Renovascular hypertension increases serum TNF and CX3CL1 in experimental Trypanosoma cruzi infection

Brazilian Journal of Medical and Biological Research (2018) 51(5): e6690, http://dx.doi.org/10.1590/1414-431X20186690 ISSN 1414-431X Research Article 1/9 Renovascular hypertension increases serum TNF and CX3CL1 in experimental Trypanosoma cruzi infection M.C. Silva1*, M.A. Azevedo3*, V.P. Figueiredo3, M.R. Moura Junior3, D. Coelho Junior2, P.M. Martinelli6, R.P. Machado1†, A.C. Alzamora1,3,4 and A. Talvani1,3,4,5 1 Departamento de Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brasil 2 Escola de Medicina, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brasil 3 Programa de Pós-Graduac¸ão em Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brasil 4 Programa de Pós-Graduac¸ão em Saúde e Nutric¸ão, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brasil 5 Programa de Pós-Graduac¸ão em Ecologia e Biomas Tropicais, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brasil 6 Departamento de Morfologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil Abstract Trypanosoma cruzi triggers a progressive inflammatory response affecting cardiovascular functions in humans and experimental models. Angiotensin II, a key effector of the renin-angiotensin system, plays roles in mediating hypertension, heart failure, and inflammatory responses. T. cruzi and AngII can induce inflammatory responses by releasing inflammatory mediators. The aim of this study was to evaluate systemic AngII, tumor necrosis factor (TNF), and CX3CL1 mediators in a two-kidney one-clip (2K1C) renovascular hypertension model using Wistar rats infected with T. cruzi. Our data showed an increase in serum AngII in uninfected and T. cruzi-infected rats 1 week after 2K1C surgery compared to non-2K1C (Sham) animals. The baseline systolic blood pressure was higher in both uninfected and infected 2K1C rats. Despite no difference in circulating parasites in the acute phase of infection, elevated serum TNF and CX3CL1 were observed at 8 weeks post-infection in 2K1C rats in association with higher cardiac inflammatory infiltration. In summary, AngII-induced hypertension associated with T. cruzi infection may act synergistically to increase TNF and CX3CL1 in the 2K1C rat model, thereby intensifying cardiac inflammatory infiltration and worsening the underlying inflammation triggered by this protozoan. Key words: Trypanosoma cruzi; Hypertension; Tumor necrosis factor; CX3CL1; Cardiac inflammation Introduction Trypanosoma cruzi is a flagellated protozoan whose membrane glycoproteins act as antigens capable of triggering an inflammatory response in mammalian hosts (1). This immune-cell activation promotes the release of inflammatory mediators and antibodies that regulate parasite entry into the bloodstream. However, because of its well-adapted escape mechanisms, the immune system typically fails and T. cruzi persists in muscle cells. Once these parasites reach the cardiac cells, they trigger a local and persistent inflammatory response that is inevitably associated with cellular and tissue destruction (2). Both human Chagas disease and experimental models of T. cruzi infection not only affect heart muscle, but also promote endothelial dysfunction of systemic blood vessels (3,4). Thus, hypertension is a common condition affecting the cardiovascular system and the functioning of other physiological systems (5). Hyperactivity of the renin-angiotensin system (RAS), particularly angiotensin II (AngII), together with sympathetic nervous system over-activity contribute to the development and maintenance of hypertension. Moreover, AngII promotes cardiac remodeling by stimulating inflammatory processes, cardiomyocyte hypertrophy, and fibroblast proliferation. This may eventually lead to cardiac fibrosis, which not only affects cardiac function, but also the general health of the individual (6). Correspondence: A. Talvani: <> Current address of M.C. Silva: Programa de Pós Graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande, MS, Brasil. † In memoriam *These authors contributed equally to this study. Received May 8, 2017 | Accepted January 22, 2018 Braz J Med Biol Res | doi: 10.1590/1414-431X20186690 Hypertension and T. cruzi infection The two-kidney, one-clip (2K1C) renovascularhypertension model has been widely used to induce overproduction of RAS (7). The time-course of this hypertensive model presents different stages after clipping of the renal artery. In the early phase (approximately 4 weeks after clipping), high blood pressure is induced by plasma renin activity and circulating AngII. In the later phase (after 8 weeks), the plasma renin activity and AngII levels are reduced, but the hypertension is maintained (8,9). Because both hypertension and T. cruzi activate inflammatory mediators, we hypothesized that both clinical conditions act synergistically to worsen local and systemic pathological effects by inducing and maintaining a longterm inflammatory response. In this study, we investigated the production of serum tumor necrosis factor (TNF), CX3CL1, and other physiological parameters in T. cruziinfected hypertensive Wistar rats. Material and Methods Animals Male Wistar rats weighing approximately 180–200 g were bred and maintained at the animal facility at Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG, Brazil. The animals were maintained in cages under standard conditions and given ad libitum access to food and water. All procedures were followed in accordance with the guidelines issued by the Brazilian College of Animal Experimentation and approved by the Ethical Committee for Experiments with Laboratory Animals at UFOP (Protocol# 2011/44). Induction of renovascular hypertension 2K1C renovascular-hypertension was induced as described previously (10). Briefly, after a 24-h fast, a group of 8 rats (150–200 g) was anesthetized with a combination of ketamine and xylazine (80 and 10 mg/kg, intraperitoneal, respectively). A U-shaped silver clip (8 mm in length and 2 mm in width) with a 0.2-mm internal diameter was placed around the left renal artery through a mid-line incision. The control group of animals (Sham group or normotensive rats) was subjected to a similar procedure, except for placement of the renal artery clip. This procedure generated two different groups: hypertensive rats (2K1C surgery group) and normotensive rats (Sham group). Experimental infection Parasitological infection was conducted using the trypomastigote-form of the Y- strain of T. cruzi. The bloodstream trypomastigote form of the parasite was maintained in Swiss mice by serial passage of infected blood (11). Immediately after 2K1C surgery, rats were intraperitoneally inoculated, with 1.2
106 trypomastigotes obtained from previously infected Swiss mice (12). Control mice were Braz J Med Biol Res | doi: 10.1590/1414-431X20186690 2/9 injected only with the vehicle, phosphate-buffered saline. This procedure generated two different groups of rats: an infected a (...truncated)