Induction and regulation of CAMP gene expression A thesis submitted in partial satisfaction of the requirements for the degree of Master of Science

The cathelicidin antimicrobial peptide LL-37 is an important component of our first line of defense against bacterial infections. Induction of antimicrobial peptides such as LL-37 might provide a novel approach in treating bacterial infections, where conventional antibiotics fail. To investigate the effect of 4-phenylbutyrate (PBA) on antimicrobial peptide expression, we initially treated various cell lines with PBA and assessed mRNA expression by real time RT-PCR. Cathelicidin antimicrobial peptide (CAMP) gene expression was found to be upregulated in all cell lines tested. Additionally, we found that the human beta defensin 1 gene (DEFB1) was upregulated in a lung epithelial cell line (VA10), but downregulated in monocytes (U937). The subsequent experiments focused on CAMP gene expression in VA10 cells. We found that PBA induced CAMP gene expression synergistically with 1,25-dihydroxyvitamin D3 at both the protein and mRNA levels. In an attempt to characterize the general mechanism of PBA induced CAMP expression, we demonstrated that the effect is likely to be secondary, as inhibition of protein synthesis by cycloheximide blocked PBA induced CAMP expression. Furthermore we show that inhibition of mitogen activated protein kinases MEK1/2 and JNK attenuates PBA induced CAMP gene expression. Finally, we reveal that α-methylhydrocinnamate (ST7), a PBA analog, similarly increases CAMP gene expression. These findings contribute to the general understanding of the regulation of antimicrobial peptide expression and suggest that PBA and/or ST7 are promising drug candidates, for treatment of microbial infections, by strengthening of the innate antimicrobial response.