Characterization of PPAR receptor activation by Troglitazone, a PPAR agonist

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Dr. David Strom Ph.D

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Medicine and Health Sciences


Troglitazone (TRO), a peroxisome proliferator-activated receptor (PPAR) agonist, was a drug used as an anti-inflammatory and anti-diabetic agent. We had previously investigated a PPAR agonist that induced apoptosis in dose dependent manner in our human colorectal cell line HCT116. Our current experiments are designed to determine if TRO is able to induce apoptosis, and if this action is mediated through the PPAR receptor subtypes. PPARɣ specifically is a known member of the steroid receptor superfamily and is a ligand-activated nuclear transcription factor that regulates lipid and glucose homeostasis. As a PPARɣ activator, TRO, a thiazolidinedione, has been shown to have the effect of inducing cell differentiation but also inhibiting cell growth, proliferation, and angiogenesis thereby facilitating apoptosis, making it a potential candidate to study as a cancer chemotherapeutic agent. Through the use of flow cytometry, TRO-induced apoptosis of tissue culture grown colorectal cancer cells was examined. Apoptosis was quantified by analyzing cells that contain less than the 2N DNA content (one hallmark of apoptosis). A dose response curve was determined for increasing concentrations of TRO vs sub2N DNA content. These studies confirm that TRO was able to induce apoptosis in our cell lines at concentrations greater than 30 M. Next we wanted to determine which PPAR receptors subtypes are being activated by TRO. HCT116 cells were exposed to various concentrations of TRO for 24hr then RNA was isolated from these cells. Specific gene targets to each PPAR receptor subtype were identified and using RT-PCR, changes in mRNAs expression was examined. Targets PPAR were consistently induced, PPAR were not induced, and PPAR were inconsistently induced. We are working to refine these experiments to get better determinations on which receptors are activated by TRO. These experiments confirm that TRO induces apoptosis in HCT116 cells. Additionally, we have identified changes in at least one target of PPAR receptors in response to TRO exposure. Further experiments are needed to exactly determine which PPAR receptors are being activated by TRO, and whether the apoptosis medicated by TRO is a result of PPAR receptor activation.


Copyright 2019 all authors

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