Papers by Marcelo Ribeiro
Digestive Diseases and Sciences, 2012
Enterocromaffin-like cells (ECL) are specialized endocrine gastric cells able to release histamin... more Enterocromaffin-like cells (ECL) are specialized endocrine gastric cells able to release histamine, which in turn controls gastric acid production by parietal cells. Helicobacter pylori infection and other conditions signal in the gastrointestinal tract via Toll-like receptors (TLRs) and modify gastric acid production, but there is no evidence of expression and function of TLRs in ECL cells. In this work, we analyzed gene and protein expression of TLR-2, 4, 5, and 9, and other molecules involved in TLR signaling in ECL cells. ECL cells were isolated from Sprague-Dawley rats. The histamine-releasing ability of TLR ligands was also evaluated after culture of the ECL cells for a short time. With ECL cells that expressed the TLR-2, TLR-4, TLR-5, and TLR-9 genes we were able to confirm protein expression for TLR-2, TLR-5, and TLR-9. Functionally, ECL cells were able to release histamine in response to TLR-2 stimulation by peptidoglycan (PGN), a TLR-2 ligand. After PGN stimulus, IRAK and p38 phosphorylation could be observed. SB 203580, a p38 inhibitor, reversed PGN-induced histamine release. Lipopolysaccharide (LPS), a TLR-4 ligand, was also able to induce histamine release in ECL cells, but by a mechanism independent of TLRs. We have demonstrated for the first time that ECL cells express TLRs and respond to TLR-2 ligand by increasing histamine release. This response could be involved in host defense against gastrointestinal bacterial pathogens but could also contribute to control of gastric acid secretion in the absence of pathogens.
O Que nos Faz Pensar?, 2019
Resumo No presente artigo pretendemos percorrer com a leitora e o leitor uma trilha reflexiva tri... more Resumo No presente artigo pretendemos percorrer com a leitora e o leitor uma trilha reflexiva tripla: sobre os efeitos da reprodução e perpetuação cultural do racismo epistêmico no ensino de filosofia; sobre os esforços antirracistas que culminaram no Brasil na promulgação da Lei 10.639/03 e da Lei 11.645/08, acrescentando diretrizes importantes em todos os níveis de nosso sistema educacional. E, por fim, sobre a Afroperspectividade, como uma abordagem teórico-metodológica relevante para combater o racismo epistêmico no ensino de filosofia.
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Papers by Marcelo Ribeiro