Induction of c-Ha-ras gene expression by double-stranded RNA and interferon requirement

Rhinovirus increases human beta-defensin-2 and -3 mRNA expression in cultured bronchial epithelial cells

Human beta-defensins (hBDs) are antimicrobial peptides that play important roles in host defense against infection, inflammation and immunity. Previous studies showed that micro-organisms and proinflammatory mediators regulate the expression of these peptides in airway epithelial cells. The aim of the present study was to investigate the modulation of expression of hBDs in cultured primary bronchial epithelial cells (PBEC) by rhinovirus-16 (RV16), a respiratory virus responsible for the common cold and associated with asthma exacerbations. RV16 was found to induce expression of hBD-2 and -3 mRNA in PBEC, but did not affect hBD-1 mRNA. Viral replication appeared essential for rhinovirus-induced beta-defensin mRNA expression, since UV-inactivated rhinovirus did not increase expression of hBD-2 and hBD-3 mRNA. Exposure to synthetic double-stranded RNA (dsRNA) molecule polyinosinic:polycytidylic acid had a similar effect as RV16 on mRNA expression of these peptides in PBEC. In line with this, PBEC were found to express TLR3, a Toll-like receptor involved in recognition of dsRNA. This study shows that rhinovirus infection of PBEC leads to increased hBD-2 and hBD-3 mRNA expression, which may play a role in both the uncomplicated common cold and in virus-associated exacerbations of asthma.

Dose-dependent activation of p21ras by IFN-beta

Recent studies have demonstrated that interferon-beta (IFN-beta) activates extracellular regulated kinases (ERKs) in myeloma cells and have revealed a link between ERKs and the Jak/Stat pathway. The upstream components of the IFN-beta pathway involved in activation of ERKs are unknown. As p21ras is often an upstream component of the ERK pathway, we have investigated p21ras activity following IFN-beta treatment of the human myeloma cell line, U266. IFN-beta was found to strongly activate p21ras at relatively low doses and to exert a negative effect at the higher doses normally employed in signaling studies. There was no direct correlation between p21ras and ERK activity, suggesting that p21ras plays an alternate role in the IFN-beta signaling pathway. These results imply a unique integration of p21ras signaling within the milieu of IFN-induced cytoplasmic signaling events.