Bacterial translocation in cirrhotic rats stimulates eNOS-derived NO production and impairs mesenteric vascular contractility

Abstract

Nitric oxide (NO) has been implicated in the arterial vasodilation and associated vascular hyporesponsiveness to vasoconstrictors observed in liver cirrhosis. Bacteria, potent activators of NO and TNF-α synthesis, are found in the mesenteric lymph nodes (MLNs) of ascitic cirrhotic rats. Here, we investigated the impact of bacterial translocation (BT) to MLNs on TNF-α production, vascular NO release, and contractility in the mesenteric vasculature of ascitic cirrhotic rats. Vascular response to the α-adrenoagonist methoxamine, which is diminished in the superior mesenteric arterial beds of cirrhotic rats, is further blunted in the presence of BT. BT promoted vascular NO release in cirrhotic rats, an effect that depended on pressure-induced shear stress and was blocked by the NO inhibitor N ω -nitro-L-arginine. Removing the endothelium had the same effect. Endothelial NO synthase (eNOS), but not the inducible isoform (iNOS), was present in mesenteric vasculature of cirrhotic rats with and without BT, and its expression was enhanced compared with controls. TNF-α was induced in MLNs by BT and accumulated in parallel in the serum. This TNF-α production was associated with elevated levels of tetrahydrobiopterin (BH 4 ), a TNF-α-stimulated cofactor and enhancer of eNOSderived NO biosynthesis and NOS activity in mesenteric vasculature. These findings establish a link between BT to MLNs and increased TNF-α production and elevated BH 4 levels enhancing eNOSderived NO overproduction, further impairing contractility in the cirrhotic mesenteric vasculature.J. Clin. Invest. 104:1223-1233. mals subjected to experimental portal hypertension (41)(42)(43)(44). TNF-α is also known to be involved in the pathogenesis of the hyperdynamic circulatory syndrome in portal hypertension (42,45). Finally, the gut and its associated lymphoid tissue, the largest immunologic organ of the body, has recently been shown to produce and release TNF-α in response to BT, even in the absence of portal or systemic spread of bacteria (46,47).We designed this study to determine (a) whether there is any relationship between BT to MLNs and vascular contractility in the superior mesenteric arterial bed in cirrhosis; (b) if so, whether this additional vascular impairment is also due to vascular NO release; and (c) if that is the case, what NOS isoform is responsible for this additional NO overproduction and by what mechanism this NOS isoform is upregulated; and (d) whether TNF-α is playing any role in this process. MethodsAll experimental procedures in this study were conducted according to the American Physiological Society principles for the care and use of laboratory animals.Induction of liver cirrhosis in rats by CCl 4. Male SpragueDawley rats (Harlan Sprague Dawley Inc., Indianapolis, Indiana, USA), weighing 100-125 g, underwent inhalation exposure to CCl 4 and had phenobarbital (0.35g/L) added to their drinking water, as described previously by ourselves and others (4,5). This protocol produces a high yield of micronodular cirrhosis in about 12-16 we...

Pathophysiological and Clinical Approach to Cirrhotic Cardiomyopathy

“…As the inflammation progresses cardio-depressant substances such as cytokines, endogenous cannabinoids, and nitric oxide are released [48]. The urokinase-type plasminogen activator receptor (suPAR) has recently been suggested to bear prognostic information [49].…”

Chronic antigenic stimuli as a possible explanation for the immunodepression caused by liver cirrhosis

“…A possible role has been attributed to the translocation of bacteria and endotoxins [lipopolysaccharide (LPS)] from the gut [9,10]. LPS increases the plasma levels of LPS binding protein (LBP), the principal plasma protein responsible for transporting LPS to immune effector cells [11].…”

Hepatorenal Sendrom

“…Dolaşım ve böbrek fonksiyonlarındaki bozukluğun birlikte oluşu ile karakterizedir (1 2/hasar Serum kreatininde bazale göre %200-300'den (>2 kat-3 kat) fazla artış 12 saatten uzun <0,5 ml/kg/saat 3/yetmezlik Serum kreatininde bazale göre %300'den (>3 kat) fazla artış (veya serum kreatinini 12 saat anüri ≥4 mg/dl ile en az 0,5 mg/dl akut artış) 24 saatte <0,3 ml/kg/saat veya Sirozlu hastalar ve deneysel hayvanlarda yapılan çalışmalar bakteriyel translokasyonun (intestinal lümenden mezenterik lenf nodlarına bakteri geçişi) da ileri evre sirozda dolaşımsal fonksiyonları bozmada rol oynayabileceğini düşündürmektedir (6,7). Bakteriyel translokasyon, inflamatuar yanıta bağlı splanknik alanda proinflamatuar sitokinlerin (başlıca tümör nekrozis faktör α ve interlökin 6) ve vazodilatör faktörlerin (nitrik oksit gibi) artmış üretimi sonucu splanknik arteriyel damarlarda vazodilatasyona neden olabilir.…”