Cyclophilin D deficiency protects against the development of mitochondrial ROS and cellular inflammation in aorta

Cyclophilin D knockdown/knockout promotes microglia M2 polarization by inhibiting STAT1 to alleviate neuroinflammation in neonatal white matter injury

The activation of microglia cells is intimately associated with the pathophysiology of neuroinflammation and neonatal white matter injury (WMI). Cyclophilin D (CypD), a matrix cyclophilin, is known to be one of the important regulators of mitochondrial permeability transition pore. Currently, CypD has been discovered the function of regulating inflammation. However, its impact on microglia in the context of neonatal WMI remains unclear. In our study, CypD inhibition ameliorated microglia activation, decreased pro-inflammatory factor levels, and increased anti-inflammatory factor levels in both neonatal WMI mice and oxygen glucose deprivation/reperfusion (OGD/R)-induced BV2 microglial cells. CypD knockout promoted myelination and rescued neurological function in mice following hypoxic-ischemic injury. In addition, CypD knockdown alleviated mitochondrial dysfunction of BV2 microglial cells. RNA-Seq indicated that CypD inhibition downregulated STAT1. Western blotting results verified that CypD inhibition significantly downregulated the phosphorylation level of STAT1. Our research revealed the protective role of CypD inhibition in neuroinflammation and mitochondrial function of microglia. Targeting CypD expression in microglia may be a potential therapeutic option for neonatal WMI.

Mechanism and treatment of intracerebral hemorrhage focus on mitochondrial permeability transition pore

Intracerebral hemorrhage (ICH) is the second most common subtype of stroke, characterized by high mortality and a poor prognosis. Despite various treatment methods, there has been limited improvement in the prognosis of ICH over the past decades. Therefore, it is imperative to identify a feasible treatment strategy for ICH. Mitochondria are organelles present in most eukaryotic cells and serve as the primary sites for aerobic respiration and energy production. Under unfavorable cellular conditions, mitochondria can induce changes in permeability through the opening of the mitochondrial permeability transition pore (mPTP), ultimately leading to mitochondrial dysfunction and contributing to various diseases. Recent studies have demonstrated that mPTP plays a role in the pathological processes associated with several neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, Huntington's disease, ischemic stroke and ischemia-reperfusion injury, among others. However, there is limited research on mPTP involvement specifically in ICH. Therefore, this study comprehensively examines the pathological processes associated with mPTP in terms of oxidative stress, apoptosis, necrosis, autophagy, ferroptosis, and other related mechanisms to elucidate the potential mechanism underlying mPTP involvement in ICH. This research aims to provide novel insights for the treatment of secondary injury after ICH.

New cyclophilin D inhibitor rescues mitochondrial and cognitive function in Alzheimer's disease

Mitochondrial dysfunction is an early pathological feature of Alzheimer disease and plays a crucial role in the development and progression of Alzheimer's disease. Strategies to rescue mitochondrial function and cognition remain to be explored. Cyclophilin D (CypD), the peptidylprolyl isomerase F (PPIase), is a key component in opening the mitochondrial membrane permeability transition pore, leading to mitochondrial dysfunction and cell death. Blocking membrane permeability transition pore opening by inhibiting CypD activity is a promising therapeutic approach for Alzheimer's disease. However, there is currently no effective CypD inhibitor for Alzheimer's disease, with previous candidates demonstrating high toxicity, poor ability to cross the blood-brain barrier, compromised biocompatibility and low selectivity. Here, we report a new class of non-toxic and biocompatible CypD inhibitor, ebselen, using a conventional PPIase assay to screen a library of ∼2000 FDA-approved drugs with crystallographic analysis of the CypD-ebselen crystal structure (PDB code: 8EJX). More importantly, we assessed the effects of genetic and pharmacological blockade of CypD on Alzheimer's disease mitochondrial and glycolytic bioenergetics in Alzheimer's disease-derived mitochondrial cybrid cells, an ex vivo human sporadic Alzheimer's disease mitochondrial model, and on synaptic function, inflammatory response and learning and memory in Alzheimer's disease mouse models. Inhibition of CypD by ebselen protects against sporadic Alzheimer's disease- and amyloid-β-induced mitochondrial and glycolytic perturbation, synaptic and cognitive dysfunction, together with suppressing neuroinflammation in the brain of Alzheimer's disease mouse models, which is linked to CypD-related membrane permeability transition pore formation. Thus, CypD inhibitors have the potential to slow the progression of neurodegenerative diseases, including Alzheimer's disease, by boosting mitochondrial bioenergetics and improving synaptic and cognitive function.

Cyclosporine A (CsA) prevents synaptic impairment caused by truncated tau by caspase-3

During Alzheimer's (AD), tau protein suffers from abnormal post-translational modifications, including cleaving by caspase-3. These tau forms affect synaptic plasticity contributing to the cognitive decline observed in the early stages of AD. In addition, caspase-3 cleaved tau (TauC3) impairs mitochondrial dynamics and organelles transport, which are both relevant processes for synapse. We recently showed that the absence of tau expression reverts age-associated cognitive and mitochondrial failure by blocking the mitochondrial permeability transition pore (mPTP). mPTP is a mitochondrial complex involved in calcium regulation and apoptosis. Therefore, we studied the effects of TauC3 against the dendritic spine and synaptic vesicle formation and the possible role of mPTP in these alterations. We used mature hippocampal mice neurons to express a reporter protein (GFP, mCherry), coupled to full-length human tau protein (GFP-T4, mCherry-T4), and coupled to human tau protein cleaved at D421 by caspase-3 (GFP-T4C3, mCherry-T4C3) and synaptic elements were evaluated. Treatment with cyclosporine A (CsA), an immunosuppressive drug with inhibitory activity on mPTP, prevented ROS increase and mitochondrial depolarization induced by TauC3 in hippocampal neurons. These results were corroborated with immortalized cortical neurons in which ROS increase and ATP loss induced by this tau form were prevented by CsA. Interestingly, TauC3 expression significantly reduced dendritic spine density (filopodia type) and synaptic vesicle number in hippocampal neurons. Also, neurons transfected with TauC3 showed a significant accumulation of synaptophysin protein in their soma. More importantly, all these synaptic alterations were prevented by CsA, suggesting an mPTP role in these negative changes derived from TauC3 expression.

Mitochondrial pores at the crossroad between cell death and inflammatory signaling

Mitochondria are cellular organelles with a major role in many cellular processes, including not only energy production, metabolism, and calcium homeostasis but also regulated cell death and innate immunity. Their proteobacterial origin makes them a rich source of potent immune agonists, normally hidden within the mitochondrial membrane barriers. Alteration of mitochondrial permeability through mitochondrial pores thus provides efficient mechanisms not only to communicate mitochondrial stress to the cell but also as a key event in the integration of cellular responses. In this regard, eukaryotic cells have developed diverse signaling networks that sense and respond to the release of mitochondrial components into the cytosol and play a key role in controlling cell death and inflammatory pathways. Modulating pore formation at mitochondria through direct or indirect mechanisms may thus open new opportunities for therapy. In this review, we discuss the current understanding of the structure and molecular mechanisms of mitochondrial pores and how they function at the interface between cell death and inflammatory signaling to regulate cellular outcomes.

Graphene oxide leads to mitochondrial-dependent apoptosis by activating ROS-p53-mPTP pathway in intestinal cells

Owing to its unique physical and chemical properties, graphene oxide (GO) has a wide range of applications in biomedical field. However, with the gradual improvement of biosafety investigations on nanomaterials, growing literatures have pointed out that GO could lead to oxidative stress, aggravation of inflammatory responses, and even irreversible lesions in human multi-tissues, while its damage to small intestinal remained unclear. In this study, we conducted an in-depth study on the toxicological effect of GO on intestinal tissues, and further clarified its toxic effect and molecular mechanism on inducing intestinal cell death. Firstly, we characterized the shape size, potential value, Fourier Transform infrared spectroscopy (FT-IR) characterization and pro-oxidant properties of GO nanosheets. The cytotoxicity of different concentrations of GO to Caco-2 and IEC-6 cell lines was thereafter observed, which was specifically manifested as invoking NADPH Oxidase 1 (NOX1) proteins, accompanied generation of reactive oxygen species (ROS). Since that, more p53 flowed into mitochondria to combine with cyclophilin D (CYPD), thus induced mitochondrial permeability transition pore (mPTP) opening. Through ROS-CyPD-mPTP signaling pathway, GO exerted imbalance of mitochondrial homeostasis, while released cytochrome c (CytC) would ultimate caspase-dependent cell apoptosis. In vivo experiment also confirmed that the microstructure of small intestine was damaged, and the apoptosis rate and oxidative markers were significantly increased in GO-treated Sprague- Dawley (SD) rats (40 mg/kg once every other day from day 1 to day 9 by oral gavage). Based on these findings, we conclude that the adverse effects of oral exposure of GO on the biological system mainly concentrate in the digestive tract, and clarify the key role of ROS-mitochondrial homeostasis-apoptosis axis in GO-derived intestinal toxicity. Considering all these results and the fact that GO exhibited intestinal toxicity, we believe that this research providing a safety reference for its biomedical applications.

Molecular mechanisms and consequences of mitochondrial permeability transition

Mitochondrial permeability transition (mPT) is a phenomenon that abruptly causes the flux of low molecular weight solutes (molecular weight up to 1,500) across the generally impermeable inner mitochondrial membrane. The mPT is mediated by the so-called mitochondrial permeability transition pore (mPTP), a supramolecular entity assembled at the interface of the inner and outer mitochondrial membranes. In contrast to mitochondrial outer membrane permeabilization, which mostly activates apoptosis, mPT can trigger different cellular responses, from the physiological regulation of mitophagy to the activation of apoptosis or necrosis. Although there are several molecular candidates for the mPTP, its molecular nature remains contentious. This lack of molecular data was a significant setback that prevented mechanistic insight into the mPTP, pharmacological targeting and the generation of informative animal models. In recent years, experimental evidence has highlighted mitochondrial F₁F_o ATP synthase as a participant in mPTP formation, although a molecular model for its transition to the mPTP is still lacking. Recently, the resolution of the F₁F_o ATP synthase structure by cryogenic electron microscopy led to a model for mPTP gating. The elusive molecular nature of the mPTP is now being clarified, marking a turning point for understanding mitochondrial biology and its pathophysiological ramifications. This Review provides an up-to-date reference for the understanding of the mammalian mPTP and its cellular functions. We review current insights into the molecular mechanisms of mPT and validated observations - from studies in vivo or in artificial membranes - on mPTP activity and functions. We end with a discussion of the contribution of the mPTP to human disease. Throughout the Review, we highlight the multiple unanswered questions and, when applicable, we also provide alternative interpretations of the recent discoveries.

Liver cyclophilin D deficiency inhibits the progression of early NASH by ameliorating steatosis and inflammation

Cyclophilin D (CypD) can stimulate the opening of the membrane permeability transition pore (mPTP) and regulate mitochondrial function. Whole-body knockout of CypD improved high fat diet-induced hepatic steatosis by reducing the excess opening of the mPTP and lipid deposition. However, whether CypD significantly ameliorates nonalcoholic steatohepatitis (NASH) has not been studied. Therefore, we established liver-specific CypD knockout (CypD LKO) mice and fed a HFHC diet to induce NASH. Compared with the wild-type mice, the CypD LKO not only showed improved lipid deposition and insulin resistance by increasing fatty acid oxidation but also displayed ameliorated hepatic inflammation, although the symptoms of fibrosis in the NASH model were not significantly improved. In addition, we used bile duct ligation (BDL) or a 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet to induce cholestatic disease and found that CypD LKO had also no significant effect on acute fibrosis. Thus, CypD LKO can inhibit the progression of early NASH by ameliorating steatosis and inflammatory symptoms. These results suggest a new strategy for the treatment of early NASH.

Calcium Ions Aggravate Alzheimer's Disease Through the Aberrant Activation of Neuronal Networks, Leading to Synaptic and Cognitive Deficits

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by the production and deposition of β-amyloid protein (Aβ) and hyperphosphorylated tau, leading to the formation of β-amyloid plaques (APs) and neurofibrillary tangles (NFTs). Although calcium ions (Ca²⁺) promote the formation of APs and NFTs, no systematic review of the mechanisms by which Ca²⁺ affects the development and progression of AD has been published. Therefore, the current review aimed to fill the gaps between elevated Ca²⁺ levels and the pathogenesis of AD. Specifically, we mainly focus on the molecular mechanisms by which Ca²⁺ affects the neuronal networks of neuroinflammation, neuronal injury, neurogenesis, neurotoxicity, neuroprotection, and autophagy. Furthermore, the roles of Ca²⁺ transporters located in the cell membrane, endoplasmic reticulum (ER), mitochondria and lysosome in mediating the effects of Ca²⁺ on activating neuronal networks that ultimately contribute to the development and progression of AD are discussed. Finally, the drug candidates derived from herbs used as food or seasoning in Chinese daily life are summarized to provide a theoretical basis for improving the clinical treatment of AD.

Identification of novel proteins and mechanistic pathways associated with early-onset hypertension by deep proteomic mapping of resistance arteries

Resistance arteries are small blood vessels that create resistance to blood flow. In hypertension, resistance arteries undergo remodeling, affecting their ability to contract and relax appropriately. To date, no study has mapped the hypertension-related proteomic changes in resistance arteries. Using a novel data-independent acquisition–mass spectrometry (DIA-MS) approach, we determined the proteomic changes in small mesenteric and renal arteries in pre- and early-onset hypertension from the spontaneously hypertensive rat (SHR) model, which represents human primary hypertension. Compared with normotensive controls, mesenteric arteries from 12-week-old SHRs had 286 proteins that were significantly up- or downregulated, whereas 52 proteins were identified as up- or downregulated in mesenteric arteries from 6-week-old SHRs. Of these proteins, 18 were also similarly regulated in SHR renal arteries. Our pathway analyses reveal several novel pathways in the pathogenesis of hypertension. Finally, using a matrisome database, we identified 38 altered extracellular-matrix-associated proteins, many of which have never previously been associated with hypertension. Taken together, this study reveals novel proteins and mechanisms that are associated with early-onset hypertension, thereby providing novel insights into disease progression.

Anti-Inflammatory Activity of Bullfrog Oil Polymeric Nanocapsules: From the Design to Preclinical Trials

BACKGROUND

Although bullfrog oil (BFO) exerts anti-inflammatory effects, it has undesirable properties limiting its use.

METHODOLOGY

BFO nanocapsules (BFONc) were produced through nanoprecipitation, and their physicochemical and morphological properties were characterized. To evaluate the biocompatibility of the formulation, a mitochondrial activity evaluation assay was conducted, and cell uptake was assessed. The in vitro anti-inflammatory activity was evaluated by measuring reactive oxygen species (ROS), nitric oxide (NO), type-6 interleukin (IL-6), and tumor necrosis factor (TNF) levels. The in vivo anti-inflammatory effect was assessed by quantifying myeloperoxidase (MPO) levels using the carrageenan-induced paw edema model.

RESULTS

BFONc showed a particle size of 233 ± 22 nm, a polydispersity index of 0.17 ± 0.03, and a zeta potential of -34 ± 2.6mV. BFONc revealed remarkable biocompatibility and did not induce changes in cell morphology. Furthermore, BFONc decreased ROS levels by 81 ± 4%; however, NO level increased by 72 ± 18%. TNF and IL-6 levels were reduced by approximately 10% and 90%, respectively. Significant in vivo anti-inflammatory activity was observed compared to dexamethasone. MPO levels were reduced up to 2 MPOs/mg.

CONCLUSION

Taken together, the results pointed out the remarkable biocompatibility and anti-inflammatory effects of BFONc.

Proximal tubule cyclophilin D mediates kidney fibrogenesis in obstructive nephropathy

The proximal tubule (PT) is highly vulnerable to acute injury, including ischemic insult and nephrotoxins, and chronic kidney injury. It has been established that PT injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we tested whether PT cyclophilin D (CypD), a mitochondrial matrix protein, is a critical factor to cause kidney fibrosis progression. To define the role of CypD in kidney fibrosis, we used an established mouse model for kidney fibrosis: the unilateral ureteral obstruction (UUO) model in global and PT-specific CypD knockout (KO). Global CypD KO blunted kidney fibrosis progression with inhibition of myofibroblast activation and fibrosis. UUO-induced tubular atrophy was suppressed in kidneys of global CypD KO but not tubular dilation or apoptotic cell death. PT cell cycle arrest was highly increased in wild-type UUO kidneys but was markedly attenuated in global CypD KO UUO kidneys. The number of macrophages and neutrophils was less in UUO kidneys of global CypD KO than those of wild-type kidneys. Proinflammatory and profibrotic factors were all inhibited in global CypD KO. In line with those of global CypD KO, PT-specific CypD KO also blunted kidney fibrosis progression, along with less tubular atrophy, renal parenchymal loss, cell cycle arrest in PT, and inflammation, indicating a critical role for PT CypD in fibrogenesis. Collectively, our data demonstrate that CypD in the PT is a critical factor contributing to kidney fibrosis in UUO, providing a new paradigm for mitochondria-targeted therapeutics of fibrotic diseases.NEW & NOTEWORTHY It has been established that renal proximal tubule (PT) injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we show that cyclophilin D, a mitochondrial matrix protein, in the PT causes kidney fibrogenesis in obstructive nephropathy. Our data suggest that targeting PT cyclophilin D could be beneficial to prevent fibrosis progression.

Berberine improves intralipid-induced insulin resistance in murine

Insulin resistance (IR) is a major metabolic risk factor even before the onset of hyperglycemia. Recently, berberine (BBR) is found to improve hyperglycemia and IR. In this study, we investigated whether BBR could improve IR independent of hyperglycemia. Acute insulin-resistant state was induced in rats by systemic infusion of intralipid (6.6%). BBR was administered via different delivery routes before or after the beginning of a 2-h euglycemic-hyperinsulinemic clamp. At the end of experiment, rats were sacrificed, gastrocnemius muscle was collected for detecting mitochondrial swelling, phosphorylation of Akt and AMPK, as well as the mitochondrial permeability regulator cyclophilin D (CypD) protein expression. We showed that BBR administration markedly ameliorated intralipid-induced IR without affecting blood glucose, which was accompanied by alleviated mitochondrial swelling in skeletal muscle. We used human skeletal muscle cells (HSMCs), AML12 hepatocytes, human umbilical vein endothelial cells, and CypD knockout mice to investigate metabolic and molecular alternations. In either HSMCs or AML12 hepatocytes, BBR (5 μM) abolished palmitate acid (PA)-induced increase of CypD protein levels. In CypD-deficient mice, intralipid-induced IR was greatly attenuated and the beneficial effect of BBR was diminished. Furthermore, we demonstrated that the inhibitory effect of BBR on intralipid-induced IR was mainly mediated by skeletal muscle, but not by intestine, liver, or microvasculature; BBR administration suppressed intralipid-induced upregulation of CypD expression in skeletal muscle. These results suggest that BBR alleviates intralipid-induced IR, which is related to the inhibition of CypD protein expression in skeletal muscle.

Mitophagy pathways and Alzheimer's disease: From pathogenesis to treatment

Alzheimer's disease (AD) is an age-dependent, incurable mental illness that is associated with the accumulation of aggregates of amyloid-beta (Aβ) and hyperphosphorylated tau fragments (p-tau). Detailed studies on postmortem AD brains, cell lines, and mouse models of AD have shown that numerous cellular alterations, including mitochondrial deficits, synaptic disruption and glial/astrocytic activation, are involved in the disease process. Mitophagy is a cellular process by which damaged/weakened mitochondria are selectively eliminated from the cell. In AD, impairments in mitophagy trigger the gradual accumulation of defective mitochondria. This review will focus on the recent progress in understanding the molecular mechanisms and pathological role of mitophagy and its implications for AD pathogenesis. We will also discuss the novel concept of the regulation of mitophagy as a therapeutic avenue for the prevention and treatment of AD.

Crosstalk between cyclophilins and T lymphocytes in coronary artery disease

Cardiovascular diseases and atherosclerosis are currently some of the most widespread diseases of our time. Within cardiovascular disease, coronary artery disease and underlying atherosclerosis were recently linked with systemic and local inflammation. Cyclophilins participate in the initiation and progression of these inflammatory-related diseases. Cyclophilins are released into the extracellular space upon inflammatory stimuli and participate in the pathology of cardiovascular diseases. The cell surface receptor for extracellular cyclophilins, the CD147 receptor, also contributes to coronary artery disease pathogenesis. Nevertheless, the physiological relevance of cyclophilin's family and their receptor in cardiovascular diseases remains unclear. The present study aimed to better understand the role of cyclophilins in cardiovascular artery disease and their relationship with inflammation. Hence, cyclophilins and pro-inflammatory interleukins were measured in the serum of 30 subjects (divided into three groups according to coronary artery disease status: 10 patients with acute coronary syndrome, 10 patients with chronic coronary artery disease, and 10 control volunteers). In addition, cyclophilin levels and CD147 receptor expression were measured in T lymphocytes purified from these subjects. Cyclophilin A, B, and C, pro-inflammatory interleukins, and CD147 membrane expression were significantly elevated in patients with coronary artery disease.

Oxidative Stress and Vascular Dysfunction in the Retina: Therapeutic Strategies

Many retinal diseases, such as diabetic retinopathy, glaucoma, and age-related macular (AMD) degeneration, are associated with elevated reactive oxygen species (ROS) levels. ROS are important intracellular signaling molecules that regulate numerous physiological actions, including vascular reactivity and neuron function. However, excessive ROS formation has been linked to vascular endothelial dysfunction, neuron degeneration, and inflammation in the retina. ROS can directly modify cellular molecules and impair their function. Moreover, ROS can stimulate the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) causing inflammation and cell death. However, there are various compounds with direct or indirect antioxidant activity that have been used to reduce ROS accumulation in animal models and humans. In this review, we report on the physiological and pathophysiological role of ROS in the retina with a special focus on the vascular system. Moreover, we present therapeutic approaches for individual retinal diseases targeting retinal signaling pathways involving ROS.