Bacterial endotoxin lipopolysaccharide induces up-regulation of glyceraldehyde-3-phosphate dehydrogenase in rat liver and lungs

Bacterial endotoxin or lipopolysaccharide (LPS) can trigger inflammatory responses and cause damage in organs such as liver and lungs when it is introduced into mammals, but the exact molecular events that mediate these responses have remained obscure. In this study, by using 2D gel electrophoresis and cDNA microarray analysis, we found that both protein and mRNA levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were significantly increased in rat liver and lungs after treatment with LPS. The results were further confirmed by Western blot and Northern blot. Given the known role of GAPDH in inducing apoptosis, our results suggest that LPS-induced GAPDH up-regulation may be an important mechanism responsible for the damage induced by Gram negative bacteria in mammalian tissue and GAPDH may be involved in the signaling pathway of LPS induced apoptosis. Our results also demonstrate that GAPDH is not a suitable internal control in gene expression studies, especially when bacterial infection is involved.