Pro‐inflammatory effect of hyperglycemia in cultured macrophages and neonatal rat ventricular cardiomyocytes is blunted by inhibition of hexosamine biosynthesis

Abstract

We have previously shown that increasing protein O‐linked‐N‐acetylglucosamine (O‐GlcNAc) levels with glucosamine (GlcN) attenuated activation of cardiac NF‐kB signaling both in vivo and in vitro. However, there is also evidence to suggest that increased hexosamine biosynthesis (HB) and O‐GlcNAc levels contributes to the adverse effects of hyperglycemia. Therefore, the goal of this study was to compare the effects of high glucose (HG, 25mM) and glucosamine (GlcN, 5mM) on the response of neonatal rat ventricular cardiomyocytes (NRVM) and mouse leukaemic monocyte macrophages (Mφ) to LPS. LPS treatment for 6hrs (Mφ, 0.1µg/ml; NRVM, 2µg/ml) significantly increased iNOS expression in both Mφ and NRVM. In Mφ cells the LPS‐induced increase in iNOS was clearly augmented with HG and this was attenuated by pretreatment with the GFAT inhibitor DON (20µM). In NRVMs the effect of HG on LPS‐induced iNOS expression was less pronounced than that seen in Mφ cells; nevertheless, treatment with DON attenuated iNOS expression in HG treated cells. DON pre‐treatment also significantly decreased O‐GlcNAc levels in both Mφ and NRVM. In both Mφ and NRVM cells GlcN treatment increased O‐GlcNAc levels and prevented the LPS‐induced increase in iNOS. These results demonstrate that HG increases sensitivity to inflammatory stimuli that can be attenuated at least in part by inhibition of HB with DON. Paradoxically, however, direct activation of HB with GlcN blunted the pro‐inflammatory effects of LPS. This suggests that the pro‐inflammatory effects of HG may be mediated by a combination of increased HB combined with another glucose‐activated pathway.