Pifithrin-α hydrobromide is an inhibitor of p53, also acts as an aryl hydrocarbon receptor (AhR) agonist.

p53^[1]
AhR^[2]

Pifithrin-α (PFT-α) hydrobromideis a water-soluble compound that could suppress p53 protein transcription. Pifithrin-α can suppress glucose oxidase (GOX)-induced p53 protein increase in whole cell lysates, but cyclosporine A (CsA) fails to show such an inhibition effect. Notably, Pifithrin-α is able to block the GOX-induced Bcl-2 protein reduction. Similarly, it is Pifithrin-α rather than CsA that able to prevent the Bax increasing in whole cell lysates^[1]. Pifithrin-α inhibits p53-dependent apoptosis through an undetermined mechanism. Pifithrin-α also acts as an aryl hydrocarbon receptor (AhR) agonist and. Pifithrin-α is a potent AhR agonist as determined by its ability to bind the AhR, induce formation of its DNA binding complex, activate reporter activity, and up-regulate the classic AhR target gene CYP1A1^[2].

When the experiment is performed with Pifthirin-α (PFT-α) hydrobromide, a pharmacological p53 inhibitor, the percentage of annexin V-positiveFoxe3^-/- SMCs decreases to WT levels. Pifithrin-α (2.2 mg/kg, i.p.) significantly reduces the incidence of aortic rupture and intramural hematomas in Foxe3^-/- mice that underwent transverse aortic constriction (TAC) (50% to 17%, P<0.05). After Pifthirin-α treatment, the mean diameter of the ascending aorta and the percentage of TUNEL-positive cells in the aortic media are also normalized to WT levels in surviving Foxe3^-/- animals (P<0.05)^[3].

• [1]. Yu W, et al. Cyclosporine A Suppressed Glucose Oxidase Induced P53 Mitochondrial Translocation and Hepatic Cell Apoptosis through Blocking Mitochondrial Permeability Transition. Int J Biol Sci. 2016 Jan 1;12(2):198-209.

  [2]. Hoagland MS, et al. The p53 Inhibitor Pifithrin-α Is a Potent Agonist of the Aryl Hydrocarbon Receptor. J Pharmacol Exp Ther. 2005 Aug;314(2):603-10.

  [3]. Kuang SQ, et al. FOXE3 mutations predispose to thoracic aortic aneurysms and dissections. J Clin Invest. 2016 Mar 1;126(3):948-61.