Lysosomal-mitochondrial cross-talk during cell death

Specific photodamage on HT-29 cancer cells leads to endolysosomal failure and autophagy blockage by cathepsin depletion

Endolysosomes perform a wide range of cellular functions, including nutrient sensing, macromolecule digestion and recycling, as well as plasma membrane repair. Because of their high activity in cancerous cells, endolysosomes are attractive targets for the development of novel cancer treatments. Light-activated compounds termed photosensitizers (PS) can catalyze the oxidation of specific biomolecules and intracellular organelles. To selectively damage endosomes and lysosomes, HT-29 colorectal cancer cells were incubated with nanomolar concentrations of meso-tetraphenylporphine disulfonate (TPPS2a), an amphiphilic PS taken up via endocytosis and activated by green light (522 nm, 2.1 J.cm-1). Several cellular responses were characterized by a combination of immunofluorescence and immunoblotting assays. We showed that TPPS2a photosensitization blocked autophagic flux without extensive endolysosomal membrane rupture. Nevertheless, there was a severe functional failure of endolysosomes due to a decrease in CTSD (cathepsin D, 55%) and CTSB (cathepsin B, 52%) maturation. PSAP (prosaposin) processing (into saposins) was also considerably impaired, a fact that could be detrimental to glycosphingolipid homeostasis. Therefore, photosensitization of HT-29 cells previously incubated with a low concentration of TPPS2a promotes endolysosomal dysfunction, an effect that can be used to improve cancer therapies.

Apoptosis and eryptosis: similarities and differences

Eryptosis is a regulated cell death (RCD) of mature erythrocytes initially described as a counterpart of apoptosis for enucleated cells. However, over the recent years, a growing number of studies have emphasized certain differences between both cell death modalities. In this review paper, we underline the hallmarks of eryptosis and apoptosis and highlight resemblances and dissimilarities between both RCDs. We summarize and critically discuss differences in the impact of caspase-3, Ca2+ signaling, ROS signaling pathways, opposing roles of casein kinase 1α, protein kinase C, Janus kinase 3, cyclin-dependent kinase 4, and AMP-activated protein kinase to highlight a certain degree of divergence between apoptosis and eryptosis. This review emphasizes the crucial importance of further studies that focus on deepening our knowledge of cell death machinery and identifying novel differences between cell death of nucleated and enucleated cells. This might provide evidence that erythrocytes can be defined as viable entities capable of programmed cell destruction. Additionally, the revealed cell type-specific patterns in cell death can facilitate the development of cell death-modulating therapeutic agents.

Strategies to address key challenges of metallacycle/metallacage-based supramolecular coordination complexes in biomedical applications

Owing to their capacity for dynamically linking two or more functional molecules, supramolecular coordination complexes (SCCs), exemplified by two-dimensional (2D) metallacycles and three-dimensional (3D) metallacages, have gained increasing significance in biomedical applications. However, their inherent hydrophobicity and self-assembly driven by heavy metal ions present common challenges in their applications. These challenges can be overcome by enhancing the aqueous solubility and in vivo circulation stability of SCCs, alongside minimizing their side effects during treatment. Addressing these challenges is crucial for advancing the fundamental research of SCCs and their subsequent clinical translation. In this review, drawing on extensive contemporary research, we offer a thorough and systematic analysis of the strategies employed by SCCs to surmount these prevalent yet pivotal obstacles. Additionally, we explore further potential challenges and prospects for the broader application of SCCs in the biomedical field.

Adiponectin attenuates H2O2-induced apoptosis in chicken skeletal myoblasts through the lysosomal-mitochondrial axis

Adiponectin has previously been investigated for exerting its protective effect against myocardial injury through anti-apoptotic and anti-oxidative actions. Therefore, the present study aimed to investigate the nature and mechanism of adiponectin inhibition of H2O2-induced apoptosis in chicken skeletal myoblasts. Skeletal muscle satellite cells were differentiated and assigned into three groups. Group C was on the blank control group, group H was stimulated with the H2O2 (500 μmol/L, 4 h) alone group, group A + H was pre-treated with adiponectin (10 μg/mL, 24 h) and stimulated with the H2O2 (500 μmol/L, 4 h) group. Cytotoxicity inhibited by adiponectin was evaluated by the CCK-8 assay. The degree of apoptosis and oxidative damage was investigated by the TdT-mediated dUTP nick end labeling (TUNEL) and reactive oxygen species (ROS) staining assays. Oxidative stress was assessed by evaluating lipid peroxidation, superoxide dismutase, and reduced glutathione. Acridine orange (AO) staining detected lysosomal membrane permeability. The changes in mitochondrial membrane potential (MMP) were analyzed using 5,5,6,6'-tetrachloro-1,1,3,3-tetraethylimidacarbocyanine iodide (JC-1) dye under a fluorescence microscope. The lysosomal function, mitochondrial function, and apoptosis-related mRNA and protein expression levels were quantified by real-time quantitative PCR and western blot, respectively. The results suggested that adiponectin treatment attenuated H2O2-induced cytotoxicity and oxidative stress in skeletal myoblasts. Compared with H2O2 treatment, TUNEL and ROS staining demonstrated lower apoptosis upon adiponectin treatment. AO staining confirmed the amelioration of lysosomal membrane damage, and JC-1 staining revealed an increase in mitochondrial membrane potential after adiponectin treatment. At the molecular level, adiponectin treatment inhibited the expression of the lysosomal apoptotic factors cathepsin B, chymotrypsin B, and the mitochondrial apoptotic pathway cytochrome-c (cyt-c) and caspase-8; decreased the apoptotic marker gene Bax; and increased the expression of the anti-apoptotic marker gene Bcl-2. Adiponectin treatment attenuated H2O2-induced apoptosis in skeletal myoblasts, possibly by inhibiting oxidative stress and apoptosis through the lysosomal-mitochondrial axis.

The HN protein of Newcastle disease virus induces cell apoptosis through the induction of lysosomal membrane permeabilization

Lysosomes are acidic organelles that mediate the degradation and recycling of cellular waste materials. Damage to lysosomes can cause lysosomal membrane permeabilization (LMP) and trigger different types of cell death, including apoptosis. Newcastle disease virus (NDV) can naturally infect most birds. Additionally, it serves as a promising oncolytic virus known for its effective infection of tumor cells and induction of intensive apoptotic responses. However, the involvement of lysosomes in NDV-induced apoptosis remains poorly understood. Here, we demonstrate that NDV infection profoundly triggers LMP, leading to the translocation of cathepsin B and D and subsequent mitochondria-dependent apoptosis in various tumor and avian cells. Notably, the released cathepsin B and D exacerbate NDV-induced LMP by inducing the generation of reactive oxygen species. Additionally, we uncover that the viral Hemagglutinin neuraminidase (HN) protein induces the deglycosylation and degradation of lysosome-associated membrane protein 1 (LAMP1) and LAMP2 dependent on its sialidase activity, which finally contributes to NDV-induced LMP and cellular apoptosis. Overall, our findings elucidate the role of LMP in NDV-induced cell apoptosis and provide novel insights into the function of HN during NDV-induced LMP, which provide innovative approaches for the development of NDV-based oncolytic agents.

Probing the dynamic crosstalk of lysosomes and mitochondria with structured illumination microscopy

Structured illumination microscopy (SIM) is a super-resolution technology for imaging living cells and has been used for studying the dynamics of lysosomes and mitochondria. Recently, new probes and analyzing methods have been developed for SIM imaging, enabling the quantitative analysis of these subcellular structures and their interactions. This review provides an overview of the working principle and advances of SIM, as well as the organelle-targeting principles and types of fluorescence probes, including small molecules, metal complexes, nanoparticles, and fluorescent proteins. Additionally, quantitative methods based on organelle morphology and distribution are outlined. Finally, the review provides an outlook on the current challenges and future directions for improving the combination of SIM imaging and image analysis to further advance the study of organelles. We hope that this review will be useful for researchers working in the field of organelle research and help to facilitate the development of SIM imaging and analysis techniques.

Contribution of mitochondria to postmortem muscle tenderization: a review

Postmortem meat tenderization is a process mediated by a series of biochemical reactions related to muscle cell death. Cell death is considered a sign that muscle has started to transform into meat. Mitochondria play a significant role in regulating and executing cell death, as they are an aggregation point for many cell death signals and are also the primary target organelle damaged by tissue anoxia. Mitochondrial damage is likely to have an expanded role in postmortem meat tenderization. This review presents current findings on mitochondrial damage induced by the accumulation of reactive oxygen species during postmortem anaerobic metabolism and on the impact of mitochondrial damage on proteolysis and discusses how this leads to improved tenderness during aging. The underlying mechanisms of mitochondrial regulation of postmortem muscle tenderization likely focus on the mitochondria's role in postmortem cell death and energy metabolism. The death process of postmortem skeletal muscle cells may exhibit multiple types, possibly involving transformation from autophagy to apoptosis and, ultimately, necroptosis or necrosis. Mitochondrial characteristics, especially membrane integrity and ATP-related compound levels, are closely related to the transformation of multiple types of dead postmortem muscle cells. Finally, a possible biochemical regulatory network in postmortem muscle tenderization is proposed.

Significant increase of anticancer efficacy in vitro and in vivo of liposome entrapped ruthenium(II) polypyridyl complexes

Two polypyridyl ruthenium(II) complexes [Ru(DIP)₂(BIP)](PF₆)₂ (DIP = 4,7-diphenyl-1,10-phenanthrolie, BIP = 2-(1,1'-biphenyl-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, Ru1) and [Ru(DIP)₂(CBIP)](PF₆)₂ (CBIP = 2-(4'-chloro-1,1'-biphenyl-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, Ru2) were synthesized. The cytotoxic activities in vitro of Ru1, Ru2 toward B16, A549, HepG2, SGC-7901, HeLa, BEL-7402, non-cancer LO2 were investigated using MTT method (3-(4,5-dimethylthiazole)-2,5-diphenltetraazolium bromide). Unexpectedly, Ru1, Ru2 can't prevent these cancer cells proliferation. To improve the anti-cancer effect, we used liposomes to entrap the complexes Ru1, Ru2 to form Ru1lipo, Ru2lipo. As expectation, Ru1lipo and Ru2lipo exhibit high anti-cancer efficacy, especially, Ru1lipo (IC₅₀ 3.4 ± 0.1 μM), Ru2lipo (IC₅₀ 3.5 ± 0.1 μM) display strong ability to block the cell proliferation in SGC-7901. The cell colony, wound healing, and cell cycle distribution show that the complexes can validly inhibit the cell growth at G2/M phase. Apoptotic studied with Annex V/PI doubling method showed that Ru1lipo and Ru2lipo can effectively induce apoptosis. Reactive oxygen species (ROS), malondialdehyde, glutathione and GPX4 demonstrate that Ru1lipo and Ru2lipo improve ROS and malondialdehyde levels, inhibit generation of glutathione, and finally result in a ferroptosis. Ru1lipo and Ru2lipo interact on the lysosomes and mitochondria and damage mitochondrial dysfunction. Additionally, Ru1lipo and Ru2lipo increase intracellular Ca²⁺ concentration and induce autophagy. The RNA-sequence and molecular docking were performed, the expression of Bcl-2 family was investigated by Western blot analysis. Antitumor in vivo experiments confirm that 1.23 mg/kg, 2.46 mg/kg of Ru1lipo possesses a high inhibitory rate of 53.53% and 72.90% to prevent tumor growth, hematoxylin-eosin (H&E) results show that Ru1lipo doesn't cause chronic organ damage and strongly promotes the necrosis of solid tumor. Taken together, we conclude that Ru1lipo and Ru2lipo cause cell death through the following pathways: autophagy, ferroptosis, ROS-regulated mitochondrial dysfunction, and blocking the PI3K/AKT/mTOR.

Synthesis, RNA-sequence and evaluation of anticancer efficacy of ruthenium(II) polypyridyl complexes toward HepG2 cells

In this article, four new Ru(II) complexes [Ru(dmbpy)₂(TFBIP)](PF₆)₂ (dmbpy = 4,4'-dimethyl-2,2'-bipyridine, TFPIP = 2-(4'-trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) (Ru1), [Ru(bpy)₂(TFBIP)](PF₆)₂ (bpy = 2,2'-bipyridine) (Ru2), [Ru(phen)₂(TFBIP)](PF₆)₂ (phen = 1,10-phenanthroline) (Ru3) and [Ru(dmp)₂(TFBIP)](PF₆)₂ (dmp = 2,9-dimethyl-1,10-phenanthroline) (Ru4) were synthesized and characterized by elemental analysis, HRMS, IR, ¹H NMR, ¹³C NMR and ¹⁹F NMR. The in vitro anticancer effect of the complexes on HepG2, A549, B16, HeLa, BEL-7402 and non-cancer LO2 cells was screened using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The results illustrate that the complexes display moderate anticancer activity. Apoptotic assay with Annexin V/PI double staining method indicated that complexes induce apoptosis in HepG2 cells. Also, the complexes interfere with the mitochondrial functions, accompanied by the production of intracellular ROS as well as a reduction of mitochondrial membrane potential. The results obtained from the western blot demonstrated that the complexes upregulate pro-apoptotic Bax and downregulate anti-apoptotic Bcl-2, which further activates caspase 3 and promotes the cleavage of PARP. RNA-sequence showed that the complexes upregulate the expression of 40 genes and downregulate 66 genes. Antitumour in vivo demonstrated that Ru1 inhibits the tumor growth with a high inhibitory rate of 51.19%. Taken together, these results revealed that complexes Ru1, Ru2, Ru3 and Ru4 induce cell death in HepG2 cells via autophagy and a ROS-mediated mitochondrial apoptotic pathway.

Serine hydroxymethyltransferase 2 knockdown induces apoptosis in ccRCC by causing lysosomal membrane permeabilization via metabolic reprogramming

Serine hydroxymethyltransferase 2 (SHMT2) plays an important role in converting serine to glycine and supplying carbon to one-carbon metabolism to sustain cancer cell proliferation. However, the expression, function, and underlying mechanisms of SHMT2 in clear cell renal cell carcinoma (ccRCC) remain largely unknown. In this study, we demonstrated that SHMT2 was upregulated in ccRCC tissues compared with controls and associated with patient survival. SHMT2 knockdown inhibited proliferation, migration, and invasion in ccRCC cells. Overexpression of SHMT2 promoted tumor progression. Mechanistically, SHMT2 depletion disrupted one-carbon metabolism, increased reactive oxygen species (ROS) levels, and decreased ATP levels via metabolic reprogramming, which destroyed cell homeostasis. The SHMT2 knockdown-induced stress activated autophagy. A mass of autophagosomes fused with lysosomes, resulting in lysosomal membrane permeabilization (LMP) and leakage of lysosomal contents into the cytoplasm, which eventually led to apoptosis. Our work reveals that SHMT2 functions as an oncogenic gene to promote ccRCC progression. SHMT2 depletion induces apoptosis by causing LMP through excessive activation of the autophagy-lysosome pathway via metabolic reprogramming.

Investigation of Molecular Mechanisms Involved in Sensitivity to the Anti-Cancer Activity of Costunolide in Breast Cancer Cells

Costunolide (CTL), an active compound isolated from Saussurea lappa Clarke and Laurus nobilis L, has been shown to induce apoptosis via reactive oxygen species (ROS) generation in various types of cancer cells. However, details of molecular mechanisms underlying the difference in sensitivity of cancer cells to CTL are still largely unknown. Here, we tested the effect of CTL on the viability of breast cancer cells and found that CTL had a more efficient cytotoxic effect against SK-BR-3 cells than MCF-7 cells. Mechanically, ROS levels were significantly increased upon CTL treatment only in SK-BR-3 cells, which leads to lysosomal membrane permeabilization (LMP) and cathepsin D release, and subsequent activation of the mitochondrial-dependent intrinsic apoptotic pathway by inducing mitochondrial outer membrane permeabilization (MOMP). In contrast, treatment of MCF-7 cells with CTL activated PINK1/Parkin-dependent mitophagy to remove damaged mitochondria, which prevented the elevation of ROS levels, thereby contributing to their reduced sensitivity to CTL. These results suggest that CTL is a potent anti-cancer agent, and its combination with the inhibition of mitophagy could be an effective method for treating breast cancer cells that are less sensitive to CTL.

An overview of hyperbaric oxygen preconditioning against ischemic stroke

Ischemic stroke (IS) has become the second leading cause of morbidity and mortality worldwide, and the prevention of IS should be given high priority. Recent studies have indicated that hyperbaric oxygen preconditioning (HBO-PC) may be a protective nonpharmacological method, but its underlying mechanisms remain poorly defined. This study comprehensively reviewed the pathophysiology of IS and revealed the underlying mechanism of HBO-PC in protection against IS. The preventive effects of HBO-PC against IS may include inducing antioxidant, anti-inflammation, and anti-apoptosis capacity; activating autophagy and immune responses; upregulating heat shock proteins, hypoxia-inducible factor-1, and erythropoietin; and exerting protective effects upon the blood-brain barrier. In addition, HBO-PC may be considered a safe and effective method to prevent IS in combination with stem cell therapy. Although the benefits of HBO-PC on IS have been widely observed in recent research, the implementation of this technique is still controversial due to regimen differences. Transferring the results to clinical application needs to be taken carefully, and screening for the optimal regimen would be a daunting task. In addition, whether we should prescribe an individualized preconditioning regimen to each stroke patient needs further exploration.

Cathepsin B Deficiency Improves Memory Deficits and Reduces Amyloid-β in hAβPP Mouse Models Representing the Major Sporadic Alzheimer's Disease Condition

The lysosomal cysteine protease cathepsin B (CTSB) has been suggested as a biomarker for Alzheimer's disease (AD) because elevated serum CTSB in AD patients has been found to correlate with cognitive dysfunction. Furthermore, CTSB gene knockout (KO) in non-transgenic and transgenic AD animal models showed that elimination of CTSB improved memory deficits. However, conflicting CTSB KO results on amyloid-β (Aβ) pathology in transgenic AD models have been reported. The conflict is resolved here as likely being due to the different hAβPP transgenes used in the different AD mouse models. CTSB gene KO reduced wild-type (Wt) β-secretase activity, brain Aβ, pyroglutamate-Aβ, amyloid plaque, and memory deficits in models that used cDNA transgenes expressing hAβPP isoform 695. But in models that used mutated mini transgenes expressing hAβPP isoforms 751 and 770, CTSB KO had no effect on Wt β-secretase activity and slightly increased brain Aβ. All models expressed the AβPP transgenes in neurons. These conflicting results in Wt β-secretase activity models can be explained by hAβPP isoform specific cellular expression, proteolysis, and subcellular processing. CTSB KO had no effect on Swedish mutant (Swe) β-secretase activity in hAβPP695 and hAβPP751/770 models. Different proteolytic sensitivities for hAβPP with Wt versus Swe β-secretase site sequences may explain the different CTSB β-secretase effects in hAβPP695 models. But since the vast majority of sporadic AD patients have Wt β-secretase activity, the CTSB effects on Swe β-secretase activity are of little importance to the general AD population. As neurons naturally produce and process hAβPP isoform 695 and not the 751 and 770 isoforms, only the hAβPP695 Wt models mimic the natural neuronal hAβPP processing and Aβ production occurring in most AD patients. Significantly, these CTSB KO findings in the hAβPP695 Wt models demonstrate that CTSB participates in memory deficits and production of pyroglutamate-Aβ (pyroglu-Aβ), which provide rationale for future investigation of CTSB inhibitors in AD therapeutics development.

Fluorescence intensity and lifetime imaging of lipofuscin-like autofluorescence for label-free predicting clinical drug response in cancer

Conventional techniques for in vitro cancer drug screening require labor-intensive formalin fixation, paraffin embedding, and dye staining of tumor tissues at fixed endpoints. This way of assessment discards the valuable pharmacodynamic information in live cells over time. Here, we found endogenous lipofuscin-like autofluorescence acutely accumulated in the cell death process. Its unique red autofluorescence could report the apoptosis without labeling and continuously monitor the treatment responses in 3D tumor-culture models. Lifetime imaging of lipofuscin-like red autofluorescence could further distinguish necrosis from apoptosis of cells. Moreover, this endogenous fluorescent marker could visualize the apoptosis in live zebrafish embryos during development. Overall, this study validates that lipofuscin-like autofluorophore is a generic cell death marker. Its characteristic autofluorescence could label-free predict the efficacy of anti-cancer drugs in organoids or animal models.

Hazards related to the presence of cadmium in food - Studies on the European soil centipede, Lithobius forficatus

The soil is an environment rich in numerous potentially toxic substances/elements when present at elevated concentrations. They can be transported through the successive levels of the trophic chain. Animals living in a contaminated environment or eating contaminated food can accumulate potentially toxic elements in their bodies. One of the potentially toxic metals is cadmium, which accumulates significantly in soils. The aim of our research was to evaluate the changes caused by cadmium supplied with the food administered to invertebrates living in uncontaminated soil. The results were compared with those obtained for animals raised in contaminated soil, where cadmium entered the body via the epidermis. As the material for studies, we chose a common European soil centipede, Lithobius forficatus. Adult specimens were divided into the following experimental groups: C - control animals, Cd12 and Cd45 - animals fed with Chironomus larvae maintained in water containing 80 mg/l CdCl₂, for 12 and 45 days, respectively. The material was analyzed using qualitative and quantitative analysis (transmission electron microscopy, confocal microscopy, flow cytometry, atomic absorption spectrometry). Eventually, we can conclude that the digestive system is an effective barrier against the effects of toxic metals on the entire organism, but among the gonads, ovaries are more protected than testes, however, this protection is not sufficient. Accumulation of spherites and mitochondrial alterations are probably involved in survival mechanisms of tissues after Cd intoxication.

Rational Design of Oxazolidine-Based Red Fluorescent pH Probe for Simultaneous Imaging Two Subcellular Organelles

A reversible pH-responsive fluorescent probe, BP, was rationally designed and synthesized, based on protonation and deprotonation gave rise to oxazolidine ring open and close. The fluorescence response of BP against pH ranges from 3.78 to 7.54, which is suitable for labeling intracellular pH-dependent organelles. BP displayed strong red emission at a relatively high pH in living HeLa cells and U87 cells. More importantly, this probe exhibited good colocalization with both mitochondria and lysosomes in these two cell lines, attributing to pH-induced structure tautomerism resulting in an oxazolidine ring open and close that triggered effective targeting of these two organelles. As organelle interactions are critical for cellular processes, this strategy of targeting dual organelles through the structure tautomerism is conducive to further developing more effective and advanced probes for real-time imaging of the interaction between mitochondria and lysosomes.

Lysosomal K+ channel TMEM175 promotes apoptosis and aggravates symptoms of Parkinson's disease

Lysosomes are degradative organelles and play vital roles in a variety of cellular processes. Ion channels on the lysosomal membrane are key regulators of lysosomal function. TMEM175 has been identified as a lysosomal potassium channel, but its modulation and physiological functions remain unclear. Here, we show that the apoptotic regulator Bcl-2 binds to and inhibits TMEM175 activity. Accordingly, Bcl-2 inhibitors activate the channel in a caspase-independent way. Increased TMEM175 function inhibits mitophagy, disrupts mitochondrial homeostasis, and increases production of reactive oxygen species (ROS). ROS further activates TMEM175 and thus forms a positive feedback loop to augment apoptosis. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD), knockout (KO) of TMEM175 mitigated motor impairment and dopaminergic (DA) neuron loss, suggesting that TMEM175-mediated apoptosis plays an important role in Parkinson's disease (PD). Overall, our study reveals that TMEM175 is an important regulatory site in the apoptotic signaling pathway and a potential therapeutic target for Parkinson's disease (PD).

Expression Plasticity of Peroxisomal Acyl-Coenzyme A Oxidase Genes Implies Their Involvement in Redox Regulation in Scallops Exposed to PST-Producing Alexandrium

Filter-feeding bivalves can accumulate paralytic shellfish toxins (PST) produced by toxic microalgae, which may induce oxidative stress and lipid peroxidation. Peroxisomal acyl-coenzyme A oxidases (ACOXs) are key enzymes functioning in maintaining redox and lipid homeostasis, but their roles in PST response in bivalves are less understood. Herein, a total of six and six ACOXs were identified in the Chlamys farreri and Patinopecten yessoensis genome, respectively, and the expansion of ACOX1s was observed. Gene expression analysis revealed an organ/tissue-specific expression pattern in both scallops, with all ACOXs being predominantly expressed in the two most toxic organs, digestive glands and kidneys. The regulation patterns of scallop ACOXs after exposure to different PST-producing algaes Alexandrium catenella (ACDH) and A. minutum (AM-1) were revealed. After ACDH exposure, more differentially expressed genes (DEGs) were identified in C. farreri digestive glands (three) and kidneys (five) than that in P. yessoensis (two), but the up-regulated DEGs showed similar expression patterns in both species. In C. farreri, three DEGs were found in both digestive glands and kidneys after AM-1 exposure, with two same CfACOX1s being acutely and chronically induced, respectively. Notably, these two CfACOX1s also showed different expression patterns in kidneys between ACDH (acute response) and AM-1 (chronic response) exposure. Moreover, inductive expression of CfACOXs after AM-1 exposure was observed in gills and mantles, and all DEGs in both tissues were up-regulated and their common DEGs exhibited both acute and chronic induction. These results indicate the involvement of scallop ACOXs in PST response, and their plasticity expression patterns between scallop species, among tissues, and between the exposure of different PST analogs.

Cathepsin B Gene Knockout Improves Behavioral Deficits and Reduces Pathology in Models of Neurologic Disorders

Cathepsin B (CTSB) is a powerful lysosomal protease. This review evaluated CTSB gene knockout (KO) outcomes for amelioration of brain dysfunctions in neurologic diseases and aging animal models. Deletion of the CTSB gene resulted in significant improvements in behavioral deficits, neuropathology, and/or biomarkers in traumatic brain injury, ischemia, inflammatory pain, opiate tolerance, epilepsy, aging, transgenic Alzheimer's disease (AD), and periodontitis AD models as shown in 12 studies. One study found beneficial effects for double CTSB and cathepsin S KO mice in a multiple sclerosis model. Transgenic AD models using amyloid precursor protein (APP) mimicking common sporadic AD in three studies showed that CTSB KO improved memory, neuropathology, and biomarkers; two studies used APP representing rare familial AD and found no CTSB KO effect, and two studies used highly engineered APP constructs and reported slight increases in a biomarker. In clinical studies, all reports found that CTSB enzyme was upregulated in diverse neurologic disorders, including AD in which elevated CTSB was positively correlated with cognitive dysfunction. In a wide range of neurologic animal models, CTSB was also upregulated and not downregulated. Further, human genetic mutation data provided precedence for CTSB upregulation causing disease. Thus, the consilience of data is that CTSB gene KO results in improved brain dysfunction and reduced pathology through blockade of CTSB enzyme upregulation that causes human neurologic disease phenotypes. The overall findings provide strong support for CTSB as a rational drug target and for CTSB inhibitors as therapeutic candidates for a wide range of neurologic disorders. SIGNIFICANCE STATEMENT: This review provides a comprehensive compilation of the extensive data on the effects of deleting the cathepsin B (CTSB) gene in neurological and aging mouse models of brain disorders. Mice lacking the CTSB gene display improved neurobehavioral deficits, reduced neuropathology, and amelioration of neuronal cell death and inflammatory biomarkers. The significance of the compelling CTSB evidence is that the data consilience validates CTSB as a drug target for discovery of CTSB inhibitors as potential therapeutics for treating numerous neurological diseases.

Current Methods to Unravel the Functional Properties of Lysosomal Ion Channels and Transporters

A distinct set of channels and transporters regulates the ion fluxes across the lysosomal membrane. Malfunctioning of these transport proteins and the resulting ionic imbalance is involved in various human diseases, such as lysosomal storage disorders, cancer, as well as metabolic and neurodegenerative diseases. As a consequence, these proteins have stimulated strong interest for their suitability as possible drug targets. A detailed functional characterization of many lysosomal channels and transporters is lacking, mainly due to technical difficulties in applying the standard patch-clamp technique to these small intracellular compartments. In this review, we focus on current methods used to unravel the functional properties of lysosomal ion channels and transporters, stressing their advantages and disadvantages and evaluating their fields of applicability.

pH Sensitive Dextran Coated Fluorescent Nanodiamonds as a Biomarker for HeLa Cells Endocytic Pathway and Increased Cellular Uptake

Fluorescent nanodiamonds are a useful for biosensing of intracellular signaling networks or environmental changes (such as temperature, pH or free radical generation). HeLa cells are interesting to study with these nanodiamonds since they are a model cell system that is widely used to study cancer-related diseases. However, they only internalize low numbers of nanodiamond particles very slowly via the endocytosis pathway. In this work, we show that pH-sensitive, dextran-coated fluorescent nanodiamonds can be used to visualise this pathway. Additionally, this coating improved diamond uptake in HeLa cells by 5.3 times (*** p < 0.0001) and decreased the required time for uptake to only 30 min. We demonstrated further that nanodiamonds enter HeLa cells via endolysosomes and are eventually expelled by cells.

Therapeutic potential of ginsenoside Rg3 and Rf for Huntington's disease

Ginseng is a popular herbal medicine and known to have protective and therapeutic effects in various diseases. Ginsenosides are active gradients representing the diverse pharmacological efficacy of ginseng. Huntington's disease (HD) is incurable genetic disorder associated with mutant huntingtin (mHtt) aggregation in the central nervous system. This study was conducted to investigate the effects of ginsenoside Rg3 and Rf on mHtt aggregation, cell viability, mitochondrial function, and apoptotic molecules on HD model. To investigate the effect of ginsenosides on HD, neural stem cells were isolated from the R6/2 mouse brain and used as a cellular model of HD. Nuclear aggregation of mHtt was measured by immunocytochemistry, and expressions of mitochondrial biogenesis and apoptotic molecules were investigated by western blot. As a result, the number of mHtt aggregates positive cells has decreased by ginsenoside Rg3 and Rf treatment in cellular model of HD. Mitochondrial biogenesis-related molecules such as PGC-1α and phosphorylated CREB were increased or showed increased tendency by ginsenoside Rg3 and Rf. Apoptotic molecules, p53, Bax, and cleaved caspase-3, were down-regulated by treatment of ginsenoside Rg3 and Rf. In addition, Lysotracker staining result showed that cellular lysosomal content was reduced by ginsenoside Rg3 and Rf. Given that ginsenoside Rg3 and Rf have the potential to reduce mHtt aggregation and cellular apoptosis, these ginsenosides can be possible therapeutic candidates for treating HD phenotypes.

Cellular compartments challenged by membrane photo-oxidation

The lipid composition impacts directly on the structure and function of the cytoplasmic as well as organelle membranes. Depending on the type of membrane, specific lipids are required to accommodate, intercalate, or pack membrane proteins to the proper functioning of the cells/organelles. Rather than being only a physical barrier that separates the inner from the outer spaces, membranes are responsible for many biochemical events such as cell-to-cell communication, protein-lipid interaction, intracellular signaling, and energy storage. Photochemical reactions occur naturally in many biological membranes and are responsible for diverse processes such as photosynthesis and vision/phototaxis. However, excessive exposure to light in the presence of absorbing molecules produces excited states and other oxidant species that may cause cell aging/death, mutations and innumerable diseases including cancer. At the same time, targeting key compartments of diseased cells with light can be a promising strategy to treat many diseases in a clinical procedure called Photodynamic Therapy. Here we analyze the relationships between membrane alterations induced by photo-oxidation and the biochemical responses in mammalian cells. We specifically address the impact of photosensitization reactions in membranes of different organelles such as mitochondria, lysosome, endoplasmic reticulum, and plasma membrane, and the subsequent responses of eukaryotic cells.

Effects of lysosomal iron involvement in the mechanism of mitochondrial apoptosis on postmortem muscle protein degradation

This study investigated the effect of lysosomal iron involvement in the mechanism of mitochondrial apoptosis on bovine muscle protein degradation during postmortem aging. Six crossbred cattle were studied to evaluate intracellular reactive oxygen species (ROS), antioxidant enzyme activity, lysosomal membrane stability, mitochondrial dysfunction-induced apoptosis, desmin and troponin-T degradation in both control and iron chelator desferrioxamine (DFO) groups. Results showed that lysosomal iron induced ROS accumulation and lysosomal membrane destabilization by decreasing the antioxidant enzyme activity (P < 0.05). Subsequently, lysosomal dysfunction mediated by iron increased mitochondrial membrane permeability and decreased mitochondrial membrane potential, thereby enhancing Bid and cytochrome c release and caspase-9/-3 activation (P < 0.05). Ultimately, lysosomal iron mediated lysosomal-mitochondrial apoptosis increased the postmortem bovine muscle desmin and troponin-T degradation (P < 0.05). The results indicated that lysosomal iron contributes to postmortem meat tenderization through the lysosomal-mitochondrial dysfunction-induced apoptosis pathway.

Role of endolysosomes and inter-organellar signaling in brain disease

Endosomes and lysosomes (endolysosomes) are membrane bounded organelles that play a key role in cell survival and cell death. These acidic intracellular organelles are the principal sites for intracellular hydrolytic activity required for the maintenance of cellular homeostasis. Endolysosomes are involved in the degradation of plasma membrane components, extracellular macromolecules as well as intracellular macromolecules and cellular fragments. Understanding the physiological significance and pathological relevance of endolysosomes is now complicated by relatively recent findings of physical and functional interactions between endolysosomes with other intracellular organelles including endoplasmic reticulum, mitochondria, plasma membranes, and peroxisomes. Indeed, evidence clearly indicates that endolysosome dysfunction and inter-organellar signaling occurs in different neurodegenerative diseases including Alzheimer's disease (AD), HIV-1 associated neurocognitive disease (HAND), Parkinson's disease (PD) as well as various forms of brain cancer such as glioblastoma multiforme (GBM). These findings open new areas of cell biology research focusing on understanding the physiological actions and pathophysiological consequences of inter-organellar communication. Here, we will review findings of others and us that endolysosome de-acidification and dysfunction coupled with impaired inter-organellar signaling is involved in the pathogenesis of AD, HAND, PD, and GBM. A more comprehensive appreciation of cell biology and inter-organellar signaling could lead to the development of new drugs to prevent or cure these diseases.

Liposomes encapsulated iridium(III) polypyridyl complexes enhance anticancer activity in vitro and in vivo

Three iridium(III) complexes [Ir(ppy)₂(CPIP)](PF₆) (Ir-1, ppy = 2-phenylpyridine, CPIP = 2-(4-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy)₂(DCPIP)](PF₆) (Ir-2, DCPIP = 2-(3,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(ppy)₂(TCPIP)](PF₆) (Ir-3, TCPIP = 2,3,5-trichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. The complexes Ir-1, Ir-2 and Ir-3 were encapsulated in liposomes to form Ir-1-Lipo, Ir-2-Lipo and Ir-3-Lipo. Morphology, size distribution, and zeta potential of liposomes were examined by transmission electron microscopy (TEM) and Zetasizer. The cytotoxic activity in vitro of Ir-1, Ir-2 and Ir-3 against cancer A549, HTC-116, HepG2, BEL-7402, Eca-109, B16, HeLa SGC-7901 and normal NIH3T3 cells was evaluated by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. Ir-2 and Ir-3 show no cytotoxic activity against the selected cancer cells, and Ir-1 displays moderate cytotoxic effect on the cell growth in A549 cells. However, Ir-1, Ir-2 and Ir-3 were encapsulated in liposomes, the cytotoxic activity was greatly enhanced. In particular, Ir-1-Lipo and Ir-2-Lipo can effectively inhibit the cell growth in A549 cells with a low IC₅₀ value of 3.1 ± 0.3 and 1.2 ± 0.4 μM. The apoptosis was assayed by flow cytometry. Ir-1, Ir-2 and Ir-3 reveal weak apoptotic effect, whereas Ir-1-Lipo, Ir-2-Lipo and Ir-3-Lipo induce an apoptotic percentage of 55.6%, 69.3% and 16.7% in A549 cells, respectively. Specially, in the assay of antitumor activity in vivo, the inhibiting percentage of tumor growth induced by Ir-2 is 27.65%, while inhibiting percentage of tumor growth caused by Ir-2-Lipo is 57.45%. Obviously, the liposomes can enhance anticancer activity in vitro and in vivo compared with the complexes. The results show that the iridium(III) complexes encapsulated liposomes induce apoptosis in A549 cells through ROS-mediated lysosome-mitochondria dysfunction pathway and target the microtubules.

Dual functions of iridium(III) 2-phenylpyridine complexes: Metastasis inhibition and lysosomal damage

Six N-phenylcarbazole/triphenylamine-appended half-sandwich iridium(III) 2-phenylpyridine complexes ([(η⁵-Cp*)Ir(C^N)Cl]) were prepared and characterized. Compared with cisplatin, these complexes exhibited potential antitumor activity against A549 and HeLa tumor cells, with IC₅₀ values (half-maximum inhibitory concentration) that changed from 2.8 ± 0.8 μM to 39.5 ± 2.7 μM, and could block the migration of tumor cells. These complexes also effectively bound to protein (binding constant: ~10⁴ M^-1) and were transported through serum proteins, catalyzed the oxidation of coenzyme nicotinamide-adenine dinucleotide. Additionally, laser confocal microscopy and flow cytometry confirmed that these complexes possessed a non-energy-dependent cellular uptake mechanism, effectively accumulated in lysosomes (Pearson colocalization coefficient: ~0.74), damaged the integrity of acidic lysosomes, led to a change in the mitochondrial membrane potential, disrupted the cell cycle (G₀/G₁ phase), and eventually induced apoptosis. Above all, these complexes are potential antitumor agents with dual functions: metastasis inhibition and lysosomal damage.

Subcellular Organelle Toxicity Caused by Arsenic Nanoparticles in Isolated Rat Hepatocytes

BACKGROUND

Arsenic, an environmental pollutant, is a carcinogenic metalloid and also an anticancer agent.

OBJECTIVE

To evaluate the toxicity of arsenic nanoparticles in rat hepatocytes.

METHODS

Freshly isolated rat hepatocytes were exposed to 0, 20, 40, and 100 μM of arsenic nanoparticles and its bulk counterpart. Their viability, reactive oxygen species level, glutathione depletion, mitochondrial and lysosomal damage, and apoptosis were evaluated.

RESULTS

By all concentrations, lysosomal damage and apoptosis were clearly evident in hepatocytes exposed to arsenic nanoparticles. Evaluation of mitochondria and lysosomes revealed that lysosomes were highly damaged.

CONCLUSION

Exposure to arsenic nanoparticles causes apoptosis and organelle impairment. The nanoparticles have potentially higher toxicity than the bulk arsenic. Lysosomes are highly affected. It seems that, instead of mitochondria, lysosomes are the first target organelles involved in the toxicity induced by arsenic nanoparticles.

Imaging stressed organellesviasugar-conjugated color-switchable pH sensors

Sugar-conjugated pH sensors discriminate stressed lysosomes in different cell starvation conditionsviared-to-green fluorescence switch.

Lithium effects on vesicular trafficking in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most commonly malignant tumors worldwide, characterized by the presence of many heterogeneous molecular cell events that contribute to tumor growth and progression. Endocytic processes are intimately involved in various pathological conditions, including cancer, since they interface with various cellular signaling programs. The ability of lithium to induce cell death and autophagy and affect cell proliferation and intracellular signaling has been shown in various experimental tumor models. The aim of this study was to evaluate the effects of lithium on vesicular transport in hepatocellular carcinoma cells. Using transmission electron microscopy we have characterized the endocytic apparatus in hepatocellular carcinoma-29 (HCC-29) cells in vivo and detailed changes in endocytotic vesicles after 20 mM lithium carbonate administration. Immunofluorescent analysis was used to quantify cells positive for EEA1-positive early endosomes, Rab11-positive recycling endosomes and Rab7-positive late endosomes. Lithium treatment caused an increase in EEA1- and Rab11-positive structures and a decrease in Rab7-positive vesicles. Thus, lithium affects diverse endocytic pathways in HCC-29 cells which may modulate growth and development of hepatocellular carcinoma.

Repair Effects of Astragalus Polysaccharides with Different Molecular Weights on Oxidatively Damaged HK-2 Cells

This study investigated the repair effects of three Astragalus polysaccharides (APSs) with different molecular weights (Mws) on injured human renal proximal tubular epithelial (HK-2) cells to reveal the effect of Mw of polysaccharide on cell repair. A damage model was established by injuring HK-2 cells with 2.6 mM oxalate, and APS0, APS1, and APS2 with Mw of 11.03, 4.72, and 2.61 KDa were used to repair the damaged cells. After repair by APSs, the morphology of damaged HK-2 cells gradually returned to normal, the destruction of intercellular junctions recovered, intracellular reactive oxygen species production amount decreased, and their mitochondrial membrane potential increased. In addition, the cell cycle progression gradually normalized, lysosome integrity increased, and cell apoptotic rates obviously declined in the repaired cells. All three APSs could promote the expression of Keap1, Nrf2, SOD1, and CAT. In addition, the expression levels of inflammation markers containing MCP-1 and IL-6 decreased after APS repair. We deduced that APSs exert their repair function by activating the Nrf2-Keap1 signaling pathway and inhibiting inflammation. Among the APSs, APS1 with a moderate Mw provided the strongest repair effect. APSs may have a preventive effect on kidney stones.

Parthenolide regulates oxidative stress-induced mitophagy and suppresses apoptosis through p53 signaling pathway in C2C12 myoblasts

Muscle redox disturbances and oxidative stress have emerged as a common pathogenetic mechanism and potential therapeutic intervention in some muscle diseases. Parthenolide (PTL), a sesquiterpene lactone found in large amounts in the leaves of feverfew, possesses anti-inflammatory, anti-migraine, and anticancer properties. Although PTL was reported to alleviate cancer cachexia and improve skeletal muscle characteristics in a cancer cachexia model, its actions on oxidative stress-induced damage in C2C12 myoblasts have not been reported and the regulatory mechanisms have not yet been defined. In our study, PTL attenuated H₂ O₂ -induced growth inhibition and morphological changes. Furthermore, PTL exhibited scavenging activity against reactive oxygen species and protected C2C12 cells from apoptosis in response to H₂ O₂ . Meanwhile, PTL suppressed collapse of the mitochondrial membrane potential, thereby contributing to normalizing H₂ O₂ -induced autophagy flux and mitophagy, correlating with inhibiting degradation of mitochondrial marker protein TIM23, the increase in LC3-II expression and the reduction of mitochondria DNA. Besides its protective effect on mitochondria, PTL also prevented H₂ O₂ -induced lysosomes damage in C2C12 cells. In addition, the phosphorylation of p53, cathepsin B, and Bax/Bcl-2 protein levels, and the translocation of Bax from the cytosol to mitochondria induced by H₂ O₂ in C2C12 cells was significantly reduced by PTL. In conclusion, PTL modulates oxidative stress-induced mitophagy and protects C2C12 myoblasts against apoptosis, suggesting a potential protective effect against oxidative stress-associated skeletal muscle diseases.

Effects of Lysosomal-Mitochondrial Apoptotic Pathway on Tenderness in Post-Mortem Bovine Longissimus Muscle

The objective of this study was to investigate the mechanism underlying lysosome-mediated apoptosis, the cross-talk between the lysosomes and mitochondria, and the effect of the pathway on bovine longissimus muscle tenderness during 7 d post-mortem aging through the observation and analysis of longissimus dorsi (LD) muscles of six crossbred cattle. Results showed that an elevated reactive oxygen species level ( P < 0.05) can damage lysosomal membrane stability ( P < 0.05) through accumulating redox-active iron of bovine muscle during post-mortem aging. In addition, the activities of cathepsins B and D increased with post-mortem aging ( P < 0.05). Moreover, cathepsin B and D activated Bid and Bax in the mitochondria ( P < 0.05). Activated Bid and Bax triggered mitochondrial membrane permeability ( P < 0.05) and further activated caspase-9 and caspase-3 ( P < 0.05), leading to apoptosis. Ultimately, the tenderness of bovine muscle was improved during post-mortem aging ( P < 0.05). Importantly, cathepsin D plays a crucial role in the lysosomal-mitochondrial apoptotic pathway and tenderness in post-mortem muscle. These findings provide new insights into the apoptotic pathway of bovine muscle during post-mortem aging.

A high-throughput microscopy method for single-cell analysis of event-time correlations in nanoparticle-induced cell death

The temporal context of cell death decisions remains generally hidden in ensemble measurements with endpoint readouts. Here, we describe a method to extract event times from fluorescence time traces of cell death-related markers in automated live-cell imaging on single-cell arrays (LISCA) using epithelial A549 lung and Huh7 liver cancer cells as a model system. In pairwise marker combinations, we assess the chronological sequence and delay times of the events lysosomal membrane permeabilization, mitochondrial outer membrane permeabilization and oxidative burst after exposure to 58 nm amino-functionalized polystyrene nanoparticles (PS-NH2 nanoparticles). From two-dimensional event-time scatter plots we infer a lysosomal signal pathway at a low dose of nanoparticles (25 µg mL-1) for both cell lines, while at a higher dose (100 µg mL-1) a mitochondrial pathway coexists in A549 cells, but not in Huh7. In general, event-time correlations provide detailed insights into heterogeneity and interdependencies in signal transmission pathways.

NIR-excited superoxide radical procreators to eradicate tumors by targeting the lyso-membrane

NIR alkylated cationic photosensitizers targeting at lyso-membrane for eradicating tumor cells through prominent superoxide radical generation (type-I PDT) via lysosome disruption pathway.

Anticancer and antibacterial activity in vitro evaluation of iridium(III) polypyridyl complexes

Three iridium(III) polypyridyl complexes [Ir(ppy)₂(PYTA)](PF₆) (1) (ppy = 2-phenylpyridine), [Ir(bzq)₂(PYTA)](PF₆) (2) (bzq = benzo[h]quinolone) and [Ir(piq)₂(PYTA)](PF₆) (3) (piq = 1-phenylisoquinoline, PYTA = 2,4-diamino-6-(2'-pyridyl)-1,3,5-triazine) were synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR. The cytotoxic activity of the complexes toward cancer SGC-7901, Eca-109, A549, HeLa, HepG2, BEL-7402 and normal LO2 cell lines was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Complex 3 shows the most effective on inhibiting the above cell growth among these complexes. The complexes locate at the lysosomes and mitochondria. AO/EB, Annex V and PI and comet assays indicate that the complexes can induce apoptosis in SGC-7901 cells. Intracellular ROS and mitochondrial membrane potential were examined under fluorescence microscopy. The results demonstrate that the complexes increase the intracellular ROS levels and induce a decrease in the mitochondrial membrane potential. The complexes can enhance intracellular Ca²⁺ concentration and cause a release of cytochrome c. The autophagy was studied using MDC staining and western blot. Complexes 1-3 can effectively inhibit the cell invasion with a concentration-dependent manner. Additionally, the complexes target tubules and inhibit the polymerization of tubules. The antimicrobial activity of the complexes against S. aureus, E. coli, Salmonella and L. monocytogenes was explored. The mechanism shows that the complexes induce apoptosis in SGC-7901 cells through ROS-mediated lysosomal-mitochondrial, targeting tubules and damage DNA pathways. Three iridium(III) complexes [Ir(N-C)₂(PYTA)](PF₆) (N-C = ppy, 1; bzq, 2; piq, 3) were synthesized and characterized. The anticancer activity of the complexes against SGC-7901 cells was studied by apoptosis, comet assay, autophagy, ROS, mitochondrial membrane potential, intracellular Ca²⁺ levels, release of cytochrome c, tubules and western blot analysis. The antibacterial activity in vitro was also assayed.

IITZ-01, a novel potent lysosomotropic autophagy inhibitor, has single-agent antitumor efficacy in triple-negative breast cancer in vitro and in vivo

Autophagy is a homeostatic process that recycles damaged organelles and long-lived proteins by delivering them in double-membrane vesicles to lysosomes for degradation. Autophagy has a prominent role in survival, proliferation, and resistance of tumors in metabolic and chemotherapeutic stress conditions. Clinical trials with chloroquine-a known autophagy inhibitor-were unable to achieve complete autophagy inhibition in vivo, warranting the search for more potent autophagy inhibitors. In a process of exploring the mechanism of action of previously identified cytotoxic s-triazine analogs, we discovered that both IITZ-01 and IITZ-02 act as potent autophagy inhibitors. Treatment with these compounds resulted in the vacuolated appearance of cells due to their specific accumulation in lysosomes. In addition, these basic compounds also deacidify lysosomes as evidenced by the decrease in lysotracker red staining and inhibit maturation of lysosomal enzymes leading to lysosomal dysfunction. IITZ-01 and IITZ-02 enhance autophagosome accumulation but inhibit autophagosomal degradation by impairing lysosomal function, finally resulting in the inhibition of autophagy. Interestingly, compound IITZ-01 exhibited more than 10-fold potent autophagy inhibition along with 12- to 20-fold better cytotoxic action than CQ. IITZ-01 and IITZ-02 also abolished mitochondrial membrane potential and triggered apoptosis through the mitochondria-mediated pathway. Furthermore, IITZ-01 and IITZ-02 displayed potent antitumor action in vivo through autophagy inhibition and apoptosis induction in MDA-MB-231 breast cancer xenograft model with IITZ-01 exhibiting superior anticancer efficacy. Overall, these data demonstrate that IITZ-01 is potent autophagy inhibitor with single-agent anticancer activity and awaits further preclinical development as potential anticancer therapeutic.

Transcription factor E3 protects against cadmium-induced apoptosis by maintaining the lysosomal-mitochondrial axis but not autophagic flux in Neuro-2a cells

Cadmium (Cd), is a well-known environmental and occupational hazard with a potent neurotoxic action. However, the mechanism underlying cadmium-induced neurotoxicity remains unclear. Herein, we exposed Neuro-2a cells to different concentrations of cadmium chloride (CdCl₂) (12.5, 25 and 50 μM) for 24 h and found that Cd significantly induced lysosomal membrane permeabilization (LMP) with the release of cathepsin B (CTSB) to the cytosol, which in turn caused the release of mitochondrial cytochrome c (Cyt c) and eventually triggered caspase-dependent apoptosis. Interestingly, Cd decreased TFE3 expression but induced the nuclear translocation of TFE3 and TFE3 target-gene expression, which might be associated with lysosomal stress mediated by Cd. Notably, Tfe3 overexpression protected against Cd-induced neurotoxicity by maintaining the lysosomal-mitochondrial axis, and the protective effect of TFE3 is not dependent on the restoration of autophagic flux. In conclusion, our study demonstrated for the first time that lysosomal-mitochondrial axis dependent apoptosis, a neglected mechanism, may be the most important reason for Cd-induced neurotoxicity and that manipulation of TFE3 signaling may be a potential therapeutic approach for treatment of Cd-induced neurotoxicity.

Heat stress induces intestinal injury through lysosome- and mitochondria-dependent pathway in vivo and in vitro

Damage to the small intestine secondary to heat stroke is a major factor in heat stroke-related morbidity and mortality. However, the underlying mechanisms by which heat stroke causes small intestinal lesions and dysfunction remain unclear. To explore the pathogenesis of small intestinal tissue and epithelial cell injury, the SW480 cell heat stress model and the mice heat stroke model were established to mimic heat stroke. Morphologic changes in intestinal tissue and increased TUNEL-positive index were induced by heat stress in vivo. Heat stress activated the lysosomal-mitochondrial apoptotic pathway in SW480 cells, increasing intracellular reactive oxygen species and causing lysosomal membrane permeabilization with subsequent release of cathepsin B to the cytosol, mitochondrial depolarization, and cytochrome C release to cytosol. An increase in the Bax/Bcl2 ratio, caspase-9 and caspase-3 were observed. N-Acetyl-L-Cysteine was shown to inhibit ROS generation, suppress permeabilization of lysosomal membranes, decrease levels of cathepsin B and cytochrome C in the cytosol, and inhibit Bax/Bcl2 ratio, caspase-9 and caspase-3 activity both in vitro and in vivo. Mitochondrial damage was alleviated when the models were pre-treated with CA-074 Me both in vitro and in vivo, decreasing cathepsin B and cytochrome C levels in the cytosol, Bax/Bcl2 ratio, caspase-9 and caspase-3 activity. In our models, heat stress-induced apoptosis of small intestinal tissue and epithelial cells through accumulation of ROS and activation of the lysosomal–mitochondrial apoptotic pathway involved the release of cathepsin B. These findings may offer potentially pharmaceutical targets and strategies to repair intestinal injury caused by heat stroke.