Trimethylamine-N-oxide,as a risk factor for atherosclerosis,induces stress in J774A.1 murine macrophages

Purpose

Trimethylamine N-oxide (TMAO) is a biomarker for kidney problems. It has also been introduced as a risk factor for atherosclerosis. The classic risk factors for atherosclerosis trigger cellular and humeral immunoreaction in macrophages through induction of heat shock protein expressions and increased levels of GRP94 and HSP70 are associated with increased atherosclerosis risk. The present study evaluated the possible effect(s) of TMAO on the expression of GRP94 and HSP70 at protein levels.

Methods

J774A.1 murine macrophages were treated with different micromolar concentrations of TMAO and 4-phenylbutyric acid (PBA), a chemical chaperone, for 8, 18, 24, and 48 h intervals. Tunicamycin was also used as a control for induction of endoplasmic reticulum stress. Western blotting was used to evaluate the expression of GRP94 and HSP70 in macrophages at protein levels.

Result

Tunicamycin greatly increased protein levels of GRP94. Similarly, but to a lesser extent compared to tunicamycin, TMAO also increased GRP94. In 24 h treated cells, only 300 μM of TMAO, and in cells treated for 48 h, all doses of TMAO produced a significant increase in relative HSP70 protein levels compared to the control. PBA failed to induce any changes in GRP94 or HSP70 protein levels.

Conclusion

GRP94 and HSP70 are stress-inducible heat shock protein, so the elevation in J774A.1 murine macrophages can clearly define cells under stress and elucidate the contribution of stress induced by TMAO that may have a part in the abnormal activation of macrophages involved in foam cell formation.