Permeability Of Inner Membrane Research Articles

Plumbagin enhances antimicrobial and anti-biofilm capacities of chlorhexidine against clinical Klebsiella pneumoniae while reducing resistance mutations.

With the widespread misuse of disinfectants, the clinical susceptibility of Klebsiella pneumoniae (K. pneumoniae) to chlorhexidine (CHX) has gradually diminished, posing significant challenges to clinical disinfection and infection control. K. pneumoniae employs overexpression of efflux pumps and the formation of thick biofilms to evade the lethal effects of CHX. Plumbagin (PLU) is a natural plant extract that enhances membrane permeability and reduces proton motive force. In this study, we elucidated the synergistic antimicrobial activity of PLU in combination with CHX, effectively reducing the MIC of CHX against K. pneumoniae to 1 µg/mL and below. Crucially, through crystal violet staining and confocal laser scanning microscopy live/dead staining, we discovered that PLU significantly enhances the anti-biofilm capability of CHX. Mechanistically, experiments involving membrane permeability, alkaline phosphatase leakage, reactive oxygen species, and RT-qPCR suggest that the combination of PLU and CHX improves the permeability of bacterial inner and outer membranes, promotes bacterial oxidative stress, and inhibits oqxA/B efflux pump expression. Furthermore, we conducted surface disinfection experiments on medical instruments to simulate clinical environments, demonstrating that the combination effectively reduces bacterial loads by more than 3 log10 CFU/mL. Additionally, results from resistance mutation frequency experiments indicate that combined treatment reduces the generation of resistant mutants within the bacterial population. In summary, PLU can serve as an adjuvant, enhancing the anti-biofilm capability of CHX and reducing the occurrence of resistance mutations, thereby extending the lifespan of CHX.IMPORTANCEAs disinfectants are extensively and excessively utilized worldwide, clinical pathogens are progressively acquiring resistance against these substances. However, high concentrations of disinfectants can lead to cross-resistance to antibiotics, and concurrent use of different disinfectants can promote bacterial resistance mutations and facilitate the horizontal transfer of resistance genes, which poses significant challenges for clinical treatment. Compared with the lengthy process of developing new disinfectants, enhancing the effectiveness of existing disinfectants with natural plant extracts is important and meaningful. CHX is particularly common and widely used compared with other disinfectants. Meanwhile, Klebsiella pneumoniae, as a clinically significant pathogen, exhibits high rates of resistance and pathogenicity. Previous studies and our data indicate a significant decrease in the sensitivity of clinical K. pneumoniae to CHX, highlighting the urgent need for novel strategies to address this issue. In light of this, our research is meaningful.

Inactivation mechanism of phenyllactic acid against Bacillus cereus spores and its application in milk beverage

Phenyllactic acid (PLA) as a natural phenolic acid exhibits antibacterial activity against non-spore-forming bacteria, while the inhibitory effect against bacterial spore remained unknown. Herein, this study investigated the inactivation effect of PLA against Bacillus cereus spores. The results revealed that the minimum inhibitory concentration of PLA was 1.25 mg/mL. PLA inhibited the outgrowth of germinated spores into vegetative cells rather than germination of spores. PLA disrupted the spore coat, and damaged the permeability and integrity of inner membrane. Moreover, PLA disturbed the establishment of membrane potential due to the inhibition of oxidative metabolism. SEM observations further visualized the morphological changes and structural disruption caused by PLA. Besides, PLA caused the degradation of DNA of germinated spores. Finally, PLA was applied in milk beverage, and showed promising inhibitory effect against B. cereus spores. This finding could provide scientific basis for the application of PLA against spore-forming bacteria in food industry.

Gasdermin D permeabilization of mitochondrial inner and outer membranes accelerates and enhances pyroptosis

Gasdermin D (GSDMD)-activated inflammatory cell death (pyroptosis) causes mitochondrial damage, but its underlying mechanism and functional consequences are largely unknown. Here, we show that the N-terminal pore-forming GSDMD fragment (GSDMD-NT) rapidly damaged both inner and outer mitochondrial membranes (OMMs) leading to reduced mitochondrial numbers, mitophagy, ROS, loss of transmembrane potential, attenuated oxidative phosphorylation (OXPHOS), and release of mitochondrial proteins and DNA from the matrix and intermembrane space. Mitochondrial damage occurred as soon as GSDMD was cleaved prior to plasma membrane damage. Mitochondrial damage was independent of the B-cell lymphoma 2 family and depended on GSDMD-NT binding to cardiolipin. Canonical and noncanonical inflammasome activation of mitochondrial damage, pyroptosis, and inflammatory cytokine release were suppressed by genetic ablation of cardiolipin synthase (Crls1) or the scramblase (Plscr3) that transfers cardiolipin to the OMM. Phospholipid scramblase-3 (PLSCR3) deficiency in a tumor compromised pyroptosis-triggered anti-tumor immunity. Thus, mitochondrial damage plays a critical role in pyroptosis.

Phosphatase A1 accessory protein PlaS from Serratia marcescens controls cell membrane permeability, fluidity, hydrophobicity, and fatty acid composition in Escherichia coli BL21

Phospholipase A1 (PlaA) plays a pivotal role in diverse applications within the food and biochemical medical industries. Herein, we investigate the impact of the accessory protein encoded by plaS from Serratia marcescens on PlaA activity in Escherichia coli. Notably, PlaS demonstrates the ability to enhance PlaA activity while concurrently exhibiting inhibitory effects on the growth of E. coli BL21 (DE3). Our study revolves around probing the inhibitory action of PlaS on E. coli BL21 (DE3). PlaS exhibits a propensity to heighten both the permeability of outer and inner cell membranes, leading to concomitant reductions in membrane fluidity and surface hydrophobicity. This phenomenon is validated through scanning electron microscopy (SEM) analysis, which highlights PlaS's capacity to compromise membrane integrity. Moreover, through a comprehensive comparative transcriptomic sequencing approach, we identify four down-regulated genes (galM, ybhC, ldtC, and kdpB) alongside two up-regulated genes (rbsB and degP). These genes are intricately associated with processes such as cell membrane synthesis and modification, energy metabolism, and transmembrane transport. Our investigation unveils the intricate gene-level mechanisms underpinning PlaS-mediated growth inhibition and membrane disruption. Consequently, our findings serve as a significant reference for the elucidation of membrane protein mechanisms, shedding light on potential avenues for future exploration.

Inactivation of Bacillus subtilis spores by a combination of high-pressure thermal treatment and potassium sorbate

Combining High-pressure Thermal Treatment (HPTT) and Potassium Sorbate (PS) may have a stronger spore inactivation effect. Spores of Bacillus subtilis were subjected to HPTT at 600 MPa-65 °C/75 °C and a combination of HPTT and PS of 0.1% and 0.2% concentrations. After these treatments, different procedures and techniques were employed to investigate the spore's inactivation. The results revealed that 4.92 ± 0.05 log spores were inactivated after treatment at 600 MPa-75 °C, while 5.97 ± 0.09 log spores were inactivated when the HPTT treatment was combined with 0.2% PS. Changes in permeability of the spore's inner membrane were characterized by OD600 value and release rates of nucleic acids, protein, and dipicolinic acid (DPA). Compared with HPTT treatment at 600 MPa-75 °C, the OD600 value of spores decreased further by about 50% after treatment with a combination of HPTT and 0.2% PS. Additionally, the combined treatments resulted in a significant increase in the OD260 and OD280 values, as well as the DPA release. The spore size analysis indicated a significant decrease in the size of spores treated with a combination of HPTT at 600 MPa-75 °C and PS of 0.2% concentration. Furthermore, the flow cytometry analysis and confocal laser scanning microscopy (CLSM) analysis indicated that the inner membrane damage of spores was higher after combined treatments than that after HPTT treatment alone. A significant reduction was also found in the Na+/K+-ATPase activity after the combined treatments. Also, the FTIR analysis revealed that the combined treatments resulted in significant adverse changes in the spores' inner membrane, cell wall, cortex, and nucleic acid. Therefore, the combination of HPTT and PS has a stronger inactivation effect and can be suggested as a promising strategy for the inactivation of Bacillus subtilis spores.

BODIPY-Functionalized Natural Polymer Coatings for Multimodal Therapy of Drug-Resistant Bacterial Infection.

The fact that multidrug resistance (MDR) could induce medical device-related infections, along with the invalidation of traditional antibiotics has become an intractable global medical issue. Therefore, there is a pressing need for innovative strategies of antibacterial functionalization of medical devices. For this purpose, a multimodal antibacterial coating that combines photothermal and photodynamic therapies (PTT/PDT) is developed here based on novel heavy atom-free photosensitizer compound, BDP-6 (a kind of boron-dipyrromethene). The photothermal conversion efficiency of BDP-6 is of 55.9%, which could improve biocompatibility during PTT/PDT process by reducing the exciting light power density. Furthermore, BDP-6, together with oxidized hyaluronic acid, is crosslinked with a natural polymer, gelatin, to fabricate a uniform coating (denoted as polyurethane (PU)-GHB) on the surface of polyurethane. PU-GHB has excellent synergistic in vitro PTT/PDT antibacterial performance against both susceptible bacteria and MDR bacteria. The antibacterial mechanisms are revealed as that hyperthermia could reduce the bacterial activity and enhance the permeability of inner membrane to reactive oxygen species by disturbing cell membrane. Meanwhile, in an infected abdominal wall hernia model, the notable anti-infection performance, good in vivo compatibility, and photoacoustic imaging property of PU-GHB are verified. A promising strategy of developing multifunctional antibacterial coatings on implanted medical devices is provided here.

Synthesis and Biological Evaluation of Piperazine Hybridized Coumarin Indolylcyanoenones with Antibacterial Potential.

A class of piperazine hybridized coumarin indolylcyanoenones was exploited as new structural antibacterial frameworks to combat intractable bacterial resistance. Bioactive assessment discovered that 4-chlorobenzyl derivative 11f showed a prominent inhibition on Pseudomonas aeruginosa ATCC 27853 with a low MIC of 1 μg/mL, which was four-fold more effective than norfloxacin. Importantly, the highly active 11f with inconspicuous hemolysis towards human red blood cells displayed quite low proneness to trigger bacterial resistance. Preliminary explorations on its antibacterial behavior disclosed that 11f possessed the ability to destroy bacterial cell membrane, leading to increased permeability of inner and outer membranes, the depolarization and fracture of membrane, and the effusion of intracellular components. Furthermore, bacterial oxidative stress and metabolic turbulence aroused by 11f also accelerated bacterial apoptosis. In particular, 11f could not only effectively inset into DNA, but also bind with DNA gyrase through forming supramolecular complex, thereby affecting the biological function of DNA. The above findings of new piperazine hybridized coumarin indolylcyanoenones provided an inspired possibility for the treatment of resistant bacterial infections.

Mechanosensitive channel MscL induces non-apoptotic cell death and its suppression of tumor growth by ultrasound.

Mechanosensitive channel of large conductance (MscL) is the most thoroughly studied mechanosensitive channel in prokaryotes. Owing to its small molecular weight, clear mechanical gating mechanism, and nanopore forming ability upon opening, accumulating studies are implemented in regulating cell function by activating mechanosensitive channel of large conductance in mammalian cells. This study aimed to investigate the potentials of mechanosensitive channel of large conductance as a nanomedicine and a mechano-inducer in non-small cell lung cancer (NSCLC) A549 cells from the view of molecular pathways and acoustics. The stable cytoplasmic vacuolization model about NSCLC A549 cells was established via the targeted expression of modified mechanosensitive channel of large conductance channels in different subcellular organelles. Subsequent morphological changes in cellular component and expression levels of cell death markers are analyzed by confocal imaging and western blots. The permeability of mitochondrial inner membrane (MIM) exhibited a vital role in cytoplasmic vacuolization formation. Furthermore, mechanosensitive channel of large conductance channel can be activated by low intensity focused ultrasound (LIFU) in A549 cells, and the suppression of A549 tumors in vivo was achieved by LIFU with sound pressure as low as 0.053MPa. These findings provide insights into the mechanisms underlying non-apoptotic cell death, and validate the nanochannel-based non-invasive ultrasonic strategy for cancer therapy.

Expression of the 2Duf protein in wild-type Bacillus subtilis spores stabilizes inner membrane proteins and increases spore resistance to wet heat and hydrogen peroxide.

This work aimed to characterize spore inner membrane (IM) properties and the mechanism of spore killing by wet heat and H2O2 with spores overexpressing the 2Duf protein, which is naturally encoded from a transposon found only in some Bacillus strains with much higher spore resistance than wild-type spores. Killing of Bacillus subtilis spores by wet heat or hydrogen peroxide (H2O2) was slower when 2Duf was present, and Ca-dipicolinic acid release was slower than killing. Viabilities on rich plates of wet heat- or H2O2 -treated spores +/- 2Duf were lower when NaCl was added, but higher with glucose. Addition of glucose but not Casamino acids addition increased treated spores' viability on minimal medium plates. Spores with 2Duf required higher heat activation for germination, and their germination was more wet-heat resistant than that of wild-type spores, processes that involve IM proteins. IM permeability and lipid mobility were lower in spores with 2Duf, although IM phospholipid composition was similar in spores +/- 2Duf. These results and previous work suggests that wet heat and H2O2 kill spores by damaging an IM enzyme or enzymes involved in oxidative phosphorylation.

Mitochondrial Permeability Transition

The mitochondrial permeability transition (PT) is a phenomenon that can be broadly defined as an increase in the permeability of the mitochondrial inner membrane [...].

Differentiating between fresh and frozen-thawed fish fillets by mitochondrial permeability measurement

In this study, we investigated the properties of mitochondria to discriminate fresh from frozen-thawed fish fillets. Mitochondria were isolated from gilthead seabream fillets and the impact of freezing was evaluated by measuring the permeability of mitochondrial membranes. Freezing led to permeabilization of mitochondrial inner membranes to reduced nicotinamide adenine dinucleotide (NADH). The increase in permeability related to freezing shock was compared to the physiological permeabilization of mitochondria isolated from gilthead seabream fillets stored at 4 °C. Two approaches were chosen to measure the increase in permeability: a spectrophotometric method to measure the consumption of NADH by complex I, and an oxygraphic method to measure O2 consumption by respiratory chains after exposure of mitochondria to NADH. Mitochondria isolated from frozen-thawed fillets were highly permeable to NADH and were no longer sensitive to a membrane permeabilizing agent: alamethicin. Altogether, our scientific approach allowed us to discriminate mitochondria isolated from fillets that have been exposed or not to a freezing shock (−80 °C) and thus to discriminate between fresh and frozen-thawed fish fillets.

Both ANT and ATPase are essential for mitochondrial permeability transition but not depolarization

An increase in permeability of the mitochondrial inner membrane, mitochondrial permeability transition (PT), is the central event responsible for cell death and tissue damage in conditions such as stroke and heart attack. PT is caused by the cyclosporin A (CSA)-dependent calcium-induced pore, the permeability transition pore (PTP). The molecular details of PTP are incompletely understood. We utilized holographic and fluorescent microscopy to assess the contribution of ATP synthase and adenine nucleotide translocator (ANT) toward PTP. In cells lacking either ATP synthase or ANT, we observed CSA-sensitive membrane depolarization, but not high-conductance PTP. In wild-type cells, calcium-induced CSA-sensitive depolarization preceded opening of PTP, which occurred only after nearly complete mitochondrial membrane depolarization. We propose that both ATP synthase and ANT are required for high-conductance PTP but not depolarization, which presumably occurs through activation of the low-conductance PT, which has a molecular nature that is different from both complexes.

Work and oxygen consumption of isolated right ventricular papillary muscle in experimental pulmonary hypertension.

Right-sided myocardial mechanical efficiency (work output/metabolic energy input) in pulmonary hypertension can be severely reduced. We determined the contribution of intrinsic myocardial determinants of efficiency using papillary muscle preparations from monocrotaline-induced pulmonary hypertensive (MCT-PH) rats. The hypothesis tested was that efficiency is reduced by mitochondrial dysfunction in addition to increased activation heat reported previously. Right ventricular muscle preparations were subjected to 5Hz sinusoidal length changes at 37°C. Work and suprabasal oxygen consumption ( ) were measured before and after cross-bridge inhibition by blebbistatin. Cytosolic cytochrome c concentration, myocyte cross-sectional area, proton permeability of the inner mitochondrial membrane and monoamine oxidase and glucose 6-phosphate dehydrogenase activities and phosphatidylglycerol/cardiolipin contents were determined. Mechanical efficiency ranged from 23% to 11% in control (n=6) and from 22% to 1% in MCT-PH (n=15) and correlated with work (r2 =0.68, P<0.0001) but not with (r2 =0.004, P=0.7919). for cross-bridge cycling was proportional to work (r2 =0.56, P=0.0005). Blebbistatin-resistant (r2 =0.32, P=0.0167) and proton permeability of the mitochondrial inner membrane (r2 =0.36, P=0.0110) correlated inversely with efficiency. Together, these variables explained the variance of efficiency (coefficient of multiple determination r2 =0.79, P=0.0001). Cytosolic cytochrome c correlated inversely with work (r2 =0.28, P=0.0391), but not with efficiency (r2 =0.20, P=0.0867). Glucose 6-phosphate dehydrogenase, monoamine oxidase and phosphatidylglycerol/cardiolipin increased in the right ventricular wall of MCT-PH but did not correlate with efficiency. Reduced myocardial efficiency in MCT-PH is a result of activation processes and mitochondrial dysfunction. The variance of work and the ratio of activation heat reported previously and blebbistatin-resistant are discussed. KEY POINTS: Mechanical efficiency of right ventricular myocardium is reduced in pulmonary hypertension. Increased energy use for activation processes has been demonstrated previously, but the contribution of mitochondrial dysfunction is unknown. Work and oxygen consumption are determined during work loops. Oxygen consumption for activation and cross-bridge cycling confirm the previous heat measurements. Cytosolic cytochrome c concentration, proton permeability of the mitochondrial inner membrane and phosphatidylglycerol/cardiolipin are increased in experimental pulmonary hypertension. Reduced work and mechanical efficiency are related to mitochondrial dysfunction. Upregulation of the pentose phosphate pathway and a potential gap in the energy balance suggest mitochondrial dysfunction in right ventricular overload is a resiult of the excessive production of reactive oxygen species.

Mechanisms of Bacillus subtilis spore inactivation by single- and multi-pulse high hydrostatic pressure (MP-HHP)

Herein we investigate the effect of multi-pulse high hydrostatic pressure (MP-HHP) on the inactivation of Bacillus subtilis spores. B. subtilis spores were subjected to MP-HHP under pressures at 200–500 MPa at temperatures of 40 and 60 °C with 3 pulses (holding time of 3 min) with a total processing time of 10 min and compared it with a single pressurization (S-HHP).Mechanism of spore inactivation by S- or MP-HHP was explored by assessing germination by heat shock treatment, spore susceptibility to lysozyme and hydrogen peroxide (H2O2), release of dipicolinic acid (DPA), and the permeability of inner membrane and cortex. Our results presented the highest spore inactivation (5.8 log reduction), when MP-HHP was applied under the highest temperature and pressure. The increased inactivation appears to be largely due to mechanical disruption of spore coat and inner and outer membranes, as evidenced by DPA release, increased susceptibility to lysozyme and H2O2 (indicative of breakage of disulfide bonds in the spore coat), and membrane permeability as assessed by spore staining and fluorescence microscopy. No differences were seen in germination between MP-HHP and S-HHP. There was no evidence of any loss of cortex lytic enzymes or degradation of small acid-soluble proteins (SASPs) during both MP-HHP and S-HHP treatments.

Evaluation of the antimicrobial activities and mechanisms of synthetic antimicrobial peptide against food-borne pathogens

Food-borne pathogens are an important challenge for the food industry. In this study, the possibility of using the previously designed and synthesized antimicrobial peptide HX-12C as a new food antimicrobial was evaluated. Bacteriostatic and bactericidal tests showed that HX-12C has strong, rapid and broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria. Outer- and inner-membrane permeabilization assays revealed that HX-12C killed food-borne pathogens by inducing membrane permeability. Further Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) also showed that HX-12C can distinctively act on the bacterial membrane leading to the leakage of cellular contents. Moreover, HX-12C also showed anti-biofilm ability in bacterial killing tests. In the food storage test, HX-12C exhibited significant antimicrobial function in raw pork and orange juice. Therefore, HX-12C has shown great potential as a new antimicrobial agent in food storage.

High Pressure Thermal Sterilization and ε-Polylysine Synergistically Inactivate Bacillus subtilis Spores by Damaging the Inner Membrane

This study was conducted to determine the sterilization effect of a combination of high pressure thermal sterilization (HPTS) and ε-polylysine (ε-PL) on Bacillus subtilis spores. The spores were treated with HPTS (550 MPa at 25, 65, and 75°C) and ε-PL at 0.1 and 0.3%. HPTS and ε-PL synergistically decreased the number of surviving spores and increased the release of the intracellular components in the spore suspension, with the maximal effects from treatment with 550 MPa at 75°C plus 0.3% ε-PL. Maximum fluidity and permeability of the cell inner membrane were observed with 550 MPa at 75°C plus 0.3% ε-PL. Changes in membrane lipids were detected from 3,000 to 2,800 cm-1 by Fourier transform infrared spectroscopy. The results provide new insights into the mechanism by which HPTS and ε-PL synergistically sterilize B. subtilis spores.

Antimicrobial activity of PvH4a, a peptide derived from histone H4 of Penaeus vannamei

Histones are important players in the formation and transcriptional regulation of eukaryotic nucleosomes. In most vertebrates, histones and histone-derived peptides have also been implicated in antimicrobial activities against various pathogenic microbes. In this study, the sera of Vibrio parahaemolyticus -infected Penaeus vannamei shrimp were filtered through 3 kDa ultrafiltration tubes followed by analysis using reversed-phase high performance liquid chromatography (HPLC). A novel histone H4-derived peptide (TVTAMDVVYALK) was identified and designated as PvH4a. Peptide PvH4a had strong antimicrobial activity against Gram-negative bacteria with the MIC value of 15.6–62.5 μg/mL ( Vibrio. parahaemolyticus, Vibrio fluvialis and Vibrio alginolyticus ) and no effect on Gram-positive bacteria ( Staphylococcus aureus and Streptococcus iniae ). In addition, PvH4a increased the inner-membrane permeability of V. parahaemolyticus concentration-dependently at 1 × MIC and had no adverse effects on normal human hepatocytes (LO2 cells) even at high concentrations (16 × MIC), with a cell survival rate of more than 90.3%. Furthermore, SEM analysis revealed that PvH4a could destroy the cell walls of Gram-negative bacteria as part of its antimicrobial action. Put together, the current findings indicate that during immune response to bacteria infection, shrimp histone H4 generates antimicrobial peptides such as PvH4a as part of the innate immune response. • A novel AMP PvH4a was identified from sera of V. parahaemolyticus -infected P. vannamei . • PvH4a had strong antimicrobial activity against Gram-negative bacteria and no adverse effects on normal human hepatocytes (LO2). • PvH4a comes from the C-terminal of shrimp P. vannamei histone H4. • The antimicrobial activity of PvH4a is executed by increasing the membrane permeability of bacterial.

Ribonuclease1 contributes to the antibacterial response and immune defense in blunt snout bream (Megalobrama amblycephala)

Ribonuclease 1 (RNase1) is a vertebrate-specific enzyme that mainly performs digestive activity in herbivorous mammals. Here we used bacterial viability assays to explore its antimicrobial activity in blunt snout bream (Megalobrama amblycephala). The results showed that Ma-RNase1 rapidly killed Gram-negative and Gram-positive bacteria at micromolar concentrations. Ma-RNase1 increased the permeability of bacterial outer and inner membranes, thus reducing the integrity of bacterial cell wall and membrane. Moreover, Ma-RNase1 effectively counteracted the tissue damage and apoptosis caused by Aeromonas hydrophila infection. Quantitative real-time PCR and immunoblot analysis indicated that RNase1 mRNA and protein were up-regulated in the kidney and gut during infection. Furthermore, A. hydrophila infection significantly induced Tnf-α and Il-1β mRNA expression in liver, but not in the RNase1 pre-treatment group. In addition, a significant increase in the expression of immune-related genes (Nf-κb and Tlr4) was found in liver, kidney and gut of A. hydrophila-infected fish, while a decrease in Myd88 and Tlr4 levels was found in liver, spleen, kidney and gut in the group pre-treated with RNase1. Collectively, these data suggest that Ma-RNase1 has antimicrobial function both in vitro and in vivo, and contributes to the protective effect and immune defense of blunt snout bream.

Mitochondrial Cyclosporine A-Independent Palmitate/Ca2+-Induced Permeability Transition Pore (PA-mPT Pore) and Its Role in Mitochondrial Function and Protection against Calcium Overload and Glutamate Toxicity.

A sharp increase in the permeability of the mitochondrial inner membrane known as mitochondrial permeability transition (or mPT) occurs in mitochondria under the conditions of Ca2+ and ROS stress. Permeability transition can proceed through several mechanisms. The most common mechanism of mPT is based on the opening of a cyclosporine A (CSA)-sensitive protein channel in the inner membrane. In addition to the CSA-sensitive pathway, mPT can occur through the transient opening of lipid pores, emerging in the process of formation of palmitate/Ca2+ complexes. This pathway is independent of CSA and likely plays a protective role against Ca2+ and ROS toxicity. The review considers molecular mechanisms of formation and regulation of the palmitate/Ca2+-induced pores, which we designate as PA-mPT to distinguish it from the classical CSA-sensitive mPT. In the paper, we discuss conditions of its opening in the biological membranes, as well as its role in the physiological and pathophysiological processes. Additionally, we summarize data that indicate the involvement of PA-mPT in the protection of mitochondria against calcium overload and glutamate-induced degradation in neurons.

Electrophysiological properties of the mitochondrial permeability transition pores: Channel diversity and disease implication

The mitochondrial permeability transition pore (mPTP) is a channel that, when open, is responsible for a dramatic increase in the permeability of the mitochondrial inner membrane, a process known as the mitochondrial permeability transition (mPT). mPTP activation during Ca2+ dyshomeostasis and oxidative stress disrupts normal mitochondrial function and induces cell death. mPTP opening has been implicated as a critical event in many diseases, including hypoxic injuries, neurodegeneration, and diabetes. Discoveries of recent years indicate that mPTP demonstrates very complicated behavior and regulation, and depending on specific induction or stress conditions, it can function as a high-conductance pore, a small channel, or a non-specific membrane leak. The focus of this review is to summarize the literature on the electrophysiological properties of the mPTP and to evaluate the evidence that it has multiple molecular identities. This review also provides perspective on how an electrophysiological approach can be used to quantitatively investigate the biophysical properties of the mPTP under physiological, pharmacological, pathophysiological, and disease conditions.