Clusterin: a marker and mediator of chemoresistance in colorectal cancer.

Intra-tumoural heterogeneity and cancer cell plasticity in colorectal cancer (CRC) have been key challenges to effective treatment for patients. It has been suggested that a subpopulation of LGR5-expressing cancer stem cells (CSCs) is responsible for driving tumour relapse and therapy resistance in CRC. However, studies have revealed that the LGR5+ve CSC population is highly sensitive to chemotherapy. It has been hypothesised that another subset of tumour cells can phenotypically revert to a stem-like state in response to chemotherapy treatment which replenishes the LGR5+ve CSC population and maintains tumour growth. Recently, a unique stem cell population marked by enriched clusterin (CLU) expression and termed the revival stem cell (RevSC) was identified in the regenerating murine intestine. This CLU-expressing cell population is quiescent during homeostasis but has the ability to survive and regenerate other stem cells upon injury. More recently, the CLU+ve signature has been implicated in several adverse outcomes in CRC, including chemotherapy resistance and poor patient survival; however, the mechanism behind this remains undetermined. In this review, we discuss recent insights on CLU in CRC and its roles in enhancing the plasticity of cells and further consider the implications of CLU as a prospective target for therapeutic intervention.

BRD7 facilitates ferroptosis via modulating clusterin promoter hypermethylation and suppressing AMPK signaling in diabetes-induced testicular damage.

BACKGROUND: Diabetes mellitus (DM)-induced testicular damage is associated with sexual dysfunction and male infertility in DM patients. However, the pathogenesis of DM-induced testicular damage remains largely undefined. METHODS: A streptozotocin (STZ)-induced diabetic model and high glucose (HG)-treated in vitro diabetic model were established. The histological changes of testes were assessed by H&E staining. Serum testosterone, iron, MDA and GSH levels were detected using commercial kits. Cell viability and lipid peroxidation was monitored by MTT assay and BODIPY 581/591 C11 staining, respectively. qRT-PCR, immunohistochemistry (IHC) or Western blotting were employed to detect the levels of BRD7, Clusterin, EZH2 and AMPK signaling molecules. The associations among BRD7, EZH2 and DNMT3a were detected by co-IP, and the transcriptional regulation of Clusterin was monitored by methylation-specific PCR (MSP) and ChIP assay. RESULTS: Ferroptosis was associated with DM-induced testicular damage in STZ mice and HG-treated GC-1spg cells, and this was accompanied with the upregulation of BRD7. Knockdown of BRD7 suppressed HG-induced ferroptosis, as well as HG-induced Clusterin promoter methylation and HG-inactivated AMPK signaling in GC-1spg cells. Mechanistical studies revealed that BRD7 directly bound to EZH2 and regulated Clusterin promoter methylation via recruiting DNMT3a. Knockdown of Clusterin or inactivation of AMPK signaling reverses BRD7 silencing-suppressed ferroptosis in GC-1spg cells. In vivo findings showed that lack of BRD7 protected against diabetes-induced testicular damage and ferroptosis via increasing Clusterin expression and activating AMPK signaling. CONCLUSION: BRD7 suppressed Clusterin expression via modulating Clusterin promoter hypermethylation in an EZH2 dependent manner, thereby suppressing AMPK signaling to facilitate ferroptosis and induce diabetes-associated testicular damage.

Clusterin expression and distribution in spermatozoa as predictor of male fertility.

Clusterin (CLU), one of the main glycoproteins in mammalian semen and the male reproductive tract, plays a role in spermatogenesis and sperm maturation. Given the poor reliability of classic seminal studies in determining male-fertilizing capacity and the differences in CLU abundance between normal and abnormal spermatozoa, we investigated the potential value of mRNA-CLU levels and protein distribution in spermatozoa as markers of sperm quality and predictors of male fertility. This multicenter study included 90 patients undergoing in vitro fertilization (IVF) treatment with their partners, and a control group of 36 fertile males with normal seminograms. We assessed the relationship between IVF treatment outcomes, seminogram variables, mRNA-CLU levels by quantitative real-time-PCR and CLU distribution by immunostaining in spermatozoa. Our study reveals CLU staining in the acrosome (p = 0.002, OR 14.8, 95% CI: 2.7-79.3) and mRNA-CLU levels (p = 0.005, OR 10.85, 95% CI: 2.0-57.4) as independent risk factors for pregnancy failure, irrespective of traditional seminogram variables. Additionally, our results suggest that CLU, and specially its secreted isoform, constitutes a component of the protein pool that human spermatozoa can produce during its maturation process, exhibiting a variable abundance and distribution in spermatozoa from fertile men compared to those in patients with altered seminograms and infertile patients with normal seminograms. Our study is the first to identify mRNA-CLU levels and CLU immunostaining in the spermatozoa acrosome as independent risk factors for pregnancy failure, with distribution patterns correlating with sperm maturity and seminogram alterations.

Urinary Concentration of Renal Biomarkers in Healthy Term Neonates: Gender Differences in GST-pi Excretion.

BACKGROUND Serum creatinine, the criterion standard in assessment of renal function, is not reliable for the neonatal period because of its dependence on renal immaturity and maternal creatinine levels. Thus, it is important to study other biomarkers of renal function in neonates. The present study aimed to measure the urinary concentration of renal biomarkers: calbindin, clusterin, GST-pi (glutathione-S-transferase-alpha), KIM-1 (kidney injury molecule 1), MCP-1 (monocyte chemoattractant protein-1), and B2M (beta 2-microglobulin) in healthy term neonates. MATERIAL AND METHODS In the study, we included 80 healthy term neonates - 40 females and 40 males. We collected the neonates' urine on their first day of life. Urinary concentrations of calbindin, clusterin, KIM-1, MCP-1, and B2M were assessed using an immunoassay for kidney toxicology research. Because dilution of the urine affects the concentrations of urinary biomarkers, we normalized them to the concentration of urinary creatinine (Cr) and present them as biomarker/Cr ratios. RESULTS We obtained the following values of the assessed biomarker/Cr ratios (median [Q1-Q3]): calbindin/Cr.: 197.04 (56.25-595.17), KIM-1/Cr: 0.09 (0.04-0.18), MCP-1/Cr: 0.05 (0.02-0.14), B2M/Cr: 126.12 (19.03-342.48), GST-pi/Cr in boys: 1.28 (0.46-3.77), GST-pi/Cr in girls: 8.66 (2.51-27.82), clusterin/Cr: 4.55 (1.79-12.97) ng/mg Cr. CONCLUSIONS We showed the urinary levels of calbindin, clusterin, GST-pi, KIM-1, MCP-1, B2M in white, West Slavic, healthy term neonates. We found that in there is an association between female sex and a higher urinary GST-pi excretion, but urinary excretion of calbindin, clusterin, KIM-1, MCP-1, and B2M is sex-independent. The urinary levels of the assessed biomarkers do not depend on the method of delivery.

Serum Clusterin Concentration and Its Glycosylation Changes as Potential New Diagnostic Markers of SARS-CoV-2 Infection and Recovery Process.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus. Glycoprotein clusterin (CLU) has many functions such as phagocyte recruitment, complement system inhibition, apoptosis inhibition, hormone and lipid transport, as well as in the immune response. The study aimed to assess the changes in CLU concentrations and the profile and degree of CLU glycosylation between patients with severe COVID-19, convalescents, and healthy subjects (control). The profile and degree of serum CLU N-glycosylation were analyzed using lectin-ELISA with specific lectins. CLU concentrations were significantly lower and relative reactivities of CLU glycans with SNA (Sambucus nigra agglutinin) were significantly higher in severe COVID-19 patients in comparison to convalescents and the control group. The relative reactivities of CLU glycans with MAA (Maackia amurensis agglutinin), together with relative reactivity with LCA (Lens culinaris agglutinin), were also significantly higher in patients with severe COVID-19 than in convalescents and the control group, but they also significantly differed between convalescents and control. The development of acute inflammation in the course of severe COVID-19 is associated with a decrease in CLU concentration, accompanied by an increase in the expression of α2,3-linked sialic acid, and core fucose. Both of these parameters can be included as useful glycomarkers differentiating patients with severe COVID-19 from convalescents and the control group, as well as convalescents and healthy subjects.

The Role of CSF Transthyretin in Human Alzheimer's Disease: Offense, Defense, or not so Innocent Bystander.

Transthyretin (TTR) is secreted by hepatocytes, retinal pigment epithelial cells, pancreatic α and ß cells, choroid plexus epithelium, and neurons under stress. The choroid plexus product is the main transporter of the thyroid hormone thyroxine (T4) to the brain during early development. TTR is one of three relatively abundant cerebrospinal fluid (CSF) proteins (Apolipoprotein J [ApoJ] (also known as clusterin), Apolipoprotein E [ApoE], and TTR) that interact with Aß peptides in vitro, in some instances inhibiting their aggregation and toxicity. It is now clear that clusterin functions as an extracellular, and perhaps intracellular, chaperone for many misfolded proteins and that variation in its gene (Clu) is associated with susceptibility to sporadic Alzheimer's disease (AD). The function of ApoE in AD is not yet completely understood, although the ApoE4 allele has the strongest genetic association with the development of sporadic late onset AD. Despite in vitro and in vivo evidence of the interaction between TTR and Aß, genomewide association studies including large numbers of sporadic Alzheimer's disease patients have failed to show significant association between variation in the TTR gene and disease prevalence. Early clinical studies suggested an inverse relationship between CSF TTR levels and AD and the possibility of using the reduced CSF TTR concentration as a biomarker. Later, more extensive analyses indicated that CSF TTR concentrations may be increased in some patients with AD. While the observed changes in TTR may be pathogenetically or biologically interesting because of the inconsistency and lack of specificity, they offered no benefit diagnostically or prognostically either independently or when added to currently employed CSF biomarkers, i.e., decreased Aß1-42 and increased Tau and phospho-Tau. While some clinical data suggest that increases in CSF TTR may occur early in the disease with a significant decrease late in the course, without additional, more granular data, CSF TTR changes are neither consistent nor specific enough to warrant their use as a specific AD biomarker.

Clusterin protects mature dendritic cells from reactive oxygen species mediated cell death.

Dendritic cells (DCs) play a key role in the induction of the adaptive immune response. They capture antigens in peripheral tissues and prime naïve T lymphocytes, triggering the adaptive immune response. In the course of inflammatory processes DCs face stressful conditions including hypoxia, low pH and high concentrations of reactive oxygen species (ROS), among others. How DCs survive under these adverse conditions remain poorly understood. Clusterin is a protein highly expressed by tumors and usually associated with bad prognosis. It promotes cancer cell survival by different mechanisms such as apoptosis inhibition and promotion of autophagy. Here, we show that, upon maturation, human monocyte-derived DCs (MoDCs) up-regulate clusterin expression. Clusterin protects MoDCs from ROS-mediated toxicity, enhancing DC survival and promoting their ability to induce T cell activation. In line with these results, we found that clusterin is expressed by a population of mature LAMP3+ DCs, called mregDCs, but not by immature DCs in human cancer. The expression of clusterin by intratumoral DCs was shown to be associated with a transcriptomic profile indicative of cellular response to stress. These results uncover an important role for clusterin in DC physiology.

Decoding CLU (Clusterin): Conquering cancer treatment resistance and immunological barriers.

One major obstacle in the treatment of cancer is the presence of proteins resistant to cancer therapy, which can impede the effectiveness of traditional approaches such as radiation and chemotherapy. This resistance can lead to disease progression and cause treatment failure. Extensive research is currently focused on studying these proteins to create tailored treatments that can circumvent resistance mechanisms. CLU (Clusterin), a chaperone protein, has gained notoriety for its role in promoting resistance to a wide range of cancer treatments, including chemotherapy, radiation therapy, and targeted therapy. The protein has also been discovered to have a role in regulating the immunosuppressive environment within tumors. Its ability to influence oncogenic signaling and inhibit cell death bolster cancer cells resistant against treatments, which poses a significant challenge in the field of oncology. Researchers are actively investigating to the mechanisms by which CLU exerts its resistance-promoting effects, with the ultimate goal of developing strategies to circumvent its impact and enhance the effectiveness of cancer therapies. By exploring CLU's impact on cancer, resistance mechanisms, tumor microenvironment (TME), and therapeutic strategies, this review aims to contribute to the ongoing efforts to improve cancer treatment outcomes.

Method to Assess the Intracellular Fate and Bioavailability of Clusterin Using Live Cell Confocal Microscopy Imaging.

Clusterin, also known as apolipoprotein J, is an ATP-independent holdase chaperone protein. Clusterin is involved in various functions including protein quality control and lipid transport. Though clusterin is secreted upon stress, the intracellular fate of clusterin after a stress response is not well understood. The protocol described here utilizes clusterin tagged to fluorescent proteins like green fluorescent protein and red fluorescent protein to understand the intracellular fate of clusterin.

Complement C7 and clusterin form a complex in circulation.

Introduction: The complement system is part of innate immunity and is comprised of an intricate network of proteins that are vital for host defense and host homeostasis. A distinct mechanism by which complement defends against invading pathogens is through the membrane attack complex (MAC), a lytic structure that forms on target surfaces. The MAC is made up of several complement components, and one indispensable component of the MAC is C7. The role of C7 in MAC assembly is well documented, however, inherent characteristics of C7 are yet to be investigated. Methods: To shed light on the molecular characteristics of C7, we examined the properties of serum-purified C7 acquired using polyclonal and novel monoclonal antibodies. The properties of serum­purified C7 were investigated through a series of proteolytic analyses, encompassing Western blot and mass spectrometry. The nature of C7 protein-protein interactions were further examined by a novel enzyme-linked immunosorbent assay (ELISA), as well as size­exclusion chromatography. Results: Protein analyses showcased an association between C7 and clusterin, an inhibitory complement regulator. The distinct association between C7 and clusterin was also demonstrated in serum-purified clusterin. Further assessment revealed that a complex between C7 and clusterin (C7-CLU) was detected. The C7-CLU complex was also identified in healthy serum and plasma donors, highlighting the presence of the complex in circulation. Discussion: Clusterin is known to dissociate the MAC structure by binding to polymerized C9, nevertheless, here we show clusterin binding to the native form of a terminal complement protein in vivo. The presented data reveal that C7 exhibits characteristics beyond that of MAC assembly, instigating further investigation of the effector role that the C7-CLU complex plays in the complement cascade.

Utilizing neurodegenerative markers for the diagnostic evaluation of amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive deterioration of upper and lower motor neurons. A definitive diagnostic test or biomarker for ALS is currently unavailable, leading to a diagnostic delay following the onset of initial symptoms. Our study focused on cerebrospinal fluid (CSF) concentrations of clusterin, tau protein, phosphorylated tau protein, and beta-amyloid1-42 in ALS patients and a control group. METHODS: Our study involved 54 ALS patients and 58 control subjects. Among the ALS patients, 14 presented with bulbar-onset ALS, and 40 with limb-onset ALS. We quantified biomarker levels using enzyme-linked immunosorbent assay (ELISA) and compared the results using the Mann-Whitney U-test. RESULTS: Significant elevations in neurodegenerative markers, including tau protein (p < 0.0001), phosphorylated tau protein (p < 0.0001), and clusterin (p = 0.038), were observed in ALS patients compared to controls. Elevated levels of tau protein and phosphorylated tau protein were also noted in both bulbar and limb-onset ALS patients. However, no significant difference was observed for beta-amyloid1-42. ROC analysis identified tau protein (AUC = 0.767) and p-tau protein (AUC = 0.719) as statistically significant predictors for ALS. CONCLUSION: Our study demonstrates that neurodegenerative marker levels indicate an ongoing neurodegenerative process in ALS. Nonetheless, the progression of ALS cannot be predicted solely based on these markers. The discovery of a specific biomarker could potentially complement existing diagnostic criteria for ALS.

Clusterin knockdown has effects on intracellular and secreted von Willebrand factor in human umbilical vein endothelial cells.

Alterations in von Willebrand factor (VWF) have an important role in human health and disease. Deficiency of VWF is associated with symptoms of bleeding and excesses of VWF are associated with thrombotic outcomes. Understanding the mechanisms that drive VWF regulation can lead to a better understanding of modulation of VWF levels in humans. We identified clusterin (CLU) as a potential candidate regulator of VWF based on a single cell RNA sequencing (scRNA-seq) analysis in control endothelial cells (ECs) and von Willebrand disease (VWD) endothelial colony-forming-cells (ECFCs). We found that patients with deficiencies of VWF (von Willebrand disease, VWD) had decreased CLU expression and ECs with low VWF expression also had low CLU expression. Based on these findings, we sought to evaluate the role of CLU in the regulation of VWF, specifically as it relates to VWD. As CLU is primarily thought to be a golgi protein involved in protein chaperoning, we hypothesized that knockdown of CLU would lead to decreases in VWF and alterations in Weibel-Palade bodies (WPBs). We used both siRNA- and CRISPR-Cas9-based approaches to modulate CLU in human umbilical vein endothelial cells (HUVECs) and evaluated VWF protein levels, VWF mRNA copy number, and WPB quantity and size. We demonstrated that siRNA-based knockdown of CLU resulted in decreases in VWF content in cellular lysates and supernatants, but no significant change in WPB quantity or size. A CRISPR-Cas9-based knockdown of CLU demonstrated similar findings of decreases in intracellular VWF content but no significant change in WPB quantity or size. Our data suggests that CLU knockdown is associated with decreases in cellular VWF content but does not affect VWF mRNA levels or WPB quantity or size.

Therapeutic Potential of Clusterin Inhibition in Human Cancer.

Clusterin (CLU) protein is involved in various pathophysiological processes including carcinogenesis and tumor progression. In recent years, the role of the secretory isoform has been demonstrated in tumor cells, where it inhibits apoptosis and favors the acquisition of resistance to conventional treatments used to treat cancer. To determine the possible therapeutic potential of inhibiting this protein, numerous studies have been carried out in this field. In this article, we present the existing knowledge to date on the inhibition of this protein in different types of cancer and analyze the importance it could have in the development of new therapies targeted against this disease.

Secreted clusterin inhibits tumorigenesis by modulating tumor cells and macrophages in human meningioma.

BACKGROUND: Meningioma is the most common primary intracranial tumor with a high frequency of postoperative recurrence, yet the biology of the meningioma malignancy process is still obscure. METHODS: To identify potential therapeutic targets and tumor suppressors, we performed single-cell transcriptome analysis through meningioma malignancy, which included 18 samples spanning normal meninges, benign and high-grade in situ tumors, and lung metastases, for extensive transcriptome characterization. Tumor suppressor candidate gene and molecular mechanism were functionally validated at the animal model and cellular levels. RESULTS: Comprehensive analysis and validation in mice and clinical cohorts indicated clusterin (CLU) had suppressive function for meningioma tumorigenesis and malignancy by inducing mitochondria damage and triggering type 1 interferon pathway dependent on its secreted isoform, and the inhibition effect was enhanced by TNFα as TNFα also induced type 1 interferon pathway. Meanwhile, both intra- and extracellular CLU overexpression enhanced macrophage polarization towards M1 phenotype and TNFα production, thus promoting tumor killing and phagocytosis. CONCLUSIONS: CLU might be a key brake of meningioma malignance by synchronously modulating tumor cells and their microenvironment. Our work provides comprehensive insights into meningioma malignancy and a potential therapeutic strategy.

Secretory Clusterin Inhibits Dopamine Neuron Apoptosis in MPTP Mice by Preserving Autophagy Activity.

Secretory clusterin (sCLU) plays an important role in the research progress of nervous system diseases. However, the physiological function of sCLU in Parkinson's disease (PD) are unclear. The purpose of this study was to examine the effects of sCLU-mediated autophagy on cell survival and apoptosis inhibition in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. We found that MPTP administration induced prolonged pole-climbing time, shortened traction time and rotarod time, significantly decreased TH protein expression in the SN tissue of mice. In contrast, sCLU -treated mice took less time to climb the pole and had an extended traction time and rotating rod time. Meanwhile, sCLU intervention induced increased expression of the TH protein in the SN of mice. These results indicated that sCLU intervention could reduce the loss of dopamine neurons in the SN area and alleviate dyskinesia in mice. Furthermore, MPTP led to suppressed viability, enhanced apoptosis, an increased Bax/Bcl-2 ratio, and cleaved caspase-3 in the SN of mice, and these effects were abrogated by sCLU intervention. In addition, MPTP increased the levels of P62 protein, decreased Beclin1 protein, decreased the ratio of LC3B-II/LC3B-I, and decreased the numbers of autophagosomes and autophagolysosomes in the SN tissues of mice. These effects were also abrogated by sCLU intervention. Activation of PI3K/AKT/mTOR signaling with MPTP inhibited autophagy in the SN of MPTP mice; however, sCLU treatment activated autophagy in MPTP-induced PD mice by inhibiting PI3K/AKT/mTOR signaling. These data indicated that sCLU treatment had a neuroprotective effect in an MPTP-induced model of PD.

Plasma BDNF/Irisin Ratio Associates with Cognitive Function in Older People.

Background: Reliable blood biomarkers are crucial for early detection and treatment evaluation of cognitive impairment, including Alzheimer's disease and other dementias. Objective: To examine whether plasma biomarkers and their combination are different between older people with mild cognitive impairment (MCI) and cognitively normal individuals, and to explore their relations with cognitive performance. Methods: This cross-sectional study included 250 older adults, including 124 participants with MCI, and 126 cognitively normal participants. Plasma brain-derived neurotrophic factor (BDNF), irisin and clusterin were measured, and BDNF/irisin ratio was calculated. Global cognition was evaluated by the Montreal Cognitive Assessment. Results: Plasma irisin levels, but not BDNF, were significantly different between MCI group and cognitively normal group. Higher irisin concentration was associated with an increased probability for MCI both before and after controlling covariates. By contrast, plasma BDNF concentration, but not irisin, was linearly correlated with cognitive performance after adjusting for covariates. Higher BDNF/irisin ratios were not only correlated with better cognitive performance, but also associated with lower risks of MCI, no matter whether we adjusted for covariates. Plasma BDNF and irisin concentrations increased with aging, whereas BDNF/irisin ratios remained stable. No significant results of clusterin were observed. Conclusions: Plasma BDNF/irisin ratio may be a reliable indicator which not only reflects the odds of the presence of MCI but also directly associates with cognitive performance.

Methionine oxidation of clusterin in Alzheimer's disease and its effect on clusterin's binding to beta-amyloid.

Clusterin is a secreted glycoprotein that participates in multiple physiological processes through its chaperon function. In Alzheimer's disease, the brain functions under an increased oxidative stress condition that causes an elevation of protein oxidation, resulting in enhanced pathology. Accordingly, it is important to determine the type of human brain cells that are mostly prone to methionine oxidation in Alzheimer's disease and specifically monitoring the methionine-oxidation levels of clusterin in human and mice brains and its effect on clusterin's function. We analyzed the level of methionine sulfoxide (MetO)-clusterin in these brains, using a combination of immunoprecipitation and Western-blott analyses. Also, we determine the effect of methionine oxidation on clusterin ability to bind beta-amyloid, in vitro, using calorimetric assay. Our results show that human neurons and astrocytes of Alzheimer's disease brains are mostly affected by methionine oxidation. Moreover, MetO-clusterin levels are elevated in postmortem Alzheimer's disease human and mouse brains in comparison to controls. Finally, oxidation of methionine residues of purified clusterin reduced its binding efficiency to beta-amyloid. In conclusion, we suggest that methionine oxidation of brain-clusterin is enhanced in Alzheimer's disease and that this oxidation compromises its chaperon function, leading to exacerbation of beta-amyloid's toxicity in Alzheimer's disease.

Clusterin attenuates blood-brain barrier damage and cognitive impairment by inhibiting astrocyte aging in mice with sepsis-associated encephalopathy.

Sepsis-associated encephalopathy (SAE) is a severe complication of sepsis, however, its exact mechanism remains unknown. This study aimed to evaluate whether clusterin is essential to the development of SAE during the aging process of astrocytes. In the study, septic mice were established with cecal ligation and puncture (CLP) and lipopolysaccharides were applied to astrocytes in vitro. Evan's blue dye was used in vivo to show blood-brain barrier (BBB) permeability. A morris water maze test was conducted to assess cognitive functions of the mice. Clusterin-knockout mice were used to examine the effect of clusterin on sepsis. The astrocytes were transfected with lentivirus expressing clusterin cDNA for clusterin overexpression or pYr-LV-clusterin small hairpin RNA for clusterin knockdown in vitro . The expression of clusterin, p-p53, p21, GDNF, and iNOS was detected. he CLP mice exhibited a higher clusterin expression in hippocampus tissue, aging astrocytes, lower GDNF expression and higher iNOS expression, accompanied with BBB damage and cognitive deficiency. Following clusterin knockout, this pathological process was further enhanced. In vitro , following lipopolysaccharides treatment, astrocytes exhibited increased clusterin, p-p53, p21, iNOS and decreased GDNF. Following clusterin knockdown, the cells exhibited a further increase in p-p53, p21, and iNOS and decrease in GDNF. Clusterin overexpression, however, helped inhibit astrocytes aging and neuroinflammation evidenced by decreased p-p53, p21, iNOS and increased GDNF. The present study has revealed that clusterin may exert its neuroprotective effect by preventing aging in astrocytes, suppressing the secretion of iNOS and promoting GNDF release.

CLU (clusterin) and PPARGC1A/PGC1α coordinately control mitophagy and mitochondrial biogenesis for oral cancer cell survival.

Mitophagy involves the selective elimination of defective mitochondria during chemotherapeutic stress to maintain mitochondrial homeostasis and sustain cancer growth. Here, we showed that CLU (clusterin) is localized to mitochondria to induce mitophagy controlling mitochondrial damage in oral cancer cells. Moreover, overexpression and knockdown of CLU establish its mitophagy-specific role, where CLU acts as an adaptor protein that coordinately interacts with BAX and LC3 recruiting autophagic machinery around damaged mitochondria in response to cisplatin treatment. Interestingly, CLU triggers class III phosphatidylinositol 3-kinase (PtdIns3K) activity around damaged mitochondria, and inhibition of mitophagic flux causes the accumulation of excessive mitophagosomes resulting in reactive oxygen species (ROS)-dependent apoptosis during cisplatin treatment in oral cancer cells. In parallel, we determined that PPARGC1A/PGC1α (PPARG coactivator 1 alpha) activates mitochondrial biogenesis during CLU-induced mitophagy to maintain the mitochondrial pool. Intriguingly, PPARGC1A inhibition through small interfering RNA (siPPARGC1A) and pharmacological inhibitor (SR-18292) treatment counteracts CLU-dependent cytoprotection leading to mitophagy-associated cell death. Furthermore, co-treatment of SR-18292 with cisplatin synergistically suppresses tumor growth in oral cancer xenograft models. In conclusion, CLU and PPARGC1A are essential for sustained cancer cell growth by activating mitophagy and mitochondrial biogenesis, respectively, and their inhibition could provide better therapeutic benefits against oral cancer.