Activation Of Mitochondrial Pathway Research Articles

Bis(thiosemicarbazide)gallium(III) Complexes as Potent Anticancer Agents by ROS Induction and Mitochondrial Pathway Activation

ABSTRACTA series of bis(thiosemicarbazide)gallium (III) complexes were synthesized and characterized by infrared spectroscopy, mass spectrometry, nuclear magnetic resonance, single‐crystal x‐ray crystallography, and density functional theory (DFT) calculation. The cytotoxicity of these gallium(III) complexes (CP 1–4) was subsequently evaluated against HCT‐116, HeLa, MDA‐MB‐231, and A549 cancer cell lines, as well as the normal cell line LO2, by MTT assays. The results indicated that CP‐1 displayed potent inhibitory effects against human colorectal cancer cells (HCT‐116) (IC50 = 0.03 ± 0.01) and human breast cancer cells (MDA‐MB‐231) (IC50 = 0.02 ± 0.01), significantly outperforming cisplatin. Moreover, CP‐2 exhibited notable selectivity towards MDA‐MB‐231 cells (IC50 = 5.01 ± 0.40) with minimal toxicity towards normal cells. Mechanistic studies revealed that treatment with CP 1–2 led to elevated intracellular reactive oxygen species (ROS) levels, resulting in cell cycle arrest at different phases. Specifically, CP‐1 induced G2/M phase arrest, inhibiting cancer cell proliferation, whereas CP‐2 hindered DNA synthesis (S phase) to impede cell proliferation. Furthermore, both CP‐1 and CP‐2 caused a reduction in mitochondrial membrane potential, activating the mitochondrial apoptotic pathway and inducing apoptosis in cancer cells. Molecular docking experiments demonstrated strong interactions between CP 1–2 and protein disulfide isomerase (PDI) at the molecular level. These findings suggest that CP‐1 and CP‐2 serve as potential anticancer agents, particularly showing promising potential in the treatment of breast cancer.

The actin binding protein profilin 1 localizes inside mitochondria and is critical for their function

The monomer-binding protein profilin 1 (PFN1) plays a crucial role in actin polymerization. However, mutations in PFN1 are also linked to hereditary amyotrophic lateral sclerosis, resulting in a broad range of cellular pathologies which cannot be explained by its primary function as a cytosolic actin assembly factor. This implies that there are important, undiscovered roles for PFN1 in cellular physiology. Here we screened knockout cells for novel phenotypes associated with PFN1 loss of function and discovered that mitophagy was significantly upregulated. Indeed, despite successful autophagosome formation, fusion with the lysosome, and activation of additional mitochondrial quality control pathways, PFN1 knockout cells accumulate depolarized, dysmorphic mitochondria with altered metabolic properties. Surprisingly, we also discovered that PFN1 is present inside mitochondria and provide evidence that mitochondrial defects associated with PFN1 loss are not caused by reduced actin polymerization in the cytosol. These findings suggest a previously unrecognized role for PFN1 in maintaining mitochondrial integrity and highlight new pathogenic mechanisms that can result from PFN1 dysregulation.

MiR-34a promotes mitochondrial pathway of apoptosis in human salivary gland epithelial cells by activating NF-κB signaling

To investigate the potential molecular mechanism of miR-34a in Sjögren's syndrome (SS). Transmission electron microscopy was used to observe the salivary gland tissues of mild and severe SS patients. SS mouse model was constructed and injected with miR-34a antagonist. HSGE cells were transfected with miR-34a mimic. Starbase predicted miR-34a binding sites and validated them with dual-luciferase reporter assays. Immunohistochemistry, HE staining, CCK-8, TUNEL assay, flow cytometry, immunofluorescence and Western Blot were used to investigate the effects of miR-34a on NF-κB signaling and mitochondrial pathway of apoptosis in HSGE cells. Severe SS patients showed obvious mitochondrial damage and apoptosis in salivary glands. MiR-34a was overexpressed and NF-κB signaling is activated in salivary glands of severe SS patients. Inhibition of miR-34a alleviated salivary gland injury in SS mice, as well as inhibited the activation of NF-κB signaling and mitochondrial pathway of apoptosis. In conclusion, miR-34a promoted NF-κB signaling by targeting IκBα, thereby causing mitochondrial pathway apoptosis and aggravating SS-induced salivary gland damage.

RANKL signaling drives skeletal muscle into the oxidative profile.

The bone-muscle unit refers to the reciprocal regulation between bone and muscle by mechanical interaction and tissue communication via soluble factors. The RANKL stimulation induces mitochondrial biogenesis and increases the oxidative capacity in osteoclasts and adipocytes. RANKL may bind to the membrane bound RANK or to osteoprotegerin (OPG), a decoy receptor that inhibits RANK-RANKL activation. RANK is highly expressed in skeletal muscle, but the contribution of RANKL to healthy skeletal muscle fiber remains elusive. Here we show that RANKL stimulation in C2C12-derived myotubes induced activation of mitochondrial biogenesis pathways as detected by RNA-seq and western blot. RANKL expanded the mitochondrial reticulum, as shown by mitochondrial DNA quantification and MitoTracker staining, and boosted the spare respiratory capacity. Using MEK and MAPK inhibitors, we found that RANKL signals via ERK and p38 to induce mitochondrial biogenesis. The soleus from OPG-/- and OPG+/- mice showed higher respiratory rates compared to C57BL6/J WT mice, which correlates with high serum RANKL levels. RANKL infusion using a mini-osmotic pump in WT mice increased the number of mitochondria, boosted the respiratory rate, increased succinate dehydrogenase activity in skeletal muscle, and improved the fatigue resistance of gastrocnemius. Therefore, our findings reveal a new role of RANKL as an osteokine-like protein that impacts muscle fiber metabolism.

Suppression of NSCLC progression via the co-administration of Danusertib, an AURK inhibitor, and KRIBB11, an HSF1 inhibitor

Aurora kinase (AURK) and heat shock factor 1 (HSF1) are commonly overexpressed in non-small cell lung cancer (NSCLC), correlating with poor prognosis. This study aims to assess the therapeutic potential of combining the Danusertib (Danu, AURK inhibitor) and KRIBB11 (HSF1 inhibitor) for NSCLC treatment. The effects of this combination were investigated in A549 cells and a tumor xenograft mouse model. The findings demonstrate that concurrent administration of Danu and KRIBB11 effectively impedes cell proliferation, induces apoptosis, and triggers G2/M cell cycle arrest. Moreover, the combination treatment upregulates pro-apoptotic proteins (Cleaved-caspase3, Cleaved-PARP, and Bax) while downregulating anti-apoptotic proteins (Bcl-2), as well as G2/M−related proteins (CDC2 and cyclin B1). Additionally, the combination treatment elevates reactive oxygen species (ROS) levels, decreases mitochondrial membrane potential, and activates the DNA damage pathway. Interestingly, we discovered that the PI3K/AKT pathway is involved in mediating the effects of both Danu and KRIBB11. Furthermore, the combination treatment inhibits tumor growth and AKT signaling in the xenograft mouse model, increases levels of the tumor tissue oxidation product malondialdehyde (MDA), and induces DNA damage. To summarize, a potential therapeutic approach for NSCLC may involve dual inhibition of AURK and HSF1, resulting in the downregulation of the PI3K/AKT signaling pathway, and the activation of ROS-mediated mitochondrial and DNA damage pathways.

In vitro Cytotoxicity of Activated Carbon from Musa Acuminate Fruit Peel Against HepG-2 Cells

Background: Cancer is a leading cause of global mortality, necessitating the development of new therapeutic options. Plant-based medicines offer advantages over conventional drugs, prompting investigations into their cytotoxic potential. This study aimed to evaluate the cytotoxicity of activated carbon derived from M. acuminate fruit peel against HepG-2 cells. Methods: Activated carbon was prepared from M. acuminate fruit peel, and its cytotoxic effects were assessed using MTT assay, DAPI/PI/EtBr staining, and comet assay. Statistical analyses were conducted to evaluate significance. Results: Dose-dependent cytotoxicity was observed, with a notable reduction in cell viability with approximately 50% cytotoxicity observed at a concentration of 86.74 μg/ml after 48 hours. Activated carbon significantly increased reactive oxygen species (ROS) synthesis, mitochondrial membrane potential attenuation, induction of apoptotic morphology, and caspase-3 activation in HepG-2 cells. Conclusion: The study demonstrates the potential of activated carbon as a natural product source for developing novel cancer medicines. Its cytotoxic effects against HepG-2 cells, mediated via ROS-mediated mitochondrial pathway and caspase-3 activation, warrant further investigation for therapeutic applications.

Unraveling the role of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer by multi-omics analyses

The role of the serine/glycine metabolic pathway (SGP) has recently been demonstrated in tumors; however, the pathological relevance of the SGP in thyroid cancer remains unexplored. Here, we perform metabolomic profiling of 17 tumor-normal pairs; bulk transcriptomics of 263 normal thyroid, 348 papillary, and 21 undifferentiated thyroid cancer samples; and single-cell transcriptomes from 15 cases, showing the impact of mitochondrial one-carbon metabolism in thyroid tumors. High expression of serine hydroxymethyltransferase-2 (SHMT2) and methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is associated with low thyroid differentiation scores and poor clinical features. A subpopulation of tumor cells with high mitochondrial one-carbon pathway activity is observed in the single-cell dataset. SHMT2 inhibition significantly compromises mitochondrial respiration and decreases cell proliferation and tumor size in vitro and in vivo. Collectively, our results highlight the importance of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer and suggest that SHMT2 is a potent therapeutic target.

PRDX6-iPLA2 aggravates neuroinflammation after ischemic stroke via regulating astrocytes-induced M1 microglia

The crosstalk between astrocytes and microglia plays a pivotal role in neuroinflammation following ischemic stroke, and phenotypic distribution of these cells can change with the progression of ischemic stroke. Peroxiredoxin (PRDX) 6 phospholipase A2 (iPLA2) activity is involved in the generation of reactive oxygen species(ROS), with ROS driving the activation of microglia and astrocytes; however, its exact function remains unexplored. MJ33, PRDX6D140A mutation was used to block PRDX6-iPLA2 activity in vitro and vivo after ischemic stroke. PRDX6T177A mutation was used to block the phosphorylation of PRDX6 in CTX-TNA2 cell lines. NAC, GSK2795039, Mdivi-1, U0126, and SB202190 were used to block the activity of ROS, NOX2, mitochondrial fission, ERK, and P38, respectively, in CTX-TNA2 cells. In ischemic stroke, PRDX6 is mainly expressed in astrocytes and PRDX6-iPLA2 is involved in the activation of astrocytes and microglia. In co-culture system, Asp140 mutation in PRDX6 of CTX-TNA2 inhibited the polarization of microglia, reduced the production of ROS, suppressed NOX2 activation, and inhibited the Drp1-dependent mitochondrial fission following OGD/R. These effects were further strengthened by the inhibition of ROS production. In subsequent experiments, U0126 and SB202190 inhibited the phosphorylation of PRDX6 at Thr177 and reduced PRDX6-iPLA2 activity. These results suggest that PRDX6-iPLA2 plays an important role in the astrocyte-induced generation of ROS and activation of microglia, which are regulated by the activation of Nox2 and Drp1-dependent mitochondrial fission pathways. Additionally, PRDX6-iPLA2 activity is regulated by MAPKs via the phosphorylation of PRDX6 at Thr177 in astrocytes.

Gemtuzumab Ozogamicin in Acute Myeloid Leukemia: Efficacy, Toxicity, and Resistance Mechanisms-A Systematic Review.

Acute myeloid leukemia (AML) is a diverse group of leukemias characterized by the uncontrolled proliferation of clonal neoplastic hematopoietic precursor cells with chromosomal rearrangements and multiple gene mutations and the impairment of normal hematopoiesis. Current efforts to improve AML outcomes have focused on developing targeted therapies that may allow for improved antileukemic effects while reducing toxicity significantly. Gemtuzumab ozogamicin (GO) is one of the most thoroughly studied molecularly targeted therapies in adults. GO is a monoclonal antibody against CD33 IgG4 linked to the cytotoxic drug calicheamicin DMH. The use of GO as a chemotherapeutic agent is not generalized for all patients who suffer from AML, particularly for those whose health prevents them from using intensive conventional chemotherapy, in which case it can be used on its own, and those who have suffered a first relapse, where its combination with other chemotherapeutic agents is possible. This systematic review aimed to comprehensively evaluate GO, focusing on its molecular structure, mode of action, pharmacokinetics, recommended dosage, resistance mechanisms, and associated toxicities to provide valuable information on the potential benefits and risks associated with its clinical use. A systematic review of eight scientific articles from 2018 to 2023 was conducted using PRISMA analysis. The results showed that GO treatment activates proapoptotic pathways and induces double-strand breaks, initiating DNA repair mechanisms. Cells defective in DNA repair pathways are susceptible to GO cytotoxicity. GO has recommended doses for newly diagnosed CD33+ AML in combination or as a single agent. Depending on the treatment regimen and patient status, GO doses vary for induction, consolidation, and continuation cycles. Multidrug resistance (MDR) involving P-glycoprotein (P-gp) is associated with GO resistance. The overexpression of P-gp reduces GO cytotoxicity; inhibitors of P-gp can restore sensitivity. Mitochondrial pathway activation and survival signaling pathways are linked to GO resistance. Other resistance mechanisms include altered pharmacokinetics, reduced binding ability, and anti-apoptotic mechanisms. GO has limited extramedullary toxicity compared to other AML treatments and may cause hepatic veno-occlusive disease (HVOD). The incidence of hepatic HVOD after GO therapy is higher in patients with high tumor burden. Hematological side effects and hepatotoxicity are prominent, with thrombocytopenia and neutropenia observed. In conclusion, GO's reintroduction in 2017 followed a thorough FDA review considering its altered dose, dosing schedule, and target population. The drug's mechanism involves CD33 targeting and calicheamicin-induced DNA damage, leading to apoptosis and resistance mechanisms, including MDR and survival signaling, which impact treatment outcomes. Despite limited extramedullary toxicity, GO is associated with hematological side effects and hepatotoxicity.

Activation of mitochondrial DNA-mediated cGAS-STING pathway contributes to chronic postsurgical pain by inducing type I interferons and A1 reactive astrocytes in the spinal cord

Chronic postsurgical pain (CPSP) is increasingly recognized as a public health issue. Recent studies indicated the innate immune pathway of cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) was involved in pain regulation. However, the detailed mechanisms remain unclear. Previous studies found A1 reactive astrocytes in the spinal cord contributed to CPSP. This study aimed to investigate the roles and mechanisms of the cGAS-STING pathway in regulating the generation of A1 reactive astrocytes during CPSP. First, CPSP model was established using skin/muscle incision and retraction (SMIR) in rats. We found that cGAS-STING pathway was activated accompanied with an increase in mitochondrial DNA in the cytosol in the spinal cord following SMIR. Second, a STING inhibitor C-176 was intrathecally administrated. We found that C-176 decreased the expression of type I interferons and A1 reactive astrocytes in the spinal cord, and alleviated mechanical allodynia in SMIR rats. Third, cyclosporin A as a mitochondrial permeability transition pore blocker was intrathecally administrated. We found that cyclosporin A decreased the leakage of mitochondrial DNA and inhibited the activation of cGAS-STING pathway. Compared with C-176, cyclosporin A exhibits similar analgesic effects. The expression of type I interferons and A1 reactive astrocytes in the spinal cord were also down-regulated after intervention with cyclosporin A. Moreover, simultaneous administration of cyclosporin A and C-176 did not show synergistic effects in SMIR rats. Therefore, our study demonstrated that the cGAS-STING pathway activated by the leakage of mitochondrial DNA contributed to chronic postsurgical pain by inducing type I interferons and A1 reactive astrocytes in the spinal cord.

6-Hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline Demonstrates Anti-Inflammatory Properties and Reduces Oxidative Stress in Acetaminophen-Induced Liver Injury in Rats.

We examined the effects of 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline on markers of liver injury, oxidative status, and the extent of inflammatory and apoptotic processes in rats with acetaminophen-induced liver damage. The administration of acetaminophen caused the accumulation of 8-hydroxy-2-deoxyguanosine and 8-isoprostane in the liver and serum, as well as an increase in biochemiluminescence indicators. Oxidative stress resulted in the activation of pro-inflammatory cytokine and NF-κB factor mRNA synthesis and increased levels of immunoglobulin G, along with higher activities of caspase-3, caspase-8, and caspase-9. The administration of acetaminophen also resulted in the development of oxidative stress, leading to a decrease in the level of reduced glutathione and an imbalance in the function of antioxidant enzymes. This study discovered that 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline reduced oxidative stress by its antioxidant activity, hence reducing the level of pro-inflammatory cytokine and NF-κB mRNA, as well as decreasing the concentration of immunoglobulin G. These changes resulted in a reduction in the activity of caspase-8 and caspase-9, which are involved in the activation of ligand-induced and mitochondrial pathways of apoptosis and inhibited the effector caspase-3. In addition, 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline promoted the normalization of antioxidant system function in animals treated with acetaminophen. As a result, the compound being tested alleviated inflammation and apoptosis by decreasing oxidative stress, which led to improved liver marker indices and ameliorated histopathological alterations.

GSDME in Endothelial Cells: Inducing Vascular Inflammation and Atherosclerosis via Mitochondrial Damage and STING Pathway Activation.

The initiation of atherosclerotic plaque is characterized by endothelial cell inflammation. In light of gasdermin E's (GSDME) role in pyroptosis and inflammation, this study elucidates its function in atherosclerosis onset. Employing Gsdme- and apolipoprotein E-deficient (Gsdme-/-/ApoE-/-) and ApoE-/- mice, an atherosclerosis model was created on a Western diet (WD). In vitro examinations with human umbilical vein endothelial cells (HUVECs) included oxidized low-density lipoprotein (ox-LDL) exposure. To explore the downstream mechanisms linked to GSDME, we utilized an agonist targeting the stimulator of the interferon genes (STING) pathway. The results showed significant GSDME activation in ApoE-/- mice arterial tissues, corresponding with atherogenesis. Gsdme-/-/ApoE-/- mice displayed fewer plaques and decreased vascular inflammation. Meanwhile, GSDME's presence was confirmed in endothelial cells. GSDME inhibition reduced the endothelial inflammation induced by ox-LDL. GSDME was linked to mitochondrial damage in endothelial cells, leading to an increase in cytoplasmic double-stranded DNA (dsDNA). Notably, STING activation partially offset the effects of GSDME inhibition in both in vivo and in vitro settings. Our findings underscore the pivotal role of GSDME in endothelial cells during atherogenesis and vascular inflammation, highlighting its influence on mitochondrial damage and the STING pathway, suggesting a potential therapeutic target for vascular pathologies.

Proteomic analysis of murine kidney proximal tubule sub-segment derived cell lines reveals preferences in mitochondrial pathway activity

The proximal tubule (PT) is a nephron segment that is responsible for the majority of solute and water reabsorption in the kidney. Each of its sub-segments have specialized functions; however, little is known about the genes and proteins that determine the oxidative phosphorylation capacity of the PT sub-segments. This information is critical to understanding kidney function and will provide a comprehensive landscape of renal cell adaptations to injury, physiologic stressors, and development. This study analyzed three immortalized murine renal cell lines (PT S1, S2, and S3 segments) for protein content and compared them to a murine fibroblast cell line. All three proximal tubule cell lines generate ATP predominantly by oxidative phosphorylation while the fibroblast cell line is glycolytic. The proteomic data demonstrates that the most significant difference in proteomic signatures between the cell lines are proteins known to be localized in the nucleus followed by mitochondrial proteins. Mitochondrial metabolic substrate utilization assays were performed using the proximal tubule cell lines to determine substrate utilization kinetics thereby providing a physiologic context to the proteomic dataset. This data will allow researchers to study differences in nephron-specific cell lines, between epithelial and fibroblast cells, and between actively respiring cells and glycolytic cells. SignificanceProteomic analysis of proteins expressed in immortalized murine renal proximal tubule cells was compared to a murine fibroblast cell line proteome. The proximal tubule segment specific cell lines: S1, S2 and S3 are all grown under conditions whereby the cells generate ATP by oxidative phosphorylation while the fibroblast cell line utilizes anaerobic glycolysis for ATP generation. The proteomic studies allow for the following queries: 1) comparisons between the proximal tubule segment specific cell lines, 2) comparisons between polarized epithelia and fibroblasts, 3) comparison between cells employing oxidative phosphorylation versus anaerobic glycolysis and 4) comparisons between cells grown on clear versus opaque membrane supports. The data finds major differences in nuclear protein expression and mitochondrial proteins. This proteomic data set will be an important baseline dataset for investigators who need immortalized renal proximal tubule epithelial cells for their research.

Biotin-modified cyclometalated iridium-based photosensitizers as mitochondria-targeted theranostic agents for tumor photodynamic therapy in vitro and in vivo

Photodynamic therapy (PDT) is a promising non-invasive treatment technique for various types of cancer. Photoluminescent cyclometalated Ir(III) complexes, a distinctive genre of photosensitizers (PSS), have garnered significant interest due to their exceptional selective toxicity towards cancerous cells and minimal cytotoxicity towards normal cells. This study aimed to investigate the application of three newly designed biotin-modified cyclometalated Ir(III) complexes (Ir1-Ir3) for the treatment of cancer. The three complexes were found to have good photocatalytic activity, with singlet oxygen (1O2) yields ranging from 0.24 to 0.65 in aqueous solutions. The results suggest that these complexes have the potential as phototherapeutic and photodiagnostic agents for cancer treatment. Additionally, the biotin fragments in the Ir1-Ir3 structures enable their selective targeting of tumor cells. Notably, Ir3 displayed negligible dark toxicity towards A549 human lung cancer cells (IC50 > 100 μM), but its value decreased to 0.25 μM after 15 min of 425 nm (40 mW/cm2) light exposure. Furthermore, these complexes exhibited low phototoxicity towards non-cancerous BHK mouse kidney cells. Further investigation demonstrated that Ir3 had potent targeting abilities for mitochondria, and could trigger cell apoptosis through the activation of ROS-mediated mitochondrial signaling pathways under 425 nm light irradiation. In vivo studies revealed that Ir3 effectively suppressed tumor growth in A549 xenograft-bearing mice when exposed to 425 nm light. These results indicate that Ir3 has the potential to be a valuable photosensitizer drug for the photodynamic treatment of tumors.

Design, synthesis, and biological evaluation of artemyrianolide H derivatives as potential antihepatoma agents

Artemyrianolide H (AH) is a germacrene-type sesquiterpenolid isolated from Artemisia myriantha, and showed potent cytotoxicity against three human hepatocellular carcinoma cell lines HepG2, Huh7, and SK-Hep-1 with IC50 values of 10.9, 7.2, and 11.9 µM, respectively. To reveal structure−activity relationship, 51 artemyrianolide H derivatives including 19 dimeric analogs were designed, synthesized, and assayed for their cytotoxicity against three human hepatoma cell lines. Among them, 34 compounds were more active than artemyrianolide H and sorafenib on the three cell lines. Especially, compound 25 exhibited the most promising activity with IC50 values of 0.7 (HepG2), 0.6 (Huh7), and 1.3 µM (SK-Hep-1), which were 15.5, 12.0, and 9.2-fold higher than that of AH and 16.4, 16.3 and 17.5-fold higher than that of sorafenib. Cytotoxicity evaluation on normal human liver cell lines (THLE-2) demonstrated good safety profile of compound 25 with SI of 1.9 (HepG2), 2.2 (Huh 7) and 1.0 (SK-Hep1). Further studies revealed that compound 25 dose-dependently arrested cells at G2/M phase which was correlated with the up-regulation of both cyclin B1 and p-CDK1, and induced apoptosis through the activation of mitochondrial pathways in HepG2 cells. In addition, the migratory and invasive abilities in HepG2 cells after treatment with 1.5 μM of compound 25 were decreased by 89% and 86% with the increase of E-cadherin expression accompanied by the decrease of N-cadherin, vimentin expression. Bioinformatics analysis based on machine learning predicted that PDGFRA and MAP2K2 might be acting targets of compound 25, and SPR assays demonstrated compound 25 were bound with PDGFRA and MAP2K2 with KD value of 0.168 nM, and 8.49 µM, respectively. This investigation proposed that compound 25 might be considered as a promising lead compound for the development of antihepatoma candidate.

AMPK/MFF Activation: Role in Mitochondrial Fission and Mitophagy in Dry Eye.

To assess the role of mitochondrial morphology and adenosine monophosphate-activated protein kinase (AMPK)/mitochondrial fission factor (MFF) in dry eye and the underlying mechanisms. Immortalized human corneal epithelial cells (HCECs) and primary HCECs were cultured under high osmotic pressure (HOP). C57BL/6 female mice were injected subcutaneously with scopolamine. Quantitative real-time PCR was used to measure mRNA expression. Protein expression was assessed by western blot and immunofluorescence staining. Mitochondrial morphology was observed by confocal microscopy and transmission electron microscopy. First, HOP induced mitochondrial oxidative damage to HCECs, accompanied by mitochondrial fission and increased mitophagy. Then, AMPK/MFF pathway proteins were increased consequent to HOP-induced energy metabolism dysfunction. Interestingly, the AMPK pathway promoted mitochondrial fission and mitophagy by increasing the recruitment of dynamin-related protein 1 (DRP1) to the mitochondrial outer membrane in the HOP group. Moreover, AMPK knockdown attenuated mitochondrial fission and mitophagy due to HOP in HCECs. AMPK activation triggered mitochondrial fission and mitophagy. Mitochondrial fission of HCECs stressed by HOP was mediated via MFF phosphorylation. MFF knockdown reversed mitochondrial fragmentation and mitophagy in HCECs treated with HOP. Inhibition of MFF protected HCECs against oxidative damage, cell death, and inflammation in the presence of HOP. Finally, we detected mitochondrial fission and AMPK pathway activation in vivo. The AMPK/MFF pathway mediates the development of dry eye by positively regulating mitochondrial fission and mitophagy. Inhibition of mitochondrial fission can alleviate oxidative damage and inflammation in dry eye and may provide experimental evidence for treating dry eye.

Cobalt chloride has beneficial effects across species through a hormetic mechanism.

Severe oxygen and iron deficiencies have evolutionarily conserved detrimental effects, leading to pathologies in mammals and developmental arrest as well as neuromuscular degeneration in the nematode Caenorhabditis elegans. Yet, similar to the beneficial effects of mild hypoxia, non-toxic levels of iron depletion, achieved with the iron chelator bipyridine or through frataxin silencing, extend C. elegans lifespan through hypoxia-like induction of mitophagy. While the positive health outcomes of hypoxia preconditioning are evident, its practical application is rather challenging. Here, we thus test the potential beneficial effects of non-toxic, preconditioning interventions acting on iron instead of oxygen availability. We find that limiting iron availability through the iron competing agent cobalt chloride has evolutionarily conserved dose-dependent beneficial effects: while high doses of cobalt chloride have toxic effects in mammalian cells, iPS-derived neurospheres, and in C. elegans, sub-lethal doses protect against hypoxia- or cobalt chloride-induced death in mammalian cells and extend lifespan and delay age-associated neuromuscular alterations in C. elegans. The beneficial effects of cobalt chloride are accompanied by the activation of protective mitochondrial stress response pathways.

Angiotensin II Regulates Mitochondrial mTOR Pathway Activity Dependent on Acyl-CoA Synthetase 4 in Adrenocortical Cells.

Two well-known protein complexes in mammalian cells, mTOR type 1 and type 2 (mTORC1/2) are involved in several cellular processes such as protein synthesis, cell proliferation, and commonly dysregulated in cancer. An acyl-CoA synthetase type 4 (ACSL4) is one of the most recently mTORC1/2 regulators described, in breast cancer cells. The expression of ACSL4 is hormone-regulated in adrenocortical cells and required for steroid biosynthesis. mTORC1/2 have been reported to be crucial in the proliferation of human adrenocortical tumor cells H295R and interestingly reported at several subcellular locations, which has brought cell biology to the vanguard of the mTOR signaling field. In the present work, we study the regulation of mTORC1/2 activation by angiotensin II (Ang II)-the trophic hormone for adrenocortical cells-the subcellular localization of mTORC1/2 signaling proteins and the role of ACSL4 in the regulation of this pathway, in H295R cells. Ang II promotes activation by phosphorylation of mTORC1/2 pathway proteins in a time-dependent manner. Mitochondrial pools of ribosomal protein S6, protein kinase B (Akt) in threonine 308, and serine 473 and Rictor are phosphorylated and activated. Glycogen synthase kinase type 3 (GSK3) is phosphorylated and inactivated in mitochondria, favoring mTORC1 activation. Epidermal growth factor, a classic mTORC1/2 activator, promoted unique activation kinetics of mTORC1/2 pathway, except for Akt phosphorylation. Here, we demonstrate that ACSL4 is necessary for mTORC1/2 effectors phosphorylation and H295R proliferation, triggered by Ang II. Ang II promotes activation of mitochondrial mTORC1/2 signaling proteins, through ACSL4, with a direct effect on adrenocortical cellular proliferation.

KCNH6 Enhanced Hepatic Glucose Metabolism through Mitochondrial Ca2+ Regulation and Oxidative Stress Inhibition.

KCNH6 has been proven to affect glucose metabolism and insulin secretion both in humans and mice. Further study revealed that Kcnh6 knockout (KO) mice showed impaired glucose tolerance. However, the precise function of KCNH6 in the liver remains unknown. Mitochondria have been suggested to maintain intracellular Ca2+ homeostasis; ROS generation and defective mitochondria can cause glucose metabolism disorders, including type 2 diabetes (T2D). Here, we found that Kcnh6 attenuated glucose metabolism disorders by decreasing PEPCK and G6pase abundance and induced Glut2 and IRS2 expression. Overexpression of Kcnh6 increased hepatic glucose uptake and glycogen synthesis. Kcnh6 attenuated intracellular and mitochondrial calcium levels in primary hepatocytes and reduced intracellular ROS and mitochondrial superoxide production. Kcnh6 suppressed oxidative stress by inhibiting mitochondrial pathway activation and NADPH oxidase expression. Experiments demonstrated that Kcnh6 expression improved hepatic glucose metabolism disorder through the c-Jun N-terminal kinase and p38MAPK signaling pathways. These results were confirmed by experiments evaluating the extent to which forced Kcnh6 expression rescued metabolic disorder in KO mice. In conclusion, KCNH6 enhanced hepatic glucose metabolism by regulating mitochondrial Ca2+ levels and inhibiting oxidative stress. As liver glucose metabolism is key to T2D, understanding KCNH6 functions may provide new insights into the causes of diabetes.

Mitochondria-targeting folic acid-modified nanoplatform based on mesoporous carbon and a bioactive peptide for improved colorectal cancer treatment

Oral colon-targeted drug delivery systems (OCDDs) are designed to deliver the therapeutic agents to colonic disease sites to improve the effectiveness of drug treatment, increase bioavailability, and reduce systemic side effects and are beneficial for the treatment of colorectal cancer (CRC) and inflammatory bowel disease (IBD). However, concerns about the biosafety of OCDDs are increasing, and changes in the physiological environment of the gastrointestinal tract can affect the therapeutic efficacy of the drug. Herein, we report about an orally administered colon-accumulating mitochondria-targeted drug delivery nanoplatform (M27-39@FA-MCNs), which was synthesized using the small peptide, M27-39, and folic acid (FA)-modified mesoporous carbon nanoparticles (FA-MCNs). The phenolic resin polymerized with phloroglucinol and formaldehyde (PF) was used for fabricating MCNs using a one-step soft-template method. Folic acid (FA) can be covalently combined with chitosan-modified MCNs to obtain FA-MCNs. The M27-39@FA-MCNs were stable with a spherical morphology and an average diameter of 129 nm. The cumulative release rate of M27-39@FA-MCNs in the artificial gastric fluid (pH = 1.2) and intestinal fluid (pH = 6.8) for 6 h was 87.77%. This nanoplatform maintains the advantages of both FA and MCNs to improve the bioactivity of M27-39 with high drug accumulation in colorectal tumor tissues and the ease of excretion, thus ameliorating its biosafety and targetability. Furthermore, M27-39@FA-MCNs induced tumor-cell apoptosis and inhibited tumor growth by disrupting mitochondrial energy metabolism and regulating the mitochondrial apoptosis signaling pathway and immune inflammatory response. Thus, such a mitochondria-targeting FA-modified nanoplatform based on mesoporous carbon and a bioactive peptide may provide a precise strategy for CRC treatment. Statement of significanceIn this study, we constructed an orally administered colon-accumulating mitochondria-targeted drug delivery nanoplatform (M27-39@FA-MCNs), which was synthesized using the small peptide (M27-39) and folic acid-modified mesoporous carbon nanoparticles (FA-MCNs). M27-39@FA-MCNs increased the targeting ability of M27-39 toward mitochondria and colon based on the properties of FA-MCNs; they also increased M27-39 accumulation and residence time in colon tumors. Oral administration of M27-39@FA-MCNs remarkably alleviated colorectal cancer (CRC) by targeting tumor cell mitochondria and interfering with the mitochondrial energy metabolism process, and inducing apoptosis related P53/Caspase-3 mitochondrial pathway activation. Therefore, M27-39@FA-MCNs may provide a safe and precise therapeutic strategy for CRC.