In the present study, we show that downregulation of CAP-18 peptide/Olaparib protein was counteracted in lung epithelium, upon oral intake of PB or NaB. Thus, treatment with these substances seems to maintain expression of critically active components of the innate defense barrier. Detection of butyrate in rabbit serum after oral treatment with NaB suggest that orally administered NaB or PB are absorbed from the intestine and reach the mucosa of various organs via the blood stream and influence CAP-18 expression in the remote organs. Indeed, we found that intravenous injection of Shigella infected rabbits with NaB also counteracted the downregulation of CAP-18 peptide/protein in the epithelia of rectum, colon and lung. Cellular pathways of cathelicidin induction by butyrate have been studied in several human cell lines or primary cultures. The common denominator for the induction by butyrate is its activity as histone deacetylase inhibitor, facilitating transcription. The involvement of MAPK signaling pathways, nuclear hormone receptors and transcription factor binding sites have also been demonstrated. Our group has recently shown that, phenylbutyarte also involves activation of MAPK in lung epithelial cells for CAMP gene induction. However, this study showed that the HDACi activity of PB is not due to a direct effect on the chromatin structure at the CAMP proximal promoter. Instead, enhanced histone acetylation facilitates expression of other genes, encoding MK-1775 critical factors, regulating CAMP gene expression. An alternative pathway has also been shown for the effect of butyrate, involving G-protein coupled receptor. Binding of short chain fatty acids including butyrate to this receptor has been shown to affect inflammatory and immune responses. Butyrate-GPCR interaction might also be involved in the induction of cathelicidin, an event that needs to be addressed. The levels of CAP-18 transcripts were enhanced in distal colon, lung and trachea in Shigella infected rabbits compared to healthy controls. These findings did not correlate with the CAP-18 peptide/protein expression in the mucosal epithelia of these organs. We have earlier observed a similar finding in the rectum of patients with shigellosis, where transcripts of several cytokines were 3�C100 fold higher compared to the corresponding protein expression. These findings suggest a bacterial or host mediated post-transcriptional regulation of certain cytokines and in the present case also CAP-18. Shiga toxin or shiga-like cytotoxins, which are known to inhibit host cell protein synthesis might be responsible for the observed low expression of CAP-18 peptide/protein and accumulation of mRNA. Translational arrest at initiation and elongation has also been demonstrated in influenza virus and adenovirus infections.