The Anti-Inflammatory Role of 3β-hydroxysteroid-△24 reductase (DHCR24) — The Association Specialists
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The Anti-Inflammatory Role of 3β-hydroxysteroid-△24 reductase (DHCR24) (406)

Robert Kasz 1 , Kristine McGrath 1 2 , Claire Tan 1 , Xiao Hong Li 1 , Alison Heather 1 2
  1. Medical and Molecular Biosciences, University of Technology, Sydney, Sydney, NSW, Australia
  2. Gene Regulation Group, Heart Research Institute, Newton, NSW, Australia

Background

Inflammation underlies insulin resistance and atherosclerosis. Extensive evidence shows that (A-I)rHDL elicits anti-inflammatory effects with most research focused on human coronary artery endothelial cells (HCAECs). Microarray data obtained in our laboratory identified dhcr24 as one of the most upregulated genes following treatment of HCAECs with (A-I)rHDL and moreover, that DHCR24 was, at least in part, mediating the anti-inflammatory effects of (A-I)rHDL. DHCR24 was originally identified as a cholesterol biosynthesis enzyme, but now has been shown to protect various cell types against oxidation, apoptosis and inflammation.

Aim

The aim of this study was to determine whether DHCR24 has anti-inflammatory effects in two key cell types, HCAECs and HuH7 cells. Inflammation of HCAECs drives the onset of atherosclerosis1 whilst inflammation of human hepatocytes (HuH7) underlies insulin resistance2.

Methods 

HCAECs and HuH7s were transfected with control and DHCR24 expression vectors to increase DHCR24 or siRNA to decrease DHCR24 before treated with TNF-α or H2O2 for 5 hours. Total RNA was extracted and RT-qPCR used to measure mRNA levels of DHCR24, as well as inflammation markers VCAM-1, ICAM-1, NOX-4, SAA1 or IL-8.

Results

RT-qPCR demonstrated that both HCAECs and HuH7 cells with increased DHCR24 expression were able to resist TNF-α and H2O2-induced inflammatory stress evidenced by decreased mRNA levels of VCAM-1, ICAM-1, NOX-4 (HCAEC) (P<0.0001 vs pControl); SAA1, and IL-8 (HuH7) (P<0.005 vs pControl). In striking contrast, decreased expression of DHCR24 led to significantly elevated inflammatory stress (P<0.0001 vs siControl) in both cell types. The protective effects are independent of DHCR24’s cholesterol synthesis role, as cholesterol content is not significantly altered in transfectants (P=0.413 vs pControl).

(A-I)rHDL treatment of HuH7 significantly upregulated the gene expression of DHCR24 (P<0.005 vs PBS control). Additionally, the anti-inflammatory functions of (A-I)rHDL are mediated, at least in part, by DHCR24 as decreased DHCR24 levels (P<0.0001 vs siControl) correlated with a loss of (A-I)r-HDL anti-inflammatory effects in HuH7 cells.

Conclusion

In summary, increased levels of DHCR24 have anti-inflammatory effects, in HCAEC and HuH7 cells. Further research into the mechanisms underlying DHCR24 potential cellular protective role is now required.

Abbreviations

(A-I) HDL: Apolipoprotein-I reconstituted high density lipoprotein; HCAEC: Human Coronary Artery Endothelial Cells; HuH7: Human hepatoma 7 cells; siRNA: short interfering RNA; VCAM-1: Vascular cell adhesion molecule 1; ICAM-1: Intracellular cell adhesion molecule 1; NOX-4: NADPH oxidase 4; SAA1: Serum Amyloid A1; IL-8: Interleukin-8

  1. Ross, R., Atherosclerosis--an inflammatory disease. N Engl J Med, 1999. 340(2): p. 115-26.
  2. Cai, D., Yuan, M., Frantz, D.F., Melendez, P.A., Hansen, L., Lee, J., and Shoelson, S.E. (2005). Local and systemic insulin resistance resulting from hepatic activation of IKK-beta and NF-kappaB. Nat Med 11, 183-190