Conjugated Linoleic Acid in the treatment of murine autoimmune glomerulonephritis

Conjugated linoleic acid (CLA) has been shown to reduce inflammation via Peroxisome Proliferator-Activated Receptor (PPAR)-γ in inflammatory disorders such as Crohn's Disease and Inflammatory Bowel Disease. We sought to determine whether CLA isomers would reduce inflammation via PPAR-γ in cultured mesangial cells, and in murine models of anti-glomerular basement membrane (anti-GBM) glomerulonephritis and Systemic Lupus Erythematosus (SLE). SV40-transformed mouse mesangial cells (MES13) were cultured with pure CLA isomers (c9,t11 or t10,c12-CLA or a 50:50 mixture prior to immune stimulation with lipopolysaccharide and interferon-γ. Next, cultured mesangial cells were transfected with small interfering RNA (siRNA) targeting PPAR-γ and treated with CLA isomers prior to immune stimulation. ELISA, qPCR, Western blot, and Griess reaction were performed to measure cytokine production, mRNA expression, induced nitric oxide synthase (iNOS) and nitrite production, respectively. Next, myeloid-specific (LysM creR2+) PPAR-γ knockout mice were treated with CLA prior to the induction of anti-GBM glomerulonephritis and evaluated for disease. Finally, NZM2410/J mice (a natural model of SLE) were treated with c9,t11-CLA and evaluated for disease progression. Treatment with CLA reduced IL-6 production in cultured mesangial cells, but not in siRNA-treated mesangial cells, supporting a PPAR-γ-mediated mechanism. CLA treatment increased both Transforming Growth Factor (TGF-β) and Interleukin-1 Receptor Antagonist (IL-1RA) mRNA expression independent of PPAR--γ. While CLA treatment reduced nitrite production and iNOS production to some degree, this was an inconsistent finding. Conversely, in the induced anti-GBM mouse model, CLA treatment increased mesangial cell IL-6 mRNA expression, reduced TGF-β expression, and had no effect on IL-1RA. Moreover, NZM2410/J mice that were fed a c9,t11-CLA-supplemented diet had reduced survival times, increased renal inflammation and increased serum IgG2a relative to controls. Taken together, these studies indicate that the in vitro MES13 cell line does not translate to the in vivo mouse model of anti-GBM induced glomerulonephritis. Furthermore, while CLA may have beneficial effects in other mouse models, it worsens disease in NZM2410/J mice. Findings from these models should be interpreted with caution.