Identification and characterisation of a prototype for a new class of competitive PPAR gamma antagonists

Understanding of the physiological role of peroxisome proliferalor-activated receptor gamma (PPARy) offers new opportunities for the treatment of cancers, immune disorders and inflammatory diseases. In contrast to PPARy agonists, few PPARy antagonists have been studied, though they do exert immunomodulalory effects. Currently, no therapeutically useful PPARy antagonist is commercially available. The aim of this study was to identify and kinetically characterise a new competitive PPARy antagonist for therapeutic use. A PPAR gamma-dependenl. transactivation assay was used to kinetically characterise (E)-2-(5-((4-melhoxy-2-(trifluoromethyl)quinolin-6-yl)methox y)-2-((4-(trifluo romethyl)benzyl)oxy)-benzylidene)-hexanoic acid (MTTB) in kidney, T and monocytic cell lines. Cytotoxic effects were analysed and intracellular accumulation of MTTB was assessed by tandem mass spectrometry (LC-MS/MS). Potential interactions of MTTB with the PPARy protein were suggested by molecular docking analysis. In contrast to non-competitive, irreversible inhibition caused by 2-chloro-5-nitrobenzanilide (GW9662), MTTB exhibited competitive antagonism against rosiglitazone in HEK293T and Jurkat T cells, with IC50 values in HEK293T cells of 4.3 mu M and 1.6 mu M, using the PPAR gamma ligand binding domain (PPAR gamma-LBD) and the full PPARy protein, respectively. In all cell lines used, however. MTTB showed much higher intracellular accumulation than GW9662. MTTB alone exhibited weak partial agonistic effects and low cytotoxicily. Molecular docking of MTTB with the PPAR gamma-LBD supported direct interaction with the nuclear receptor. MTTB is a promising prototype for a new class of competitive PPARy antagonists. It has weak partial agonistic and clear competitive antagonistic characteristics associated with rapid cellular uptake. Compared to commercially available PPARy modulators, this offers the possibility of dose regulation of PPARy and immune responses.