Involvment of nitric oxide, prostaglandins and tumor necrosis factor on the development of ectopic endometrial implants (peritoneal) and its repercussions on pain and fertility in rats / Envolvimento de óxido nítrico, prostaglandinas e fator de necrose tumoral no desenvolvimento de implantes endometriais ectópicos (peritoneais) e suas repercussões sobre a dor e infertilidade em ratas

Francisco das Chagas Medeiros

Endometriosis is a disease characterized by the presence of endometrial glands and stroma out of the uterine cavity and of the myometrium. It may cause tumor, pain (chronic pelvic pain, dyspareunia and dysmenorrhea) and infertility. Currently available evidence indicates that endometrial cells misplaced during menses into the peritoneal cavity in women with endometriosis, implant and proliferate in the ectopic locations, an action that is associated with mobilization of the immune cells into the peritoneal cavity and a profound local and systemic immune response. An increase in the amount of peritoneal fluid is a characteristic finding in endometriosis and associated with improved presence of immune cells like macrophages as well as a wide range of soluble substances derived from those macrophages like prostaglandins, interleukins, TNF, growth factors and reactive oxygen species. It is likely the role of medication for this disease will expand in the future. Also the mechanisms of all these substances must be elucidated in the pathogenesis of endometriosis. The purpose of this study is to verify: (i) the drugs effects that selectively inhibits one of the enzymes ciclooxigenase type 1 (COX-1) responsible for the physiologic events of the organism and the induced COX-2, involved in the inflammatory process; (ii) the effects of L-NAME, a competitive antagonist of nitric oxide as well as NO synthase actvity assayed by 3H-labelled citrulline from labelled L-arginine and (iii) the effects of TNF-alfa modulating drugs (Thalidomide and pentoxifilline) on the development of experimental endometriosis and on its related pain and infertility in female rats. Experimental endometriosis was developed in female Wistar rats and the animals were divided into tests groups. The treatment was given from the 5th to the 14th day of endometriosis induction to verify the effects on growth of endometriomas evaluated by its wet weight and histopathology and acutely 30 minutes before the nociceptive stimulus in order to evaluating pain (writhing test) and fertility was assessed through the percentage of pregnant rats. Aspirin (30mg/kg - an inhibitor of intermediate selectivity among COXs); piroxicam (1mg/kg) and indomethacin (2mg/kg), specific selective inhibitors of COX-1 and nabumetone (5 and 15mg/kg) and meloxicam (0.4mg/kg) relative selective inhibitors against COX-2 were used per os. All the accomplished treatments decreased significantly the pain as evaluated by the writhing test. The mean wet weights of the endometriomas (g%) were as shown [Endo control: 0.595 0.085; Aspirin: 0.122 0.019; piroxicam: 0.766 0.35; indomethacin: 2.058 0.96 and for Nabumetone 5mg: 0.252 0.032; Nabumetone 15mg: 0.135 0.03 and meloxicam: 0.387 0.04]. As to fertility, the percentage of pregnant animals were as follows: Endo control, 40%; intact control, 100%; Sham operated, 100%; Indomethacin, Zero%; meloxicam, 60%; Aspirin, 60% and Nabumetone 5 and 15, 50 e 58% respectively. The treatments with Aspirin and Nabumetone had decreased the development of the endometriomas significantly as well as contributed to the relief of the pain and increasing fertility. These results suggest the role of COX-1 and -2 in the pathophysiology of endometriosis related pain, fertility and on its growth. NO synthase actvity assayed by 3H-labelled citrulline from labelled L-arginine. The nitric oxide synthase was expressed as pmol of citrulline/mg protein/min. The endometriomas expressed iNOS at the: 5th day: 1.94 + 0.5; 10th day: 2.46 0.2 and day 15: 1.17 0.3 as well as cNOS that decreased in a time-dependent way (5th day: 2.48 0.7; 10th day: 1.8 0.19; and day 15: 0.78 0.3). This decreasing activity of cNOS was probably found by the endometrial shedding that occurs normally in the course of this disease as well as by the fibrosis that surrounds the endometriomas and the increasing iNOS by the inflammatory peritoneal and tissue reaction that is frequently found in endometriosis. The use of L-NAME also decreased the wet weight of endometriomas as well as ameliorates the pain and fertility in a dose dependent fashion. Pentoxifylline (30mg/Kg/day) administered subcutaneously for 10 consecutive days during the established phase of endometriosis (days 5-14 post induction) was effective in decreasing the expression of nitric oxide synthase, both induced and constitutive. The results of the present study as those previously shown suggest the involvement of nitric oxide in the development of experimental endometriosis. TNF-alfa modulating drugs proved to reduce the mean weights of endometrial implants, obtained at day 15 of endometriosis induction with pentoxifylline (30 mg/Kg), thalidomide (5mg/Kg) and dexamethasone (0.2mg/Kg) treated rats (control: 0.595 0.085g%; pentoxifylline: 0.06 0.008g%; thalidomide: 0.206 0.049g% and dexamethasone: 0.145 0.02g%). The results of the present study suggest the involvement of TNF-alfa in the pathophysiology of experimental endometriosis. The peritoneal levels of TNF-alfa evaluated in intact rats showed 28.95 1.18ng of TNF-alfa/ml. The levels of TNF-alfa increased in the peritoneal fluid in a time dependent way after the peritoneal implant (endometriotic rat). These drugs also attenuated pain and increased fertility.

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