Effect of nitric oxide donors and nitric oxide synthase inhibitors in neonatal rat endotoxic shock

doi:10.1016/S0006-2952(99)00128-8

Biochemical Pharmacology

Volume 58, Issue 4, 15 August 1999, Pages 687-691

https://doi.org/10.1016/S0006-2952(99)00128-8 Get rights and content

Abstract

Previous studies have shown an increased mortality in response to endotoxin in 24-hr-old neonatal rats compared with older neonates and adults. This increased susceptibility may be related to increased nitric oxide (NO) and thromboxane (TxB₂₎ production. Twenty-four-hour-old neonatal rat pups were given either N^G-nitro-l-arginine methyl ester (l-NAME; a nonspecific NO synthase inhibitor), S-methylthioisourea (SMT; a specific NO synthase inhibitor), or molsidomine (a NO donor) subcutaneously prior to or after an ld₅₀ of intracardiac endotoxin. Mortality was followed for 72 hr. There was no statistically significant difference in mortality between control animals and those pretreated with l-NAME, SMT, or molsidomine. A trend toward increased mortality with nonspecific NO synthase inhibition and decreased mortality with the NO donor was noted. Splenic cells were obtained for in vitro cytokine stimulation studies. In vitro adherent splenic cell stimulation studies confirmed an increase in NO production with NO donor pretreatment and decreased production of NO with NO synthase inhibition pretreatment. There was no difference in TxB₂ production with either the NO synthase inhibitor or the NO donor. In conclusion, at the several doses employed, neither nonselective or selective NO synthase inhibitors nor NO donors prevented endotoxin-induced mortality in rat neonatal shock. Although these findings do not preclude possible involvement of NO in neonatal pathophysiology, increased NO production thus does not appear to be the primary determinant of the increased susceptibility of the neonatal rat to endotoxic shock.

Section snippets

Animals

All rats used in these experiments were housed in the facilities for laboratory animals provided by the Department of Laboratory Animal Resources. The Medical University of South Carolina laboratory animal care is in accordance with the National Institutes of Health guidelines. The Medical University of South Carolina has full accreditation from the American Association for the Accreditation of Laboratory Animal Care, effective November 5, 1987. Pregnant Sprague–Dawley rats were purchased from

Mortality studies

The percent of mortality of the neonatal pups in response to the various doses of l-NAME and molsidomine was determined (Table 1). The ld₅₀ of endotoxin in 24-hr-old neonatal rat pups was determined previously to be 0.024 mg/kg [17]. Increasing doses of l-NAME given prior to administration of an ld₅₀ of endotoxin did not cause a statistically significant change in mortality. However, the trend was toward a higher mortality with increasing doses of l-NAME pretreatment. Increasing doses of

Discussion

Previous work from our group demonstrated a profound sensitivity of 24-hr-old rats to endotoxic shock compared with adult rats [17]. Zeller et al.[21] also demonstrated an increased susceptibility of 10-day-old rats to endotoxin compared with adult rats. The increased susceptibility of neonates to infection is well established. However, the exact pathophysiologic mechanisms of this increased susceptibility to endotoxin and infection remain unclear. Klein et al.[22] demonstrated decreased

Acknowledgements

This work was supported, in part, by Children’s Hospital Fund Grant CR 21 and by National Institutes of Health Grant GM 27673.

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Citation Excerpt :
The list of these actions includes the prevention or reversal of the following abnormalities caused by the LPS challenge: depression of cardiac output (Fishman et al., 1997; Liaudet et al., 1996; Rosselet et al., 1998) and venous return (Fishman et al., 1997); altered microvascular permeability, leading to plasma extravasation and hypovolemia (Filep et al., 1997), endothelial dysfunction evaluated ex vivo in the aorta (Szabo et al., 1996a) and the pulmonary circulation (Fischer et al., 1999); loss of pulmonary vasoreactivity to inhaled NO (Holzmann et al., 1999); myocardial hypocontractility (Afulukwe et al., 2000; Ullrich et al., 2000); pulmonary edema (Heremans et al., 2000) and lung injury (Arkovitz et al., 1996; Fatehi-Hassanabad et al., 1996; Wang et al., 1999); liver injury (Kengatharan et al., 1996; Liaudet et al., 1997a, 1998; Ruetten et al., 1996; Szabo et al., 1994; Thiemermann et al., 1995; Wang et al., 1998); kidney dysfunction or injury (Fatehi-Hassanabad et al., 1996; Liaudet et al., 1997a; Schwartz et al., 1997; Szabo et al., 1994; Wu et al., 1996); injury to the gastrointestinal tract (Castaneda et al., 1999; Liaudet et al., 1997a) and pancreas (Liaudet et al., 1998; Ruetten et al., 1996; Wu et al., 1996); bacterial translocation from the gut lumen to the mesenteric lymph nodes (Unno et al., 1997); indications of tissue dysoxia such as systemic lactic acidosis (Liaudet et al., 1996, 1997a, 1997b; Rosselet et al., 1998); and reduced ATP content (Levy et al., 1999; Liaudet et al., 1997a) or mitochondrial respiration (Unno et al., 1997) in various organs. In contrast to observations made with nonselective compounds, administration of selective iNOS inhibitors to endotoxemic rodents decreased (Gryglewski et al., 1998; Liaudet et al., 1998; Szabo et al., 1994, 1996a; Takano et al., 1997; Tunctan et al., 1998; Wu et al., 1995; Yen et al., 1997) or did not change mortality (Cochran et al., 1999; Heremans et al., 2000; Koga et al., 1995; Yen et al., 1997), but never increased it. At least two studies support the finding that in endotoxemia, iNOS-derived NO may inhibit eNOS, leading to an endothelial dysfunction that may be reversed by selective iNOS inhibitors.
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.
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Chemotherapy and Metabolic InhibitorsEffect of nitric oxide donors and nitric oxide synthase inhibitors in neonatal rat endotoxic shock

Abstract

Section snippets

Animals

Mortality studies

Discussion

Acknowledgements

Biochem Biophys Res Commun

Chest

Lancet

Neonatal neutrophil host defenseProspects for immunologic enhancement during neonatal sepsis

Am J Dis Child

Diagnosis and treatment of sepsis in the neonate

Sepsis neonatorum

N Engl J Med

Pathogenesis and management of neonatal sepsis and meningitis

Curr Probl Pediatr

Neonatal infections

Pharmacological support of the cardiovasculature in septic shock

Neonatal sepsis

Nitric oxidePhysiology, pathophysiology and pharmacology

Pharmacol Rev

Effects of three inhibitors of nitric oxide synthase on host resistance to bacterial infection

Inflamm Res

Inhibition of nitric oxide synthase in experimental gram-negative sepsis

J Infect Dis

Inhibition of nitric oxide formation does not affect endotoxin lethality in rats

J Endotox Res

Effects of nitric oxide synthase inhibition on regional hemodynamics and oxygen transport in endotoxic dogs

Shock

Nω-Amino-l-arginine, an inhibitor of nitric oxide synthase, raises vascular resistance but increases mortality rates in awake canines challenged with endotoxin

J Exp Med

Age-related mortality and adherent splenic cell mediator production to endotoxin in the rat

Shock

Beneficial effects of interleukin-6 in neonatal mouse models of group B streptococcal disease

Infect Immun

Chemotherapy and Metabolic Inhibitors
Effect of nitric oxide donors and nitric oxide synthase inhibitors in neonatal rat endotoxic shock

N^ω-Amino-l-arginine, an inhibitor of nitric oxide synthase, raises vascular resistance but increases mortality rates in awake canines challenged with endotoxin