Permeability Transition Research Articles

N-terminal cleavage of cyclophilin D boosts its ability to bind F-ATP synthase.

Cyclophilin (CyP) D is a regulator of the mitochondrial F-ATP synthase. Here we report the discovery of a form of CyPD lacking the first 10 (mouse) or 13 (human) N-terminal residues (ΔN-CyPD), a protein region with species-specific features. NMR studies on recombinant human full-length CyPD (FL-CyPD) and ΔN-CyPD form revealed that the N-terminus is highly flexible, in contrast with the rigid globular part. We have studied the interactions of FL and ΔN-CyPD with F-ATP synthase at the OSCP subunit, a site where CyPD binding inhibits catalysis and favors the transition of the enzyme complex to the permeability transition pore. At variance from FL-CyPD, ΔN-CyPD binds OSCP in saline media, indicating that the N-terminus substantially decreases the binding affinity for OSCP. We also provide evidence that calpain 1 is responsible for generation of ΔN-CyPD in cells. Altogether, our work suggests the existence of a novel mechanism of modulation of CyPD through cleavage of its N-terminus that may have significant pathophysiological implications.

Cardioprotective Effect of Chronic Hypoxia Involves Inhibition of Mitochondrial Permeability Transition Pore Opening

The aim of the study was to examine the potential role of mitochondrial permeability transition pore (mPTP) in the cardioprotective effect of chronic continuous hypoxia (CH) against acute myocardial ischemia/reperfusion (I/R) injury. Adult male Wistar rats were adapted to CH for 3 weeks, while their controls were kept under normoxic conditions. Subsequently, they were subjected to I/R insult while being administered with mPTP inhibitor, cyclosporin A (CsA). Infarct size and incidence of ischemic and reperfusion arrhythmias were determined. Our results showed that adaptation to CH as well as CsA administration reduced myocardial infarct size in comparison to the corresponding control groups. However, administration of CsA did not amplify the beneficial effect of CH, suggesting that inhibition of mPTP opening contributes to the protective character of CH.

Benzylurea Protects hPDLFs Against LPS-Induced Mitochondrial Dysfunction Through MTCH2.

The aim of this study is to explore the mechanism of benzylurea in the inflammatory injury of human periodontal ligament fibroblasts (hPDLFs). An inflammation model of hPDLFs was established using LPS. Nuclear transport of nuclear transcription factor-κB (NF-κB), secretion of cytokines, and the morphology and distribution of F-actin were determined. Mitochondrial function was assessed by measuring mitochondrial membrane potential (MMP), mitochondrial permeability transition pore (mPTP), and reactive oxygen species (ROS) levels. The expression of mitochondrial carrier homolog 2 (MTCH2) and Cytochrome b5 type B (CYB5B) was detected. Benzylurea alleviated the effects of lipopolysaccharide (LPS) on the proliferation and apoptosis of hPDLFs. It reduced the release of inflammatory cytokines and inhibited NF-κB nuclear translocation. Benzylurea improved mitochondrial function by regulating MMP and preventing excessive mPTP opening. Furthermore, LPS elevated the expression of MTCH2 and reduced the expression of CYB5B in hPDLFs. However, these effects can be inhibited by benzylurea. The altered expression of MTCH2 directly affected CYB5B expression, the release of inflammatory cytokines, and the activation of nuclear translocation of NF-κB. CYB5B may act as an effector of MTCH2, with benzylurea enhancing mitochondrial function and protecting hPDLFs from LPS-induced injury through MTCH2.

Changes in apoptosis in large yellow croaker (Larimichthys crocea) after death: considering the influence of mitochondria and microorganisms

The apoptosis of large yellow croaker stored at 4 °C after death and the effects of five microorganisms extracted from fillets on apoptosis indicators were studied. The results showed that mitochondrial permeability transition pore (MPTP), apoptosis rate, mitochondrial swelling, caspase activity, and cytochrome c (cyt-c) redox state of samples at 0 h were the highest during postmortem storage (p < 0.05). The continuous opening of MPTP and mitochondrial swelling during postmortem storage led to an increase in cyt-c redox status and affected caspase activity. MPTP opening was significantly affected by the inoculation samples with Acinetobacter haemolyticus and Chryseobacterium (p < 0.05). The samples inoculated with Psychrobacter and Pseudomonas had a significant effect on the cyt-c redox state (p < 0.05). The samples inoculated with Pseudomonas and Acinetobacter haemolyticus had a significant effect on caspase activity (p < 0.05). Although this study found that microorganisms can affect apoptosis, it provides a foundation for future in-depth research. However, apoptosis is affected by a variety of signaling molecules, and in order to explore its specific mechanism, more extensive exploration is needed.

Buyang Huanwu Decoction restores the balance of mitochondrial dynamics after cerebral ischemia-reperfusion through calcium overload reduction by the PKCε-Nampt-Sirt5 axis

Ethnopharmacological relevanceStroke is a common condition that poses a significant threat to human health. Buyang Huanwu Decoction (BYHWD) is a traditional treatment used for stroke management. However, the exact mechanism by which BYHWD mitigates cerebral ischemia-reperfusion by regulating calcium overload and restoring mitochondrial function is not yet fully understood. AimThe objective of this research was to examine the neuroprotective properties of BYHWD in reducing the damage produced by cerebral ischemia/reperfusion (I/R) injury via the modulation of calcium overload and mitochondrial dynamics (MD). MethodsMCAO/R model success was evaluated via PSI laser scatter flowmetry. The neurological function scores were assessed. The cerebral infarct (CI) volume was detected via TTC staining. NeuN expression was detected via immunohistochemistry, and degenerated neurons were observed via FJC staining. The mitochondrial permeability transition pore (mPTP), the mitochondrial membrane potential (MMP), and ATP were detected. The reactive oxygen species (ROS) content and the NAD+/NADH ratio were determined. The glutamate (Glu) and glutamine (Gln) contents as well as the Ca2+ concentration were determined. The expression of PKCε, p-PKCε, namely, Sirt5, GLS, Drp1, p-Drp1 616, Fis1, Opa1, and Mfn2 was determined via Western blotting. Immunohistochemistry was used to detect p-PKCε, which is expressed at high levels. Immunofluorescence was used to detect p-Drp1 616, Opa1 and Sirt5 fluorescence intensity. ResultsBYHWD treatment enhanced neurological function, decreased the amount of CI, mitigated neuronal damage, decreased mPTP opening, restored the MMP, increased ATP synthesis, and decreased the ROS content after brain I/R. It also increased PKCε, p-PKCε, Sirt5, GLS, Opa1 and Mfn2 expression; downregulated p-Drp1 616, Drp1 and Fis1 expression; elevated the NAD+/NADH ratio and Gln content; and decreased the Glu content and Ca2+ concentration. The effects of BYHWD were reversed by the administration of the PKCε inhibitor εV1-2. BYHWD administration led to increased PKCε mRNA expression. ConclusionsBYHWD modulates MD by diminishing calcium overload through the PKCε-Nampt-Sirt5 axis, which restores mitochondrial function and mitigates brain I/R damage.

Regulated cell death in chronic kidney disease: current evidence and future clinical perspectives.

Chronic kidney disease (CKD) is the progressive loss of kidney function/structure over a period of at least 3months. It is characterised histologically by the triad of cell loss, inflammation and fibrosis. This literature review focuses on the forms of cell death that trigger downstream inflammation and fibrosis, collectively called regulated cell death (RCD) pathways. Discrete forms of RCD have emerged as central mediators of CKD pathology. In particular, pathways of regulated necrosis - including mitochondrial permeability transition pore (mPTP)-mediated necrosis, necroptosis, ferroptosis and pyroptosis - have been shown to mediate kidney pathology directly or through the release of danger signals that trigger a pro-inflammatory response, further amplifying tissue injury in a cellular process called necroinflammation. Despite accumulating evidence in pre-clinical models, no clinical studies have yet targeted these RCD modes in human CKD. The review summarizes recent advances in our understanding of RCD pathways in CKD, looks at inter-relations between the pathways (with the emphasis on propagation of death signals) and the evidence for therapeutic targeting of molecules in the RCD pathways to prevent or treat CKD.

Double Braking Effects of Nanomedicine on Mitochondrial Permeability Transition Pore for Treating Idiopathic Pulmonary Fibrosis.

Mitochondrial permeability transition pore (mPTP) opening is a key hallmark of injured type II alveolar epithelial cells (AECIIs) in idiopathic pulmonary fibrosis (IPF). Inhibiting mPTP opening in AECIIs is considered a potential IPF treatment. Herein, a "double braking" strategy on mPTP by cyclosporin A (CsA) derived ionizable lipid with 3D structure (3D-lipid) binding cyclophilin D (CypD) and siRNA downregulating mitochondrial calcium uniporter (MCU) expression is proposed for treating IPF. 3D-lipid and MCU targeting siRNA (siMCU) are co-assembled to form stable 3D-LNP/siMCU nanoparticles (NPs), along with helper lipids. In vitro results demonstrated that these NPs effectively inhibit mPTP opening by 3D-lipid binding with CypD and siRNA downregulating MCU expression, thereby decreasing damage-associated molecular patterns (DAMPs) release and suppressing epithelial-to-mesenchymal transition (EMT) process in bleomycin-induced A549 cells. In vivo results revealed that 3D-LNP/siMCU NPs effectively ameliorated collagen deposition, pro-fibrotic factors secretion, and fibroblast activation in bleomycin-induced pulmonary fibrosis (PF) mouse models. Moreover, compared to the commercial MC3-based formulation, optimized Opt-MC3/siRNA NPs with incorporating 3D-lipid as the fifth component, showed superior therapeutic efficacy against PF due to their enhanced stability and higher gene silencing efficiency. Overall, the nanomedicine containing 3D-lipid and siMCU will be a promising and potential approach for IPF treatment.

The Switching of the Type of a ROS Signal from Mitochondria: The Role of Respiratory Substrates and Permeability Transition

Flashes of superoxide anion (O2−) in mitochondria are generated spontaneously or during the opening of the permeability transition pore (mPTP) and a sudden change in the metabolic state of a cell. Under certain conditions, O2− can leave the mitochondrial matrix and perform signaling functions beyond mitochondria. In this work, we studied the kinetics of the release of O2− and H2O2 from isolated mitochondria upon mPTP opening and the modulation of the metabolic state of mitochondria by the substrates of respiration and oxidative phosphorylation. It was found that mPTP opening leads to suppression of H2O2 emission and activation of the O2− burst. When the induction of mPTP was blocked by its antagonists (cyclosporine A, ruthenium red, EGTA), the level of substrates of respiration and oxidative phosphorylation and the selective inhibitors of complexes I and V determined the type of reactive oxygen species (ROS) emitted by mitochondria. It was concluded that upon complete and partial reduction and complete oxidation of redox centers of the respiratory chain, mitochondria emit H2O2, O2−, and nothing, respectively. The results indicate that the mPTP- and substrate-dependent switching of the type of ROS leaving mitochondria may be the basis for O2−- and H2O2-selective redox signaling in a cell.

Melatonin attenuates liver ischemia-reperfusion injury via inhibiting the PGAM5-mPTP pathway

Phosphoglycerate mutase/protein phosphatase (PGAM5)-mediated cell death plays an important role in multiple liver diseases. However, few studies have confirmed the regulatory mechanism of melatonin acting on PGAM5-mediated cell death in the context of liver ischemia-reperfusion (I/R) injury. The liver I/R injury model and cell hypoxia-reoxygenation model were established after melatonin pretreatment. Liver injury, cell activity, cell apoptosis, oxidative stress index, and PGAM5 protein expression were detected. To investigate the role of PGAM5 in melatonin-mediated liver protection during I/R injury, PGAM5 silencing, and overexpression were performed before melatonin pretreatment. Our results indicated that PGAM5 was significantly elevated by I/R injury, and predominantly localized in the necrosis area. However, treatment with melatonin blocked PGAM5 activation and conferred a survival advantage of hepatocytes in liver I/R injury, similar to the results achieved by silencing PGAM5. In terms of mechanism, we illustrated that activated PGAM5 promoted mitochondrial permeability transition pore (mPTP) opening, and administration of melatonin inhibited mPTP opening and interrupted hepatocytes death via blocking PGAM5. Our data indicated that the PGAM5-mPTP axis is responsible for I/R-induced liver injury. In contrast, melatonin supplementation blocked the PGAM5-mPTP axis and thus decreased cell death, providing a protective advantage to hepatocytes in I/R. These results established a new paradigm in melatonin-mediated hepatocyte protection under the burden of I/R attack.

Apelin/APJ signaling in IGF-1-induced acute mitochondrial and antioxidant effects in spontaneously hypertensive rat myocardium.

IGF-1 and apelin are released in response to exercise training with beneficial effects. Previously we demonstrated that a swimming routine is effective to convert pathological into physiological cardiac hypertrophy, and that IGF-1 improves contractility and the redox state, in spontaneously hypertensive rats (SHR). Now, we hypothesize that the apelinergic pathway is involved in the cardioprotective effects of IGF-1 in the SHR. We assessed the redox state and mitochondrial effects of IGF-1 or apelin in the presence/absence of AG1024 or ML221 [pharmacological antagonists of IGF1 (IGF1R) and apelin (APJ) receptors, respectively] in SHR isolated cardiomyocytes or perfused hearts. Acute IGF-1 (10 nmol/L) significantly: -reduced H2O2 production (IGF-1:62 ± 6; control:100 ± 8.1, %), -increased the activity of superoxide dismutase (IGF-1:193 ± 17, control: 100 ± 13,%), -prevented H2O2-induced ΔΨm loss (TMREF10min/F0 min: IGF-1:0.93 ± 0.017, control: 0.72 ± 0.029), -reduced mitochondrial permeability transition pore (mPTP) opening estimated by the calcium retention capacity (nmol/mg protein, IGF-1:251 ± 34, control:112 ± 5), and -increased P-AMPK (IGF-1:129 ± 0.9, control: 100 ± 2%) and P-AKT (IGF-1:143 ± 17 control:100 ± 6, %). These effects were suppressed not only by the antagonism of IGF1R but also of APJ. Moreover, IGF-1 significantly increased APJ (IGF-1:198 ± 29 control:100 ± 15,%) and apelin mRNAs (IGF-1:251 ± 48, control:100 ± 6,%). On the other hand, an equipotent dose of exogenous apelin (50 nmol/L) emulated IGF-1 effects being cancelled by the antagonism of APJ however not by AG1024. IGF-1/IGF1R stimulates the apelinergic pathway, improving the redox balance and mitochondria status in the pathologically hypertrophied myocardium of the SHR.

Cyclophilin D plays a critical role in the survival of senescent cells.

Senescent cells play a causative role in many diseases, and their elimination is a promising therapeutic strategy. Here, through a genome-wide CRISPR/Cas9 screen, we identify the gene PPIF, encoding the mitochondrial protein cyclophilin D (CypD), as a novel senolytic target. Cyclophilin D promotes the transient opening of the mitochondrial permeability transition pore (mPTP), which serves as a failsafe mechanism for calcium efflux. We show that senescent cells exhibit a high frequency of transient CypD/mPTP opening events, known as 'flickering'. Inhibition of CypD using genetic or pharmacologic tools, including cyclosporin A, leads to the toxic accumulation of mitochondrial Ca2+ and the death of senescent cells. Genetic or pharmacological inhibition of NCLX, another mitochondrial calcium efflux channel, also leads to senolysis, while inhibition of the main Ca2+ influx channel, MCU, prevents senolysis induced by CypD inhibition. We conclude that senescent cells are highly vulnerable to elevated mitochondrial Ca2+ ions, and thattransient CypD/mPTP opening is a critical adaptation mechanism for the survivalof senescent cells.

The Role of Mitochondrial Permeability Transition in Bone Metabolism, Bone Healing, and Bone Diseases.

Bone is a dynamic organ with an active metabolism and high sensitivity to mitochondrial dysfunction. The mitochondrial permeability transition pore (mPTP) is a low-selectivity channel situated in the inner mitochondrial membrane (IMM), permitting the exchange of molecules of up to 1.5 kDa in and out of the IMM. Recent studies have highlighted the critical role of the mPTP in bone tissue, but there is currently a lack of reviews concerning this topic. This review discusses the structure and function of the mPTP and its impact on bone-related cells and bone-related pathological states. The mPTP activity is reduced during the osteogenic differentiation of mesenchymal stem cells (MSCs), while its desensitisation may underlie the mechanism of enhanced resistance to apoptosis in neoplastic osteoblastic cells. mPTP over-opening triggers mitochondrial swelling, regulated cell death, and inflammatory response. In particular, mPTP over-opening is involved in dexamethasone-induced osteoblast dysfunction and bisphosphonate-induced osteoclast apoptosis. In vivo, the mPTP plays a significant role in maintaining bone homeostasis, with many bone disorders linked to its excessive opening. Genetic deletion or pharmacological inhibition of the over-opening of mPTP has shown potential in enhancing bone injury recovery and alleviating bone diseases. Here, we review the findings on the relationship of the mPTP and bone at both the cellular and disease levels, highlighting novel avenues for pharmacological approaches targeting mitochondrial function to promote bone healing and manage bone-related disorders.

Effects of Anesthesia with Pentobarbital/Ketamine on Mitochondrial Permeability Transition Pore Opening and Ischemic Brain Damage.

The alteration of mitochondrial functions, especially the opening of the mitochondrial permeability transition pore (mPTP), has been proposed as a key mechanism in the development of lesions in cerebral ischemia, wherefore it is considered as an important target for drugs against ischemic injury. In this study, we aimed to investigate the effects of mitochondrial complex I inhibitors as possible regulators of mPTP using an in vitro brain ischemia model of the pentobarbital/ketamine (PBK)-anesthetized rats. We found that PBK anesthesia itself delayed Ca2+-induced mPTP opening and partially recovered the respiratory functions of mitochondria, isolated from rat brain cortex and cerebellum. In addition, PBK reduced cell death in rat brain slices of cerebral cortex and cerebellum. PBK inhibited the adenosine diphosphate (ADP)-stimulated respiration of isolated cortical and cerebellar mitochondria respiring with complex I-dependent substrates pyruvate and malate. Moreover, pentobarbital alone directly increased the resistance of isolated cortex mitochondria to Ca2+-induced activation of mPTP and inhibited complex I-dependent respiration and mitochondrial complex I activity. In contrast, ketamine had no direct effect on functions of isolated normal cortex and cerebellum mitochondria. Altogether, this suggests that modulation of mitochondrial complex I activity by pentobarbital during PBK anesthesia may increase the resistance of mitochondria to mPTP opening, which is considered the key event in brain cell necrosis during ischemia.

Effects of Salicylic and Acetylsalicylic Acids in Mitochondrial and Erythrocyte Membranes

For further clarification of the mechanisms of pharmacological effects of salicylic and acetylsalicylic acids, the interactions of these acids with mitochondrial and erythrocyte membranes were studied and the role of calcium ions in the effects of salicylic and acetylsalicylic acids was examined. Salicylic acid and to a lesser extent acetylsalicylic acid at 0.5−2.0 mM concentration effectively inhibited the respiratory activity of isolated rat liver mitochondria, by uncoupling respiration and phosphorylation processes, induced depolarization of the mitochondrial membrane and potentiated Ca2+-stimulated formation of mitochondrial permeability transition pores in EGTA-free media. Cyclosporine A and ruthenium red partially inhibited the mitochondrial pore opening process induced by salicylic and acetylsalicylic acids both in the absence and presence of Ca2+ ions. Salicylic acid (180–360 µM) markedly accelerated proton-induced lysis of human erythrocytes (at pH 3.2) and caused hyperpolarization of erythrocyte membranes (at pH 5.5, but not at pH 7.4), probably as a result of proton transfer to the cytoplasm of the cell. Thus, salicylic and acetylsalicylic acids interact with mitochondrial and plasma membranes, act as effective proton/Ca2+ ionophores and stimulate the mitochondrial calcium uniporter.

A pathogenic mutation in the ALS/FTD gene VCP induces mitochondrial hypermetabolism by modulating the permeability transition pore

Valosin-containing protein (VCP) is a ubiquitously expressed type II AAA+ ATPase protein, implicated in both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This study aimed to explore the impact of the disease-causing VCPR191Q/wt mutation on mitochondrial function using a CRISPR/Cas9-engineered neuroblastoma cell line. Mitochondria in these cells are enlarged, with a depolarized mitochondrial membrane potential associated with increased respiration and electron transport chain activity. Our results indicate that mitochondrial hypermetabolism could be caused, at least partially, by increased calcium-induced opening of the permeability transition pore (mPTP), leading to mild mitochondrial uncoupling. In conclusion, our findings reveal a central role of the ALS/FTD gene VCP in maintaining mitochondrial homeostasis and suggest a model of pathogenesis based on progressive alterations in mPTP physiology and mitochondrial energetics.

Modulation of mitochondrial permeability transition pores in reperfusion injury: Mechanisms and therapeutic approaches.

Ischemia/reperfusion injury is attracting continuous interest in science for two reasons: because it affects several clinical conditions and because it has been identified, albeit in broad terms, the molecular entity becoming activated by the reperfusion damage paradoxes. Indeed, calcium, oxygen-dependent oxidative stress and pH would activate conformational changes in the mitochondrial cristae embedded F1/FO ATP synthase, allowing the formation of pores in the inner mitochondrial membrane thus increasing its permeability. This is a key determinant for mitochondrial stress, cell death and tissue dysfunction. Targeting each of these factors has never contributed to improved clinical outcome of the patients affected by reperfusion damage; now, the focus on the PTP opening could represent the closest target to solve this pathway made by extensive cell death when the tissues become revascularized. In this review, we summarized last knowledge about the structure, the modulation and the therapeutic targeting of the PTP, focusing on ATP synthase and cardiac ischemia/reperfusion.

Development of a Mitochondrial Membrane Permeability Transition Prognosis System in Colon Adenocarcinoma: Risk Stratification and Therapeutic Target Identification.

Explore the role of mitochondrial membrane permeability transition (MPT) in colon adenocarcinoma (COAD). Further exploration of risk stratification for COAD prognostic assessment has important clinical value. MPT-related pathways play a key role in the pathogenesis of many human diseases, including tumorigenesis. Its impact on COAD is still unknown. Bioinformatics analysis was conducted by analyzing the GEO database and TCGA database, and the bioinformatics results were verified by in vitro experiments. Through the analysis of the transcriptome data of 1008 COAD samples in the GEO database and TCGA database, the differential expressions of MPT-related genes in COAD were explored, followed by molecular subtype analysis based on MPT characteristics by univariate Cox algorithm analysis and the consensus clustering algorithm. The gene signature associated with MPT molecular subtypes was further identified and the MPT scoring system was established by the LASSO-univariate Cox analysis algorithm. After evaluating the prognostic value of the MPT scoring system in COAD patients via nomogram establishment, the clinical value of the MPT scoring system was comprehensively analyzed through somatic mutation characteristics analysis, immunotherapy response analysis, immunoinfiltration analysis, and drug sensitivity analysis. CCK-8, WB, PCR, colony formation method, and Transwell method were used to verify the effect of the screened target on the proliferation and invasion of COAD cells. We successfully established a scoring system related to MPT and validated the prognostic value of COAD patients. The potential clinical value of the MPT scoring system was also analyzed. VSIG4 was selected for further in vitro experiments to verify the effect of the screened targets on the proliferation and invasion ability of COAD cells. We established an MPT scoring system for effective risk stratification of COAD patients, demonstrating the impact of MPT on the development of COAD and its potential value as an intervention factor.

Mitochondrial non-energetic function and embryonic cardiac development.

The initial contraction of the heart during the embryonic stage necessitates a substantial energy supply, predominantly derived from mitochondrial function. However, during embryonic heart development, mitochondria influence beyond energy supplementation. Increasing evidence suggests that mitochondrial permeability transition pore opening and closing, mitochondrial fusion and fission, mitophagy, reactive oxygen species production, apoptosis regulation, Ca2+ homeostasis, and cellular redox state also play critical roles in early cardiac development. Therefore, this review aims to describe the essential roles of mitochondrial non-energetic function embryonic cardiac development.

Role of Z-DNA Binding Protein 1 Sensing Mitochondrial Z-DNA and Triggering Necroptosis in Oxalate-Induced Acute Kidney Injury.

Calcium oxalate-induced acute kidney injury is a severe condition in which the kidneys suffer rapid damage due to the deposition of oxalate crystals. Known factors contributing to cell death induced by calcium oxalate include receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein dependent necroptosis, as well as necrosis involving peptidylprolyl isomerase F (PPIF) mediated mitochondrial permeability transition. However, the detailed molecular mechanisms linking mitochondrial dysfunction to RIPK3 activation are not fully understood. Mice with gene knock-out of Zbp1, Ripk3, or Mlkl and mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were used in an oxalate-induced AKI model. Proximal renal tubule cells were isolated and cultured for further investigation. Human oxalate nephropathy biopsy samples were analyzed. Specific gene deletions of Zbp1, Ripk3, or Mlkl in proximal renal tubules significantly reduced the severity of oxalate-induced AKI by preventing necroptosis and subsequent inflammation. Notably, mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were protected from AKI. In cultured proximal tubular cells, calcium oxalate damaged mitochondria, accompanied by an increase in Bax and a decrease in BCL2 and TAFM, leading to the release of mitochondrial Z-DNA. ZBP1 sensed this mitochondrial Z-DNA and then recruited RIPK3 via the RIP homotypic interaction motifs (RHIM), which in turn activated MLKL through RIPK3 phosphorylation, leading to necroptosis and contributing to AKI. ZBP1 plays a critical role in sensing mitochondrial Z-DNA and initiating RIPK3/MLKL-mediated necroptosis, contributing to the development of oxalate-induced AKI.

Naringin alleviates fluoride-induced neurological impairment: A focus on the regulation of energy metabolism mediated by mitochondrial permeability transition pore

The neurological impairment induced by fluoride is associated with mitochondrial dysfunction. Normal mitochondrial permeability transition pore (mPTP) opening plays a pivotal role in mitochondrial function. However, it remains unclear whether p53-dependent mPTP-related mitochondrial apoptosis is associated with fluoride-induced neurological impairment, and the alleviation of naringin on those. In vivo, NaF-treated rats had impaired learning and memory abilities, damaged hippocampal structure, and higher respiratory exchange rates (RER). In vitro, the increased apoptosis rates, excessive opening of mPTP, and decreased mitochondrial membrane potential (MMP) were observed in PC12 cells treated with NaF. The protein expressions of p53, CytoC, and cleaved caspase 3 were significantly increased in hippocampi of rats treated with 50 mg/L and 100 mg/L NaF and in 40 mg/L and 80 mg/L NaF-treated PC12 cells, while the protein expression of CypD remains stable. And the changes of p53 and CypD were also confirmed by the immunofluorescence staining in vivo. After inhibiting the expression of p53 with pifithrin-α and p53-siRNA, the decreased apoptosis rates and mPTP opening, increased MMP, and decreased protein expressions of p53, CytoC, and cleaved caspase 3 were observed in NaF-treated PC12 cells. Rats, treated with NaF and naringin, had alleviated impaired neurological function, and had lower RER than rats treated with NaF alone. And compared with those in the NaF group, the decreased apoptosis rates and mPTP opening, and increased MMP were also found in PC12 cells treated with NaF and naringin. Furthermore, hippocampi of rats and PC12 cells treated with NaF and naringin had decreased protein expressions of p53, CytoC, and cleaved caspase 3. Our results indicate that fluoride activates the p53-dependent mPTP-related mitochondrial apoptosis, which then affects energy metabolism, resulting in neurological impairment. Additionally, naringin can alleviate this damage, and further studies on the potential health benefits of naringin are needed.