Cutting edge: Leptin-induced RORγt expression in CD4+ T cells promotes Th17 responses in systemic lupus erythematosus

Abstract

Th17 CD4(+) cells promote inflammation and autoimmunity. In this study, we report that Th17 cell frequency is reduced in ob/ob mice (that are genetically deficient in the adipokine leptin) and that the administration of leptin to ob/ob mice restored Th17 cell numbers to values comparable to those found in wild-type animals. Leptin promoted Th17 responses in normal human CD4(+) T cells and in mice, both in vitro and in vivo, by inducing RORγt transcription. Leptin also increased Th17 responses in (NZB × NZW)F1 lupus-prone mice, whereas its neutralization in those autoimmune-prone mice inhibited Th17 responses. Because Th17 cells play an important role in the development and maintenance of inflammation and autoimmunity, these findings envision the possibility to modulate abnormal Th17 responses via leptin manipulation, and they reiterate the link between metabolism/nutrition and susceptibility to autoimmunity.

Figure 1

Leptin increases Th17 cell frequency in vitro and in vivo. Splenocytes from untreated ob/ob mice were stimulated under Th17 polarizing conditions and leptin was added at scalar doses during the last 18 hours of culture. The figure shows representative (a) and cumulative data from total splenocytes (b) and gated CD4⁺ T cells (c) from 8 mice in three independent experiments. (d-e) Representative (d) and cumulative data (e) from two experiments on splenocytes from ob/ob mice (n = 10) that were treated in vivo with leptin or saline (as control), according to the protocol described in the Materials and Methods. (f) IL-17⁺ T cells in PBMC from ob/ob mice treated with leptin (n = 10 per group, two experiments). *P<0.01, **P<0.007.

Figure 2

Leptin increases RORγt transcription and IL-17 production in CD4⁺ T cells. Sorted RORγt^-/- CD4⁺ T cells were stimulated with anti-CD3/CD28 Ab for 24 hours, transduced with retrovirus encoding RORγt, and restimulated with anti-CD3/CD28 Ab and scalar doses of leptin for 18 hours. The figure shows the flow cytometry results of RORγt (GFP) (a) and IL-17 expression (b) in the presence of scalar doses of leptin. c. Flow cytometry for RORγt expression in ob/ob CD4⁺ T cells cultured under polarizing (closed circles) or non-polarizing (open circles) conditions in the presence of scalar doses of leptin during the last 18 hours, stimulated (straight lines) or not (dashed lines) with PMA/ionomycin *P<0.05 in the comparison between polarizing and non-polarizing conditions.

Figure 3

Leptin promotes Th17 responses in NZB/W lupus mice. Representative (a) and cumulative data (b) (n = 8) from NZB/W mouse splenocytes cultured with scalar doses of leptin for 18 hours and stimulated with PMA/iomycin during the last 5 hr. Representative (c) and cumulative data (d) in PBMC (n = 8 per group) or splenocytes (e) (n = 8 per group) from NZB/W mice treated with saline, leptin or anti-leptin Ab (see Materials and Methods for details). *P<0.04, **P<0.006, ***P<0.002, ****P<0.004, *****P<0.02.