Interleukin-1beta does not contribute to genetic strain-based differences in iNOS expression and activity in chicken macrophages.

The expression of IL-1beta and inducible nitric oxide synthase (iNOS) from iNOS hypo (GB2, B(6)B(6)) and hyper (K-strain, B(15)B(15)) responder chickens was examined. Compared to GB2, macrophages from K-strain expressed higher iNOS mRNA as quantitated by reverse transcriptase polymerase (RT-PCR) chain reaction after stimulation with 1 microgram/ml of Escherichia coli (E. coli) lipopolysaccharide (LPS). On the contrary, IL-1beta mRNA expression was comparable between K and GB2 macrophages at 3h post-LPS stimulation but persisted up to 9h only in GB2 macrophages. The LPS-inducible interleukin-1 (IL-1) surface receptor expression, measured by flow cytometry, was higher in GB2 than on K-strain macrophages. Blocking of IL-1 receptor by the anti-IL-1 receptor antibody reduced the LPS-mediated iNOS expression by 50% as quantified by competitive RT-PCR. Furthermore, iNOS activity (nitrite) was also reduced to 50%. However, this magnitude of inhibition was similar in both K and GB2 macrophages. While these observations suggest that IL-1beta is involved in mediating LPS-induced iNOS expression and activity, the differential response of GB1 and K-strain macrophages in terms of LPS-induced iNOS expression and activity is unlikely to be modulated by IL-1beta.