Abstract P019: Renal Mitochondrial Bioenergetics In Salt-sensitive Hypertension Is Affected By ANP

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Regina Sultanova ◽  
Mark Domondon ◽  
Anna Nikiforova ◽  
Ryan Schibalski ◽  
Daria Ilatovskaya
Keyword(s):  
Mitochondrial Function ◽  
Calcium Influx ◽  
Kidney Injury ◽  
Mitochondrial Calcium ◽  
Mitochondrial Bioenergetics ◽  
Amplex Red ◽  
Respiratory Chain Activity ◽  
Mitochondrial Calcium Uptake ◽  
Salt Sensitive Hypertension

There are clinical data suggesting that low levels of Atrial Natriuretic Peptide (ANP) aggravate susceptibility to salt-sensitive (SS) hypertension. ANP is known to affect mitochondria in many tissues, however, little is known about the effects of ANP on renal mitochondrial function. According to our earlier studies, Dahl SS rats lacking ANP exhibit increased blood pressure and pronounced kidney injury. We hypothesized that in SS hypertension ANP deficiency affects renal mitochondrial bioenergetics and contributes to renal function impairment. SS hypertension was induced in male SS NPPA-/- ( Nppa knockout in Dahl SS background, KO) and SS WT (wild type, WT) rats by a high salt (HS) 4% NaCl diet administered for 21 days. Age-matched control animals were fed a normal (NS) 0.4% NaCl salt diet. A combination of in vivo studies, molecular biology and tests of mitochondria isolated from renal cortex (seahorse respiration and spectrofluorimetry assays using TMRM, Amplex Red and MCLA) were used to probe the role ANP in mitochondrial function. Data was analyzed with ANOVA followed by Holm-Sidak post hoc. We report a significant decrease in mitochondrial membrane potential in the SS NPPA-/- rats vs SS WT (25 ± 4% decrease in KO vs WT on NS, and a 16 ± 5% decrease in KO on HS). Furthermore, mitochondrial H 2 O 2 (57.7 ± 7.4 (WT) vs 57.6 ± 1.3 au (KO), p<0.0001) and superoxide (36.6± 1.8 au (WT) vs 67.9 ± 5.2 au (KO), p<0.0001) levels were increased in the KO on a HS diet. Next, we antioxidant capacity was elevated in the SS NPPA-/- rats on HS diet in comparison with SS WT , and increased SOD2 levels were observed in the KO animals. Furthermore, SS NPPA-/- rats exhibit higher MCU (mitochondrial calcium uniporter) activity than SS WT , implying an ANP-dependent effect on mitochondrial calcium influx. Seahorse assay revealed dramatic elevation of the basal, ATP-linked, maximal and spare oxygen consumption rate (OCR) in the cortical mitochondria of the knockout rats on HS, while in HS fed SS WT rats these OCR parameters were, as expected, reduced (vs NS). Therefore, deficiency of circulating ANP leads to significant changes of renal mitochondrial bioenergetics, potentially via effects on mitochondrial calcium uptake, which in turn affects respiratory chain activity leading to oxidative stress.

scholarly journals ApoE4 (Δ272–299) induces mitochondrial‐associated membrane formation and mitochondrial impairment by enhancing GRP75-modulated mitochondrial calcium overload in neuron

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tao Liang ◽  
Weijian Hang ◽  
Jiehui Chen ◽  
Yue Wu ◽  
Bin Wen ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Er Stress ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Function ◽  
Calcium Transport ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Mitochondrial Impairment

Abstract Background Apolipoprotein E4 (apoE4) is a major genetic risk factor of Alzheimer’s disease. Its C-terminal-truncated apoE4 (Δ272–299) has neurotoxicity by affecting mitochondrial respiratory function. However, the molecular mechanism(s) underlying the action of apoE4 (Δ272–299) in mitochondrial function remain poorly understood. Methods The impact of neuronal apoE4 (Δ272–299) expression on ER stress, mitochondrial-associated membrane (MAM) formation, GRP75, calcium transport and mitochondrial impairment was determined in vivo and in vitro. Furthermore, the importance of ER stress or GRP75 activity in the apoE4 (Δ272–299)-promoted mitochondrial dysfunction in neuron was investigated. Results Neuronal apoE4 (Δ272–299) expression induced mitochondrial impairment by inducing ER stress and mitochondrial-associated membrane (MAM) formation in vivo and in vitro. Furthermore, apoE4 (Δ272–299) expression promoted GRP75 expression, mitochondrial dysfunction and calcium transport into the mitochondria in neuron, which were significantly mitigated by treatment with PBA (an inhibitor of ER stress), MKT077 (a specific GRP75 inhibitor) or GRP75 silencing. Conclusions ApoE4 (Δ272–299) significantly impaired neuron mitochondrial function by triggering ER stress, up-regulating GRP75 expression to increase MAM formation, and mitochondrial calcium overload. Our findings may provide new insights into the neurotoxicity of apoE4 (Δ272–299) against mitochondrial function and uncover new therapeutic targets for the intervention of Alzheimer’s disease.

MCU-complex-mediated mitochondrial calcium signaling is impaired in Barth syndrome

2021 ◽  
Author(s):  
Sagnika Ghosh ◽  
Mohammad Zulkifli ◽  
Alaumy Joshi ◽  
Manigandan Venkatesan ◽  
Allen Cristel ◽  
...  
Keyword(s):  
Calcium Signaling ◽  
Cardiac Tissue ◽  
Barth Syndrome ◽  
Regulatory Subunit ◽  
Mitochondrial Calcium ◽  
Mitochondrial Bioenergetics ◽  
Mouse Muscle ◽  
Calcium Dependent ◽  
The Stability ◽  
Mitochondrial Calcium Uptake

Abstract Calcium signaling via mitochondrial calcium uniporter (MCU) complex coordinates mitochondrial bioenergetics with cellular energy demands. Emerging studies show that the stability and activity of the pore-forming subunit of the complex, MCU, is dependent on the mitochondrial phospholipid, cardiolipin (CL), but how this impacts calcium-dependent mitochondrial bioenergetics in CL-deficiency disorder like Barth syndrome (BTHS) is not known. Here we utilized multiple models of BTHS including yeast, mouse muscle cell line, as well as BTHS patient cells and cardiac tissue to show that CL is required for the abundance and stability of the MCU-complex regulatory subunit MICU1. Interestingly, the reduction in MICU1 abundance in BTHS mitochondria is independent of MCU. Unlike MCU and MICU1/MICU2, other subunit and associated factor of the uniporter complex, EMRE and MCUR1, respectively, are not affected in BTHS models. Consistent with the decrease in MICU1 levels, we show that the kinetics of MICU1-dependent mitochondrial calcium uptake is perturbed and acute stimulation of mitochondrial calcium signaling in BTHS myoblasts fails to activate pyruvate dehydrogenase, which in turn impairs the generation of reducing equivalents and blunts mitochondrial bioenergetics. Taken together, our findings suggest that defects in mitochondrial calcium signaling could contribute to cardiac and skeletal muscle pathologies observed in BTHS patients.

scholarly journals Dynamin-Related Protein 1 Deficiency Promotes Recovery from AKI

2017 ◽  
Vol 29 (1) ◽  
pp. 194-206 ◽  
Author(s):  
Heather M. Perry ◽  
Liping Huang ◽  
Rebecca J. Wilson ◽  
Amandeep Bajwa ◽  
Hiromi Sesaki ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Mitochondrial Function ◽  
Ischemia Reperfusion Injury ◽  
Mitochondrial Dynamics ◽  
Ischemia Reperfusion ◽  
Mitochondrial Fission ◽  
Kidney Injury ◽  
Related Protein

The proximal tubule epithelium relies on mitochondrial function for energy, rendering the kidney highly susceptible to ischemic AKI. Dynamin-related protein 1 (DRP1), a mediator of mitochondrial fission, regulates mitochondrial function; however, the cell-specific and temporal role of DRP1 in AKI in vivo is unknown. Using genetic murine models, we found that proximal tubule–specific deletion of Drp1 prevented the renal ischemia-reperfusion–induced kidney injury, inflammation, and programmed cell death observed in wild-type mice and promoted epithelial recovery, which associated with activation of the renoprotective β-hydroxybutyrate signaling pathway. Loss of DRP1 preserved mitochondrial structure and reduced oxidative stress in injured kidneys. Lastly, proximal tubule deletion of DRP1 after ischemia-reperfusion injury attenuated progressive kidney injury and fibrosis. These results implicate DRP1 and mitochondrial dynamics as an important mediator of AKI and progression to fibrosis and suggest that DRP1 may serve as a therapeutic target for AKI.

Abstract 15: The Role Of Opioid Receptors In Podocytes In The Development Of Hypertension In Dahl Salt-sensitive Rats

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Daria Golosova ◽  
Oleg Palygin ◽  
Vladislav Levchenko ◽  
Christine A Klemens ◽  
Ashraf El-Meanawy ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Opioid Receptors ◽  
Calcium Influx ◽  
Kidney Injury ◽  
Calcium Flux ◽  
Calcium Handling ◽  
Opioid Use ◽  
Intracellular Calcium Level ◽  
Stimulation Of

The rise in opioid use underscores the importance to better understand the direct and indirect effects of opioids on renal function and blood pressure. Although opioid use is associated with predictors of cardiovascular diseases, these drugs are common analgesics for hypertensive patients. We hypothesize that stimulation of opioid receptors (ORs) leads to elevated intracellular calcium level in podocytes ultimately leading to cell apoptosis, development of albuminuria and consequent progression of hypertension. Live calcium imaging experiments on freshly isolated glomeruli from rat and human kidneys, as well as human immortalized podocyte cell line, was performed to test the effect of specific ORs agonists. Following experiments assessed the effect of opioid signaling on the development of hypertension and kidney function in Dahl salt-sensitive (SS) rats, which were fed a 0.4% (LS) or 8% (HS) NaCl diets for 14 days with or without a daily i.v. bolus infusion of BRL52537, a potent and selective kappa-OR agonist. Stimulation of kappa-ORs, but not mu-ORs or delta-ORs, mediated calcium influx in podocytes through activation of TRPC6 channels. The effect of BRL52537 was completely abolished when we used the 0 mM calcium media or when a TRPC6 channel inhibitor (SAR7334) was applied. Triggering the kappa-OR/TRPC6 pathway induced podocyte cell shape changes via actin cytoskeleton remodeling. In vivo studies revealed that rats chronically treated with BRL52537 exhibited augmented blood pressure (MAP was 179 ± 15 vs. 151 ± 11 mmHg), albuminuria, and elevation in podocyte calcium. Western blot analysis revealed elevated levels of nephrin in urine samples and pro-caspase-3 in renal cortex. Moreover, TRPC6 expression was elevated under hypertensive conditions and further promoted pathological increase in calcium influx in response to kappa-OR stimulation. Summarizing the data, the opioid-induced increase in the calcium flux in podocytes is expected to contribute to kidney injury leading to progression of salt-induced hypertension. These data demonstrate that the kappa-OR/TRPC6 signaling pathway directly influences podocyte calcium handling, provoking the development of kidney injury in the opioid treated hypertensive cohort.

scholarly journals The mitochondrial calcium uniporter promotes arrhythmias caused by high-fat diet

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Leroy C. Joseph ◽  
Michael V. Reyes ◽  
Edwin A. Homan ◽  
Blake Gowen ◽  
Uma Mahesh R. Avula ◽  
...  
Keyword(s):  
Mitochondrial Dysfunction ◽  
High Fat Diet ◽  
Calcium Uptake ◽  
Saturated Fat ◽  
Calcium Handling ◽  
Mitochondrial Calcium ◽  
High Fat ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake

AbstractObesity and diabetes increase the risk of arrhythmia and sudden cardiac death. However, the molecular mechanisms of arrhythmia caused by metabolic abnormalities are not well understood. We hypothesized that mitochondrial dysfunction caused by high fat diet (HFD) promotes ventricular arrhythmia. Based on our previous work showing that saturated fat causes calcium handling abnormalities in cardiomyocytes, we hypothesized that mitochondrial calcium uptake contributes to HFD-induced mitochondrial dysfunction and arrhythmic events. For experiments, we used mice with conditional cardiac-specific deletion of the mitochondrial calcium uniporter (Mcu), which is required for mitochondrial calcium uptake, and littermate controls. Mice were used for in vivo heart rhythm monitoring, perfused heart experiments, and isolated cardiomyocyte experiments. MCU KO mice are protected from HFD-induced long QT, inducible ventricular tachycardia, and abnormal ventricular repolarization. Abnormal repolarization may be due, at least in part, to a reduction in protein levels of voltage gated potassium channels. Furthermore, isolated cardiomyocytes from MCU KO mice exposed to saturated fat are protected from increased reactive oxygen species (ROS), mitochondrial dysfunction, and abnormal calcium handling. Activation of calmodulin-dependent protein kinase (CaMKII) corresponds with the increase in arrhythmias in vivo. Additional experiments showed that CaMKII inhibition protects cardiomyocytes from the mitochondrial dysfunction caused by saturated fat. Hearts from transgenic CaMKII inhibitor mice were protected from inducible ventricular tachycardia after HFD. These studies identify mitochondrial dysfunction caused by calcium overload as a key mechanism of arrhythmia during HFD. This work indicates that MCU and CaMKII could be therapeutic targets for arrhythmia caused by metabolic abnormalities.

scholarly journals Sirtuin 5 depletion impairs mitochondrial function in human proximal tubular epithelial cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timo N. Haschler ◽  
Harry Horsley ◽  
Monika Balys ◽  
Glenn Anderson ◽  
Jan-Willem Taanman ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Mitochondrial Function ◽  
Kidney Injury ◽  
Tubular Epithelial Cells ◽  
Atp Production ◽  
Form And Function ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular

AbstractIschemia is a major cause of kidney damage. Proximal tubular epithelial cells (PTECs) are highly susceptible to ischemic insults that frequently cause acute kidney injury (AKI), a potentially life-threatening condition with high mortality. Accumulating evidence has identified altered mitochondrial function as a central pathologic feature of AKI. The mitochondrial NAD+-dependent enzyme sirtuin 5 (SIRT5) is a key regulator of mitochondrial form and function, but its role in ischemic renal injury (IRI) is unknown. SIRT5 expression was increased in murine PTECs after IRI in vivo and in human PTECs (hPTECs) exposed to an oxygen/nutrient deprivation (OND) model of IRI in vitro. SIRT5-depletion impaired ATP production, reduced mitochondrial membrane potential, and provoked mitochondrial fragmentation in hPTECs. Moreover, SIRT5 RNAi exacerbated OND-induced mitochondrial bioenergetic dysfunction and swelling, and increased degradation by mitophagy. These findings suggest SIRT5 is required for normal mitochondrial function in hPTECs and indicate a potentially important role for the enzyme in the regulation of mitochondrial biology in ischemia.

Abstract P401: The Anti-arrhythmic Effects Of VDAC Isoforms Are Mediated By Glutamate 73 Through Regulation Of Mitochondrial Calcium Transport

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Lauren Crisman ◽  
Hirohito Shimizu ◽  
Adam Langenbacher ◽  
Jie Huang ◽  
Kevin Wang ◽  
...  
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Cellular Processes ◽  
Excess Calcium ◽  
Evolutionarily Conserved ◽  
Mitochondrial Calcium Uptake

Mitochondria critically regulate cellular processes such as bioenergetics, metabolism, calcium homeostasis and apoptosis. VDAC proteins are abundant proteins that control the passage of ions and metabolites across the outer mitochondrial membrane. We have previously shown that activation of VDAC2, is able to buffer excess calcium and thereby suppress calcium overload induced arrhythmogenic events in vitro and in vivo. However, the mechanism by which VDAC2 regulates calcium transport and cardiac contractions remained unclear. It is also unclear whether all three VDAC isoforms (VDAC1,2 and 3) possess similar cardioprotective activity. The zebrafish tremblor/ncx1 mutant lacks functional NCX1 in cardiomyocytes leading to calcium overload, and the manifestation of fibrillation-like phenotypes. Using the tremblor/ncx1 mutant as a model, we observed isoform-specific differences between the VDAC family members. VDAC1 and VDAC2 enhanced mitochondrial calcium trafficking and restore rhythmic contraction in tremblor mutants, whereas, VDAC3 did not. We found that the differing rescue capabilities of VDAC proteins were dependent upon residues in their N-terminal halves. Phylogenetic analysis further revealed the presence of an evolutionarily conserved glutamate at position 73 (E73) within VDAC1 and VDAC2, but a glutamine (Q73) in VDAC3. Excitingly, we showed that replacing VDAC2 E73 with Q73 ablated its calcium transporting activity. Conversely, substituting the Q73 with E73 allows VDAC3 to gain calcium trafficking and cardioprotective abilities. Overall, our study demonstrates an essential role for the evolutionarily conserved glutamate-73 in determining the anti-arrhythmic effect of VDAC isoforms through their regulation of mitochondrial calcium uptake.

scholarly journals Mitochondrial calcium uptake regulates tumour progression in embryonal rhabdomyosarcoma

2021 ◽  
Author(s):  
Reshma Taneja ◽  
Hsin Yao Chiu ◽  
Amos Hong Pheng Loh
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Uptake ◽  
Cellular Proliferation ◽  
Myogenic Differentiation ◽  
Tumour Progression ◽  
Embryonal Rhabdomyosarcoma ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uptake

Embryonal rhabdomyosarcoma (ERMS) is characterized by a failure of cells to complete skeletal muscle differentiation. Although ERMS cells are vulnerable to oxidative stress, the relevance of mitochondrial calcium homeostasis in oncogenesis is unclear. Here, we show that ERMS cell lines as well as primary tumours exhibit elevated expression of the Mitochondrial Calcium Uniporter (MCU). MCU knockdown resulted in impaired mitochondrial calcium uptake and a reduction in mitochondrial reactive oxygen species (mROS) levels. Phenotypically, MCU knockdown cells exhibited reduced cellular proliferation and motility, with an increased propensity to differentiate in vitro and in vivo. RNA-sequencing of MCU knockdown cells revealed a significant reduction in genes involved in TGF? signalling that play prominent roles in oncogenesis and inhibition of myogenic differentiation. Interestingly, modulation of mROS production impacted TGF? signalling. Our study elucidates mechanisms by which mitochondrial calcium dysregulation promotes tumour progression and suggests that targeting the MCU complex to restore mitochondrial calcium homeostasis could be a therapeutic avenue in ERMS.

Sign in / Sign up

Export Citation Format

Share Document