Efeito do número de EPIYA-C da proteína CagA de Hellicobacter pylori na concentração gástrica de citocinas associadas à resposta Th17 em pacientes com gastrite e carcinoma gástrico

• Ano de defesa: 2012
• Autor(a) principal: Fernanda Diniz Prates
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Microbiologia
• Link de acesso: http://hdl.handle.net/1843/BUOS-94MFA4

Helicobacter pylori infection is considered to play an important role in the pathogenesis of gastric carcinoma. The CagA gene, which encodes the virulence factor CagA, is considered an important risk factor for thedevelopment of gastric cancer. CagA is translocated into the gastric epithelial cell, Iocalizes to the inner surface of the plasmatic membrane and is phosphorylated by multiple members of the Src kinase family. Phosphorylation of CagA occurs within tyrosine phosphorylation motifs containing five sequence aminoacids (EPIYA). Phosphorylated CagA forms a physical complex with SHP-2 triggering the SHP2/MAPK/ERK 1/2 signaling pathway, which leads to cellular changes that predispose to carcinogenesis. Further, the MAPK/ERK 1/2 pathway negative control of STAT3 is thought to be lost when SHP-2 is linked to the EPIYA-C motifs, thereby also increasing the expression of STAT3. Although both pathways may induce cytokine transcription, we are unaware of studies evaluating the effect of infection with CagA strains with different number of EPIYA-C phosphorylation site on the concentration of gastric cytokines associated with commitment of Th17 cell, which has been associated with carcinogenesis. Therefore, we determined the gastric concentrations of IL-1B, IL-6, IL-17, IL-23 e TGF[3, as well as IL-8 e IL-11 in the gastric mucosa of patients with gastritis and gastric carcinoma, infected by CagA strains with different number of EPIYA-C motifs. A total of 206 patients (105 with gastritis and 101 with gastric carcinoma) were included. cagA-EPIYA-C motifs were determined by PCR and the profiles were confirmed by sequencing. The cytokine gastric concentrations were evaluated by ELISA. The concentrations of all cytokines were significantly higher in the non-tumoral gastric mucosa of patients with gastric carcinoma than in the gastric mucosa of patients with gastritis. The gastric levels of IL-8 and IL-23 were significantly higher in patients colonized by cagA-positive strains than in those colonized by cagA-negative strains. When we analyzed only cagA-positive strain, the gastric levels of IL-11, IL-17 and IL-23 were significantly higher in patients colonized by CagA-positive strains with two or more EPIYA-C segments than in those infected with strains containing less than two EPIYA-C segments. In the gastric carcinoma patients, higher gastric levels of IL-6, IL-11, IL-17, IL-23 and TGF-B were significantly associated with increased number of EPIYA-C segments. By comparing gastric areas with and without tumor in the patients with gastric cancer, the concentrations of all cytokines were higher in the former. The findings of this study provide further evidence of the relevance of CagA protein in thepathogenesis of gastric cancer and in understanding the mechanisms by which CagA protein participates in the gastric carcinogenesis induced by H. pylori.