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Gupte R, Dhagia V, Rocic P, Ochi R, Gupte SA. Glucose-6-phosphate dehydrogenase increases Ca 2+ currents by interacting with Ca v1.2 and reducing intrinsic inactivation of the L-type calcium channel. Am J Physiol Heart Circ Physiol 2020; 319:H144-H158. [PMID: 32442021 DOI: 10.1152/ajpheart.00727.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Pyridine nucleotides, such as NADPH and NADH, are emerging as critical players in the regulation of heart and vascular function. Glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the pentose phosphate pathway, is the primary source and regulator of cellular NADPH. In the current study, we have identified two isoforms of G6PD (slow and fast migrating) and functionally characterized the slow migrating isoform of G6PD (G6PD545) in bovine and human arteries. We found that G6PD545 is eluted in the caveolae fraction of vascular smooth muscle (VSM) and has a higher maximum rate of reaction (Vmax: 1.65-fold) than its fast migrating isoform (G6PD515). Interestingly, caveolae G6PD forms a complex with the pore-forming α1C-subunit of the L-type Ca2+ channel, Cav1.2, as demonstrated by a proximity ligation assay in fixed VSMCs. Additionally, Förster resonance energy transfer (FRET) analysis of HEK293-17T cells cotransfected with red fluorescent protein (RFP)-tagged G6PD545 (C-G6PD545) and green fluorescent protein (GFP)-tagged Cav1.2-(Cav1.2-GFP) demonstrated strong FRET signals as compared with cells cotransfected with Cav1.2-GFP and C-G6PD515. Furthermore, L-type Ca2+ channel conductance was larger and the voltage-independent component of availability (c1) was augmented in C-G6PD545 and Cav1.2-GFP cotransfectants compared with those expressing Cav1.2-GFP alone. Surprisingly, epiandrosterone, a G6PD inhibitor, disrupted the G6PD-Cav1.2 complex, also decreasing the amplitude of L-type Ca2+ currents and window currents, thereby reducing the availability of the c1 component. Moreover, overexpression of adeno-G6PD545-GFP augmented the KCl-induced contraction in coronary arteries compared with control. To determine whether overexpression of G6PD had any clinical implication, we investigated its activity in arteries from patients and rats with metabolic syndrome and found that G6PD activity was high in this disease condition. Interestingly, epiandrosterone treatment reduced elevated mean arterial blood pressure and peripheral vascular resistance in metabolic syndrome rats, suggesting that the increased activity of G6PD augmented vascular contraction and blood pressure in the metabolic syndrome. These data suggest that the novel G6PD-Cav1.2 interaction, in the caveolae fraction, reduces intrinsic voltage-dependent inactivation of the channel and contributes to regulate VSM L-type Ca2+ channel function and Ca2+ signaling, thereby playing a significant role in modulating vascular function in physiological/pathophysiological conditions.NEW & NOTEWORTHY In this study we have identified a novel isozyme of glucose-6-phosphate dehydrogenase (G6PD), a metabolic enzyme, that interacts with and contributes to regulate smooth muscle cell l-type Ca2+ ion channel function, which plays a crucial role in vascular function in physiology and pathophysiology. Furthermore, we demonstrate that expression and activity of this novel G6PD isoform are increased in arteries of individuals with metabolic syndrome and in inhibition of G6PD activity in rats of metabolic syndrome reduced blood pressure.
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Affiliation(s)
- Rakhee Gupte
- Department of Pharmacology, New York Medical College, Valhalla, New York.,Department of Biochemistry, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Vidhi Dhagia
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Petra Rocic
- Department of Pharmacology, New York Medical College, Valhalla, New York.,Department of Biochemistry, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Rikuo Ochi
- Department of Pharmacology, New York Medical College, Valhalla, New York.,Department of Biochemistry, College of Medicine, University of South Alabama, Mobile, Alabama
| | - Sachin A Gupte
- Department of Pharmacology, New York Medical College, Valhalla, New York.,Department of Biochemistry, College of Medicine, University of South Alabama, Mobile, Alabama
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Ochi R, Chettimada S, Kizub I, Gupte SA. Dehydroepiandrosterone inhibits I Ca,L and its window current in voltage-dependent and -independent mechanisms in arterial smooth muscle cells. Am J Physiol Heart Circ Physiol 2018; 315:H1602-H1613. [PMID: 30379558 DOI: 10.1152/ajpheart.00291.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Dehydroepiandrosterone (DHEA) is an adrenal steroid hormone, which has the highest serum concentration among steroid hormones with DHEA sulfate (DHEAS). DHEA possesses an inhibitory action on glucose-6-phosphate dehydrogenase (G6PD), the first pentose-phosphate pathway enzyme that reduces NADP+ to NADPH. DHEA induced relaxation of high K+-induced contraction in rat arterial strips, whereas DHEAS barely induced it. We studied the effects of DHEA on L-type Ca2+ current ( ICa,L) of A7r5 arterial smooth muscle cells and compared the mechanism of inhibition with that produced by the 6-aminonicotinamide (6-AN) competitive inhibitor of G6PD. DHEA moderately inhibited ICa,L that was elicited from a holding potential (HP) of -80 mV [voltage-independent inhibition (VIDI)] and accelerated decay of ICa,L during the depolarization pulse [voltage-dependent inhibition (VDI)]. DHEA-induced VDI decreased peak ICa,L at depolarized HPs. By applying repetitive depolarization pulses from multiple HPs, novel HP-dependent steady-state inactivation curves ( f∞-HP) were constructed. DHEA shifted f∞-HP to the left and inhibited the window current, which was recorded at depolarized HPs and obtained as a product of current-voltage relationship and f∞-HP. The IC50 value of ICa,L inhibition was much higher than serum concentration. DHEA-induced VDI was downregulated by the dialysis of guanosine 5'- O-(2-thiodiphosphate), which shifted f∞-voltage to the right before the application of DHEA. 6-AN gradually and irreversibly inhibited ICa,L by VIDI, suggesting that the inhibition of G6PD is involved in DHEA-induced VIDI. In 6-AN-pretreated cells, DHEA induced additional inhibition by increasing VIDI and generating VDI. The inhibition of G6PD underlies DHEA-induced VIDI, and DHEA additionally induces VDI as described for Ca2+ channel blockers. NEW & NOTEWORTHY Dehydroepiandrosterone, the most abundantly released adrenal steroid hormone with dehydroepiandrosterone sulfate, inhibited L-type Ca2+ current and its window current in aortic smooth muscle cells. The IC50 value of inhibition decreased with the depolarization of holding potential to 15 µM at -20 mV. The inhibition occurred in a voltage-dependent manner as described for Ca2+ channel blockers and in a voltage-independent manner because of the inhibition of glucose-6-phosphate dehydrogenase.
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Affiliation(s)
- Rikuo Ochi
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama , Mobile, Alabama.,Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Sukrutha Chettimada
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama , Mobile, Alabama.,Harvard Medical School , Boston, Massachusetts
| | - Igor Kizub
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Sachin A Gupte
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama , Mobile, Alabama.,Department of Pharmacology, New York Medical College, Valhalla, New York
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Elvis-Offiah UB, Bafor EE, Eze GI, Igbinumwen O, Viegelmann C, Edrada-Ebel R. In vivo investigation of female reproductive functions and parameters in nonpregnant mice models and mass spectrometric analysis of the methanol leaf extract of Emilia Coccinea(Sims) G Dons. Physiol Rep 2016. [PMCID: PMC5260090 DOI: 10.14814/phy2.13047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
In Southern Nigeria, the leaves of Emilia coccinea (Sims) G Dons are used traditionally for birth control. This study was therefore aimed at evaluating the activities of the methanolic leaf extract of Emilia coccinea (EM) on parameters that affect reproduction as well as the acute toxic effects of the plant using nonpregnant female mice models. Leaves of EM were extracted by maceration with 99.8% methanol. Oral acute toxicity profiles were examined. The effects of EM on female reproductive cycle were determined after oral treatment with EM at 1000 and 100 mg/kg/day daily for 6 days using stilbesterol (1 mg/kg/day) and normal saline as controls. The activities of EM (1000 mg/kg/day and 100 mg/kg/day p.o) on reproductive hormones and organs were also studied using estradiol valerat (100 mg/kg/day p.o), progesterone (10 mg/kg/day s.c.), and normal saline as controls. The extract did not induce any observable toxic effect after 24 h. At 1000 mg/kg, the extract significantly shortened the estrus cycle (P < 0.05) while prolonging the estrus phase which were comparable to that observed with stilbesterol. The extract also increased uterine weight and altered the histology of uterine and ovarian tissues. The female reproductive hormones were additionally altered at 1000 mg/kg and the effects were comparable to that of estradiol valerat such as to indicate possible antifertility effects. LC‐HRFTMS analysis showed 9 putatively identified compounds with pyrrolizidine alkaloid occurring at the highest intensity among the identified compounds. In conclusion, the leaf extracts of EM has been shown in this study to exhibit antiovulatory and estrogenic activities which would support the traditional use of the plant in Nigeria.
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Affiliation(s)
- Uloma B. Elvis-Offiah
- Department of Science Laboratory Technology; Faculty of Life Sciences; University of Benin; Benin City Nigeria
| | - Enitome E. Bafor
- Department of Pharmacology and Toxicology; Faculty of Pharmacy; University of Benin; Benin City Nigeria
| | - Gerald I. Eze
- Department of Anatomy; School of Basic Medical Sciences; University of Benin; Benin City Nigeria
| | - Osamwonyi Igbinumwen
- Haematology Department; University of Benin Teaching Hospital; Benin City Nigeria
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Molnar D, Linders J, Mayer C, Schubert R. Insertion stability of poly(ethylene glycol)-cholesteryl-based lipid anchors in liposome membranes. Eur J Pharm Biopharm 2016; 103:51-61. [DOI: 10.1016/j.ejpb.2016.03.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 03/15/2016] [Accepted: 03/21/2016] [Indexed: 10/22/2022]
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Ochi R, Dhagia V, Lakhkar A, Patel D, Wolin MS, Gupte SA. Rotenone-stimulated superoxide release from mitochondrial complex I acutely augments L-type Ca2+ current in A7r5 aortic smooth muscle cells. Am J Physiol Heart Circ Physiol 2016; 310:H1118-28. [PMID: 26873970 DOI: 10.1152/ajpheart.00889.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 02/07/2016] [Indexed: 11/22/2022]
Abstract
Voltage-gated L-type Ca(2+) current (ICa,L) induces contraction of arterial smooth muscle cells (ASMCs), and ICa,L is increased by H2O2 in ASMCs. Superoxide released from the mitochondrial respiratory chain (MRC) is dismutated to H2O2 We studied whether superoxide per se acutely modulates ICa,L in ASMCs using cultured A7r5 cells derived from rat aorta. Rotenone is a toxin that inhibits complex I of the MRC and increases mitochondrial superoxide release. The superoxide content of mitochondria was estimated using mitochondrial-specific MitoSOX and HPLC methods, and was shown to be increased by a brief exposure to 10 μM rotenone. ICa,L was recorded with 5 mM BAPTA in the pipette solution. Rotenone administration (10 nM to 10 μM) resulted in a greater ICa,L increase in a dose-dependent manner to a maximum of 22.1% at 10 μM for 1 min, which gradually decreased to 9% after 5 min. The rotenone-induced ICa,L increase was associated with a shift in the current-voltage relationship (I-V) to a hyperpolarizing direction. DTT administration resulted in a 17.9% increase in ICa,L without a negative shift in I-V, and rotenone produced an additional increase with a shift. H2O2 (0.3 mM) inhibited ICa,L by 13%, and additional rotenone induced an increase with a negative shift. Sustained treatment with Tempol (4-hydroxy tempo) led to a significant ICa,L increase but it inhibited the rotenone-induced increase. Staurosporine, a broad-spectrum protein kinase inhibitor, partially inhibited ICa,L and completely suppressed the rotenone-induced increase. Superoxide released from mitochondria affected protein kinases and resulted in stronger ICa,L preceding its dismutation to H2O2 The removal of nitric oxide is a likely mechanism for the increase in ICa,L.
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Affiliation(s)
- Rikuo Ochi
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Vidhi Dhagia
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Anand Lakhkar
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Dhara Patel
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Michael S Wolin
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Sachin A Gupte
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
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