Trypanosoma cruzi Infection Induces Proliferation of Vascular Smooth Muscle Cells

Abstract

Trypanosoma cruzi infection causes cardiomyopathy and vasculopathy. Previous studies have demonstrated that infection of human umbilical vein endothelial and smooth muscle cells resulted in activation of extracellular signal-regulated kinase (ERK).In the present study, smooth muscle cells were infected with trypomastigotes, and immunoblot analysis revealed an increase in the expression of cyclin D1 and proliferating cell nuclear antigen (PCNA), important mediators of smooth muscle cell proliferation. Interestingly, after infection, the expression of caveolin-1 was reduced in both human umbilical vein endothelial cells and smooth muscle cells. Immunoblot and immunohistochemical analyses of lysates of carotid arteries obtained from infected mice revealed increased expression of PCNA, cyclin D1, its substrate, phospho-Rb (Ser780), and phospho-ERK1/2. The expression of the cyclin-dependent kinase inhibitor p21Cip1/Waf1 , caveolin-1, and caveolin-3 was reduced in carotid arteries obtained from infected mice. There was an increase in the abundance of pre-pro-endothelin-1 mRNA in the carotid artery and aorta from infected mice. The ET A receptor was also elevated in infected arteries. ERK activates endothelin-1, which in turn exerts positive feedback activating ERK, and cyclin D1 is a downstream target of both endothelin-1 and ERK. There was significant incorporation of bromodeoxyuridine into smooth muscle cell DNA when treatment was with conditioned medium obtained from infected endothelial cells. Taken together, these data suggest that T. cruzi infection stimulates smooth muscle cell proliferation and is likely a result of the upregulation of the ERK-cyclin D1-endothelin-1 pathway.Chagas' disease, caused by Trypanosoma cruzi, results in acute myocarditis and chronic cardiomyopathy (38, 39) accompanied by a vasculopathy (23,30,31,34,37,43). The precise etiology of chagasic heart disease is multifactorial, involving parasite persistence (41), inflammation (13, 35), autoimmunity (20), and vascular dysfunction (37). The evidence for vascular dysfunction in Chagas' disease includes infection-associated microvascular spasm, reduction in blood flow, increased platelet aggregation in experimental infection, and increased myocardial inflammation and fibrosis (24,34,40).T. cruzi infects many cell types that comprise the cardiovascular system, including cardiac myocytes, cardiac fibroblasts, endothelial cells, and vascular smooth muscle cells. The interaction of the parasite with endothelial cells is among the first encounters in the host-parasite relationship. Studies from our laboratory and others have demonstrated that infection of endothelial cells with T. cruzi results in the expression of proinflammatory cytokines (35), vascular adhesion molecules (13), and the vasoactive peptide endothelin-1 (ET-1) (27)(28)(29).The cells of the cardiovascular system synthesize ET-1 and have endothelin receptors. ET-1 acts locally on cells such as cardiac myocytes, cardiac fibroblasts, endothelial cells, and smooth muscle cells via two t...

Regulation of host cell cyclin D1 byTrypanosoma cruziin myoblasts

“…[2][3][4][5] In the present study we reaffirmed in cultured L 6 E 9 myoblasts that infection indeed increased the levels of cyclin D1. In order to examine the mechanism by which the parasite causes increased cyclin D1 levels, we used two cyclin D1 reporters which were transfected into myoblasts, either the luciferase reporter construct of the full length (1745) cyclin D1 gene promoter or a cyclin D1 luciferase reporter construct mutated at the AP-1 and ATF binding sites.…”

“…19 We have also demonstrated previously that infection caused a reduction in the expression of caveolin-1 both in vitro and in vivo. 2,3,5 Despite these findings, the mechanism(s) by which host cyclin D1 abundance was regulated by T. cruzi in the myocardium had not been previously investigated. We anticipated that infection of myoblasts would result in an increase in transcription of cyclin D1, resulting in increased cyclin D1 protein levels.…”

“…The consequences of T. cruzi infection on host cell cycle regulatory proteins have been extensively investigated both in cultured cells and mouse models. [2][3][4][5][6] Previously we demonstrated that T. cruzi infection of CD1 mice resulted in increased cyclin D1 expression, increased ERK activation and increased AP-1 and NFκB DNA binding activity. 4 As we have previously shown, cyclin D1 gene expression is regulated in part by transcriptional activation, which can be mediated by the MAPK pathway and NFκB.…”

Transcriptome profile of Trypanosoma cruzi-infected cells: simultaneous up- and down-regulation of proliferation inhibitors and promoters

“…In this context, inhibition of host cell proliferation seems important in establishing parasite intracellular clusters, leading to parasite escape from the immune system and propagation. However, there was a previous report of an increase in expression of cyclin D1 and proliferating cell nuclear antigen (PCNA) in infected smooth muscle cells, both of which mediate cell proliferation (Hassan et al 2006). Further studies are required to determine the actual contributions of the cell proliferation regulators observed in the present study to cell growth inhibition of parasite-infected host cells and the in vivo significance of this phenomenon.…”

Expression of cytokines and chemokines and microvasculature alterations of the tongue from patients with chronic Chagas’ disease

“…Lower magnification (×3,000) and higher magnification (×20,000) ). On the other hand, the increased area of the vascular wall may be due to endothelial proliferation (Gavin et al 1998) or proliferation of vascular smooth muscle cells induced by T. cruzi (Hassan et al 2006). According to our results, another possibility is that the denervation of peripheral nervous system induced by Chagas' disease increases the lumen area of blood vessels.…”