Rutkai 2015 Abstract MiPschool Greenville 2015

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Sex-differences in mitochondrial respiration is mediated by nitric oxide in rat cerebral arteries.

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Rutkai I, Katakam P, Busija D (2015)

Event: MiPschool Greenville 2015

Previous studies have provided evidence that circulating sex hormones alter mitochondrial dynamics of the cerebral circulation. However, the underlying mechanisms for this sex-based difference have not been determined in intact cerebral arteries. Due to higher nitric oxide synthase (NOS) levels in female vs male cerebral arteries, we tested the hypothesis that differences in NOS signaling mechanisms contribute to sex-based differences in mitochondrial respiration.

The Seahorse XFe24 analyzer was used to measure mitochondrial oxygen consumption rate (OCR; pM/min/μg protein) in large, isolated cerebral arteries from age matched male, female, and ovariectomized female, Sprague Dawley rats. The ovariectomized rats were treated with either a 21 d release, 0.5 mg of 17 -estradiol pellet (OVX+E) or placebo (OVX). The OCR was measured in the absence and presence of the NOS inhibitor, L-NAME, under basal conditions. Western blot was used to investigate the arterial expression of mitochondrial and non-mitochondrial proteins.

Mitochondrial respiration in female arteries in the absence of L-NAME (vehicle) normalized to protein levels (pM/min/g protein) including basal respiration (96.9 ± 15.2), ATP production (33 ± 5.3), proton leak (63.6 ± 10.5), maximal respiration (147.2 ± 21.6), and spare respiratory capacity (50.4 ± 8.4) were significantly elevated (p<0.05) compared with male (36.3 ± 8.5, 15.1 ± 4, 21.2 ± 4.6, 62.8 ± 16 and 26 ± 7.3, respectively). Treatment with 100 M L-NAME caused a significant increase over vehicle values in the OCR of male arteries for basal respiration (98.7 ± 8.8), ATP production (48.6 ± 8.6), proton leak (43.2 ± 11.7), maximal respiration (117.7 ± 16.7), and spare capacity (85.9 ± 9.7). However, L-NAME treatment in the female group caused a significant increase only in maximal respiration and spare capacity (224.3 ± 25.8 and 125.6 ± 20.2, respectively) compared with vehicle.

Treatment with 17 -estradiol caused higher serum estradiol levels (146.9 ± 18.16 pg/ml) and increased uterus weight (0.15 ± 0.0058 g) in the OVX+E compared with the OVX (14.7 ± 1.2 pg/ml, 0.07 ± 0.003, respectively; p<0.05). The components of mitochondrial respiration in pM/min/μg protein including basal respiration (147 ± 9), ATP production (44 ± 4), proton leak (102 ± 7), and maximal respiration (212 ± 13) were elevated in OVX+E compared with OVX (105 ± 13, 21 ± 4, 50 ± 6, 138 ± 10, respectively; p<0.05).

Expression of the mitochondrial DNA encoded Complexes I and III, the nuclear DNA encoded Complexes II, IV, V, and the voltage-dependent anion channel protein were higher in female compared with male but similar in the OVX and OVX+E groups. The ratios of phosphorylated eNOS and total eNOS and phosphorylated nNOS and total nNOS were significantly higher in the female (2.2 ± 0.6%, 1.2 ± 0.2%, respectively) and OVX+E (1.43 ± 0.06, 1.9 ± 0.3, respectively) compared with the male (0.88 ± 0.2%, 0.5 ± 0.2%, respectively) and OVX group (0.92 ± 0.06, 1.2 ± 0.13, respectively) arteries.


Labels: MiParea: Respiration, Gender 


Organism: Rat  Tissue;cell: Endothelial;epithelial;mesothelial cell 

Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase 

Coupling state: LEAK, ROUTINE, ET 


Event: Oral 


Affiliations

Tulane Univ School Med, Dept Pharmacology, New Orleans, LA, USA. - irutkai@tulane.edu


Abstract continued

Our findings provide direct evidence for sex-specific differences in mitochondrial function of isolated cerebral arteries. Estradiol replacement enhances the efficacy of the oxidative phosphorylation resulting in increased mitochondrial respiration which is not due to increased mitochondrial protein expression but may be due to enhanced NO availability. Inhibition of NOS enhanced mitochondrial respiration in cerebral arteries from male and female rats, but the relative effects of NOS inhibition were greater in male than female arteries.