Resposta inflamatória, apoptose e fibrose renal na Leishmaniose visceral canina: estudo histomorfométrico e molecular

Abstract

Pathogenesis of Visceral Leishmaniasis (VL) is associated with altered chemokine expression and defective migration of immune cells. Apoptosis is usually associated with resolution of inflammation. However, in kidneys of L. infantum infected dogs, apoptosis seems to be balancing inflammatory recruitment and acting as a marker of inflammatory activity, not as a resolution event. Fibrosis is an expected event in chronic inflammation and canine visceral leishmaniasis is always associated with a long and chronic evolution. The aim of this work was to quantify some molecules related to apoptosis, inflammation and fibrosis; correlate these findings with the clinical symptoms and the presence of renal histopathological lesions in naturally infected dogs by Leishmania infantum. Diagnosis of leishmaniasis was confirmed by IFA and ELISA, imprints, culture and PCR. Fragments of kidney were collected and processed for histological examination. Sixteen dogs with visceral leishmaniasis and seven noninfected controls were used. mRNA of some cytokines and chemokines were measured by qPCR. Morphometry were evaluated in 20 representative histological fields. Symptomatic dogs showed more intense inflammation and higher cellularity of the inflammatory infiltrates than asymptomatic ones, which were higher than controls. Glomerular and tubular cells showed a higher apoptotic index in symptomatic animals as compared to controls. Apoptosis within the inflammatory infiltrates was highest in symptomatic dogs, intermediary in asymptomatic and smallest in controls. Asymptomatic dogs had only discrete and focal inflammation. More intense intertubular fibrosis occurred in infected dogs. Adventitial fibrosis were more intense in symptomatic dogs than in asymptomatic ones, which had higher measurements than control dogs. MCP2, CCL4, Bax, Bcl2, caspase 9, Fas, IFN-, TNF-, IL-4, IL-10, IL- 12, IL-13 e TGF- expressions were upregulated in symptomatic dogs and down 6 regulated in asymptomatic dogs when compared with non-infected controls. Furthermore, IL-4, Bax\Bcl2 and CCL4 was more expressed in symptomatic dogs as compared with asymptomatic animals. IL-6, IFN-/TGF- e IL-12/TGF- , MCP-1, CCL5, caspase 3, caspase 8, Bax, and Bcl-2 expression was upregulated in both groups studied. IL-2 expression was down regulated in both infected groups. TNF-/TGF- was upregulated in asymptomatic dogs and down regulated in symptomatic dogs. Renal inflammation in VL is not associated with tissue infection. Our studies reveal an additional role for IL-4 in the negative regulation of chemokine expression associated with Th1 recruitment to inflamed tissues. IFN- , TNF-, IL-4, IL-12 and IL-10 may be used as inflammatory markers for symptomatic infection in kidney. Therefore, in kidneys of Leishmania infected dogs, apoptosis may also occur in active inflammation, and seems to be balancing inflammatory recruitment. In conclusion, our results suggested that the renal fibrosis as an eventual consequence of immunopathologic mechanisms, involving injury of the vasculature and of the stroma; and, importantly, our study suggest an IL-13-driven pathway of fibrogenesis that is TGF- dependent.