Pharmacological LRH-1/Nr5a2 inhibition limits pro-inflammatory cytokine production in macrophages and associated experimental hepatitis

Abstract

Liver receptor homolog-1 (LRH-1, Nr5a2) is an orphan nuclear receptor mainly expressed in tissues of endodermal origin, where its physiological role has been extensively studied. LRH-1 has been implicated in liver cell differentiation and proliferation, as well as glucose, lipid, and bile acid metabolism. In addition, increasing evidence highlights its role in immunoregulatory processes via glucocorticoid synthesis in the intestinal epithelium. Although the direct function of LRH-1 in immune cells is fairly elucidated, a role of LRH-1 in the regulation of macrophage differentiation has been recently reported. In this study, we aimed to investigate the role of LRH-1 in the regulation of pro-inflammatory cytokine production in macrophages. Our data demonstrate that pharmacological inhibition, along with LRH-1 knockdown, significantly reduced the lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines in the macrophage line RAW 264.7 cells, as well as in primary murine macrophages. This inhibitory effect was found to be independent of defects of LRH-1-regulated cell proliferation or toxic effects of the LRH-1 inhibitors. In contrast, LRH-1 inhibition reduced the mitochondrial ATP production and metabolism of macrophages through downregulation of the LRH-1 targets glucokinase and glutminase-2, and thus impairing the LPS-induced macrophage activation. Interestingly, in vivo pharmacological inhibition of LRH-1 also resulted in reduced tumor necrosis factor (TNF) production and associated decreased liver damage in a macrophage-and TNF-dependent mouse model of hepatitis. Noteworthy, despite hepatocytes expressing high levels of LRH-1, pharmacological inhibition of LRH-1 per se did not cause any obvious liver damage. Therefore, this study proposes LRH-1 as an emerging therapeutic target in the treatment of inflammatory disorders, especially where macrophages and cytokines critically decide the extent of inflammation.

Nuclear‐mitochondrial crosstalk: On the role of the nuclear receptor liver receptor homolog‐1 (NR5A2) in the regulation of mitochondrial metabolism, cell survival, and cancer

“…Similarly, the macrophagedependent production of TNFα and concomitant triggering of hepatocyte apoptosis was markedly reduced after LRH-1 inhibition in a murine hepatitis model in vivo. 11 Taken together these findings suggest that LRH-1 is regulating apoptotic processes also in cells of the hematopoietic system. On one hand, LRH-1 seems to regulate apoptosis directly, in a cell-autonomous manner, but on the other hand also affects the expression of death ligands, and thus induction of the extrinsic apoptotic pathway in neighboring or target cells.…”

“…135 In line with these findings, pharmacological inhibition of LRH-1 impaired mitochondrial ATP production through a decrease in glucokinase and also GLS2 expression in macrophages. 11 Unsurprisingly, upregulation of GLUTs, including GLUT4, 137 as well as increased expression of glycolytic enzymes, such as hexokinases, has been reported in different cancer cells that highly depend on glucose as an energy source. 138 Despite their critical role in glycolysis, the expression and mitochondrial association of hexokinases has further been linked to cellular growth, survival, and prevention of mitochondrial cell death in healthy, but above all also in malignant cells.…”

“…163 In our own studies investigating the role of LRH-1 in the hematopoietic system, we were able to confirm the antagonist effect of both inhibitors in macrophage and T cells in vitro and in vivo. 9,11 While investigating the role of LRH-1 in cells of the immune system, we recently observed that LRH-1 inhibitors also have anticancer effects in leukemic T and B cells. Unpublished data indicate that Cpd3d2 as well as SR1848 strongly suppress the proliferation capacity of acute lymphoblastic leukemia (ALL) cells in vitro.…”

“…160 Similarly promising, we could show that also injection of a single dose of Cpd3d2 into mice can have therapeutic effects on immune cell-mediated hepatitis without showing any general toxicity. 9,11 Even though hepatocytes express high levels of LRH-1 and various metabolic processes in the liver are dependent on LRH-1, no obvious liver damage or hepatocyte apoptosis was observed after pharmacological inhibition of LRH-1 alone. 11 Thus, it is feasible to believe that residual LRH-1 activity after Cpd3d2 treatment is sufficient to maintain normal physiological functions of the liver, and likely also other tissues and organs expressing high levels of LRH-1.…”

“…9,11 Even though hepatocytes express high levels of LRH-1 and various metabolic processes in the liver are dependent on LRH-1, no obvious liver damage or hepatocyte apoptosis was observed after pharmacological inhibition of LRH-1 alone. 11 Thus, it is feasible to believe that residual LRH-1 activity after Cpd3d2 treatment is sufficient to maintain normal physiological functions of the liver, and likely also other tissues and organs expressing high levels of LRH-1. As immune cells and transformed cells appear to have less spare capacity of residual LRH-1 activity, this opens a therapeutic window of opportunity for the treatment of inflammatory disorders and cancer.…”