Thyroxine Affects Lipopolysaccharide-Induced Macrophage Differentiation and Myocardial Cell Apoptosis via the NF-κB p65 Pathway Both In Vitro and In Vivo

Abstract EN

Background.

Numerous studies have demonstrated that the inflammatory response is involved in the progression of lipopolysaccharide- (LPS-) induced myocardial cell apoptosis.

Accumulating evidence has shown that thyroxine participates in diseases by downregulating the inflammatory response.

This study aimed at investigating whether thyroxine alleviates LPS-induced myocardial cell apoptosis.

Methods.

Bone marrow-derived macrophages (Mø) were treated with LPS and thyroxine, and Mø differentiation and Mø-related cytokine expression were measured.

The effect of Mø differentiation on mouse cardiomyocyte (MCM) apoptosis was also detected in vitro.

In addition, C57BL/6 mice underwent thyroidectomy and were treated with LPS 35 days later; subsequently, Mø differentiation and myocardial cell apoptosis in hearts were analyzed.

To determine whether the nuclear factor-kappa B (NF-κB) p65 pathway mediates the effect of thyroxine on Mø differentiation and myocardial cell apoptosis, the specific NF-κB p65 pathway inhibitor JSH-23 was administered to mice that underwent a thyroidectomy.

Results.

Levothyroxine treatment significantly reduced the activation of the NF-κB p65 pathway, decreased M1 macrophage (Mø1) differentiation and Mø1-related cytokine mRNA levels in LPS-treated Mø, and increased M2 macrophage (Mø2) differentiation and Mø2-related cytokine mRNA expression.

The protective effects of levothyroxine on MCM apoptosis mediated by LPS-treated Mø were alleviated by JSH-23.

In mice, thyroidectomy aggravated LPS-induced cardiac injury and cardiac dysfunction, further promoted NF-κB p65 activation, and increased cardiac Mø1 expression and myocardial cell apoptosis but decreased cardiac Mø2 expression.

JSH-23 treatment significantly ameliorated the thyroidectomy-induced increases in myocardial cell apoptosis and Mø differentiation.

Conclusions.

Thyroxine alleviated the Mø1/Mø2 imbalance, reduced the inflammatory response, decreased myocardial cell apoptosis, and protected against cardiac injury and cardiac dysfunction in LPS-treated mice.

Thyroxine may be a novel therapeutic strategy to prevent and treat LPS-induced cardiac injury.