Effect of a synthetic lipid immunomodulator on the regulation of the transcription factor NF-κB

Macrophage activation plays a central role in host defense against a variety of pathogens via inducible messengers. The transcription factor NF-kappaB controls the synthesis of cytokines involved in immune responses. In quiescent cells, NF-kappaB is located in the cytosol bound to an inhibitor I kappaB. Upon appropriate signal, NF-kappaB translocates to the nucleus and binds to DNA. The present study investigated the involvement of an immunomodulator, (diHDA-glycerol) on the NF-kappaB/I kappaB complex. Results were compared to those obtained with lipopolysaccharide (LPS) as a major virulence factor in bacterial sepsis. Data showed that exposure of J774.1 cells either to LPS or diHDA-glycerol substantially increased with time the nuclear levels of NF-kappaB complexes. Antibodies to various NF-kappaB proteins supershifted p50, p65 and to a lesser extent c-rel. Western blot analyses showed a rapid cytosolic I kappaB-alpha turn over following LPS exposure in contrast to diHDA-glycerol treatment. Further experiments investigated the involvement of protein kinase C (PKC) by using two inhibitors, staurosporine and H7. Pretreatment of J774.1 with either inhibitor prior to diHDA-glycerol or LPS exposure decreased NF-kappaB activation. Our results indicate that diHDA-glycerol was acting on NF-kappaB through I kappaB regulative mechanisms differing from those used by LPS. DiHDA-glycerol is likely acting on many other transcription factors targeting distinct genes implied in up regulation of the immune system.