Role of PHB2 in mitochondrial calcium dynamics and mitophagy / 中国药理学与毒理学杂志

OBJECTIVE Mitochondria plays a crucial role in cellular homeostasis by regulating various pro-cesses,including calcium signaling and mitophagy.This study aimed to explore the involvement of prohibitin 2(PHB2),an inner mitochondrial membrane protein,in the modulation of mitochondrial calcium dynamics and mitoph-agy.METHODS HEK293T cells were used as the experi-mental cells and were divided into control,PHB2 knock-down,and PHB2 overexpression groups.To evaluate mitochondrial calcium dynamics,Rhod-2 AM and Mito-Tracker Green fluorescence dyesrhod-2 staining and laser confocal microscopy were employed to visualize mito-chondrial calcium imaging.Additionally,Green-5N was utilized to measure the rate of mitochondrial calcium uptake.The mitochondrial membrane potential was assessed using JC-10 staining and laser confocal micros-copy,while cellular ATP levels were determined using ATP assay kits.Furthermore,mitochondrial autophagy was induced by treatment with CCCP,and the expression lev-els of TOM20,LC3,and PARKIN,key mitophagy-related proteins,were analyzed using Western blotting.RESULTS The results demonstrated that compared to the control group,the overexpression of PHB2 increased mitochon-drial calcium concentration,mitochondrial calcium uptake rate,ATP level and expression levels of LC3 and PAR-KIN,but decreased mitochondrial membrane potential and TOM20 expression.In contrast,PHB2 knockdown reduced mitochondrial calcium concentration,ATP level and expression levels of LC3 and PARKIN,but elevated mitochondrial membrane potential,and TOM20 expres-sion.CONCLUSION This study provides evidence that PHB2 plays a vital role in regulating mitochondrial calci-um dynamics,which in turn influences mitochondrial func-tion and modulates mitochondrial autophagy.These find-ings contribute to our understanding of the molecular mechanisms underlying the interplay between PHB2,mitochondrial calcium signaling,and mitophagy.

Protective effects of ginkgolide k on focal cerebral ischemia reperfusion injury in rats on the basis of amelioration of mitochondrial calcium uniporter / 中国药学杂志

OBJECTIVE: To explore whether the protective mechanism of ginkgolide K on cerebral focal ischemia reperfusion injury in rats induced by middle cerebral artery occlusion (MCAO) was associated with the amelioration of mitochondrial calcium uniporter ( MCU) or not. METHODS: Sprague Dawley (SD) rats were divided into 5 big groups randomly: sham operation group, MCAO group, GK added into RR group, GK group and GK added into SM group. The MCAO rat model were established after cerebral artery ischemia for 2 h and reperfusion for 22 h. Zea Longa 5 score system was used to evaluate neurological deficit score; Determination of brain water content and cerebral infarction areas were determined using gravimetric method and by triphenyltetrazolium chloride(TTC) staining method, respectively. In addition, malondialdehyde (MDA) and superoxide dismutase (SOD), nitric oxide synthase (NOS), nitric oxide (NO) were detected by Elisa. Additionally, mitochondrial[Ca2+] i concentration was estimated with the fluorescence spectrophotomete. The morphological change of the injured brains were observed by HE staining. The expression of caspase-3/8/9 protein were detected by Western blot. RESULTS: Compared with GK group, GK + RR group relieved obviously the neurological deficit score and reduced the cerebral infarction areas, brain water content, mitochondrial[Ca2+]i concentration and MDA, caspase-3/8/9 protein expression while enhance SOD activity. However, the effect of SM on the GK protective activity in MCAO rat injury was the opposite in comparison to GK + RR group. CONCLUSION: The stimulative effect of RR and the inhibitory effect of SM on the GK protection in MCAO rat had proves that the protective mechanism of GK on MCAO rat injury is associate with its down-regulation of the transport capacity of MCU, leading the attenuation of mitochondrial[Ca2+]i influx.

Nobiletin attenuates neurotoxic mitochondrial calcium overload through K⁺ influx and ΔΨ(m) across mitochondrial inner membrane

Mitochondrial calcium overload is a crucial event in determining the fate of neuronal cell survival and death, implicated in pathogenesis of neurodegenerative diseases. One of the driving forces of calcium influx into mitochondria is mitochondria membrane potential (ΔΨ(m)). Therefore, pharmacological manipulation of ΔΨ(m) can be a promising strategy to prevent neuronal cell death against brain insults. Based on these issues, we investigated here whether nobiletin, a Citrus polymethoxylated flavone, prevents neurotoxic neuronal calcium overload and cell death via regulating basal ΔΨ(m) against neuronal insult in primary cortical neurons and pure brain mitochondria isolated from rat cortices. Results demonstrated that nobiletin treatment significantly increased cell viability against glutamate toxicity (100 µM, 20 min) in primary cortical neurons. Real-time imaging-based fluorometry data reveal that nobiletin evokes partial mitochondrial depolarization in these neurons. Nobiletin markedly attenuated mitochondrial calcium overload and reactive oxygen species (ROS) generation in glutamate (100 µM)-stimulated cortical neurons and isolated pure mitochondria exposed to high concentration of Ca²⁺ (5 µM). Nobiletin-induced partial mitochondrial depolarization in intact neurons was confirmed in isolated brain mitochondria using a fluorescence microplate reader. Nobiletin effects on basal ΔΨ(m) were completely abolished in K⁺-free medium on pure isolated mitochondria. Taken together, results demonstrate that K⁺ influx into mitochondria is critically involved in partial mitochondrial depolarization-related neuroprotective effect of nobiletin. Nobiletin-induced mitochondrial K⁺ influx is probably mediated, at least in part, by activation of mitochondrial K⁺ channels. However, further detailed studies should be conducted to determine exact molecular targets of nobiletin in mitochondria.

Protection of MICU1 against myocardial hypertrophy induced by angiotensin Ⅱ / 解放军医学杂志

Objective To investigate the role of mitochondrial calcium uptake 1 (MICUI) in myocardial hypertrophy of mice and underlying mechanism.Methods The model of myocardial hypertrophy was established via incubation of mouse cardiac myocytes (MCM) with 300nmol/L angiotensin Ⅱ (Ang Ⅱ) for 48 hours in vitro.After that,MICU1 specific small interfering RNA (siRNA) was delivered to knockdown MICU1 levels in MCM.On the other hand,adenovirus-mediated over-expression of MICU 1 was transfected into MCM.Accordingly,the expressions of ANP and BNP in myocardial cells were measured by qRT-PCR.Mitochondrial membrane potential and ATP contents were detected byJC-1 assay kit and ATP assay kit,respectively.Then,Western blotting and qRT-PCR were used to detect the levels of MICU1 in myocardial cells.The mitochondrial Ca2+ contents were measured via atomic absorption flame spectroscopy.The size of myocardial cells was determined by α-actinin staining.Results Mitochondrial membrane potential and ATP contents in hypertrophic cardiomyocytes induced by Ang Ⅱ were both decreased.Meanwhile,myocardial hypertrophy significantly increased mitochondrial Ca2+ contents but decreased MICU1 levels.With the method of genetic intervention,we found that MICUI deficiency exacerbated mitochondrial Ca2+ overload,increased cell surface and elevated the expression of BNP.Conversely,the overexpression of MICU1 obviously decreased mitochondrial Ca2+ overload,cell surface of MCM and expressions of ANP and BNP.Conclusion MICU1 alleviates Ang Ⅱ-induced myocardial hypertrophy via inhibiting mitochondrial Ca2+ overload.

Mitochondrial calcium uniporter inhibition attenuates mouse bone marrow-derived mast cell degranulation induced by beta-1,3-glucan

Mast cells are primary mediators of allergic inflammation. Beta-1,3-glucan (BG) protects against infection and shock by activating immune cells. Activation of the BG receptor induces an increase in intracellular Ca2+, which may induce exocytosis. However, little is known about the precise mechanisms underlying BG activation of immune cells and the possible role of mitochondria in this process. The present study examined whether BG induced mast cell degranulation, and evaluated the role of calcium transients during mast cell activation. Our investigation focused on the role of the mitochondrial calcium uniporter (MCU) in BG-induced degranulation. Black mouse (C57) bone marrow-derived mast cells were stimulated with 0.5 microg/ml BG, 100 microg/ml peptidoglycan (PGN), or 10 microM A23187 (calcium ionophore), and dynamic changes in cytosolic and mitochondrial calcium and membrane potential were monitored. BG-induced mast cell degranulation occurred in a time-dependent manner, and was significantly reduced under calcium-free conditions. Ruthenium red, a mitochondrial Ca2+ uniporter blocker, significantly reduced mast cell degranulation induced by BG, PGN, and A23187. These results suggest that the mitochondrial Ca2+ uniporter has an important regulatory role in BG-induced mast cell degranulation.

Role of mitochondrial calcium uniporter in hypoxic preconditioning / 中国病理生理杂志

AIM: To investigate the role of mitochondrial calcium uniporter (MCU) in the cardioprotection by hypoxic preconditioning (HPC) and its relationship to mitochondrial permeability transition pore (MPTP). METHODS: Intraventricular balloon technique was employed to measure the left ventricular developed pressure (LVDP), the maximum rise/fall rate of left ventricular pressure (?dp/dt_ max ), and the left ventricular end-diastolic pressure (LVEDP) in Langendorff isolated rat heart. The hypoxia was achieved by ligation of left anterior coronary artery for 30 min followed by release of ligation for 120 min as reoxygenation. Hypoxic preconditioning was set as two episodes of 5 min global hypoxia and 5 min reoxygenation. RESULTS: Both HPC and treatment with ruthenium red (5 ?mol/L) during the first 10 min reoxygenation improved recovery of LVDP, ?dp/dt_ max and decreased LVEDP, which was associated with reduced infarct size and lactate dyhydrogenase release. These protective effects were attenuated by treatment with spermine (20 ?mol/L) during the first 10 min reoxygenation. Administration of cyclosporin A (0.2 ?mol/L) during the last 5 min of hypoxia period and first 15 min of reoxygenation period reduced the injury effect by spermine. CONCLUSION: These results indicate that inhibition of MCU is involved in the cardioprotection of HPC via inhibiting MPTP.