP. At 24 h post-CLP, sepsis resulted in 9% survival. An intravenous bolus of ascorbate (200 mg/kg body wt) given 30 min prior to CLP prevented the protein carbonyl and NOx increases, partially restored the baseline arterial pressure, and completely protected against all arteriolar iNOS mRNA increases, arteriolar constriction hyporesponsiveness, and pressor response impairment. Survival increased to 65%. In septic mice, iNOS gene knockout resulted in protection of arteriolar constriction and pressor responses identical to that provided by ascorbate. Ascorbate bolus given 3 h post-CLP protected against the increase in plasma NOx concentration and against the pressor response impairment. We conclude that ascorbate may protect arteriolar vasoconstrictor responsiveness in sepsis by inhibiting excessive NO production.

Gene transfer of extracellular superoxide dismutase improves relaxation of aorta after treatment with endotoxin

Lipopolysaccharide (LPS) impairs vascular function, in part by generation of reactive oxygen species. One goal of this study was to determine whether gene transfer of extracellular SOD (ECSOD) improves vascular responsiveness in LPS-treated rats. A second goal was to determine whether effects of ECSOD are dependent on the heparin-binding domain of the enzyme, which facilitates binding of ECSOD to the outside of cells. Adenoviruses containing ECSOD (AdECSOD), ECSOD with deletion of its heparin-binding domain (AdECSOD-HBD), or a control virus (AdLacZ) were injected intravenously into rats. Three days later, vehicle or LPS (10 mg/kg ip) was injected. After 24 h, vascular reactivity was examined in aortic rings in vitro. Maximum relaxation to acetylcholine was 95 +/- 1% (means +/- SE) after AdlacZ plus vehicle and 77 +/- 3% after AdlacZ plus LPS (P < 0.05). Responses to calcium ionophore A-23187 and submaximal concentrations of nitroprusside also were impaired by LPS. Gene transfer of ECSOD, but not AdECSOD-HBD, improved (P < 0.05) relaxation to acetylcholine and A-23187 after LPS. Maximum relaxation to acetylcholine was 88 +/- 3% after LPS plus AdECSOD. Superoxide was increased in aorta after LPS, and the levels were reduced after AdECSOD but not AdECSOD-HBD. LPS-induced adhesion of leukocytes to aortic endothelium was reduced by AdECSOD but not by AdECSOD-HBD. We conclude that after gene transfer in vivo, binding of ECSOD to arteries effectively decreases the numbers of adherent leukocytes and levels of superoxide and improves impaired endothelium-dependent relaxation produced by LPS.

From molecules to mammals: what's NOS got to do with it?

Nitric oxide synthases (NOSs) generate nitric oxide (NO) and the by-product l-citrulline, via the catalytic combination of l-arginine and molecular oxygen. In mammals, there are three NOS genes: nNOS (NOS1), iNOS (NOS2) and eNOS (NOS3). The molecular structure, enzymology and pharmacology of these enzymes have been well defined, and reveal critical roles for the NOS system in a variety of important processes. The studies of NOS enzymes using knockout and transgenic mouse models have provided an invaluable contribution, highlighting critical roles in neuronal, renal, pulmonary, gastro-intestinal, skeletal muscle, reproductive and cardiovascular biology. This review will outline the data gleaned from complementary knockout and transgenic over-expression models in mice, and focus on the interactions between NOS enzymes and pathophysiology of the vascular system. These studies are a paradigm for the near future, which will involve the translation of an enormous amount of genomic data into physiological insights that penetrate the realms of both health care and biology.

In vivo vascular effects of genistein on a rat model of septic shock induced by lipopolysaccharide

The aim of this study was to investigate the effects of in vivo administration of genistein on rat cardiovascular abnormalities induced by lipopolysaccharide (LPS). Four hours after injection, LPS (10 mg/kg) caused a stable fall in mean arterial pressure (13%) accompanied by ex vivo vascular hyporeactivity to noradrenaline (NA) and relaxation to l-arginine (L-arg), which were inhibited by previous incubation with l-NAME. Endotoxin also caused impairment of aortic relaxant response to acetylcholine, increase nitrite and malonaldehyde plasma levels by 8.6-fold and 2-fold, respectively, and induced aortic expression of inducible nitric-oxide synthase (iNOS) and nitrotyrosine protein. Genistein (1 mg/kg) and daidzein (1 mg/kg) reduced contractile response to NA in vascular tissue, but only genistein was able to inhibit hyporesponsiveness to NA, relaxation to l-arg, increase in nitrite plasma levels, and iNOS expression produced by endotoxin. Moreover, genistein restored impaired aortic relaxation to acetylcholine, lipid peroxidation, and suppressed long-term hypotension. In conclusion, genistein administrated in vivo prevents hypotension and vascular alterations induced by LPS. These protective effects are mediated by both its antioxidant properties and the inhibition of nitric oxide overproduction from de novo synthesis of iNOS due to its tyrosine kinase inhibitor effect.

Effects of iNOS-related NO on hearts exposed to liposoluble iron

Inducible nitric oxide synthase (iNOS) protects heart against ischemia/reperfusion injury. However, it is unknown whether the beneficial effects of iNOS are mediated by the interaction of NO with radical oxygen species (ROS). To address this issue, we examined the effects of liposoluble iron-induced ROS generation in isolated perfused hearts from rats treated with lipopolysaccharide (LPS). LPS administration (10 mg/kg, i.p., 6 h before heart removal) induced iNOS expression and increased NO production as indicated by a 3-fold elevation of nitrite level in coronary effluents relative to control hearts. An enhanced expression of hemeoxygenase 1 protein was also observed in septic hearts compared to control. Iron-induced perfusion and contractile deficits were ameliorated by LPS with more important coronary than myocardial benefits. In iron-loaded hearts, oxidative stress as measured by the 2,3 dihydroxybenzoic acid/salicylic acid concentration ratio in cardiac tissue was 23% lower in septic than in control heart although the difference did not reach significance. In addition, the presence of the NO synthase inhibitor N-nitro-L-arginine in the perfusion medium totally blocked NO production but did not reverse the protective effects of LPS. The results indicate that LPS protects from iron-induced cardiac dysfunction by mechanisms independent on ex vivo NO production and suggest that NO acts as a trigger rather than a direct mediator of the cardioprotective effects of LPS in heart exposed to iron.

Protection against lipopolysaccharide-induced endothelial dysfunction in resistance and conduit vasculature of iNOS knockout mice

Endothelial dysfunction is a characteristic of, and may be pathogenic in, inflammatory cardiovascular diseases, including sepsis. The mechanism underlying inflammation-induced endothelial dysfunction may be related to the expression and activity of inducible nitric oxide synthase (iNOS). This possibility was investigated in isolated resistance (mesenteric) and conduit (aorta) arteries taken from lipopolysaccharide (LPS)-treated (12.5 mg/kg i.v.) or saline-treated iNOS knockout (KO) and wild-type (WT) mice. LPS pretreatment (for 15 h, but not 4 h) profoundly suppressed responses to acetylcholine (ACh) and significantly reduced sensitivity to the NO donor spermine-NONOate (SPER-NO) in aorta and mesenteric arteries of WT mice. This effect was temporally associated with iNOS protein expression in both conduit and resistance arteries and with a 10-fold increase in plasma NOx levels. In contrast, no elevation of plasma NOx was observed in LPS-treated iNOS KO animals, and arteries dissected from these animals did not express iNOS or display hyporeactivity to ACh or SPER-NO. The mechanism underlying this phenomenon may be suppression of eNOS expression, as observed in arteries of WT animals, that was absent in arteries of iNOS KO animals. These results clearly demonstrate that iNOS induction plays an integral role in mediation of the endothelial dysfunction associated with sepsis in both resistance and conduit arteries.

Nitric oxide synthase inhibition as therapy for sepsis: a decade of promise

BACKGROUND

Inhibition of nitric oxide synthase (NOS) has held promise as a novel and important therapeutic target for sepsis for over a decade. However, the question as to whether an inhibitor of NOS will prove to be efficacious in human septic shock remains unanswered.

METHODS

Review of the pertinent English-language medical literature.

RESULTS

Observations of the induction of NOS (iNOS, NOS2) by proinflammatory cytokines led to the hypothesis that nitric oxide (NO) relaxes vascular smooth muscle, thereby producing vasodilation and hypotension in sepsis. Other effects of NO in vascular tone may be manifested by refractoriness to vasopressors or myocardial dysfunction. However, such negative effects of NO are balanced by the role of NO in maintaining microvascular perfusion and host defenses against invading pathogens. Initial animal studies of septic shock modulated by the administration of competitive inhibitors of NOS demonstrated that NOS inhibition might be beneficial therapy for clinical septic shock. However, subsequent animal studies have produced variable results, and a phase III clinical trial of a nonselective NOS inhibitor has failed to show benefit for therapy of septic shock.

CONCLUSION

A better understanding of the effects of NOS and its inhibitors is needed as is an understanding of the underlying pathophysiology of sepsis. Moreover, a nontoxic, short-acting, titratable, specific inhibitor of NOS2 has yet to be identified and tested. Until then, efforts should be designed to describe more completely the role of NO in the pathophysiology of sepsis.

Vasoconstrictor responsiveness of tail arteries from endotoxaemic rats

Continuous infusion of lipopolysaccharide in conscious rats mimics some aspects of cardiovascular dysfunction in septic shock. In the present study, contractile responsiveness of tail arteries taken from rats infused with lipopolysaccharide was investigated. Contractile responses to alpha,beta-methylene ATP and potassium chloride, but not to methoxamine, were greater after 24 h lipopolysaccharide infusion than in 2-h saline, 24-h saline and 2-h lipopolysaccharide groups. N(G)-nitro-L-arginine methyl ester augmented contractions to alpha,beta-methylene ATP and methoxamine in the 2-h saline, 24-h saline and 2-h lipopolysaccharide groups, but had no significant effect in the 24-h lipopolysaccharide group. Endothelium-independent vasorelaxant responses to sodium nitroprusside were greater in the 24-h lipopolysaccharide group compared to the other three groups. Relaxations to acetylcholine were not significantly different. In vitro incubation in medium containing lipopolysaccharide for 24 h had no significant effect on contractile responses of tail arteries compared to controls incubated in medium alone. These data indicate a possible impaired nitric oxide and/or endothelial function in tail arteries isolated from rats 24 h after lipopolysaccharide infusion. As hypercontractility was not evoked following in vitro incubation with lipopolysaccharide, the involvement of in vivo neurohumoral factors/mechanisms in the pathology of these changes is implicated.

Kidney disease, genotype and the pathogenesis of vasculopathy

PURPOSE OF REVIEW

The two leading causes of end-stage renal disease in the United States are diabetes mellitus and hypertensive nephrosclerosis, accounting for over two-thirds of all cases. In many patients both diseases are associated with small- and large-vessel disease, commonly attributed to hypertension or accelerated atherosclerosis. Recent investigations, however, have suggested that renal large-vessel and microvascular disease may be independent contributors to progressive kidney failure.

RECENT FINDINGS

Although genes have not been definitely linked to renal vascular disease, population- and family-based epidemiology of kidney disease, segregation analysis of Pima and Caucasian families in which diabetic nephropathy is clustered, and the positional cloning of genes responsible for rare, familial glomerulosclerosis syndromes support the hypothesis that genes regulate the pathogenesis of renal disease. This review highlights developments in our current understanding of vasculopathy and its role in renal disease, and it summarizes evidence suggesting that genetic determinants for the vascular phenotype are associated with common causes of chronic renal failure.

SUMMARY

With the application of genomics and proteomics methodologies to drug discovery, the identification of renal susceptibility genes should identify new mechanisms of progressive renal disease pathogenesis and generate novel target molecules for the treatment of kidney disease.

1-Benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole (YC-1) derivatives as novel inhibitors against sodium nitroprusside-induced apoptosis

Antiapoptotic agents based on 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole (22, YC-1) derivatives were explored for effective treatment of sepsis and septic shock. We found that compound 22, 1-benzyl-3-(5'-methoxymethyl-2'-furyl)indazole (27), and 1-phenyl-3-(5'-hydroxymethyl-2'-furyl)indazole (23) were the most effective inhibitors of sodium nitroprusside-induced vascular smooth muscle cell apoptosis. These three compounds are proposed as potential therapeutic agents for the treatment of sepsis.

The role of NOS in heart failure: lessons from murine genetic models

Nitric Oxide Synthases (NOSs) are a group of related proteins that produce nitric oxide (NO). In mammals, there are three known members of this gene family: nNOS (NOS1), iNOS (NOS2) and eNOS (NOS3). Each has been disrupted by targeted gene ablation in mice and the corresponding phenotypes examined. These mice have allowed an examination of the contribution of each NOS in a variety of experimental models and continue to provided insights into the patho-physiological role of NOS and NO. With increasing sophistication, murine transgenic approaches continue to offer a wealth of information, and invaluable tools to further study the NOS system. The focus of this review will be an examination of the tools available, and the insights gained from studies done on murine NOS genetic models in the context of heart failure.

Is nitric oxide overproduction the target of choice for the management of septic shock?

Sepsis is a heterogeneous class of syndromes caused by a systemic inflammatory response to infection. Septic shock, a severe form of sepsis, is associated with the development of progressive damage in multiple organs, and is a leading cause of patient mortality in intensive care units. Despite important advances in understanding its pathophysiology, therapy remains largely symptomatic and supportive. A decade ago, the overproduction of nitric oxide (NO) had been discovered as a potentially important event in this condition. As a result, great hopes arose that the pharmacological inhibition of NO synthesis could be developed into an efficient, mechanism-based therapeutic approach. Since then, an extraordinary effort by the scientific community has brought a deeper insight regarding the feasibility of this goal. Here we present in summary form the present state of knowledge of the biological chemistry and physiology of NO. We then proceed to a systematic review of experimental and clinical data, indicating an up-regulation of NO production in septic shock; information on the role of NO in septic shock, as provided by experiments in transgenic mice that lack the ability to up-regulate NO production; effects of pharmacological inhibitors of NO production in various experimental models of septic shock; and relevant clinical experience. The accrued evidence suggests that the contribution of NO to the pathophysiology of septic shock is highly heterogeneous and, therefore, difficult to target therapeutically without appropriate monitoring tools, which do not exist at present.