Clusterin: physiologic and pathophysiologic considerations

Fish decay-accelerating factor (DAF) regulates intestinal complement pathway and immune response to bacterial challenge

Decay-accelerating factor (DAF) is an essential member of the complement regulatory protein family that plays an important role in immune response and host homeostasis in mammals. However, the immune function of DAF has not been well characterized in bony fish. In this study, a complement regulatory protein named CiDAF was firstly characterized from Ctenopharyngodon idella and its potential roles were investigated in intestine following bacterial infection. Similar to mammalian DAFs, CiDAF has multiple complement control protein (CCP) functional domains, suggesting the evolutionary conservation of DAFs. CiDAF was broadly expressed in all tested tissues, with a relatively high expression level detected in the spleen and kidney. In vivo immune challenge experiments revealed that CiDAF strongly responded to bacterial pathogens (Aeromonas hydrophila and Aeromonas veronii) and PAMPs (lipopolysaccharide (LPS) or muramyl dipeptide (MDP)) challenges. In vitro RNAi experiments indicated that knockdown of CiDAF could upregulate the expression of complement genes (C4b, C5 and C7) and inflammatory cytokines (TNF-α, IL-1β and IL-8). Moreover, 2000 ng/mL of CiDAF agonist progesterone effectively alleviated LPS- or MDP-induced intestinal inflammation by regulating expression of complement factors, TLR/PepT1 pathway genes and inflammatory cytokines. Overall, these findings revealed that CiDAF may act as a negative regulator of intestinal complement pathway and immune response to bacterial challenge in grass carp.

The Complement System and C4b-Binding Protein: A Focus on the Promise of C4BPα as a Biomarker to Predict Clopidogrel Resistance

The complement system plays a dual role in the body, either as a first-line defense barrier when balanced between activation and inhibition or as a potential driver of complement-associated injury or diseases when unbalanced or over-activated. C4b-binding protein (C4BP) was the first circulating complement regulatory protein identified and it functions as an important complement inhibitor. C4BP can suppress the over-activation of complement components and prevent the complement system from attacking the host cells through the binding of complement cleavage products C4b and C3b, working in concert as a cofactor for factor I in the degradation of C4b and C3b, and consequently preventing or reducing the assembly of C3 convertase and C5 convertase, respectively. C4BP, particularly C4BP α-chain (C4BPα), exerts its unique inhibitory effects on complement activation and opsonization, systemic inflammation, and platelet activation and aggregation. It has long been acknowledged that crosstalk or interplay exists between the complement system and platelets. Our unpublished preliminary data suggest that circulating C4BPα exerts its antiplatelet effects through inhibition of both complement activity levels and complement-induced platelet reactivity. Plasma C4BPα levels appear to be significantly higher in patients sensitive to, rather than resistant to, clopidogrel, and we suggest that a plasma C4BPα measurement could be used to predict clopidogrel resistance in the clinical settings.

Clusterin is upregulated by erastin, a ferroptosis inducer and exerts cytoprotective effects in pancreatic adenocarcinoma cells

Ferroptosis is a novel form of cell death, which is distinguished from apoptosis and necrosis, and characterized by accumulation of lipid-based reactive oxygen species (ROS) in an iron-dependent manner. Erastin, a small molecule, was widely reported to trigger ferroptosis in various kinds of cancer cells, including pancreatic cancer cells by inducing ROS accumulation. However, how erastin treatment exerts cytotoxicity is not still fully understood. In this study, the effects of erastin in causing pancreatic cancer cell death via inducing ferroptosis and apoptosis are investigated. As expected, erastin treatment caused ROS accumulation, increase in iron concentration and non-apoptotic cell death, which is different from that of induced by apoptosis inducer, staurosporine. Interestingly, erastin treatment caused the upregulation of clusterin, which contributes to the regulation of malignant behaviors of pancreatic cancer, including preventing apoptosis and inducing chemoresistance. Without erastin treatment, overexpressed clusterin significantly promoted cell proliferation, which is consistent with its cytoprotective roles. After erastin treatment, overexpressed clusterin decreased erastin-induced ROS accumulation and cell death. By measuring iron concentration, reduced glutathione (GSH) and glutathione peroxidase 4 (GPX4), it is revealed that clusterin caused resistance to erastin-induced ferroptosis potentially via maintaining the enzymatic activity of GPX4, without disturbing GSH amount. Thus, ferroptosis inducer, erastin, may crosstalk with apoptotic cell death via regulating clusterin, indicating a more complex regulatory network between ferroptosis and apoptosis.

Stomach clusterin as a gut-derived feeding regulator

The stomach has emerged as a crucial endocrine organ in the regulation of feeding since the discovery of ghrelin. Gut-derived hormones, such as ghrelin and cholecystokinin, can act through the vagus nerve. We previously reported the satiety effect of hypothalamic clusterin, but the impact of peripheral clusterin remains unknown. In this study, we administered clusterin intraperitoneally to mice and observed its ability to suppress fasting-driven food intake. Interestingly, we found its synergism with cholecystokinin and antagonism with ghrelin. These effects were accompanied by increased c-fos immunoreactivity in nucleus tractus solitarius, area postrema, and hypothalamic paraventricular nucleus. Notably, truncal vagotomy abolished this response. The stomach expressed clusterin at high levels among the organs, and gastric clusterin was detected in specific enteroendocrine cells and the submucosal plexus. Gastric clusterin expression decreased after fasting but recovered after 2 hours of refeeding. Furthermore, we confirmed that stomachspecific overexpression of clusterin reduced food intake after overnight fasting. These results suggest that gastric clusterin may function as a gut-derived peptide involved in the regulation of feeding through the gut-brain axis. [BMB Reports 2024; 57(3): 149-154].

Assessment of osteopontin as an early nephrotoxicity indicator in human renal proximal tubule cells and its application in evaluating lanthanum-induced nephrotoxicity

Nephrotoxicity is a common adverse effect induced by various chemicals, necessitating the development of reliable toxicity screening models for nephrotoxicity assessment. In this study, we assessed a group of nephrotoxicity indicators derived from different toxicity pathways, including conventional endpoints and kidney tubular injury biomarkers such as clusterin (CLU), kidney injury molecule-I (KIM-1), osteopontin (OPN), and neutrophil gelatinase-associated lipocalin (NGAL), using HK-2 and induced pluripotent stem cells (iPSCs)-derived renal proximal tubular epithelial-like cells (PTLs). Among the biomarkers tested, OPN emerged as the most discerning and precise marker. The predictive potential of OPN was tested using a panel of 10 nephrotoxic and 5 non-nephrotoxic compounds. The results demonstrated that combining OPN with the half-maximal inhibitory concentration (IC50) enhanced the diagnostic accuracy in both cellular models. Additionally, PTLs cells showed superior predictive efficacy for nephrotoxicity compared to HK-2 cells in this investigation. The two cellular models were utilized to evaluate the nephrotoxicity of lanthanum. The findings indicated that lanthanum possesses nephrotoxic properties; however, the degree of nephrotoxicity was relatively low, consistent with the outcomes of in vivo experiments.

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.

Hepatokines: the missing link in the development of insulin resistance and hyperandrogenism in PCOS?

The liver plays a critical role in several metabolic pathways, including the regulation of glucose and lipid metabolism. Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease worldwide, is closely associated with insulin resistance (IR) and metabolic syndrome (MetS). Hepatokines, newly discovered proteins secreted by hepatocytes, have been linked to the induction of these metabolic dysregulations. Polycystic ovary syndrome (PCOS), the most common endocrine disorder in women of reproductive age, has been associated with NAFLD and IR, while hyperandrogenism additionally appears to be implicated in the pathogenesis of the latter. However, the potential role of hepatokines in the development of metabolic disorders in PCOS has not been fully investigated. Therefore, the aim of this review is to critically appraise the current evidence regarding the interplay of hepatokines with NAFLD, hyperandrogenism, and IR in PCOS.

Overview of Antibiotic-Induced Nephrotoxicity

Drug-induced nephrotoxicity accounts for up to 60% of cases of acute kidney injury (AKI) in hospitalized patients and is associated with increased morbidity and mortality in both adults and children. Antibiotics are one of the most common causes of drug-induced nephrotoxicity. Mechanisms of antibiotic-induced nephrotoxicity include glomerular injury, tubular injury or dysfunction, distal tubular obstruction from casts, and acute interstitial nephritis (AIN) mediated by a type IV (delayed-type) hypersensitivity response. Clinical manifestations of antibiotic-induced nephrotoxicity include acute tubular necrosis (ATN), AIN, and Fanconi syndrome. Given the potential nephrotoxic effects of antibiotics on critically ill patients, the use of novel biomarkers can provide information to optimize dosing and duration of treatment and can help prevent nephrotoxicity when traditional markers, such as creatinine, are unreliable. Use of novel kidney specific biomarkers, such as cystatin C and urinary kidney injury molecule-1 (KIM-1), may result in earlier detection of AKI, dose adjustment, or discontinuation of antibiotic and development of nonnephrotoxic antibiotics.

Clinical usefulness of urinary biomarkers for early prediction of acute kidney injury in patients undergoing transaortic valve implantation

This study aimed to reveal the clinical usefulness of urinary biomarkers for the early prediction of AKI onset after transcatheter aortic valve implantation (TAVI) (n = 173). In this study, 22 (12.7%) patients had AKI, of which 21 had mild AKI and 1 had moderate AKI. Higher levels of urinary liver-type fatty acid binding protein (L-FABP), [tissue inhibitor of metalloproteinases-2] × [insulin-like growth factor-binding protein 7], clusterin and urinary albumin before, after and 4 h after TAVI were associated with AKI onset. However, the time point of higher urinary N-acetyl-β-D-glucosaminidase levels related to AKI onset was only before TAVI. No significant differences were found in the area under the receiver-operator characteristic curves (AUC) for predicting AKI onset between urinary biomarkers before TAVI. After TAVI, the AUC (0.81) of urinary albumin was significantly higher than those of any other urinary biomarkers. The sensitivity (0.86) in urinary albumin after TAVI and specificity (0.98) in urinary L-FABP before TAVI were the highest among urinary biomarkers. In conclusion, urinary biomarkers may be clinically useful for early differentiation of patients with a higher or lower risk for AKI onset or early prediction of post-TAVI onset of AKI.

Regulation of psoriasis, colitis, and the intestinal microbiota by clusterin

Psoriasis, a chronic and systemic inflammatory disorder characterized by activation of the interleukin (IL)-23/IL-17 axis, may be associated with the intestinal microbiota through the so-called "gut-skin axis." Clusterin is a glycoprotein ubiquitously distributed in mammalian tissues; however, its role in psoriasis is unclear. Therefore, we evaluated the role of clusterin in psoriatic skin inflammation, systemic inflammation, and colitis using a murine model of IMQ-induced psoriasis. In IMQ-treated clusterin-knockout (clusterin-/-) mice, the expressions of inflammatory cytokines in clusterin-silenced human keratinocytes and intestinal microbial composition were analyzed. We also examined clusterin expression in the skin tissues of patients with psoriasis. IMQ-induced psoriatic skin inflammation is suppressed in clusterin-/- mice. Long-term administration of IMQ induced systemic inflammation and colitis; however, both were alleviated by the genetic deletion of clusterin. Genetic silencing of clusterin in human keratinocytes inhibited the production of inflammatory cytokines involved in the initiation and progression of psoriasis. The composition of the intestinal microbiota in IMQ-treated clusterin-/- and wild-type mice was different. Genetic deletion of clusterin suppressed the increase in the Firmicutes/Bacteroidetes (F/B) ratio. Skin tissues of patients with psoriasis showed high clusterin expression. In conclusion, inhibition of clusterin decreased psoriatic skin inflammation, systemic inflammation, colitis, and altered the F/B ratio in an IMQ-induced murine psoriasis model.

The normalizing effects of the CYP46A1 activator efavirenz on retinal sterol levels and risk factors for glaucoma in Apoj-/- mice

Apolipoprotein J (APOJ) is a multifunctional protein with genetic evidence suggesting an association between APOJ polymorphisms and Alzheimer's disease as well as exfoliation glaucoma. Herein we conducted ocular characterizations of Apoj^-/- mice and found that their retinal cholesterol levels were decreased and that this genotype had several risk factors for glaucoma: increased intraocular pressure and cup-to-disk ratio and impaired retinal ganglion cell (RGC) function. The latter was not due to RGC degeneration or activation of retinal Muller cells and microglia/macrophages. There was also a decrease in retinal levels of 24-hydroxycholesterol, a suggested neuroprotectant under glaucomatous conditions and a positive allosteric modulator of N-methyl-D-aspartate receptors mediating the light-evoked response of the RGC. Therefore, Apoj^-/- mice were treated with low-dose efavirenz, an allosteric activator of CYP46A1 which converts cholesterol into 24-hydroxycholesterol. Efavirenz treatment increased retinal cholesterol and 24-hydroxycholesterol levels, normalized intraocular pressure and cup-to-disk ratio, and rescued in part RGC function. Retinal expression of Abcg1 (a cholesterol efflux transporter), Apoa1 (a constituent of lipoprotein particles), and Scarb1 (a lipoprotein particle receptor) was increased in EVF-treated Apoj^-/- mice, indicating increased retinal cholesterol transport on lipoprotein particles. Ocular characterizations of Cyp46a1^-/- mice supported the beneficial efavirenz treatment effects via CYP46A1 activation. The data obtained demonstrate an important APOJ role in retinal cholesterol homeostasis and link this apolipoprotein to the glaucoma risk factors and retinal 24-hydroxycholesterol production by CYP46A1. As the CYP46A1 activator efavirenz is an FDA-approved anti-HIV drug, our studies suggest a new therapeutic approach for treatment of glaucomatous conditions.

Clusterin and Its Isoforms in Oral Squamous Cell Carcinoma and Their Potential as Biomarkers: A Comprehensive Review

Oral squamous cell carcinoma (OSCC) is a prevalent type of head and neck cancer, ranked as the sixth most common cancer worldwide, accounting for approximately 300,000 new cases and 145,000 deaths annually. Early detection using biomarkers significantly increases the 5-year survival rate of OSCC by up to 80-90%. Clusterin (CLU), also known as apolipoprotein J, is a sulfated chaperonic glycoprotein expressed in all tissues and human fluids and has been reported to be a potential biomarker of OSCC. CLU has been implicated as playing a vital role in many biological processes such as apoptosis, cell cycle, etc. Abnormal CLU expression has been linked with the development and progression of cancers. Despite the fact that there are many studies that have reported the involvement of CLU and its isoforms in OSCC, the exact roles of CLU and its isoforms in OSCC carcinogenesis have not been fully explored. This article aims to provide a comprehensive review of the current understanding of CLU structure and genetics and its correlation with OSCC tumorigenesis to better understand potential diagnostic and prognostic biomarker development. The relationship between CLU and chemotherapy resistance in cancer will also be discussed to explore the therapeutic application of CLU and its isoforms in OSCC.

Urinary Proteins of Female Domestic Dog (Canis familiaris) during Ovarian Cycle

The presence and identity of non-volatile chemical signals remain elusive in canines. In this study, we aim to evaluate the urinary proteins of female domestic dogs in the estrus and anestrus phases to evidence the presence of non-volatile chemical signals and to elucidate their identities. We collected urine samples from eight female dogs in the estrus and anestrus phases. A total of 240 proteins were identified in the urine samples using liquid chromatography-mass spectrometry (LC-MS analysis). The comparison of the proteins revealed a significant difference between the estrus and anestrus urine. We identified proteins belonging to the lipocalin family of canines (beta-lactoglobulin-1 and beta-lactoglobulin-2, P33685 and P33686, respectively), one of whose function was the transport of pheromones and which was present only in the estrus urine samples. Moreover, proteins such as Clusterin (CLU), Liver-expressed antimicrobial peptide 2 (LEAP2), and Proenkephalin (PENK) were more abundant in the estrus urine when compared to the anestrus urine. LEAP2 was recently described as a ghrelin receptor antagonist and implicated in regulating food intake and body weight in humans and mice. Proenkephalin, a polypeptide hormone cleaved into opioid peptides, was also recognized as a candidate to determine kidney function. As of yet, none of these have played a role in chemical communication. Clusterin, an extracellular chaperone protecting from protein aggregation implicated in stress-induced cell apoptosis, is a plausible candidate in chemical communication, which is a claim that needs to be ascertained further. Data are available via ProteomeXchange with the identifier PXD040418.

Differential Cytokine Responses and the Clinical Severity of Adult and Pediatric Nephropathia Epidemica

Nephropathia epidemica (NE), caused by the hantavirus infection, is endemic in Tatarstan Russia. The majority of patients are adults, with infection rarely diagnosed in children. This limited number of pediatric NE cases means there is an inadequate understanding of disease pathogenesis in this age category. Here, we have analyzed clinical and laboratory data in adults and children with NE to establish whether and how the disease severity differs between the two age groups. Serum cytokines were analyzed in samples collected from 11 children and 129 adult NE patients during an outbreak in 2019. A kidney toxicity panel was also used to analyze urine samples from these patients. Additionally, serum and urine samples were analyzed from 11 control children and 26 control adults. Analysis of clinical and laboratory data revealed that NE was milder in children than in adults. A variation in serum cytokine activation could explain the differences in clinical presentation. Cytokines associated with activation of Th1 lymphocytes were prominent in adults, while they were obscured in sera from pediatric NE patients. In addition, a prolonged activation of kidney injury markers was found in adults with NE, whilst only a short-lasting activation of these markers was observed in children with NE. These findings support previous observations of age differences in NE severity, which should be considered when diagnosing the disease in children.

Alpha 2-macroglobulin acts as a clearance factor in the lysosomal degradation of extracellular misfolded proteins

Proteostasis regulates protein folding and degradation; its maintenance is essential for resistance to stress and aging. The loss of proteostasis is associated with many age-related diseases. Within the cell, molecular chaperones facilitate the refolding of misfolded proteins into their bioactive forms, thus preventing undesirable interactions and aggregation. Although the mechanisms of intracellular protein degradation pathways for intracellular misfolded proteins have been extensively studied, the protein degradation pathway for extracellular proteins remain poorly understood. In this study, we identified several misfolded proteins that are substrates for alpha 2-macroglobulin (α₂M), an extracellular chaperone. We also established a lysosomal internalization assay for α₂M, which revealed that α₂M mediates the lysosomal degradation of extracellular misfolded proteins. Comparative analyses of α₂M and clusterin, another extracellular chaperone, indicated that α₂M preferentially targets aggregation-prone proteins. Thus, we present the degradation pathway of α2M, which interacts with aggregation-prone proteins for lysosomal degradation via selective internalization.

Selective reaction monitoring approach using structure-defined synthetic glycopeptides for validating glycopeptide biomarkers pre-determined by bottom-up glycoproteomics

Clusterin is a heavily glycosylated protein that is upregulated in various cancer and neurological diseases. The findings by the Hancock and Iliopoulos group that levels of the tryptic glycopeptide derived from plasma clusterin, 372Leu-Ala-Asn-Leu-Thr-Gln-Gly-Glu-Asp-Gln-Tyr-Tyr-Leu-Arg385 with a biantennary disialyl N-glycan (A2G2S2 or FA2G2S2) at Asn374 differed significantly prior to and after curative nephrectomy for clear cell renal cell carcinoma (RCC) patients motivated us to verify the feasibility of this glycopeptide as a novel biomarker of RCC. To determine the precise N-glycan structure attached to Asn374, whether A2G2S2 is composed of the Neu5Acα2,3Gal or/and the Neu5Acα2,6Gal moiety, we synthesized key glycopeptides having one of the two putative isomers. Selective reaction monitoring assay using synthetic glycopeptides as calibration standards allowed "top-down glycopeptidomics" for the absolute quantitation of targeted label-free glycopeptides in a range from 313.3 to 697.5 nM in the complex tryptic digests derived from serum samples of RCC patients and healthy controls. Our results provided evidence that the Asn374 residue of human clusterin is modified dominantly with the Neu5Acα2,6Gal structure and the levels of clusterin bearing an A2G2S2 with homo Neu5Acα2,6Gal terminals at Asn374 decrease significantly in RCC patients as compared with healthy controls. The present study elicits that a new strategy integrating the bottom-up glycoproteomics with top-down glycopeptidomics using structure-defined synthetic glycopeptides enables the confident identification and quantitation of the glycopeptide targets pre-determined by the existing methods for intact glycopeptide profiling.

The Most Promising Biomarkers of Allogeneic Kidney Transplant Rejection

Clinical transplantology is a constantly evolving field of medicine. Kidney transplantation has become standard clinical practice, and it has a significant impact on reducing mortality and improving the quality of life of patients. Allogenic transplantation induces an immune response, which may lead to the rejection of the transplanted organ. The gold standard for evaluating rejection of the transplanted kidney by the recipient's organism is a biopsy of this organ. However, due to the high invasiveness of this procedure, alternative diagnostic methods are being sought. Therefore, the biomarkers may play an essential predictive role in transplant rejection. A review of the most promising biomarkers for early diagnosis and prognosis prediction of allogenic kidney transplant rejection summarizes novel data on neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), C-X-C motif chemokine 10 (CXCL-10), cystatin C (CysC), osteopontin (OPN), and clusterin (CLU) and analyses the dynamics of changes of the biomarkers mentioned above in kidney diseases and the mechanism of rejection of the transplanted kidney.

Impact of retrograde intrarenal surgery on biomarkers that are associated with renal parenchyma injury, a preliminary study

PURPOSE

The primary objective of this preliminary study was to assess the changes in concentration of biomarkers, which indicate renal injury, after RIRS.

MATERIALS AND METHODS

Within this prospective study, we included 21 patients with nephrolithiasis requiring treatment with RIRS. From each patient, blood and urine samples were taken at fixed intervals before and after RIRS. Kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), calbindin, albumin, clusterin, gluthation S-transferase-π (GST-π), beta-2-microglobulin (B2M), osteopontin, cystatin c, and trefoil-factor-3 (TFF3) were measured in urine. Creatinine, cystatin c and uric acid were analyzed in the blood samples.

RESULTS

A significant increase of the biomarkers clusterin, GST-π, B2M, NGAL and cystatin c was observed after RIRS. However, the biomarkers gradually normalized during the first 14 postoperative days. The parameters surgery time, cumulative stone volume, and BMI did not significantly influence the biomarker concentrations. In the case of GST-π and NGAL a significant positive, yet minuscule effect of age was observed.

CONCLUSIONS

With our study, we identified 5 out of 12 assessed renal injury biomarkers that showed a significant increase after RIRS. The increase was only temporary and all markers normalized within 14 days. Further studies are needed to determine the clinical value of these identified markers to assess the long-term impact of intrarenal pressure elevation during RIRS.

Clusterin, other extracellular chaperones, and eye disease

Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.

Influence of Risk Factors for Male Infertility on Sperm Protein Composition

Male infertility is a common health problem that can be influenced by a host of lifestyle risk factors such as environment, nutrition, smoking, stress, and endocrine disruptors. These effects have been largely demonstrated on sperm parameters (e.g., motility, numeration, vitality, DNA integrity). In addition, several studies showed the deregulation of sperm proteins in relation to some of these factors. This review inventories the literature related to the identification of sperm proteins showing abundance variations in response to the four risk factors for male infertility that are the most investigated in this context: obesity, diabetes, tobacco smoking, and exposure to bisphenol-A (BPA). First, we provide an overview of the techniques used to identify deregulated proteins. Then, we summarise the main results obtained in the different studies and provide a compiled list of deregulated proteins in relation to each risk factor. Gene ontology analysis of these deregulated proteins shows that oxidative stress and immune and inflammatory responses are common mechanisms involved in sperm alterations encountered in relation to the risk factors.

Graphical models for mean and covariance of multivariate longitudinal data

Joint mean-covariance modeling of multivariate longitudinal data helps to understand the relative changes among multiple longitudinally measured and correlated outcomes. A key challenge in the analysis of multivariate longitudinal data is the complex covariance structure. This is due to the contemporaneous and cross-temporal associations between multiple longitudinal outcomes. Graphical and data-driven tools that can aid in visualizing the dependence patterns among multiple longitudinal outcomes are not readily available. In this work, we show the role of graphical techniques: profile plots, and multivariate regressograms, in developing mean and covariance models for multivariate longitudinal data. We introduce an R package MLGM (Multivariate Longitudinal Graphical Models) to facilitate visualization and modeling mean and covariance patterns. Through two real studies, microarray data from the T-cell activation study and Mayo Clinic's primary biliary cirrhosis of the liver study, we show the key features of MLGM. We evaluate the finite sample performance of the proposed mean-covariance estimation approach through simulations.

Prediction of drug-induced kidney injury in drug discovery

Drug induced kidney injury is one of the leading causes of failure of drug development programs in the clinic. Early prediction of renal toxicity potential of drugs is crucial to the success of drug candidates in the clinic. The dynamic nature of the functioning of the kidney and the presence of drug uptake proteins introduce additional challenges in the prediction of renal injury caused by drugs. Renal injury due to drugs can be caused by a wide variety of mechanisms and can be broadly classified as toxic or obstructive. Several biomarkers are available for in vitro and in vivo detection of renal injury. In vitro static and dynamic (microfluidic) cellular models and preclinical models can provide valuable information regarding the toxicity potential of drugs. Differences in pharmacology and subsequent disconnect in biomarker response, differences in the expression of transporter and enzyme proteins between in vitro to in vivo systems and between preclinical species and humans are some of the limitations of current experimental models. The progress in microfluidic (kidney-on-chip) platforms in combination with the ability of 3-dimensional cell culture can help in addressing some of these issues in the future. Finally, newer in silico and computational techniques like physiologically based pharmacokinetic modeling and machine learning have demonstrated potential in assisting prediction of drug induced kidney injury.

Netrin-1 and clusterin: Innovative potential diagnostic biomarkers for early renal damage in β-thalassemia major children

BACKGROUND

Children with β-thalassemia major (β-TM) suffer from tubular dysfunction even before the onset of any renal impairment symptoms and/or clinical signs. Therefore, identifying innovative biomarkers allowing early renal damage detection has focused attention.

AIM

This study aims to preliminary assess Netrin-1(NTN-1) and clusterin (CLU) in β-TM children and explore their possible roles as surrogate noninvasive biomarkers of renal tubular dysfunction.

SUBJECTS AND METHODS

In this study, 40 β-TM children and 30 healthy children were enrolled. Routine serum and urinary biochemical variables were determined. Urinary NTN-1 and CLU levels were measured using ELISA and their mRNA expression in PBMCs were assayed using real-time PCR. Serum TNF-α, MDA levels and GST activity were measured.

RESULTS

Urinary NTN-1 and CLU concentrations and mRNA relative expression levels in PBMCs were significantly increased in β-TM children relative to controls. Oxidative stress and inflammatory markers revealed significant elevation in β-TM children compared to controls. The change in these parameters correlated significantly with other renal parameters. ROC curves analysis showed that urinary NTN-1 and CLU levels are of promising diagnostic performance.

CONCLUSION

Our results suggest that NTN-1 and CLU are qualified as new noninvasive biomarker panels for early detection of renal injury in β-TM children. Moreover, urinary NTN-1 is recommended as a precise one during the clinical practices.

Circulating IL-6, clusterin and irisin in obese subjects with different grades of obesity: association with insulin resistance and sexual dimorphism

Objective

There are discrepancies about the relationship of IL-6, clusterin and irisin with obesity and obesity associated insulin resistance and also about their sexual dimorphism. This study aimed at evaluating the circulating levels of IL-6, clusterin and irisin in obese subjects of both sexes who had different grades of obesity and examining their sexual dimorphism and their association with insulin resistance.

Methods

This study included 176 non-diabetic subjects of both sexes who were classified according to their sex into two groups; the male and the female groups. The male group (88 men) was classified according to BMI into; group 1 (22 lean men), group 2 (22 class I obese men), group 3 (22 class II obese men) and group 4 (22 class III obese men). The female group (88 women) was classified according to BMI exactly as the male group. Metabolic parameters, IL-6, clusterin, and irisin levels were measured. Data were analyzed by ANOVA test, post hoc Tukey's test and independent t-test. Pearson correlation was used to assess the association between variables.

Results

In obese subjects of both sexes, circulating IL-6, clusterin and irisin levels were significantly elevated and positively correlated with HOMA-IR. Obese males showed significantly higher HOMA-IR, IL-6, clusterin and irisin levels than obese females.

Conclusion

Obesity in both sexes, especially in males was associated with high levels of IL-6, clusterin and irisin and worsened the metabolic pattern. Circulating IL-6, clusterin and irisin may represent possible therapeutic targets for insulin resistance in obese subjects.

Comprehensive Identification of Potential Crucial Genes and miRNA-mRNA Regulatory Networks in Papillary Thyroid Cancer

Background

Thyroid cancer is the most common endocrine malignancy, with a recent global increase of 20% in age-related incidence. Ultrasonography and ultrasonography-guided fine-needle aspiration biopsy (FNAB) are the most widely used diagnostic tests for thyroid nodules; however, it is estimated that up to 25% of thyroid biopsies are cytologically inconclusive. Molecular markers can help guide patient-oriented and targeted treatment of thyroid nodules and thyroid cancer.

Methods

Datasets related to papillary thyroid cancer (PTC) or thyroid carcinoma (GSE129562, GSE3678, GSE54958, GSE138042, and GSE124653) were downloaded from the GEO database and analysed using the Limma package of R software. For functional enrichment analysis, the Kyoto Encyclopedia of Genes and Genomes pathway analysis and Gene Ontology were applied to differentially expressed genes (DEGs) using the Metascape website. A protein-protein interaction (PPI) network was built from the STRING database. Gene expression, protein expression, immunohistochemistry, and potential functional gene survival were analysed using the GEPIA website, the Human Protein Atlas website, and the UALCAN website. Potential target miRNAs were predicted using the miRDB and Starbase datasets.

Results

We found 219 upregulated and 310 downregulated DEGs, with a cut-off of p < 0.01 and ∣log FC | >1.5. The DEGs in papillary thyroid cancer were mainly enriched in extracellular structural organisation. At the intersection of the PPI network and Metascape MCODEs, the hub genes in common were identified as FN1, APOE, CLU, and SDC2. In the targeted regulation network of miRNA-mRNA, the hsa-miR-424-5p was found to synchronously modulate two hub genes. Survival analysis showed that patients with high expression of CLU and APOE had better prognosis.

Conclusions

CLU and APOE are involved in the molecular mechanism of papillary thyroid cancer. The hsa-miR-424-5p might have the potential to reverse the processes of papillary thyroid cancer by modulating the hub genes. These are potential targets for the treatment of patients with papillary thyroid cancer.

Analysis of the uterine flush fluid proteome of healthy mares and mares with endometritis or fibrotic endometrial degeneration

The objective of this study was to evaluate the differences in the uterine flush fluid proteome between healthy mares and mares with endometritis or fibrotic endometrial degeneration (FED). Uterine flush fluid samples were collected from healthy mares (n=8; oestrus n=5 and dioestrus n=3) and mares with endometritis (n=23; oestrus n=14 and dioestrus n=9) or FED (n=7; oestrus n=6 and dioestrus n=1). Proteomic analysis was performed using label-free liquid chromatography-tandem mass spectrometry. Of 216 proteins identified during oestrus, 127 were common to all three groups, one protein was exclusively detected in healthy mares, 47 proteins were exclusively detected in mares with endometritis and four proteins were exclusively detected in mares with FED. Of 188 proteins identified during dioestrus, 113 proteins were common between healthy mares and mares with endometritis, eight proteins were exclusively detected in healthy mares and 67 proteins were exclusively detected in mares with endometritis. Quantitative analysis revealed a subset of proteins differing in abundance between the three groups during oestrus and between healthy mares and mares with endometritis during dioestrus. These results provide a springboard for evaluation of specific proteins as biomarkers of uterine health and disease and for investigation of their roles in the establishment and maintenance of pregnancy.

Serum Clusterin: A Potential Marker for Assessing the Clinical Severity and Short-Term Prognosis of Hepatitis B Virus-Related Acute-on-Chronic Liver Failure

Background

Acute-on-chronic liver failure (ACLF) is a clinical syndrome characterized by acute deterioration of liver function and high short-term mortality. Clusterin, with biological functions similar to small heat shock proteins, can protect cells from apoptosis induced by various stressors. The aim of this study was to detect the level of serum clusterin in hepatitis B virus- (HBV-) related ACLF and to assess the predictive value of clusterin for the short-term prognosis of HBV-ACLF.

Methods

We detected serum clusterin by ELISA in 108 HBV-ACLF patients, 63 HBV-non-ACLF patients, and 44 normal controls.

Results

Serum clusterin was markedly lower in HBV-ACLF patients (median, 51.09 μg/mL) than in HBV-non-ACLF patients (median, 188.56 μg/mL) and normal controls (median, 213.45 μg/mL; all P < 0.05). Nonsurviving HBV-ACLF patients who died within 90 days had much lower clusterin levels than did surviving patients, especially those who died within 28 days (nonsurvival group vs. survival group: 39.82 ± 19.34 vs. 72.26 ± 43.52, P < 0.001; survival time ≤ 28 vs. survival time > 28: median 28.39 vs. 43.22, P = 0.013). The results showed that for identifying HBV-ACLF, the sensitivity of clusterin (93.7%) was similar to the sensitivities of the international normalized ratio (INR; 94.4%) and total bilirubin (TBIL; 94.8%), but its specificity (90.7%) was higher than that of prothrombin activity (PTA; 65.8%) and TBIL (69.8%) and was similar to INR (88.9%). As the concentration of clusterin increased, the mortality of HBV-ACLF patients decreased significantly from 59.3% to 7.0%. Clusterin had better ability for predicting the prognosis of HBV-ACLF patients than did the model for end-stage liver disease (MELD) score and the chronic liver failure consortium (CLIF-C) ACLF score (MELD vs. clusterin: P = 0.012; CLIF-C ACLF vs. clusterin: P = 0.031).

Conclusion

Serum clusterin is a potential biomarker for HBV-ACLF which can be used to assess clinical severity and the short-term prognosis of patients with this disease and may help clinicians identify HBV-ACLF with greater specificity and improved prognostic accuracy than existing prognostic markers.

Extracellular Amyloid Deposits in Alzheimer's and Creutzfeldt-Jakob Disease: Similar Behavior of Different Proteins?

Neurodegenerative diseases are characterized by the deposition of specific protein aggregates, both intracellularly and/or extracellularly, depending on the type of disease. The extracellular occurrence of tridimensional structures formed by amyloidogenic proteins defines Alzheimer's disease, in which plaques are composed of amyloid β-protein, while in prionoses, the same term "amyloid" refers to the amyloid prion protein. In this review, we focused on providing a detailed didactic description and differentiation of diffuse, neuritic, and burnt-out plaques found in Alzheimer's disease and kuru-like, florid, multicentric, and neuritic plaques in human transmissible spongiform encephalopathies, followed by a systematic classification of the morphological similarities and differences between the extracellular amyloid deposits in these disorders. Both conditions are accompanied by the extracellular deposits that share certain signs, including neuritic degeneration, suggesting a particular role for amyloid protein toxicity.

Cell Culture Experiments Reveal that High S100B and Clusterin Levels may Convey Hypoxia-tolerance to the Hooded Seal (Cystophora cristata) Brain

While the brain of most mammals suffers from irreversible damage after only short periods of low oxygen levels (hypoxia), marine mammals are excellent breath-hold divers that have adapted to hypoxia. In addition to physiological adaptations, such as large oxygen storing capacity and strict oxygen economy during diving, the neurons of the deep-diving hooded seal (Cystophora cristata) have an intrinsic tolerance to hypoxia. We aim to understand the molecular basis of this neuronal hypoxia tolerance. Previously, transcriptomics of the cortex of the hooded seal have revealed remarkably high expression levels of S100B and clusterin (apolipoprotein J) when compared to the ferret, a non-diving carnivore. Both genes have much-debated roles in hypoxia and oxidative stress. Here, we evaluated the effects of S100B and of two isoforms of clusterin (soluble and nucleus clusterin) on the survival, metabolic activity and the amount of reactive oxygen species (ROS) in HN33 neuronal mouse cells exposed to hypoxia and oxidative stress. S100B and soluble clusterin had neuroprotective effects, with reduced ROS-levels and retention of normoxic energy status of cells during both stress conditions. The protective effects of nucleus clusterin were restricted to hypoxia. S100B and clusterin showed purifying selection in marine and terrestrial mammals, indicating a functional conservation across species. Immunofluorescence revealed identical cellular distributions of S100B and clusterin in mice, ferrets and hooded seals, further supporting the functional conservation. Taken together, our data suggest that the neuroprotective effects of all three proteins are exclusively facilitated by their increased expression in the brain of the hooded seal.

Clusterin regulates macrophage expansion, polarization and phagocytic activity in response to inflammation in the kidneys

Clusterin (CLU) is a multifunctional protein localized extracellularly and intracellularly. Although CLU-knockout (KO) mice are more susceptible to renal ischemia-reperfusion injury (IRI), the mechanisms underlying the actions of CLU in IRI are not fully understood. Macrophages are key regulators of IRI severity and tissue repair. Therefore, we investigated the role of CLU in macrophage polarization and phagocytosis. Renal IRI was induced in wild-type (WT) or CLU-KO C57BL/6 mice by clamping the renal pedicles for 30 min at 32°C. Peritoneal macrophages were activated via an intraperitoneal injection of lipopolysaccharide (LPS). Renal tissue damage was examined using histology, whereas leukocyte phenotypes were assessed using flow cytometry and immunohistochemistry. We found that monocytes/macrophages expressed the CLU protein that was upregulated by hypoxia. The percentages of macrophages (F4/80⁺ , CD11b⁺ or MAC3⁺ ) infiltrating the kidneys of WT mice were significantly less than those in CLU-KO mice after IRI. The M1/M2 phenotype ratio of the macrophages in WT kidneys decreased at day 7 post-IRI when the injury was repaired, whereas that in KO kidneys increased consistently as tissue injury persisted. In response to LPS stimulation, WT mice produced fewer M1 macrophages, but not M2, than the control did. Phagocytosis was stimulated by CLU expression in macrophages compared with the CLU null controls and by the exogenous CLU protein. In conclusion, CLU suppresses macrophage infiltration and proinflammatory M1 polarization during the recovery period following IRI, and enhances phagocytic activity, which may be partly responsible for tissue repair in the kidneys of WT mice after injury.

Diagnostic value of clusterin immunostaining in hepatocellular carcinoma

Background

Histologic distinction between well differentiated hepatocellular carcinoma (HCC) and benign hepatocellular mass lesions is a known challenge. Existing biomarkers are of limited diagnostic value. Our previous studies observed an enhanced canalicular expression pattern of clusterin (CLU) in HCC, which was not observed in benign hepatocellular mass lesions such as hepatocellular adenoma. The aim of this study was to further investigate its diagnostic value for HCC by examining the expression pattern of CLU in a large number of non-hepatocellular tumors, and by comparing it with two other commonly used hepatocellular markers pCEA and CD10 that also show a canalicular staining pattern in HCC.

Methods

Enhanced canalicular staining patterns of CLU, pCEA and CD10 were analyzed on 54 surgically resected well to moderately differentiated HCCs on whole tissue sections, of which 37 had surrounding regenerative nodules while the remaining 17 had a non-cirrhotic background. CLU immunostaining was also performed on tissue microarray sections that contained 74 HCCs (40 of which were also stained for pCEA and CD10), 55 normal liver tissue samples, and 1305 non-hepatocellular tumors from multiple organs.

Results

Enhanced CLU canalicular staining was observed in 70% (89/128) HCCs but not in regenerative nodules, normal liver tissues or any non-hepatocellular tumors. The sensitivity and specificity for enhanced canalicular staining pattern of CLU in HCCs were 0.70 and 1.00. This enhanced canalicular pattern was observed in only 26 and 23% HCCs for CD10 and pCEA, respectively. These results further demonstrate that the distinctive enhanced canalicular pattern of CLU is unique to HCC.

Conclusions

CLU is superior to pCEA and CD10 as a diagnostic immunomarker in that it can help distinguish well to moderately differentiated HCC not only from non-HCC malignancies but also from benign hepatocellular mass lesions.

Plasma-Based Proteomics Profiling of Patients with Hyperthyroidism after Antithyroid Treatment

Thyroid hormones critically modulate body homeostasis and haemostasis by regulating energy and metabolism. Previous studies have focused on individual pathways or proteins that are affected by increases in thyroid hormone levels, while an overall plasma proteomic signature of this increased level is lacking. Herein, an integrated untargeted proteomic approach with network analysis was used to identify changes in circulating proteins in the plasma proteome between hyperthyroid and euthyroid states. Plasma from 10 age-matched subjects at baseline (hyperthyroid) and post treatment with carbimazole (euthyroid) was compared by difference gel electrophoresis (DIGE) and matrix-assisted laser desorption/ionization time of flight (MALDI TOF) mass spectrometry (MS). A total of 20 proteins were identified with significant difference in abundance (analysis of variance (ANOVA) test, p ≤ 0.05; fold-change ≥ 1.5) between the two states (12 increased and 8 decreased in abundance in the hyperthyroid state). Twelve protein spots corresponding to ten unique proteins were significantly more abundant in the hyperthyroid state compared with the euthyroid state. These increased proteins were haptoglobin (HP), hemopexin (HPX), clusterin (CLU), apolipoprotein L1 (APOL1), alpha-1-B glycoprotein (A1BG), fibrinogen gamma chain (FGG), Ig alpha-1 chain C region (IGHA1), complement C6 (C6), leucine rich alpha 2 glycoprotein (LRG1), and carboxypeptidase N catalytic chain (CPN1). Eight protein spots corresponding to six unique proteins were significantly decreased in abundance in the hyperthyroid samples compared with euthyroid samples. These decreased proteins were apolipoprotein A1 (APOA1), inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4), plasminogen (PLG), alpha-1 antitrypsin (SERPINA1), fibrinogen beta chain (FGB), and complement C1r subcomponent (C1R). The differentially abundant proteins were investigated by ingenuity pathway analysis (IPA). The network pathway identified related to infectious disease, inflammatory disease, organismal injury and abnormalities, and the connectivity map focused around two central nodes, namely the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p38 mitogen-activated protein kinase (MAPK) pathways. The plasma proteome of patients with hyperthyroidism revealed differences in the abundance of proteins involved in acute phase response signaling, and development of a hypercoagulable and hypofibrinolytic state. Our findings enhance our existing knowledge of the altered proteins and associated biochemical pathways in hyperthyroidism.

DNAJA4 deficiency augments hyperthermia-induced Clusterin and ERK activation: two critical protective factors of human keratinocytes from hyperthermia-induced injury

BACKGROUND

Hyperthermia upregulates DNAJA4, a member of heat shock proteins (HSPs) 40 family, in human keratinocytes and HPV-infected tissue. DNAJA4 deficiency enhances growth arrest induced by hyperthermia. Clusterin (CLU) and phosphorylated ERK (p-ERK) play a role in regulating cell proliferation and apoptosis, under environmental stress.

OBJECTIVES

To examine the downstream molecules and signalling pathways of DNAJA4 and assess their roles in cell cycle and apoptosis of keratinocytes in response to hyperthermia.

METHODS

Wild-type and DNAJA4-knockout (KO) HaCaT cells were exposed to either 44 °C (hyperthermia) or 37 °C (control) for 30 min. The expression levels of CLU and p-ERK were determined by RT-PCR and Western blotting. RNAi and PD98059 were used to inhibit the expression of CLU and p-ERK, respectively. Cell viability, cell cycle and apoptosis were analysed by MTS assay and flow cytometry. Fresh biopsy samples of human normal foreskin or condyloma acuminatum (CA) were utilized to examine the expression of CLU and p-ERK after ex vivo culture at 44 °C.

RESULTS

The expression of CLU and p-ERK was significantly increased by hyperthermia treatment at 44 °C in HaCaT cells, foreskin and HPV-infected tissues. In HaCaT cells subjected to hyperthermia, DNAJA4 deficiency further augmented the expression of CLU and p-ERK. CLU deficiency enhanced the p-ERK expression. Hyperthermia-induced CLU and p-ERK exerted protective roles mainly through inhibiting apoptosis and maintaining cell cycle, respectively.

CONCLUSIONS

In keratinocytes, CLU and p-ERK are induced by hyperthermia, an effect which can be further enhanced by DNAJA4 deficiency. CLU deficiency also increases p-ERK expression. Both CLU and p-ERK are critical protective factors of human keratinocytes from hyperthermia-induced injury.

Recent advances in risk factors associated with ocular exfoliation syndrome

Exfoliation syndrome is generally considered a progressive age-related systemic disorder of the extracellular matrix, which is clinically characterized through the observation of flaky white aggregates on ocular tissues. Exfoliation syndrome is directly linked to exfoliative glaucoma in elderly patients, where it is known as the most common identifiable cause of open-angle glaucoma. Despite the identification of various risk factors associated with exfoliation syndrome, the exact pathogenesis of this syndrome has not been fully elucidated. There is a growing number of genome-wide association studies in different populations around the world to identify genetic factors underlying exfoliation syndrome. Besides variants in LOXL1 and CACNA1A genes, new loci have been recently identified which are believed to be associated with exfoliation syndrome. Among different genetic factors, functional variants might help to better understand mechanisms underlying this systemic disorder. Besides genetic factors, epigenetic regulation of different gene expression patterns has been thought to play a role in its pathogenesis. Other factors have been also considered to be involved in the development of exfoliation syndrome at cellular organelles level where mitochondrial impairment and autophagy dysfunction have been suggested in relation to exfoliation syndrome. This review addresses the most recent findings on genetic factors as well as cellular and molecular mechanisms involved in both the development and progression of exfoliation syndrome.

Dynamics of clusterin protein expression in the brain and plasma following experimental traumatic brain injury

Progress in the preclinical and clinical development of neuroprotective and antiepileptogenic treatments for traumatic brain injury (TBI) necessitates the discovery of prognostic biomarkers for post-injury outcome. Our previous mRNA-seq data revealed a 1.8–2.5 fold increase in clusterin mRNA expression in lesioned brain areas in rats with lateral fluid-percussion injury (FPI)-induced TBI. On this basis, we hypothesized that TBI leads to increases in the brain levels of clusterin protein, and consequently, increased plasma clusterin levels. For evaluation, we induced TBI in adult male Sprague-Dawley rats (n = 80) by lateral FPI. We validated our mRNA-seq findings with RT-qPCR, confirming increased clusterin mRNA levels in the perilesional cortex (FC 3.3, p < 0.01) and ipsilateral thalamus (FC 2.4, p < 0.05) at 3 months post-TBI. Immunohistochemistry revealed a marked increase in extracellular clusterin protein expression in the perilesional cortex and ipsilateral hippocampus (7d to 1 month post-TBI), and ipsilateral thalamus (14d to 12 months post-TBI). In the thalamus, punctate immunoreactivity was most intense around activated microglia and mitochondria. Enzyme-linked immunoassays indicated that an acute 15% reduction, rather than an increase in plasma clusterin levels differentiated animals with TBI from sham-operated controls (AUC 0.851, p < 0.05). Our findings suggest that plasma clusterin is a candidate biomarker for acute TBI diagnosis.

Clusterin Attenuates Hepatic Fibrosis by Inhibiting Hepatic Stellate Cell Activation and Downregulating the Smad3 Signaling Pathway

Clusterin is a glycoprotein that is expressed in most human tissues and found in body fluids. In our previous studies we demonstrated that clusterin has a protective effect against hepatic lipid accumulation and renal fibrosis; however, the role of clusterin in hepatic fibrosis is unknown. Here, we examined whether clusterin had protective effects against hepatic fibrosis using in vitro and in vivo models. Clusterin was upregulated in the livers of human cirrhotic patients and in thioacetamide (TAA)-induced and bile duct ligation mouse models of liver fibrosis. Loss and overexpression of clusterin promoted and attenuated hepatic fibrosis after TAA injection, respectively. In addition, we found that clusterin attenuates hepatic fibrosis by inhibiting the activation of hepatic stellate cells and Smad3 signaling pathways. Thus, clusterin plays an important role in hepatic fibrosis.

Clusterin enhances AKT2-mediated motility of normal and cancer prostate cells through a PTEN and PHLPP1 circuit

Clusterin (CLU) is a chaperone-like protein with multiple functions. sCLU is frequently upregulated in prostate tumor cells after chemo- or radiotherapy and after surgical or pharmacological castration. Moreover, CLU has been documented to modulate the cellular homolog of murine thymoma virus akt8 oncogene (AKT) activity. Here, we investigated how CLU overexpression influences phosphatidylinositol 3'-kinase (PI3K)/AKT signaling in human normal and cancer epithelial prostate cells. Human prostate cells stably transfected with CLU were broadly profiled by reverse phase protein array (RPPA), with particular emphasis on the PI3K/AKT pathway. The effect of CLU overexpression on normal and cancer cell motility was also tested. Our results clearly indicate that CLU overexpression enhances phosphorylation of AKT restricted to isoform 2. Mechanistically, this can be explained by the finding that the phosphatase PH domain leucine-rich repeat-containing protein phosphatase 1 (PHLPP1), known to dephosphorylate AKT2 at S474, is markedly downregulated by CLU, whereas miR-190, a negative regulator of PHLPP1, is upregulated. Moreover, we found that phosphatase and tensin homolog (PTEN) was heavily phosphorylated at the inhibitory site S380, contributing to the hyperactivation of AKT signaling. By keeping AKT2 phosphorylation high, CLU dramatically enhances the migratory behavior of prostate epithelial cell lines with different migratory and invasive phenotypes, namely prostate normal epithelial 1A (PNT1A) and prostatic carcinoma 3 (PC3) cells. Altogether, our results unravel for the first time a circuit by which CLU can switch a low migration phenotype toward a high migration phenotype, through miR-190-dependent downmodulation of PHLPP1 expression and, in turn, stabilization of AKT2 phosphorylation.

Biomarkers of Drug-Induced Kidney Toxicity

Blood urea nitrogen and serum creatinine are imperfect markers of kidney function because they are influenced by many renal and nonrenal factors independent of kidney function. A biomarker that is released directly into the blood or urine by the kidney in response to injury may be a better early marker of drug-induced kidney toxicity than blood urea nitrogen and serum creatinine. Urine albumin and urine protein, as well as urinary markers kidney injury molecule-1 (KIM-1), β2-microglobulin (B2M), cystatin C, clusterin, and trefoil factor-3 (TFF-3) have been accepted by the Food and Drug Administration and European Medicines Agency as highly sensitive and specific urinary biomarkers to monitor drug-induced kidney injury in preclinical studies and on a case-by-case basis in clinical trials. Other biomarkers of drug-induced kidney toxicity that have been detected in the urine of rodents or patients include IL-18, neutrophil gelatinase-associated lipocalin, netrin-1, liver-type fatty acid-binding protein (L-FABP), urinary exosomes, and TIMP2 (insulin-like growth factor-binding protein 7)/IGFBP7 (insulin-like growth factor-binding protein 7), also known as NephroCheck, the first Food and Drug Administration-approved biomarker testing platform to detect acute kidney injury in patients. In the future, a combined use of functional and damage markers may advance the field of biomarkers of drug-induced kidney toxicity. Earlier detection of drug-induced kidney toxicity with a kidney-specific biomarker may result in the avoidance of nephrotoxic agents in clinical studies and may allow for earlier intervention to repair damaged kidneys.

Comparative Proteome Analysis of Epicardial and Subcutaneous Adipose Tissues from Patients with or without Coronary Artery Disease

BACKGROUND AND AIMS

Owing to its unique anatomical structure and metabolism, epicardial adipose tissue (EAT) has attracted amount of attention in coronary artery disease (CAD) research. Here, we analyzed differences in proteome composition in epicardial (EAT) and subcutaneous adipose tissues (SAT) from patients with or without CAD.

METHODS

EAT and SAT samples were collected from 6 CAD patients and 6 non-CAD patients. Isobaric Tagging for Relative and Absolute Quantitation (iTRAQ) analysis combined with liquid chromatography tandem-mass spectrometry (LC-MS/MS) was performed to identify the differentially expressed proteins.

RESULTS

In total, 2348 proteins expressed in EAT and 2347 proteins expressed in SAT were separately identified. 385 differentially expressed proteins were found in EAT and 210 proteins were found in SAT in CAD patients compared to non-CAD patients. Many proteins differentially expressed in EAT of CAD patients were involved in biological functions associated with CAD development such as cell-to-cell signaling and interaction, inflammatory response, and lipid metabolism. Differential expressions of proteins (MMP9, S100A9, and clusterin) in EAT or SAT were involved in several signaling pathways such as mitochondrial dysfunction, acute phase inflammation, and LXR/RXR activation, which was confirmed by western blotting, and similar results were obtained.

CONCLUSIONS

The largest profiles of differentially expressed proteins in EAT and SAT between CAD patients and non-CAD patients were identified. The significant signal pathways, mitochondrial dysfunction, and LXR/RXR activation, which differential proteins were involved in, were firstly found to play roles in EAT of CAD patients, and clusterin was firstly found to be upregulated in EAT of CAD patients.

Effects of Calcium Oxalate on Expression of Clusterin and Lower Urinary Tract Symptoms in Prostatitis and Benign Prostatic Hyperplasia Patients with Calculi

Background

Prostatic calculi are common in urological treatments. Our major purpose in the present study was to explore the occurrence and composition of prostatic calculi, and investigate the effect of calcium oxalate (CaOx) on clusterin expression and lower urinary tract symptom (LUTS) in prostatitis and benign prostatic hyperplasia (BPH) patients with calculi.

Material/Methods

From December 2016 to January 2017, a total of 79 prostatitis patients aged more than 50 years were enrolled. The patients were divided into 3 groups: group A had small calculi (discrete, small echoes); group B had large calculi (large masses of multiple echoes, much coarser), and group C had no calculi. Immunohistochemical analysis was performed to evaluate the tissue scores. The clusterin expression was detected by quantitative real-time CR (qRT-PCR), Western blot, and immunofluorescence.

Results

According to multifactor analysis, age was significantly associated with prostatic calculus. The composition of prostatic calculus was an independent factor of LUTS. The clusterin expression was elevated in group B. The mRNA and protein levels of clusterin in prostatitis and BPH patients with stones were obviously higher than those in prostatitis and BPH patients without stones. CaOx enhanced clusterin expression in a dose-dependent manner.

Conclusions

Large prostatic calculi were associated with LUST. Furthermore, CaOx enhanced clusterin expression, leading to large prostatic calculi. These results may provide a therapeutic strategy for prostatitis and BPH.

Gentamicin induced acute renal damage and its evaluation using urinary biomarkers in rats

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Gentamicin induced dose dependent and temporal change in urinary biomarkers.

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Histological changes were minimal to severe on Day 4 & 8 respectively at both doses.

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Several fold increase in urinary biomarkers on Day 4 and 8 at both doses.

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On Day 8, increase in urinary and serum markers and histological changes.

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Clusterin is highly sensitive urinary biomarkers.

Consistent, sensitive biomarkers of acute kidney injury in animal models and humans have historically represented a poorly met need for investigators and clinicians. Detection of early kidney damage using urinary biomarkers is essential to assess the adversity in preclinical toxicology studies, which will help in reducing attrition of lead candidates in drug development. This study was undertaken to evaluate recently identified urinary biomarkers use in identifying acute kidney injury compared to traditional serum markers in experimentally induced nephrotoxicity in male Sprague Dawley (SD) rats. Gentamicin induced nephrotoxicity in Sprague Dawley rats is commonly detected using serum markers and histological evaluation of kidneys. Gentamicin, an aminoglycoside was administered at 30 and 100 mg/kg/day dose (subcutaneous) for seven consecutive days to induce nephrotoxicity. On day 4 and day 8 post treatment, serum and urine samples from these rats were analyzed for traditional serum/urine and novel urinary biomarkers and microscopic evaluation of kidneys.

On Day 4, no statistically significant change in serum BUN and creatinine level, but increase in urinary microalbumin (mALB) and urinary protein (UP) noticed in both doses of Gentamicin treated rats. On Day 8 significant increase in serum blood urea nitrogen (BUN), serum creatinine, UP and urinary mALB at 100 mg/kg/day, increase in total protein and decrease in albumin in 30 and 100 mg/kg/day and decrease in BUN and creatinine at 100 mg/kg of Gentamicin treated rats. The BUN and creatinine levels or fold change was comparable between control and 30 mg/kg of Gentamicin on Day 8, however, there was 5.6 and 3.4 fold change in BUN and Creatinine level noticed at 100 mg/kg/day of Gentamicin. On Day 4 and 8, significant increase in urinary levels of Clusterin was noted with animals administered both doses of Gentamicin. Similarly, significant increase in urinary levels of kidney injury molecule 1 (Kim-1), Cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) were noticed with animals administered Gentamicin at 100 mg/kg/day on both Day 4 and 8. All these markers have shown dose-dependent change.

Histological changes seen on Day 4 and Day 8 were of minimal to mild and moderate to severe in nature at both doses, respectively. The results demonstrated the sensitiveness and accuracy of detecting acute renal damage with novel urinary biomarkers, and their use in diagnosing early kidney damage. This helps in adversity assessment in animal toxicology studies and advocating right treatment to patients who have early renal injury which otherwise can only be diagnosed by elevated levels of traditional biomarkers in blood only after >30% of kidneys is damaged.

Changes in salivary analytes in canine parvovirus: A high-resolution quantitative proteomic study

The present study evaluated the changes in salivary proteome in parvoviral enteritis (PVE) in dogs through a high-throughput quantitative proteomic analysis. Saliva samples from healthy dogs and dogs with severe parvovirosis that survived or perished due to the disease were analysed and compared by Tandem Mass Tags (TMT) analysis. Proteomic analysis quantified 1516 peptides, and 287 (corresponding to 190 proteins) showed significantly different abundances between studied groups. Ten proteins were observed to change significantly between dogs that survived or perished due to PVE. Bioinformatics' analysis revealed that saliva reflects the involvement of different pathways in PVE such as catalytic activity and binding, and indicates antimicrobial humoral response as a pathway with a major role in the development of the disease. These results indicate that saliva proteins reflect physiopathological changes that occur in PVE and could be a potential source of biomarkers for this disease.

Clusterin is highly expressed in tubular complexes during spontaneous pancreatitis of spontaneous hypertensive rats

Pancreatitis is an inflammatory disorder of pancreas which leads to varying degrees of pancreatic endocrine and exocrine dysfunction and manifests in either acute or chronic forms. Spontaneous pancreatitis in experimental animals has rarely been reported. Here, we found acute to chronic courses of spontaneous pancreatitis in spontaneously hypertensive rats (SHRs), showing the formation of tubular complexes (TCs) and enhanced islet regeneration. We investigated the expression pattern of clusterin in the pancreas of SHRs based on immunohistochemistry (IHC). IHC analysis revealed the strong expression of clusterin in dedifferentiated duct-like cells and regenerative islets of TCs. These results imply that clusterin might be involved in the formation of TCs and parenchymal regeneration during rat pancreatitis.

Vitamin E and lycopene reduce coal burning fluorosis-induced spermatogenic cell apoptosis via oxidative stress-mediated JNK and ERK signaling pathways

Although fluoride has been widely used in toothpaste, mouthwash, and drinking water to prevent dental caries, the excessive intake of fluoride can cause fluorosis which is associated with dental, skeletal, and soft tissue fluorosis. Recent evidences have drawn the attention to its adverse effects on male reproductive system that include spermatogenesis defect, sperm count loss, and sperm maturation impairment. Fluoride induces oxidative stress through the activation of mitogen activated protein kinase (MAPK) cascade which can lead to cell apoptosis. Vitamin E (VE) and lycopene are two common antioxidants, being protective to reactive oxygen species (ROS)-induced toxic effects. However, whether and how these two antioxidants prevent fluoride-induced spermatogenic cell apoptosis are largely unknown. In the present study, a male rat model for coal burning fluorosis was established and the histological lesions and spermatogenic cell apoptosis in rat testes were observed. The decreased expression of clusterin, a heterodimeric glycoprotein reported to regulate spermatogenic cell apoptosis, was detected in fluoride-treated rat testes. Interestingly, the co-administration with VE or lycopene reduced fluorosis-mediated testicular toxicity and rescued clusterin expression. Further, fluoride caused the enhanced Jun N-terminal kinase (JNK, c-Jun) and extracellular signal-regulated protein kinase (ERK) phosphorylation, which was reduced by VE or lycopene. Thus, VE and lycopene prevent coal burning fluorosis-induced spermatogenic cell apoptosis through the suppression of oxidative stress-mediated JNK and ERK signaling pathway, which could be an alternative therapeutic strategy for the treatment of fluorosis.

Clusterin, a Novel DEC1 Target, Modulates DNA Damage-Mediated Cell Death

Differentiated embryonic chondrocyte expressed gene 1 (DEC1, also known as Sharp2/Stra13/BHLHE40) is a basic helix-loop-helix transcription factor that plays an important role in circadian rhythms, cell proliferation, apoptosis, cellular senescence, hypoxia response, and epithelial-to-mesenchymal transition of tumor cells. Secretory clusterin (sCLU) is a cytoprotective protein that guards against genotoxic stresses. Here, clusterin (CLU) was identified as a novel target gene of DEC1 and suppresses DNA damage-induced cell death in tumor cells. Mechanistically, based on chromatin immunoprecipitation and luciferase assays, DEC1 binds to and activates the promoter of the CLU gene. DEC1 and DNA-damaging agents induce sCLU expression, whereas DEC1 knockdown decreases the expression of sCLU upon DNA damage. Moreover, the data demonstrate that DEC1 inhibits, whereas sCLU knockdown enhances, DNA damage-induced cell death in MCF7 breast cancer cells. Given that DEC1 and sCLU are frequently overexpressed in breast cancers, these data provide mechanistic insight into DEC1 as a prosurvival factor by upregulating sCLU to reduce the DNA damage-induced apoptotic response. Together, this study reveals sCLU as a novel target of DEC1 which modulates the sensitivity of the DNA damage response.Implications: DEC1 and sCLU are frequently overexpressed in breast cancer, and targeting the sCLU-mediated cytoprotective signaling pathway may be a novel therapeutic approach. Mol Cancer Res; 16(11); 1641-51. ©2018 AACR.

Stem Cells as Potential Targets of Polyphenols in Multiple Sclerosis and Alzheimer's Disease

Alzheimer's disease (AD) and multiple sclerosis are major neurodegenerative diseases, which are characterized by the accumulation of abnormal pathogenic proteins due to oxidative stress, mitochondrial dysfunction, impaired autophagy, and pathogens, leading to neurodegeneration and behavioral deficits. Herein, we reviewed the utility of plant polyphenols in regulating proliferation and differentiation of stem cells for inducing brain self-repair in AD and multiple sclerosis. Firstly, we discussed the genetic, physiological, and environmental factors involved in the pathophysiology of both the disorders. Next, we reviewed various stem cell therapies available and how they have proved useful in animal models of AD and multiple sclerosis. Lastly, we discussed how polyphenols utilize the potential of stem cells, either complementing their therapeutic effects or stimulating endogenous and exogenous neurogenesis, against these diseases. We suggest that polyphenols could be a potential candidate for stem cell therapy against neurodegenerative disorders.

Urinary clusterin-a novel urinary biomarker associated with pediatric lupus renal histopathologic features and renal survival

BACKGROUND

Lupus nephritis (LN) is a major risk factor for systemic lupus erythematous (SLE)-related morbidity and mortality. With the aim of bypassing renal biopsy, we analyzed urinary biomarkers for their ability to predict renal histopathologic features and end-stage kidney disease (ESKD).

METHODS

Urinary albumin, ß2-microglobulin (B2M), cystatin C, kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), clusterin, calbindin, interleukin-18 (IL-18), neutrophil gelatinase-associated lipocalin (NGAL), trefoil factor 3 (TFF3), osteopontin, and glutathione S-transferase π (GST-π) levels were measured at time of renal biopsy. Renal histopathologies were carefully reviewed.

RESULTS

Urine from 60 pediatric SLE cases with LN, 29 without and 22 healthy controls were collected. Median age at SLE diagnosis was 12.92 years (range = 4.27-17.30 years) and 10 cases progressed to ESKD during a period of 4.12 ± 2.17 years. Urinary albumin and clusterin were significantly elevated (p = 0.035 and 0.048, respectively) in patients with tubulointerstitial renal lesions. Urinary clusterin among all urinary markers, performed best at predicting ESKD with cutoff of 0.61 × 10^-4 (AUC = 0.804; p = 0.002). Interestingly, elevation of urinary clusterin likely resulted from local over-expression in tubulointerstitial tissue since the level of serum clusterin was not concomitantly higher (p = 0.424).

CONCLUSION

Urinary biomarkers are emerging as non-invasive indicators for lupus-related renal histopathology and renal outcome prediction in pediatric SLE patients. Urinary clusterin, a newly identified biomarker, is an indicator that shows an association with tubulointerstitial renal lesions and demonstrates the best ability to predict ESKD.