Μελέτη ενδοτοξιναιμίας και βακτηριακής μετακίνησης στον πειραματικό αποφρακτικό ίκτερο

Abstract

Invasive diagnostic and therapeutic procedures in the presence of obstructive jaundice are associated with a high morbidity and mortality rate, primarily due to septic complications and renal impairement. Bacterial translocation is known as the passage of viable bacteria or endotoxins from the gut to the mesenteric lymph nodes and other organs which may commence or exacerbate the septic state. This study was undertaken to investigate the influence of experimental obstructive jaundice in wistar rats on portal and systematic (aortal) endotoxaemia, on bacterial translocation (ΒΤ) to mesenteric lymph nodes and distant organs, and on liver and ileal histology and apoptosis. In addition, in an attempt for therapeutic intervention we have explored the possible beneficial effect of immunonutrition in obstructive jaundice by administration of glutamine or arginine per os. The amino-acid glutamine although non essential and in abundance, is required as an enterocyte fuel while it seems to possess anabolic properties for the liver, skeletal muscle, intestinal mucosa and the immune system (e.g. lymphocytes, macrophages) and its supplementation has resulted in beneficial clinical outcomes. Glutamine supplements have been used to protect the intestinal mucosa and enhance the immune system. Various authors have postulated that glutamine may prevent or attenuate BT. Arginine plays an important role in many functions including protein synthesis and katabolism. Arginine is important in the function of lymphocytes and improves cellular immune response when administered. In addition it is the sole precursor amino acid in the generation of the immunity-enhancing agent nitric oxide (NO) by NO-synthase. In animals and humans in sepsis plasma L-arginine concentrations are markedly low, may become an indispensable amino acid, and low arginine concentrations are correlated with a worse prognosis. Arginine deficiency was demonstrated in bile duct ligated rats. Dietary L- arginine has been shown to enhance the immune system and wound healing. In obstructive jaundice the absence of intraluminal bile deprives the gut from its bacteriostatic, endotoxin neutralizing and mucosal trophic effect leading to increased intestinal bacterial and endotoxin load together with mucosal atrophy. These alterations promote bacterial and endotoxin translocation into the portal circulation and subsequently, through a decreased clearance capacity of Kupffer cells due to cholestasis, into the systemic circulation. Systemic endotoxaemia activates further a systemic inflammatory response, with dysfunctions of remote organs which in a vicious circle aggrevates the intestinal barrier dysfunction and liver injury. Sevenry-five male Wistar rats were randomly divided in four groups (15 each): I controls, II sham operated, III bile duct ligation (BDL), IV BDL + glutamine (3%in drinking water) and V BDL + arginine (2% in drinking water). Ileal samples for histology, DNA and protein content, liver biopsies, mesenteric lymph nodes (MLN) for cultures, portal and systemic blood samples for endotoxin measurements were obtained 10 days later. Compared to control, a significant increase in contaminated MLN and liver samples and in endotoxaemia was noted in group III (P < 0.01) which was significantly reduced in group IV and V (P < 0.05). Group IV presented also a significantly higher number of mitoses/crypt (M/c) , less apoptotic body counts (as did group V) and a higher DNA content compared to group III (P < 0.05). Liver biopsies from group III displayed typical changes of large duct obstruction that were significantly improved after glutamine or arginine treatment, with decreased ductular proliferation. Two main features highlight the forementioned dual role of the liver in sepsis: the first is the importance of the liver blood supply and particularly the portal flow, which arises from the splachnomesenteric vascular bed, a region especially subject to vasoconstriction and bacterial translocation. The second is the cellular heterogenicity of the liver, which is mainly hepatocytes, Kupffer cells, and endothelial sinusoidal cells. All of these cell types are involved in the immune, anti-infectious, and metabolic responses through multiple cell cross-talk and interactions. We had a beneficial effect on alterations of portal triads in the liver of glutamine or arginine supplemented rats. The mechanisms involved are not fully elucidated but possible explanations could be either the reduction of BT or an immunostimulatory up regulation by administered two immunonutrients. In conclusion, the present study verifies the increased incidence of bacterial and endotoxin translocation in experimental obstructive jaundice. Apoptosis in the small bowel of bile duct ligated rats is also increased. Oral administration of glutamine or arginine was shown to reduce both BT and endotoxaemia, improved histology in the terminal ileum and liver and also decreased apoptosis in the small bowel in extrahepatic experimental jaundice. These findings offer further insight in the pathophysiology of obstructive jaundice and suggest important biological effects of immunonutrition. Understanding the pathophysiology of barrier alterations in obstructive jaundice at the cellular and molecular level will allow novel treatment approaches and a better prognosis for patients in clinical settings.