A genetic locus accentuates the effect of volume overload on adverse left ventricular remodeling in male and female rats

Increased expression and intramitochondrial translocation of cyclophilin-D associates with increased vulnerability of the permeability transition pore to stress-induced opening during compensated ventricular hypertrophy

Opening of the permeability transition pore (PTP) of mitochondria is a critical permeation event that compromises cell viability and may constitute a factor that participates to the loss of cardiomyocytes in compromised hearts. Mitochondria from hearts with volume overload-induced compensated hypertrophy are more vulnerable to opening of the PTP opening in response to a Ca2+ stress. Several of the factors known to affect PTP opening, including respiratory function, membrane potential, the rate of mitochondrial Ca2+ uptake and endogenous levels of Ca2+ in the mitochondrial matrix, were not altered by volume overload. In contrast, there was an 80% increase in the abundance of the PTP regulating protein cyclophilin-D and a 3.7 fold enhancement of Cyp-D binding to membrane, which all predispose to PTP opening. Mitochondria from volume overloaded animals also displayed elevated rates of production of reactive oxygen species, which may be causally related to both the intramitochondrial translocation of cyclophilin-D and PTP opening, since incubation of cardiac mitochondria with terbutylhydroperoxyde in vitro increased to binding of cyclophilin-D to mitochondrial membranes in a dose-related fashion, except when cyclosporin A (a ligand of cyclophilin D with a known ability to delay PTP opening) was present prior to the addition of terbutylhydroperoxyde. Taken together, these results constitute the first evidence obtained in a pathophysiologic situation that increased abundance of cyclophilin-D within mitochondrial membranes may increase mitochondrial vulnerability to stress, and thus possibly initiate a vicious cycle of cellular dysfunction that may ultimately lead to activation of cell death.

Distinct quantitative trait loci for kidney, cardiac, and aortic mass dissociated from and associated with blood pressure in Dahl congenic rats

Blood pressure (BP) is largely determined by quantitative trait loci (QTLs) in Dahl salt-sensitive (DSS) rats. Little is known about QTLs controlling kidney (K), cardiac (C), and aortic (A) mass (i.e. Km, Cm, and Am, respectively) of DSS rats independent of BP. Their identification can facilitate our understanding of end organ damage. In this work, 36 congenic strains were employed to define QTLs for Km, Cm, and Am either independent of or associated with BP. Five new QTLs, i.e., KmQTLs, that influence Km independent of Cm, Am, and BP were defined. Four new CakmQTLs were defined for Cm, Am, and Km independent of BP. Among them, the CakmC10QTL1 interval contained 13 genes and undefined loci, and none was known to influence the phenotypes in question, paving the way for a novel gene discovery. Among 17 individual QTLs for BP, 14 also affected Cm, Km, and Am, i.e., they are BpcakmQTLs. In contrast, one BpQTL had no effect on Cm, Am, and Kam. Therefore, BP and Cm, Am, and Km have distinct and shared genetic determinants. The discovery of individual Km and Cakm QTLs will likely facilitate the identification of mechanisms underlying renal, cardiac, and/or aortic hypertrophy independent of hypertension.