Th137 - T Cell-specific Deletion of rab4a Leads to Hepatic Mtor Activation, Liver Inflammation, and Reduction of Regulatory T Cell Expression in Systemic Lupus Erythematosus

Nick Huang, MD, PhD; Brandon Wyman, BS – MD/PhD Student, Medicine, SUNY Upstate Medical University; Manuel Duarte, BS; Joshua Lewis, BS; Katalin Banki, MD – SUNY Upstate Medical University; Andras Perl, MD, PhD – SUNY Distinguished Professor, Medicine, SUNY Upstate Medical University

Abstract Text: HRES-1/Rab4 (Rab4A) is a GTPase that mediates the accumulation of oxidative stress-generating mitochondria and activation of the mechanistic target of rapamycin (mTOR) in T cells of systemic lupus erythematosus (SLE) patients and livers of SLE-prone mice. We investigated the impact of Rab4A on liver disease, mTOR activation, and immunity in SLE-prone mice. Constitutively active Rab4A (Rab4AQ72L) and T cell-specific deletion of Rab4A (Rab4ACD4KO) were generated on lupus-prone SLE1.2.3. B6-triple congenic (B6.TC) mice. Rapamycin 3µg/g (or carboxymethylcellulose vehicle control) was administered to 27-week-old B6.TC mice 3 times weekly for 14 weeks. Liver chunks were homogenized for Western Blot analysis or fixed in formalin for histopathology and splenocytes were analyzed by flow cytometry. Among vehicle-treated mice, B6.TC.Rab4ACD4KO livers had more inflammatory foci/mm2 (0.39±0.092) compared to B6.TC.Rab4AQ72L livers (0.13±0.027; p=0.0498). B6.TC.Rab4ACD4KO livers had elevated p-4EBP1, a target of mTORC1, compared to B6.TC.Rab4AQ72L livers (p=0.0428). B6.TC.Rab4ACD4KO livers had more CD3+ pixels/mm2 (664126±113298) compared to B6.TCWT (270447±68656; p=0.019) and B6.TC.Rab4AQ72L (135154±10457; p=0.042) and more B220+ Pixels/mm2 (19837±973) compared to B6.TC.Rab4AQ72L mice (5683±2169; p=0.004). CD3 and B220 clustered together within the inflammatory foci of the B6.TC.Rab4ACD4KO livers. Flow cytometry of B6.TC.Rab4ACD4KO splenocytes showed a 65% decrease in the populations of FoxP3+CTLA-4+ CD4+ T cells (p=0.0486) and a 45% decrease in FoxP3+Helios+ CD4+ T cells (p=0.033) compared to B6.TC.Rab4AQ72L mice. T cell-specific deletion of Rab4A promoted inflammation, mTOR activation, and T and B cell clustering in the livers of lupus-prone B6.TC mice, which may be driven by defects in regulatory T cell populations.