Expression of clusterin in pancreatic acinar cell injuries in vivo and in vitro

Clusterin enhances cell survival by suppressing neuronal nitric-oxide synthase expression in the rhodopsin S334ter-line3 retinitis pigmentosa model

Environmental changes in the retina, including oxidative stress-induced cell death, influence photoreceptor degeneration in Retinitis Pigmentosa (RP). Previously, we tested and discovered that a cytoprotective chaperone protein, clusterin, produced robust preservation of rod photoreceptors of a rat autosomal dominant rhodopsin transgenic model of RP, S334ter-line3. To investigate the biochemical and molecular cytoprotective pathways of clusterin, we examined and compared a known source of cone cell death, nitric oxide (NO), observing nNOS expression using antibody against nNOS in RP retinas with intravitreal injections of saline, clusterin (10 μg/ml), or a non-isoform-selective NOS inhibitor (25 mM), L-NAME, or with an intraperitoneal injection (IP) of L-NAME (100 mg/kg). Rhodopsin-immunoreactive rod photoreceptor cells and nNOS-immunoreactive cells were quantified with immunohistochemistry in the presence or absence of L-NAME or clusterin, and the total nNOS retinal expression was determined by immunoblot analysis. In this study, the level of nNOS expression was significantly up-regulated postnatally (P) at P15 (P < 0.05), P30 (P < 0.001) and P60 (P < 0.0001) in RP retinas compared to normal controls. Clusterin treatment suppressed the up-regulated nNOS expression in RP retinas (P < 0.0001) and was enhanced in Type II amacrine cells. Additionally, IP injection of L-NAME at P15 prolonged rod survival in the later stage of RP retinas (P < 0.001). Conversely, rod survival in L-NAME-treated RP retinas was not equivalent to the rod survival number seen in clusterin-treated retinas, which suggests induction of nNOS expression in RP retinas and its reduction by clusterin is only partly responsible for the rescue observed through the reduction of nNOS expression in S334ter-line3 rat retinas.

Clusterin Protects Lipotoxicity-Induced Apoptosis via Upregulation of Autophagy in Insulin-Secreting Cells

BACKGROUND

There is a great need to discover factors that could protect pancreatic β-cells from apoptosis and thus prevent diabetes mellitus. Clusterin (CLU), a chaperone protein, plays an important role in cell protection in numerous cells and is involved in various cellular mechanisms, including autophagy. In the present study, we investigated the protective role of CLU through autophagy regulation in pancreatic β-cells.

METHODS

To identify the protective role of CLU, mouse insulinoma 6 (MIN6) cells were incubated with CLU and/or free fatty acid (FFA) palmitate, and cellular apoptosis and autophagy were examined.

RESULTS

Treatment with CLU remarkably upregulated microtubule-associated protein 1-light chain 3 (LC3)-II conversion in a doseand time-dependent manner with a significant increase in the autophagy-related 3 (Atg3) gene expression level, which is a mediator of LC3-II conversion. Moreover, co-immunoprecipitation and fluorescence microscopy experiments showed that the molecular interaction of LC3 with Atg3 and p62 was markedly increased by CLU. Stimulation of LC3-II conversion by CLU persisted in lipotoxic conditions, and FFA-induced apoptosis and dysfunction were simultaneously improved by CLU treatment. Finally, inhibition of LC3-II conversion by Atg3 gene knockdown markedly attenuated the cytoprotective effect of CLU.

CONCLUSION

Taken together, these findings suggest that CLU protects pancreatic β-cells against lipotoxicity-induced apoptosis via autophagy stimulation mediated by facilitating LC3-II conversion. Thus, CLU has therapeutic effects on FFA-induced pancreatic β-cell dysfunction.

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.

Clusterin inhibition mediates sensitivity to chemotherapy and radiotherapy in human cancer

Since its discovery in 1983, the protein clusterin (CLU) has been isolated from almost all human tissues and fluids and linked to the development of different physiopathological processes, including carcinogenesis and tumor progression. During the last few years, several studies have shown the cytoprotective role of secretory CLU in tumor cells, inhibiting their apoptosis and enhancing their resistance to conventional treatments including hormone depletion, chemotherapy, and radiotherapy. In an effort to determine the therapeutic potential that the inhibition of this protein could have on the development of new strategies for cancer treatment, numerous studies have been carried out in this field, with results, in most cases, satisfactory but sometimes contradictory. In this document, we summarize for the first time the current knowledge of the effects that CLU inhibition has on sensitizing tumor cells to conventional cancer treatments and discuss its importance in the development of new strategies against cancer.

Protective effect of clusterin on rod photoreceptor in rat model of retinitis pigmentosa

Retinitis Pigmentosa (RP) begins with the death of rod photoreceptors and is slowly followed by a gradual loss of cones and a rearrangement of the remaining retinal neurons. Clusterin is a chaperone protein that protects cells and is involved in various pathophysiological stresses, including retinal degeneration. Using a well-established transgenic rat model of RP (rhodopsin S334ter), we investigated the effects of clusterin on rod photoreceptor survival. To investigate the role of clusterin in S334ter-line3 retinas, Voronoi analysis and immunohistochemistry were used to evaluate the geometry of rod distribution. Additionally, immunoblot analysis, Bax activation, STAT3 and Akt phosphorylation were used to evaluate the pathway involved in rod cell protection. In this study, clusterin (10μg/ml) intravitreal treatment produced robust preservation of rod photoreceptors in S334ter-line3 retina. The mean number of rods in 1mm² was significantly greater in clusterin injected RP retinas (postnatal (P) 30, P45, P60, & P75) than in age-matched saline injected RP retinas (P<0.01). Clusterin activated Akt, STAT3 and significantly reduced Bax activity; in addition to inducing phosphorylated STAT3 in Müller cells, which suggests it may indirectly acts on photoreceptors. Thus, clusterin treatment may interferes with mechanisms leading to rod death by suppressing cell death through activation of Akt and STAT3, followed by Bax suppression. Novel insights into the pathway of how clusterin promotes the rod cell survival suggest this treatment may be a potential therapeutic strategy to slow progression of vision loss in human RP.

Clusterin and Pycr1 alterations associate with strain and model differences in susceptibility to experimental pancreatitis

Acute pancreatitis has several underlying etiologies, and results in consequences ranging from mild to complex multi-organ failure. The wide range of pathology suggests a genetic predisposition for progression. We compared the susceptibility to acute pancreatitis in BALB/c and FVB/N mice, coupled with proteomic analysis, in order to identify potential protein associations with pancreatitis progression.

METHODS

Pancreatitis was induced in BALB/c and FVB/N mice by administration of cerulein or feeding a choline-deficient, ethionine-supplemented (CDE) diet. Histology and changes in serum amylase were examined. Proteome profiling in cerulein-treated mice was performed using 2-dimensional differential in gel electrophoresis (2D-DIGE) followed by mass spectrometry analysis and biochemical validation.

RESULTS

Male and female FVB/N mice manifested more severe cerulein-induced pancreatitis as compared with BALB/c mice, but both strains were similarly susceptible to CDE-induced pancreatitis. Few of the 2D-DIGE alterations were validated by immunoblotting. Clusterin was markedly up-regulated after cerulein-induced pancreatitis in FVB/N but less-so in BALB/c mice. Pyrroline-5-carboxylate reductase (Pycr1), an enzyme involved in proline biosynthesis, had higher basal levels in FVB/N male and female mouse pancreata compared with BALB/c pancreata, and was relatively more resistant to degradation in FVB/N pancreata. However, serum and pancreas tissue proline levels were similar in the two strains.

CONCLUSION

FVB/N is more susceptible than BALB/c mice to cerulein-induced but not CDE-induced pancreatitis. Most of the 2D-DIGE alterations in the two strains likely relate to posttranslational modifications rather than protein level differences. Clusterin levels increase dramatically in association with pancreatitis severity, while Pycr1 is higher in FVB/N versus BALB/c pancreata basally and after induction of pancreatitis. Changes in proline metabolism may represent a novel potential genetic modifier in the context of pancreatitis.

Clusterin expression in gastrointestinal neuroendocrine tumours is highly correlated with location and is helpful in determining the origin of liver metastases

AIMS

Clusterin (CLU) is a sulphated glycoprotein implicated in many physiological and pathological processes, including tumorigenesis. We have previously demonstrated that CLU is highly expressed in pancreatic neuroendocrine tumours (NETs). The aims of this study were: to investigate CLU expression in gastrointestinal NETs; the potential correlation between this expression and different clinicopathological parameters; and its usefulness in the differential diagnosis of liver metastases.

METHODS AND RESULTS

Immunohistochemistry using an anti-CLU antibody was performed on paraffin sections from 108 primary NETs [G3 (13 cases), G2 (18 cases), and G1 (77 cases), according to the 2010 WHO classification] and 60 metastases. Cytoplasmic positivity was scored qualitatively and quantitatively. The pattern of staining was also assessed. Two-step statistical analyses (univariate and multivariate logistic regression) were performed. More than 90% of small-intestine NETs were completely negative. The probability of obtaining a positive CLU score was higher for the appendix, the stomach, the duodenum and the rectum than for the small intestine and colon. All G3 NETs and most G2 NETs were negative as compared with G1. CLU expression in the metastatic foci was identical to that of the primary tumour.

CONCLUSIONS

Clusterin expression in gastrointestinal NETs is highly correlated with location and probably also with grading, in both the primary tumour and metastases. Underexpression of CLU in small-intestine NETs is helpful for identifying the origin of liver metastases: a strong CLU score in a liver biopsy makes the small intestine highly unlikely as a primary site.

Kidney Injury Biomarkers in Hypertensive, Diabetic, and Nephropathy Rat Models Treated with Contrast Media

Contrast-induced nephropathy (CIN) refers to a decline in renal function following exposure to iodinated contrast media (CM). The present study was initiated to explore the role of known human risk factors (spontaneous hypertension, diabetes, protein-losing nephropathy) on CIN development in rodent models and to determine the effect of CM administration on kidney injury biomarkers in the face of preexisting kidney injury. Spontaneously hypertensive rats (hypertension), streptozotocin-treated Sprague Dawley rats (diabetes), and Dahl salt-sensitive rats (protein-losing nephropathy) were given single intravenous injections of the nonionic, low osmolar contrast medium, iohexol. Blood urea nitrogen (BUN), serum creatinine (sCr), and urinary biomarkers; albumin, lipocalin 2 (Lcn-2), osteopontin (Opn), kidney injury molecule 1 (Kim-1), renal papillary antigen 1 (Rpa-1), α-glutathione S-transferase (α-Gst), µ-glutathione S-transferase (µ-Gst), and beta-2 microglobulin (β2m) were measured in disease models and appropriate controls to determine the response of these biomarkers to CM administration. Each disease model produced elevated biomarkers of kidney injury without CM. Preexisting histopathology was exacerbated by CM but little or no significant increases in biomarkers were observed. When 1.5-fold or greater sCr increases from pre-CM were used to define true positives, receiver–operating characteristic curve analysis of biomarker performance showed sCr was the best predictor of CIN across disease models. β2m, Lcn-2, and BUN were the best predictors of histopathology defined kidney injury.

Clusterin is protective in pancreatitis through anti-apoptotic and anti-inflammatory properties

Clusterin is overexpressed in pancreas during the acute phase of pancreatitis. We intended to clarify the role of clusterin expression in stressed exocrine pancreas. We performed in vitro experiments in transfected AR4-2J cells with modified expression levels of clusterin and in vivo studies in clusterin-deficient mice. AR4-2J cells were exposed to agents mimicking cell-stress during pancreatitis (cerulein, hydrogen peroxide, staurosporine or lysophosphatidylcholine). Clusterin-overexpressing AR4-2J cells showed higher viability after cell stress and accordingly reduced rates of apoptosis and lessened caspase-3 activation. Blockage of endogenous clusterin expression reduced viability and enhanced apoptosis. Presence of clusterin reduced NF-kappaB activation and expression of the NF-kappaB target genes TNF-alpha and MOB-1 under cell stress. Clusterin-deficient mice showed a more severe course of acute experimental pancreatitis with enhanced rates of apoptosis and inflammatory cell infiltration. We concluded that clusterin was protective during inflammation of exocrine pancreas because of its anti-apoptotic and anti-inflammatory functions.

Clusterin is highly expressed in pancreatic endocrine tumours but not in solid pseudopapillary tumours

AIMS

Clusterin is a sulphated glycoprotein, implicated in many processes, including tumorigenesis. Several studies have reported its overexpression in many human neoplasms, including prostatic and pancreatic adenocarcinoma, but its expression has not been described previously in other pancreatic tumours. Our aim was to investigate the expression of clusterin by immunohistochemistry in 30 endocrine pancreatic tumours (ENTs) and 22 solid pseudopapillary tumours (SPPTs) to document its potential in differential diagnosis, and the possible correlation between this expression and clinicopathological parameters.

METHODS AND RESULTS

Cytoplasmic positivity was scored qualitatively (weak, moderate or strong immunoreactivity) and quantitatively on a four-tiered scale. The pattern of immunoreactivity (cytoplasmic, secretory or Golgi pattern) was also assessed. Except for scattered tumour cells in five cases, all SPPTs were negative, while all ENTs showed strong immunoreactivity in a variable proportion of tumour cells. Neither the reactivity score nor the pattern of immunoreactivity was correlated with tumour size, vascular permeation, perineural invasion or lymph node metastasis.

DISCUSSION

The expression of clusterin in all ENTs is of interest and could be an additional useful marker in the differential diagnosis with SPPTs. However, the lack of correlation between clusterin expression and clinicopathological parameters rules out a role as a predictive marker for endocrine tumour aggressiveness.

Combination therapy with an angiotensin-converting enzyme inhibitor and an angiotensin II receptor blocker synergistically suppresses chronic pancreatitis in rats

We recently demonstrated that both lisinopril and candesartan, an angiotensin-converting enzyme inhibitor and angiotensin II type 1 receptor blocker, respectively, attenuate pancreatic inflammation and fibrosis in male Wistar Bonn/Kobori (WBN/Kob) rats. The purpose of the present study was to assess whether combination therapy with low doses of both, ineffective when given alone, might synergistically exert protective effects. Lisinopril, candesartan, or a combination of both in drinking water was administered to 10-week-old male WBN/Kob rats for 10 weeks. Parameters of inflammation and fibrosis, positive immunostaining for alpha-smooth muscle actin, and gene expression of cytokine and growth factors were assessed, as well as circulating renin-angiotensin system components. Dose-dependent effects of combination therapy were also investigated. Only combination therapy attenuated gross alterations in the pancreas, as quantitatively confirmed by increases in pancreatic weights and decreases in myeloperoxidase activity, hydroxyproline content, histologic scores, relative fibrosis area, and relative area of alpha-smooth muscle actin-positive cells. Combination therapy suppressed up-regulation of tumor necrosis factor-alpha, platelet-derived growth factor-receptor beta, and transforming growth factor-beta1 mRNA in the pancreas. Dose dependence of combination therapy was recognized with reference to improvement in these parameters. The conclusions are that combination therapy synergistically alleviated pancreatic inflammation and fibrosis in male WBN/Kob rats. This effect may be related to suppression of tumor necrosis factor-alpha, platelet-derived growth factor-receptor beta, and transforming growth factor-beta1 mRNA. Compared with the either therapy alone, combination therapy with an angiotensin-converting enzyme inhibitor and an angiotensin II type 1 receptor blocker may be more beneficial for treating chronic pancreatitis.

Expression of vacuole membrane protein 1 (VMP1) in spontaneous chronic pancreatitis in the WBN/Kob rat

OBJECTIVES

VMP1 is a stress-induced gene that is overexpressed in acute pancreatitis. Its overexpression promotes the formation of intracellular vacuoles and cell death. We investigated the expression of VMP1 mRNA and its relation to apoptosis in spontaneous chronic pancreatitis in the WBN/Kob rat.

METHODS

Four-week-old male WBN/Kob rats were fed a special breeding diet, MB-3, for 20 weeks. Rats were killed every 4 weeks, and the pancreas was examined. VMP1 mRNA expression was determined by reverse transcriptase polymerase chain reaction with a semiquantitative analysis, direct sequencing, and in situ hybridization. Immunohistochemistry for proliferating cell nuclear antigen (PCNA) and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) were used to detect cell proliferation and apoptosis, respectively.

RESULTS

Vacuolar formation was most prominent at 12 weeks, when chronic pancreatitis occurred. VMP1 mRNA was also strongly expressed at 12 weeks. In situ hybridization revealed VMP1 mRNA was expressed in acinar cells. Apoptosis was increased at 12 and 20 weeks, and PCNA expression was strongest at 16 weeks in the course of chronic pancreatitis.

CONCLUSIONS

VMP1 mRNA expression paralleled the formation of vacuoles and apoptosis in acinar cells in the course of chronic pancreatitis in WBN/Kob rats.

Inhibition of Mist1 homodimer formation induces pancreatic acinar-to-ductal metaplasia

The pancreas consists of three main cell lineages (endocrine, exocrine, and duct) that develop from common primitive foregut precursors. The transcriptional network responsible for endocrine cell development has been studied extensively, but much less is known about the transcription factors that maintain the exocrine and duct cell lineages. One transcription factor that may be important to exocrine cell function is Mist1, a basic helix-loop-helix (bHLH) factor that is expressed in acinar cells. In order to perform a molecular characterization of this protein, we employed coimmunoprecipitation and bimolecular fluorescence complementation assays, coupled with electrophoretic mobility shift assay studies, to show that Mist1 exists in vivo as a homodimer complex. Analysis of transgenic mice expressing a dominant-negative Mist1 transgene (Mist1(mutant basic) [Mist1(MB)]) revealed the cell autonomous effect of inhibiting endogenous Mist1. Mist1(MB) cells become disorganized, exhibit a severe depletion of intercellular gap junctions, and express high levels of the glycoprotein clusterin, which has been shown to demarcate immature acinar cells. Inhibition of Mist1 transcriptional activity also leads to activation of duct-specific genes, such as cytokeratin 19 and cytokeratin 20, suggesting that alterations in the bHLH network produce a direct acinar-to-ductal phenotypic switch in mature cells. We propose that Mist1 is a key transcriptional regulator of exocrine pancreatic cells and that in the absence of functional Mist1, acinar cells do not maintain their normal identity.

Expression of clusterin in human pancreatic cancer

INTRODUCTION

Clusterin, also known as apolipoprotein J, has been implicated in numerous processes, including active cell death. Clusterin is reported to be overexpressed in breast and prostate cancers. However, its expression in pancreatic cancer is yet to be reported.

AIM AND METHODOLOGY

To examine clusterin expression and apoptosis in 52 pancreatic tissues, including specimens from 33 cases of pancreatic cancer, by immunohistochemistry.

RESULTS

Clusterin was expressed in 49% (16) of 33 cases of pancreatic cancer, 50% (13) of 26 cases of chronic pancreatitis, and 67% (4) of 6 cases of mucinous cystadenoma. It was not expressed in normal pancreas. Clusterin mRNA was also expressed in the pancreatic cancer cell lines. Clusterin was significantly more highly expressed at stage I and II (well-differentiated and moderately differentiated cancers). Clusterin and apoptosis were localized in the same cells in pancreatic cancer. However, clusterin expression was not significantly associated with apoptosis in any pancreatic disease. Clusterin-positive patients with pancreatic cancer survived significantly longer.

CONCLUSION

These results suggest that clusterin expression is induced in pancreatic cancer as well as chronic pancreatitis and that downregulation of clusterin may be involved in the progression of pancreatic cancer.

Induction of chemokines in rat pancreatic acinar cell injury

INTRODUCTION

The pathogenesis of chronic pancreatitis (CP), especially of acinar cell injury, is still unclear. Interleukin (IL)-8 is a chemokine that is involved in various inflammatory diseases.

AIM

To examine whether IL-8 and other chemokines are expressed in experimental acinar cell injury.

METHODOLOGY

IL-8 expression was analyzed in spontaneous CP in the WBN/Kob rat and in rat pancreatic acinar AR4-2J cells treated with various stimuli using reverse transcription-polymerase chain reaction (semiquantitative) and immunohistochemistry.

RESULTS

Chronic pancreatitis developed at 12 weeks in the WBN/Kob rats. IL-8, macrophage chemoattractant protein-1, and macrophage inflammatory protein-2 mRNA was expressed from 4 weeks and peaked at 12 weeks. Immunohistochemistry showed a strong expression of IL-8 in acinar cells, proliferating ductular cells, and interstitial infiltrating cells. In contrast, normal pancreatic tissues lacked IL-8 expression. Further, IL-8 mRNA and protein were detectable in AR4-2J cells treated with the various stimuli, such as menadione, tumor necrosis factor-alpha and transforming growth factor beta1.

CONCLUSION

These results suggest that IL-8 is expressed in the pancreatic parenchyma and infiltrates in CP and that it plays a role in the initial pathogenesis of CP together with other chemokines and cytokines.

Expression of tumor necrosis factor-alpha, interleukin-6, and interferon-gamma in spontaneous chronic pancreatitis in the WBN/Kob rat

To clarify the pathophysiological significance of cytokines in chronic pancreatitis (CP), we analyzed tissue expressions of various cytokines in the onset and progression of spontaneous CP in the WBN/Kob rat. Four-week-old male WBN/Kob rats were fed a special pellet diet (MB-3) for 20 weeks, and 6 rats were killed every 4 weeks. Pathologically, CP occurred at 12 weeks and progressed thereafter. The inflammation and fibrosis peaked at 12 and 16 weeks, respectively. By semiquantitative reverse transcription-polymerase chain reaction, the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and interferon (IFN)-gamma mRNAs peaked at 8, 12, and 16 weeks, respectively. Immunohistochemistry showed IL-6 expression in infiltrating inflammatory cells and vascular endothelial cells, whereas TNF-alpha was expressed in both acinar and infiltrating cells. IFN-gamma was localized to acinar, infiltrating and ductal cells, and its expression intensity showed significant correlation with those of fibrosis, type III collagen and alpha-smooth muscle actin. The in situ hybridization results were consistent with the RT-PCR data. These results suggest that tissue expressions of TNF-alpha and IL-6 are involved in the onset of pancreatitis and that IFN-gamma expression is related to the progression of CP.