Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Effects of Active Protein C and COX Enzymes on Renal Cortical

Perfusion and Glucose Transporters in Septic Rat
Sepsis is defined as a systemic inflammatory response triggered by endotoxins or exotoxins, which are secreted by Gram (-) or (+) bacteria, including tissue damage and multiple organ injury which are resulted from inflammatory substances released from monocytes, macrophages, endothelial cells and neutrophils upon their activation.

Cyclooxygenases (COX’s) are rate limiting enzymes in the biosynthesis of prostaglandins (PG’s). Prostaglandins are a different group of autocrine and paracrine hormones mediating a variety of cellular and physiological events. Three isoforms of COX known as COX-1, COX-2 and COX-3 are present. COX-2 is proinflammatory, and an enzyme which is induced by mitogens, tumor promoters, cytokines and growth factors, and is controlled at transcriptional and posttranslational levels.

Protein C is a member of family of the Vitamin K-dependent blood coagulation proteins family. It is converted to activated protein C (APC), its activated form, by thrombin/thrombomodulin complex. APC has many effects such as anticoagulant effect, inactivation of coagulation factors Va and VIIIa, and inhibition of thrombin production, and is used for the treatment of septic shock and severe sepsis in our day.

This study was carried out to assess effects of indomethacin, an inhibitor of activated protein C and cyclooxygenases, on cardiac functions and renal cortical blood flow, and gene expression of glucose transporter SGLT-2 in renal proximal tubules.

In the study, three-months old 48 male Sprague Dawley (weighing 250-300 g) rats were used. Animals were divided into 8 groups, each including 6 individuals, as 4 control and 4 septic groups. 10 mg/kg Escherichia coli lipopolysaccharide (LPS) to develop sepsis, 1% dimethyl sulfoxide (DMSO), nonspecific cyclooxygenase inhibitor indomethacin (5 mg/kg) and activated protein C (33 µg/kg) dissolved in 15 ml/kg of lactated Ringer's solution for one and a half hours, and combination of these were administered intravenously (iv) under anesthesia. Control group was administered only 1% DMSO in 0,5 ml % 0.9 physiological saline solution (PSS), while 0,5 ml PSS and indomethacin dissolved in 1% DMSO were given to other group via infusion pump within 15 minutes. Renal blood flow, arterial blood pressure and heart rate of the animals were recorded during the experiments. At the end of the experiments, immunoreactivity for liver-type fatty acid-binding protein (L-FABP), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and myeloperoxidase (MPO) was immunohistochemically measured in tissue samples, while distributions of TNF-, COX and nitrite/nitrate in tissue homogenates were biochemically determined through ELISA.

Administration of both APC and indomethacin and their combination appears to have recovered values of mean arterial pressure (p<0.01), systolic pressure (p<0.05), diastolic pressure (p<0.001) and renal cortical blood flow (p<0.05) significantly, which were decreased by LPS, in this study. When compared to LPS group, renal APC application lowers the reactivity of IL-6, iNOS and L-FABP, whereas indomethacin decreases IL-6 and MPO reactivities immunohistochemically; however, elevated expression of SGLT-2 gene is lowered to normal levels.

As a result, this study showed that application of APC and indomethacin, solely or in combination, can recover hemodynamic values and renal blood flow, and decreases levels of proinflammatory cytokines which are high, and the resulting renal damage in septic rats. Additionally, it was determined that these substances are able to regulate impaired glucose metabolism and especially SGLT-2 expression.