TY - JOUR T1 - Cytoprotective Properties of Novel Nonpeptide Calpain Inhibitors in Renal Cells JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 88 LP - 94 DO - 10.1124/jpet.302.1.88 VL - 302 IS - 1 AU - Xiuli Liu AU - Jay F. Harriman AU - Rick G. Schnellmann Y1 - 2002/07/01 UR - http://jpet.aspetjournals.org/content/302/1/88.abstract N2 - Calpains are cytosolic, Ca2+-activated, neutral cysteine proteases. Rabbit renal proximal tubule (RPT) cells express both μ- and m-calpain. Although multiple calpain inhibitors protect against RPT cell death, most calpain inhibitors lack specificity, membrane permeability, and/or potency. A group of novel catalytic site-directed calpain inhibitors, including chloroacetic acidN′-[6,7-dichloro-4-(4-methoxy-phenyl)-3-oxo-3,4-dihydroquinoxalin-2-yl]hydrazide (SJA7019) and chloroacetic acid N′-(6,7-dichloro-4-phenyl-3-oxo-3,4-dihydroquinoxalin-2-yl) hydrazide (SJA7029), were identified to be potent calpain inhibitors in vitro. The goals of this study were to determine the action of these two compounds on 1) RPT calpain activity using fluorescein isothiocyanate-casein zymography, 2) antimycin A-induced RPT extracellular 45Ca2+ influx and cell death, and 3) hypoxia/reoxygenation-induced RPT cellular dysfunction and death. The results showed that the SJA compounds inhibited RPT μ- andm-calpain with equal potency (approximate IC50, 30 μM) and efficacy, and blocked antimycin A-induced extracellular Ca2+ influx and cell death. In addition, SJA7029 blocked cell death and allowed the recovery of mitochondrial function and active Na+ transport in RPTs subjected to hypoxia/reoxygenation. In summary, the SJA compounds 1) were more potent inhibitors of calpains than catalytic site-directed peptide inhibitors in this model, 2) prevented extracellular Ca2+ influx during the late phase of cell death, and 3) are true cytoprotectants and allow recovery of RPT cellular functions after injury. The American Society for Pharmacology and Experimental Therapeutics ER -