Prohibitin Expression Research Articles

Prohibitin overexpression predicts poor prognosis and promotes cell proliferation and invasion through ERK pathway activation in gallbladder cancer.

BackgroundProhibitin (PHB), a pleiotropic protein overexpressed in several tumor types, has been implicated in the regulation of cell proliferation, invasive migration and survival. However, PHB expression and its biological function in gallbladder cancer (GBC) remain largely unknown.MethodsPHB and p-ERK protein expressions were determined in human GBC tissues by immunohistochemistry (IHC). The effects of PHB knockdown on GBC cell proliferation and invasiveness were evaluated using Cell Counting Kit-8 (CCK-8) cell viability, cell cycle analysis, transwell invasion and gelatin zymography assays. Subcutaneous xenograft and tail vein-lung metastasis tumor models in nude mice were employed to further substantiate the role of PHB in GBC progression.ResultsPHB protein was overexpressed in GBC tissues and was significantly associated with histological grade, tumor stage and perineural invasion. Furthermore, PHB expression was negatively associated with overall survival in GBC patients. In vitro experimental studies demonstrated that the downregulation of PHB expression by lentivirus-mediated shRNA interference not only inhibited the ERK pathway activation but also reduced the proliferative and invasive capacities of GBC cells.Moreover, PD0325901, a specific inhibitor of MEK, markedly impaired PHB- mediated phosphorylation of ERK protein. IHC statistical analyses further validated that PHB expression was positively correlated with ERK protein phosphorylation levels in GBC tissue samples. In vivo, PHB depletion also resulted in dramatic reductions in the growth and metastasis of GBC cells.ConclusionOur findings demonstrate that PHB overexpression predicts poor survival in GBC patients. PHB could serve as a novel prognostic biomarker and a potential therapeutic target for GBCs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-016-0346-7) contains supplementary material, which is available to authorized users.

Expression of a mutant prohibitin from the aP2 gene promoter leads to obesity-linked tumor development in insulin resistance-dependent manner.

A critical unmet need for the study of obesity-linked cancer is the lack of preclinical models that spontaneously develop obesity and cancer sequentially. Prohibitin (PHB) is a pleiotropic protein that has a role in adipose and immune functions. We capitalized on this attribute of PHB to develop a mouse model for obesity-linked tumor. We achieved this by expressing Y114F-PHB (m-PHB) from the aP2 gene promoter for simultaneous manipulation of adipogenic and immune signaling functions. The m-PHB mice develop obesity in a sex-neutral manner, but only male mice develop impaired glucose homeostasis and hyperinsulinemia similar to transgenic mice expressing PHB. Interestingly, only male m-PHB mice develop histiocytosis with lymphadenopathy, suggesting that metabolic dysregulation or m-PHB alone is not sufficient for the tumor development and that both are required for tumorigenesis. Moreover, ovariectomy in female m-PHB mice resulted in impaired glucose homeostasis, hyperinsulinemia and consequently tumor development similar to male m-PHB mice. These changes were not observed in sham-operated control m-Mito-Ob mice, further confirming the role of obesity-related metabolic dysregulation in tumor development in m-PHB mice. Our data provide a proof-of-concept that obesity-associated hyperinsulinemia promotes tumor development by facilitating dormant mutant to manifest and reveals a sex-dimorphic role of PHB in adipose-immune interaction or immunometabolism. Targeting PHB may provide a unique opportunity for the modulation of immunometabolism in obesity, cancer and in immune diseases.

Flavaglines Ameliorate Experimental Colitis and Protect Against Intestinal Epithelial Cell Apoptosis and Mitochondrial Dysfunction.

Flavaglines are a family of natural compounds shown to have anti-inflammatory and cytoprotective effects in neurons and cardiomyocytes. Flavaglines target prohibitins as ligands, which are scaffold proteins that regulate mitochondrial function, cell survival, and transcription. This study tested the therapeutic potential of flavaglines to promote intestinal epithelial cell homeostasis and to protect against a model of experimental colitis in which inflammation is driven by epithelial ulceration. Survival and homeostasis of Caco2-BBE and IEC-6 intestinal epithelial cell lines were measured during treatment with the flavaglines FL3 or FL37 alone and in combination with the proinflammatory cytokines tumor necrosis factor (TNF) α and interferon γ. Wild-type mice were intraperitoneally injected with 0.1 mg/kg FL3 or vehicle once daily for 4 days during dextran sodium sulfate-induced colitis to test the in vivo anti-inflammatory effect of FL3. FL3 and FL37 increased basal Caco2-BBE and IEC-6 cell viability, decreased apoptosis, and decreased epithelial monolayer permeability. FL3 and FL37 inhibited TNFα- and interferon γ-induced nuclear factor kappa B and Cox2 expression, apoptosis, and increased permeability in Caco2-BBE cells. FL3 and FL37 protected against TNFα-induced mitochondrial superoxide generation by preserving respiratory chain complex I activity and prohibitin expression. p38-MAPK activation was essential for the protective effect of FL3 and FL37 on barrier permeability and mitochondrial-derived reactive oxygen species production during TNFα treatment. Mice administered FL3 during dextran sodium sulfate colitis exhibited increased colonic prohibitin expression and p38-MAPK activation, preserved barrier function, and less inflammation. These results suggest that flavaglines exhibit therapeutic potential against colitis and preserve intestinal epithelial cell survival, mitochondrial function, and barrier integrity.

Characterization of Prohibitins in Male Reproductive System and their Expression under Oxidative Stress

We investigated the expression and location of prohibitin 1 and 2 of theprohibitin family in the male reproductive system and their potential rolesduring the oxidative stress response in a rat model. Semiquantitative polymerase chain reaction, Western blot, immunohistochemistry and indirect immunofluorescence were performed toexamine the expression and localization of prohibitins. Oxidative damage wasevaluated using a commercially available malondialdehyde kit. Histological damage induced by doxorubicin injection was examined by hematoxylin and eosin staining. Prohibitin 1 and 2 were ubiquitously expressed in various human tissues with distinct high expression in the epididymis. In the human testis and epididymis they were localized in the cytoplasm of diverse cell types. Prohibitin 1 was located on the entire tail region of human ejaculated spermatozoa while prohibitin 2 was specifically localized on the equatorial region. In spermatozoa from young men with asthenozoospermia the percent of spermatozoa with positive staining as well as the fluorescence intensity of prohibitin 2 was much lower than in the spermatozoa of healthy donors. Uniform expression of prohibitins in the testis and epididymis of the rat during postnatal development suggested conserved and vital biological functions. Moreover under oxidative stress induced by doxorubicin injection the expression of prohibitin 1 and 2 was significantly down-regulated in the rat testis with significant histomorphological changes. To our knowledge this research represents the first systematic study of prohibitins in the male reproductive system. It lays the foundation forfurther functional studies and provides potential therapeutic targets for infertility induced by oxidative stress.

MiR-23a binds to p53 and enhances its association with miR-128 promoter

Apoptosis plays an important role in cardiac pathology, but the molecular mechanism by which apoptosis regulated remains largely elusive. Here, we report that miR-23a promotes the apoptotic effect of p53 in cardiomyocytes. Our results showed that miR-23a promotes apoptosis induced by oxidative stress. In exploring the molecular mechanism by which miR-23a promotes apoptosis, we found that it sensitized the effect of p53 on miR-128 regulation. It promoted the association of p53 to the promoter region of miR-128, and enhanced the transcriptional activation of p53 on miR-128 expression. miR-128 can downregulate prohibitin expression, and subsequently promote apoptosis. Our data provides novel evidence revealing that miR-23a can stimulate transcriptional activity of p53.

Prohibitin( PHB) roles in granulosa cell physiology.

Ovarian granulosa cells (GC) play an important role in the growth and development of the follicle in the process known as folliculogenesis. In the present review, we focus on recent developments in prohibitin (PHB) research in relation to GC physiological functions. PHB is a member of a highly conserved eukaryotic protein family containing the repressor of estrogen activity (REA)/stomatin/PHB/flotillin/HflK/C (SPFH) domain (also known as the PHB domain) found in diverse species from prokaryotes to eukaryotes. PHB is ubiquitously expressed in a circulating free form or is present in multiple cellular compartments including mitochondria, nucleus and plasma membrane. In mitochondria, PHB is anchored to the mitochondrial inner membrane and forms complexes with the ATPases associated with proteases having diverse cellular activities. PHB continuously shuttles between the mitochondria, cytosol and nucleus. In the nucleus, PHB interacts with various transcription factors and modulates transcriptional activity directly or through interactions with chromatin remodeling proteins. Many functions have been attributed to the mitochondrial and nuclear PHB complexes such as cellular differentiation, anti-proliferation, morphogenesis and maintenance of the functional integrity of the mitochondria. However, to date, the regulation of PHB expression patterns and GC physiological functions are not completely understood.

The potential function of prohibitin during spermatogenesis in Chinese fire-bellied newt Cynops orientalis.

Prohibitin proteins are multifunctional proteins located mainly at the inner membrane of mitochondria expressed in universal species. They play a vital role in mitochondria's function, cell proteolysis, senescence, apoptosis and as a substrate for ubiquitination. In this study, we used PCR cloning, protein and nucleotide acids alignment, protein structure prediction, western blot, in situ hybridization and immunofluorescence to study the characteristics of the prohibitin gene and the potential role of prohibitin in spermatogenesis and spermiogenesis processes in the Chinese fire-bellied newt Cynops orientalis. First, we cloned a 1452-bp full-length cDNA from the testis of Cynops orientalis. Second, we found that the 272 amino acids of prohibitin have a SPFH family domain. Thirdly, the western blots showed high expression of prohibitin in testis while the protein size was approximately 32kDa. Fourthly, the results of in situ hybridization and immunofluorescence experiments showed that most of the prohibitins travelled with the mitochondria's migration in Cynops orientalis. The quantities of mRNA decreased as spermiogenesis proceeded, although the signals of prohibitins existed during the whole period of spermatogenesis and spermiogenesis. In the mature germ cells, the signals of prohibitins were weak and aggregated at the end of the cell. Finally, we discovered that the Sertoli cells had a large quantity of prohibitins and we made several assumptions of prohibitins' potential roles in those cells. This is the first time that the relationship between mitochondria and prohibitin in different stages of the sperm cells in Cynops orientalis has been examined, which also revealed that Sertoli cells have abundant prohibitins.

Prohibitin protects proximal tubule epithelial cells against oxidative injury through mitochondrial pathways

Oxidative stress mediated by reactive oxygen species (ROS) contributes to renal tubular atrophy and fibrosis following renal transplantation. Studies have shown that mitochondrial chaperone prohibitin (PHB) has antioxidant effects. Here we used the human renal proximal tubule epithelial cell line, HK-2 cells as an in vitro model to assess the role of PHB in hydrogen peroxide (H2O2)-induced renal tubular oxidative injury. Our results showed that H2O2 treatment inhibited PHB expression in a time-dependent manner in HK-2 cells. PHB overexpression could protect cell from oxidative stress-induced injury by inhibiting H2O2-induced cell apoptosis and intracellular ROS generation and promoting endogenous antioxidant defense components including glutathione peroxidase, catalase, superoxide dismutase, and glutathione. Furthermore, oxidative stress-induced cell injury was suppressed in PHB-overexpressed tubule epithelial cells through mitochondria-mediated pathway, including inhibition of mitochondrial uncoupling protein 2 or UCP2 and Bax expression, mitochondrial ROS production, promotion of ATP production and Bcl-2 expression, inhibition of mitochondrial membrane potential loss and release of cytochrome c from mitochondria to cytoplasm, and followed by caspase-3 activation. Meanwhile, inhibition of PHB expression by small interference RNA resulted in less resistance of HK-2 cells to H2O2 toxicity as shown in decreased cell viability, increased apoptosis, ROS production, and mitochondrial dysfunction. These data indicated that PHB protected the tubule epithelial cells from oxidative stress-induced damage through the inhibition of oxidative damage, mitochondria dysfunction, and ultimately inhibition of cell apoptosis, and that increasing PHB content in mitochondria constituted a new therapeutic target for transient ischemic injury and chronic allograft nephropathy or CAN following renal transplantation.

The change of prohibitin in the kidney injury of db/db mice and its intervention

Objective To study the molecular mechanisms of prohibitin in the diabetic nephropathy and its effect. Methods C57BLKS/J db/db mice were selected randomly as diabetic model group (DM group, n=8) and the db/m mice were selected as control group (CC, n=8), and C57BLKS/J db/db mice lavage treated with GSPB2 for 10 weeks were considered as treatment group (30mg/kg body weight/day, DMT, n=8). At the end of 18 weeks, fasting blood glucose (FBG), advanced glycation end products (AGEs) and monocyte chemotactic protein 1 (MCP1) were determined. Morphological changes of the kidney tissue were examined by light microscopy and transmission electron microscope. The expression of prohibitin in the kidney tissue was determined by Western blot. Results The body weight was higher in DM groups than in control group at 8, 12, 16, 18 weeks (all P<0.01). The body weight was significantly inhibited at 12, 16, 18 weeks after GSPB2 administration in the DMT group as compared to the DM group (all P<0.05). Serum FBG, AGEs and MCP-1 levels were significantly higher in DM group than in control group (all P<0.01). GSPB2 significantly decreased the serum levels of FBG, AGEs and MCP-1 in db/db mice (all P<0.01). The glomerular volume, mesangial cell proliferation, extracellular matrix in DM group was significantly increased as compared with CC group by light microscopy. GSPB2 significantly reduced the glomerular volume, mesangial cell proliferation in db/db mice. The result of ultrastructural microscopy showed that in DM group, mesangial cell was inserted into the sub-endothelium, basement membrane became thicken, the number of podocytes was decreased and the podocytes were fused, and the thicken basement membrane and podocytes injure were improved in the DMT group. Moreover, the protein expression of prohibitin was higher in DM group than in control group (P<0.01), while GSPB2 could decrease the protein expression of prohibitin (P<0.01). Conclusions The mechanism of protective effects of GSPB2in diabetic nephropathy can be attributed to its anti-glycation, anti-inflammatory and the increase of prohibitin expression, which will provide a theoretical basis for the prevention and treatment of diabetic nephropathy. Key words: Diabetic nephropathy; Ceu prohibitin; Procyanidins

Multifaceted role of prohibitin in cell survival and apoptosis

Human eukaryotic prohibitin (prohibitin-1 and prohibitin-2) is a membrane protein with different cellular localizations. It is involved in multiple cellular functions, including energy metabolism, proliferation, apoptosis, and senescence. The subcellular localization of prohibitin may determine its functions. Membrane prohibitin regulate the cellular signaling of membrane transport, nuclear prohibitin control transcription activation and the cell cycle, and mitochondrial prohibitin complex stabilize the mitochondrial genome and modulate mitochondrial dynamics, mitochondrial morphology, mitochondrial biogenesis, and the mitochondrial intrinsic apoptotic pathway. Moreover, prohibitin can translocates into the nucleus or the mitochondria under apoptotic signals and the subcellular shuttling of prohibitin is necessary for apoptosis process. Apoptosis is the process of programmed cell death that is important for the maintenance of normal physiological functions. Consequently, any alteration in the content, post-transcriptional modification (i.e. phosphorylation) or the nuclear or mitochondrial translocation of prohibitin may influence cell fate. Understanding the mechanisms of the expression and regulation of prohibitin may be useful for future research. This review provides an overview of the multifaceted and essential roles played by prohibitin in the regulation of cell survival and apoptosis.

Effect of estrogen on expression of prohibitin in white adipose tissue and liver of diet-induced obese rats.

Prohibitin (PHB) is a ubiquitously expressed and highly conserved protein that participates in diverse cellular processes, and its functions are linked to a variety of diseases. In the present study, to explore transcriptional activation and signaling pathways involved in PHB regulation in response to sex hormone treatment, we investigated the effects of estrogen (17-β-estradiol, E2) on regulation of PHB in several metabolic tissues from male and female rats. Elevated expression of PHB was prominent in white adipose tissue (WAT) and the liver, and E2 stimulated PHB expression in both ND and HFD-fed rats. To further confirm the expression of PHB which was increased in WAT and the liver, we analyzed PHB expression levels in 3T3-L1 and C9 cells after the treatment of E2. Transcription and protein levels of PHB were dose-dependently increased by E2 treatment in both cell types, supporting our in vivo data. To further evaluate the possible role of E2 in elevation of PHB via estrogen receptors (ER), the potent ER inhibitor fulvestrant was treated to 3T3-L1 and C9 cells. Fulvestrant markedly suppressed both transcription and protein levels of PHB, suggesting that PHB expression in both tissues may be regulated through ERs. GeneMANIA, a predictive web interface, was used to show that Phb is regulated via the intracellular steroid hormone receptor signaling pathway, suggesting a role for ERs in expression of Phb as well as other metabolically important genes. Based on these results, we expect that targeting PHB would be a useful therapeutic approach for treatment of obesity.

The establishment of Raji drug-resistant cell line and analyses of prohibitin and miR-27a expression

目的建立阿霉素（ADR）耐药Raji细胞株（Raji/A)，检测线粒体抗增殖蛋白(Prohibitin，PHB）及微小RNA-27a (miR-27a）在Raji细胞及其敏感株（Raji/S）中的表达变化并探讨其临床意义。方法建立Raji/A细胞株，采用CCK-8法检测细胞增殖抑制率，采用相差显微镜观察细胞一般形态并计数，采用RT-PCR方法检测Raji/A及Raji/S细胞中PHB mRNA与miR-27a的表达水平，采用Western blot法检测PHB1蛋白在Raji/A及Raji/S细胞线粒体中的表达水平。结果不同浓度ADR处理48 h，Raji/A及Raji/S细胞的半数抑制浓度(IC50）分别为344.17及1.12 µg/ml，耐药倍数为306.47倍。Raji/A与Raji/S细胞经4 µg/ml ADR处理24 h，凋亡率分别为（13.48±2.20)％及（69.89±1.94)%，差异有统计学意义(P<0.05)。PHB1 mRNA在Raji/A细胞中的表达明显高于Raji/S细胞，为(7.66±3.27)倍(P<0.05)；PHB2 mRNA在Raji/A细胞中的表达是Raji/S的(1.25±0.47）倍，差异无统计学意义(P>0.05)；miR-27a在Raji/A细胞中的表达明显高于Raji/S细胞，为（128.40±31.59)倍(P<0.05)。PHB1蛋白在Raji/A及Raji/S细胞线粒体中的相对表达量分别为9.87±0.22及1.96±0.06(P<0.05)。结论成功构建稳定Raji/A细胞模型，PHB1及miR-27a在Raji/A细胞中表达升高，其高表达可能参与Raji细胞ADR耐药机制。

Antiosteoporotic Effects of Huangqi Sanxian Decoction in Cultured Rat Osteoblasts by Proteomic Characterization of the Target and Mechanism.

Huangqi Sanxian decoction (HQSXD) is routinely used for the treatment of osteoporosis in the Chinese traditional healthcare system. However, the targets and mechanism underlying the effect of HQSXD on osteoporosis have not been documented. In the present study, seropharmacology and proteomic approaches (two-dimensional gel electrophoresis combined with mass spectrometry) were used to investigate the effects and possible target proteins of HQSXD on osteoblast. We found that HQSXD-treated rat serum significantly enhanced osteoblast proliferation, differentiation, and mineralization. In HQSXD-S-treated osteoblasts, there were increases in the expression of N-formyl peptide receptor 2 and heparan sulfate (glucosamine) 3-O-sulfotransferase 3A1 and reduction in the expression of alpha-spectrin, prohibitin, and transcription elongation factor B (SIII), polypeptide 1. The identified proteins are associated with cell proliferation, differentiation, signal transcription, and cell growth. These findings might provide valuable insights into the mechanism of antiosteoporotic effect affected by HQSXD treatment in osteoblasts.

Reduction of prohibitin expression contributes to left ventricular hypertrophy via enhancement of mitochondrial reactive oxygen species formation in spontaneous hypertensive rats

Left ventricular hypertrophy (LVH) in hypertension is characterized by thickening of myocardium and decrease in heart chamber volume in response to mechanical or pathological stress, but the underlying molecular mechanisms remain to be defined. In this work, we investigate whether mitochondrial prohibitin (PHB) was involved in the progression of LVH in spontaneous hypertensive rats (SHR). First, it was found that mitochondrial dysfunction occurred in left ventricles of SHR. Through analysis using quantitative reverse transcription polymerase chain reaction and Western blotting, it was found that PHB mRNA and mitochondrial PHB levels in left ventricles of SHR were significantly lower than that in Wistar–Kyoto rats. Furthermore, PHB mRNA levels were negatively correlated to left ventricles weight-to-body weight ratio in SHR. Knockdown of PHB led to increased formation of mitochondrial reactive oxygen species (ROS) and reduced activities of complex I, mitochondrial adenosine triphosphate generation and mitochondrial membrane potential in cultured cardiomyocytes. Knockdown of PHB contributed to the cardiomyocyte hypertrophy, which could be attenuated by treatment with the Tempol. Angiotensin II (AngII) was increased in plasma and left ventricles of SHR. Incubation with AngII reduced mitochondrial PHB expression in cardiomyocytes, which was reversed when pretreated with losartan. In conclusion, reduction of PHB expression in left ventricles in SHR contributed to LVH, at least in part, through promoting mitochondrial ROS formation.

Gene expression changes of regucalcin and prohibitin in cirrhotic rat liver and the related effects of compound glutathione inosine injection intervention

To study expression of regucalcin (RGN) and prohibitin (PHB) genes in cirrhotic rat liver and to investigate the related effects of compound glutathione inosine injection (CGII) intervention. Forty male Wistar rats were randomly divided into a control group (n=12) and a model group (n=28).The model was established by injecting sterile porcine serum (0.5 mL) into the rat abdominal cavity, twice weekly for 8 consecutive weeks; the control group rats were treated with physiological saline injection (0.5 mL) into the abdominal cavity with the same frequency and time span. During the modeling period, four rats from the model group were randomly selected at different time points to examine changes in liver pathology. Upon pathology confirmation of liver cirrhosis, the porcine serum injection was terminated. The remaining 24 rats in the model group were randomly divided into a fibrosis group and a CGII treatment group.The CGII group received CGII (intramuscular injection of 0.018 mL 100g-1 body weight) once a day for 6 continuous weeks; the fibrosis rats were treated with the same dosage of physiological saline with the same frequency and time span.Liver tissue morphology was examined by both hematoxylin-eosin and Masson's staining. RGN and PHB expression at the mRNA and protein levels in liver tissues were detected by real time RT-PCR and immunohistochemical staining, respectively. Both the mRNA and protein expression levels of RGN and PHB were significantly lower in the liver tissues of the fibrosis group than in the control group.CGII intervention led to significant alleviation of the liver fibrosis severity; moreover, the mRNA and protein expression levels of RGN and PHB were significantly higher than those in the fibrosis group. Down-regulation of regucalcin and prohibitin gene expression might contribute to the pathogenesis of liver cirrhosis.

Knockdown of prohibitin expression promotes glucose metabolism in eutopic endometrial stromal cells from women with endometriosis

In this in-vitro study, the effect of prohibitin (PHB) on glucose metabolism in eutopic endometrial stromal cells from women with endometriosis was investigated. Endometrial stromal cells were isolated from endometrium in women with endometriosis, in women without endometriosis, or from endometrioma tissues. Glucose metabolic phenotype of stromal cells were examined in vitro. Quantitative polymerase chain reaction was used to measure the mRNA expression of glycolysis-related genes. Glucose consumption and lactate production were examined after knockdown of PHB expression in women with endometriosis with siRNA. In endometrioma tissue, significantly increased glucose consumption, lactate production and aberrant expression of glycolysis-related enzymes were found in women with endometriosis compared with women who do not have endometriosis (P < 0.05 versus P < 0.001). In women with endometriosis, PHB mRNA and protein were under-expressed in endometrioma tissue; in women without endometriosis, PHB mRNA and protein were over-expressed. Knockdown of PHB expression in women with endometriosis increased glucose consumption, although it had no effect on lactate production. This study suggests that aberrant expression of glycolysis-related enzymes in endometrioma tissue is associated with enhanced glycolytic metabolism. The malignant-like feature may be partially caused by low-expression of PHB gene in endometriotic stromal cells.

Effect of all-trans retinoic acid treatment on prohibitin and renin-angiotensin-aldosterone system expression in hypoxia-induced renal tubular epithelial cell injury.

All-trans retinoic acid (ATRA) exerts various effects on physiological processes such as cell growth, differentiation, apoptosis and inflammation. Prohibitins (PHB), including prohibitin 1 (PHB1) and prohibitin 2 (PHB2), are evolutionary conserved and pleiotropic proteins implicated in various cellular functions, including proliferation, tumor suppression, apoptosis, transcription, and mitochondrial protein folding. The renin-angiotensin-aldosterone system plays a pivotal role in the regulation of blood pressure and volume homeostasis. All these factors and systems have been implicated in renal interstitial fibrosis. Therefore, the objective of this study was to investigate the effect of ATRA treatment on the renin-angiotensin-aldosterone system and expression of prohibitins to further understand its role in the processes leading to renal interstitial fibrosis. The hypoxic and oxidative stress conditions in obstructive renal disease were simulated in a hypoxia/reoxygenation model with renal tubular epithelial cells (RTEC) as a model system. Subsequently, the effect of ATRA on mRNA and protein expression levels was determined and correlations were established between factors involved in the renin-angiotensin-aldosterone system, the prohibitins, cellular redox status, renal interstitial fibrosis and ATRA treatment. Correlation analysis showed that both PHB1 and PHB2 protein levels were negatively correlated with angiotensin I, ACE1, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA (PHB1: r = -0.792, -0.834, -0.805, -0.795, -0.778, -0.798, -0.751, -0.682; PHB2: r = -0.872, -0.799, -0.838, -0.773, -0.769, -0.841, -0.794, -0.826; each p < 0.05), but positively correlated with ACE2, SOD, and GSH (PHB1: r = 0.796, 0.879, 0.824; PHB2: r = 0.785, 0.914, 0.849; each p < 0.05). ACE1 was positively correlated with angiotensin I, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA, and negatively correlated with ACE2, SOD, and GSH (each p < 0.05). ACE2 was negatively correlated with ACE1, angiotensin I, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA, and positively correlated with SOD and GSH (each p < 0.05). The results suggest that ATRA acts as a positive regulator of PHB1, PHB2 and ACE2, and as a negative regulator of ACE1, angiotensin I, and angiotensin II in a RTEC model system under hypoxia/reoxygenation conditions.

Prohibitin 1 modulates mitochondrial function of Stat3

Mitochondrial dysfunction in intestinal epithelial cells (IEC) is thought to precede the onset of inflammatory bowel diseases (IBD). Expression of Prohibitin 1 (PHB), a mitochondrial protein required for optimal electron transport chain (ETC) activity, is decreased in mucosal biopsies during active and inactive IBD. In addition to its activities as a transcription factor, Signal Transducer and Activator of Transcription 3 (Stat3) resides in the mitochondria of cells where phosphorylation at S727 is required for optimal ETC activity and protects against stress-induced mitochondrial dysfunction. Here, we show that PHB overexpression protects against mitochondrial stress and apoptosis of cultured IECs induced by TNFα, which is a pro-inflammatory cytokine involved in IBD pathogenesis. Expression of pS727-Stat3 dominant negative eliminates protection by PHB against TNFα-induced mitochondrial stress and apoptosis. PHB interacts with pS727-Stat3 in the mitochondria of cultured IECs and in colonic epithelium from wild-type mice. Our data suggest a protective role of PHB that is dependent on pS727-Stat3 to prevent mitochondrial dysfunction in IECs. Reduced levels of PHB during IBD may be an underlying factor promoting mitochondrial dysfunction of the intestinal epithelium.

Prohibitin expression deregulation in gastric cancer is associated with the 3' untranslated region 1630 C>T polymorphism and copy number variation.

PHB is a reported oncogene and tumor suppressor in gastric cancer. Here, we evaluated whether the PHB copy number and the rs6917 polymorphism affect its expression in gastric cancer. Down-regulation and up-regulation of PHB were observed in the evaluated tumors. Reduced expression was associated with tumor dedifferentiation and cancer initiation. The T allele of the rs6917 polymorphism was associated with reduced PHB mRNA levels. Moreover, the up-regulation of PHB appeared to be regulated by the gain of additional gene copies. Thus, PHB copy number variation and differential expression of the rs6917 polymorphism may play a role in PHB transcriptional regulation.

Prohibitin viral gene transfer protects hippocampal CA1 neurons from ischemia and ameliorates postischemic hippocampal dysfunction.

Prohibitin is a multi-functional protein involved in numerous cellular activities. Prohibitin overexpression protects neurons from injury in vitro, but it is unclear whether prohibitin can protect selectively vulnerable hippocampal CA1 neurons in a clinically relevant injury model in vivo and, if so, whether the salvaged neurons remain functional. A mouse model of transient forebrain ischemia that mimics the brain damage produced by cardiac arrest in humans was used to test whether prohibitin expression protects CA1 neurons from injury. Prohibitin-expressing viral vector was microinjected in mouse hippocampus to upregulate prohibitin. Prohibitin overexpression protected CA1 neurons from transient forebrain ischemia. The protection was associated with dampened postischemic reactive oxygen species generation, reduced mitochondrial cytochrome c release, and decreased caspase-3 activation. Importantly, the improvement in CA1 neuronal viability translated into an improvement in hippocampal function: prohibitin expression ameliorated the spatial memory deficit induced by ischemia, assessed by the Y-maze test, and restored postischemic synaptic plasticity assessed by long-term potentiation, indicating that the neurons spared form ischemic damage were functionally competent. These data demonstrate that prohibitin overexpression protects highly vulnerable CA1 neurons from ischemic injury in vivo and suggest that the effect is mediated by reduction of postischemic reactive oxygen species generation and preservation of mitochondrial outer membrane integrity that prevents activation of apoptosis. Measures to enhance prohibitin expression could have translational value in ischemic brain injury and, possibly, other forms of brain injury associated with mitochondrial dysfunction.