Expression and distribution of connexin 32 in rat liver with experimentally induced fibrosis / Expressão e distribuição da conexina 32 em fígados de ratos com fibrose induzida experimentalmente

The connexin 32 (Cx32) is a protein that forms the channels that promote the gap junction intercellular communication (GJIC) in the liver, allowing the diffusion of small molecules through cytosol from cell-to-cell. Hepatic fibrosis is characterized by a disruption of normal tissue architeture by cellular lesions, and may alter the GJIC. This work aimed to study the expression and distribution of Cx32 in liver fibrosis induced by the oral administration of dimethylnitrosamine in female Wistar rats. The necropsy of the rats was carried out after five weeks of drug administration. They presented a hepatic fibrosis state. Sections from livers with fibrosis and from control livers were submitted to immunohistochemical, Real Time-PCR and Western-Blot analysis to Cx32. In fibrotic livers the Cxs were diffusely scattered in the cytoplasm, contrasting with the control livers, where the Cx32 formed junction plaques at the cell membrane. Also it was found a decrease in the gene expression of Cx32 without reduction in the protein quantity when compared with controls. These results suggest that there the mechanism of intercellular communication between hepatocytes was reduced by the fibrotic process, which may predispose to the occurrence of a neoplastic process, taken in account that connexins are considered tumor suppressing genes.

A conexina 32 (Cx32) é uma proteína que constitui os canais que promovem as comunicações intercelulares via junções comunicantes (CIJC) no fígado, permitindo difusão de pequenas moléculas citoplasmáticas de uma célula à outra. A fibrose hepática caracteriza-se pela alteração da arquitetura normal do fígado e podem alterar as CIJCs. O objetivo deste trabalho foi estudar a expressão e distribuição de Cx32 na fibrose hepática. O objetivo do presente trabalho foi estudar a expressão e distribuição da Cx32 em fígados com fibrose induzida pela administração oral de dimetilnitrosamina em fêmeas de ratos Wistar. A necropsia foi realizada após cinco semanas da última administração da droga e observou-se um quadro de fibrose hepática. Amostras dos fígados com fibrose e de animais controle foram submetidas à análise imunoistoquímica, por Real Time-PCR e por Western-Blot verificando-se a presença de Cx32 difusa e dispersa no citoplasma dos fígados com fibrose. No grupo controle a Cx32 localizou-se na membrana citoplasmática com a formação de placas juncionais. O fígado com fibrose também revelou diminuição da expressão gênica de Cx32, embora sem a redução da quantidade do produto protéico, quando comparado ao grupo controle. Estes resultados sugerem que o mecanismo de comunicação intercelular entre os hepatócitos reduziu-se durante o processo fibrótico, o que pode predispor a ocorrência de processos neoplásicos, uma vez que as conexinas são consideradas genes supressores de tumores.

Mechanistic pathways of antioxidant cytoprotection by a novel IH636 grape seed proanthocyanidin extract.

To understand the bioavailability and mechanistic pathways of cytoprotection by IH636 grape seed proanthocyanidin extract (GSPE, commercially known as ActiVin) a series of in vitro and in vivo studies were conducted. Comparative protective abilities of GSPE, and vitamins C and E, singly and in combination, were assessed against smokeless tobacco extract (STE)-induced oxidative stress, DNA fragmentation and apoptotic cell death in a primary culture of normal human oral keratinocytes. GSPE protected against STE-induced oxidative stress, DNA damage and apoptotic cell death, and provided better protection as compared to vitamins C and E, singly and in combination. The bioavailability and protective ability of GSPE were examined against acetaminophen (AP)-induced hepato- and nephrotoxicity, amiodarone (AM)-induced lung toxicity, doxorubicin (DX)-induced cardiotoxicity and dimethylnitrosamine (DM)-induced spleenotoxicity in mice. GSPE-fed animals were compared with GSPE-untreated mice to evaluate the protective ability of GSPE against these structurally diverse drugs/chemicals. Serum chemistry changes, histopathology and DNA damage were evaluated. Results indicate that GSPE preexposure prior to the drugs/chemicals such as AP, AM, DX or DM treatment, provided near complete protection in terms of serum chemistry changes and inhibition of both forms of cell death, e.g., apoptosis and necrosis. DNA damage in various tissues triggered by these agents was significantly reduced in GSPE-fed animals. Histopathological examination of multiple target organs provided similar data. The results suggest that GSPE exposure is bioavailable and provides significant multiorgan protection against structurally diverse drug- and chemical-induced toxic assaults. Further, these studies exhibited a series of mechanistic information including free radical scavenging ability, anti-endonucleolytic activity, cytochrome P450 2E1 inhibitory activity, anti-necrotic, anti-apoptotic and anti-carcinogenic activities, modulatory effects on antioxidative and apoptotic regulatory genes such as Bcl2, c-myc and p53, which may be responsible for the novel chemoprotective properties exhibited by GSPE.