Expression of interferon-stimulated gene 20 (ISG20), an antiviral effector protein, in glomerular endothelial cells: possible involvement of ISG20 in lupus nephritis

Abstract

Background

In addition to regulating the antiviral response, increased expression of Toll-like receptor 3 (TLR3) in resident renal cells plays a role in developing some forms of glomerulonephritis. TLR3 activation leads to type I interferon (IFN) production, which induces the expression of IFN-stimulated genes (ISGs). However, the role of ISG20 expression in resident renal cells remains unclear.

Methods

Cultured normal human glomerular endothelial cells (GECs) were treated with polyinosinic-polycytidylic acid (poly IC), Escherichia coli lipopolysaccharide (LPS), R848, and CpG (TLR3, TLR4, TLR7, and TLR9 agonists, respectively). The mRNA levels of ISG20, CX3CL1/fractalkine, and CXCL10/IP-10 were measured by quantitative reverse transcription-polymerase chain reaction. ISG20 protein expression was assessed by Western blotting. RNA interference was used to knockdown IFN-β and ISG20 expression. CX3CL1 protein levels were assessed by enzyme-linked immunosorbent assay. We performed immunofluorescence to examine endothelial ISG20 expression in biopsy specimens from patients with lupus nephritis (LN).

Results

In GECs, the expression of ISG20 mRNA and protein was increased by polyIC, not by LPS, R848, or CpG treatment. Moreover, ISG20 knockdown prevented poly IC-induced CX3CL1 expression but had no effect on CXCL10 expression. Intense endothelial ISG20 immunoreactivity was observed in biopsy specimens obtained from patients with proliferative LN.

Conclusion

In GECs, ISG20 was regulated via TLR3 but not via TLR4, TLR7, or TLR9 signaling. Moreover, ISG20 was involved in regulating CX3CL1 production. In addition to regulating antiviral innate immunity, ISG20 may act as a mediator of CX3CL1 production, thereby inducing glomerular inflammation, particularly in patients with LN.

Keywords:

• CX3CL1
• interferon-stimulated gene 20
• glomerular endothelial cells
• lupus nephritis
• toll-like receptor 3

Acknowledgement

A preprint version of the core tip of this MS has been published previously (Karasawa T, Sato R, Imaizumi T, et al. Implication of glomerular endothelial expression of interferon-stimulated gene 20, an antiviral effector protein, in human kidney inflammation. https://www.researchsquare.com/article/rs-1770007/v1.).

Ethics statement

This article does not contain any studies involving human participants or animals performed by any of the authors that otherwise requires ethical approval.

Patient consent

All authors read and approved the final manuscript.

Author contributions

T.I. and H.T. designed the study; T.K., R.S., M.F., T.A., K.T., S.K., K.S. and T.I. performed the experiments; T.K. and H.T. wrote the manuscript; and D.M. and K.T. provided technical support. K.J. performed immunostaining for ISG20 in renal biopsy specimens. T.I. and H.T. gave conceptual advice.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data generated or analyzed during this study are included in this article.

Additional information

Funding

Ministry of Education, Culture, Sports, Science and Technology of Japan (22K07862 to H.T.).