All-trans retinoic acid treatment is associated with prohibitin expression in renal interstitial fibrosis rats

Vitamin A and retinoid signaling in the kidneys

Vitamin A (VA, retinol) and its metabolites (commonly called retinoids) are required for the proper development of the kidney during embryogenesis, but retinoids also play key roles in the function and repair of the kidney in adults. Kidneys filter 180-200 liters of blood per day and each kidney contains approximately 1 million nephrons, which are often referred to as the 'functional units' of the kidney. Each nephron consists of a glomerulus and a series of tubules (proximal tubule, loop of Henle, distal tubule, and collecting duct) surrounded by a network of capillaries. VA is stored in the liver and converted to active metabolites, most notably retinoic acid (RA), which acts as an agonist for the retinoic acid receptors ((RARs α, β, and γ) to regulate gene transcription. In this review we discuss some of the actions of retinoids in the kidney after injury. For example, in an ischemia-reperfusion model in mice, injury-associated loss of proximal tubule (PT) differentiation markers occurs, followed by re-expression of these differentiation markers during PT repair. Notably, healthy proximal tubules express ALDH1a2, the enzyme that metabolizes retinaldehyde to RA, but transiently lose ALDH1a2 expression after injury, while nearby myofibroblasts transiently acquire RA-producing capabilities after injury. These results indicate that RA is important for renal tubular injury repair and that compensatory mechanisms exist for the generation of endogenous RA by other cell types upon proximal tubule injury. ALDH1a2 levels also increase in podocytes, epithelial cells of the glomeruli, after injury, and RA promotes podocyte differentiation. We also review the ability of exogenous, pharmacological doses of RA and receptor selective retinoids to treat numerous kidney diseases, including kidney cancer and diabetic kidney disease, and the emerging genetic evidence for the importance of retinoids and their receptors in maintaining or restoring kidney function after injury. In general, RA has a protective effect on the kidney after various types of injuries (eg. ischemia, cytotoxic actions of chemicals, hyperglycemia related to diabetes). As more research into the actions of each of the three RARs in the kidney is carried out, a greater understanding of the actions of vitamin A is likely to lead to new insights into the pathology of kidney disorders and the development of new therapies for kidney diseases.

LPLUNC1 reduces glycolysis in nasopharyngeal carcinoma cells through the PHB1-p53/c-Myc axis

Cancer cells prefer glycolysis to support their proliferation. Our previous studies have shown that the long palate, lung, and nasal epithelial cell clone 1 (LPLUNC1) can upregulate prohibitin 1 (PHB1) expression to inhibit the proliferation of nasopharyngeal carcinoma (NPC) cells. Given that PHB1 is an important regulator of cell energy metabolism, we explored whether and how LPLUNC1 regulated glucose glycolysis in NPC cells. LPLUNC1 or PHB1 overexpression decreased glycolysis and increased oxidative phosphorylation (OXPHOS)-related protein expression in NPC cells, promoting phosphorylated PHB1 nuclear translocation through 14-3-3σ. LPLUNC1 overexpression also increased p53 but decreased c-Myc expression in NPC cells, which were crucial for the decrease in glycolysis and increase in OXPHOS-related protein expression induced by LPLUNC1 overexpression. Finally, we found that treatment with all-trans retinoic acid (ATRA) reduced the viability and clonogenicity of NPC cells, decreased glycolysis, and increased OXPHOS-related protein expression by enhancing LPLUNC1 expression in NPC cells. Therefore, the LPLUNC1-PHB1-p53/c-Myc axis decreased glycolysis in NPC cells, and ATRA upregulated LPLUNC1 expression, ATRA maybe a promising drug for the treatment of NPC.

Effects of Treadmill Exercise on Mitochondrial DNA Damage and Cardiomyocyte Telomerase Activity in Aging Model Rats Based on Classical Apoptosis Signaling Pathway

In order to explore the effect of treadmill exercise on mitochondrial DNA damage and myocardial telomerase activity in aging model rats based on the classical apoptosis signaling pathway, a total of 36 clean-grade male SD rats are selected. After modeling, the rats are randomly divided into groups, namely, control and 3 times/w and 6 times/w exercise rats, with 12 rats in each group. After the rats of each group are modeled, the myocardial tissue and cells are collected, the apoptosis of myocardial cells is detected by TUNEL method, and the protein expressions of Bax and Bcl-2 in myocardial tissue are detected by western blotting. The mtDNA content of the control rats is the highest, which is significantly higher than that of the exercise group ( $P<0.05$ ); the expression of mtDNA content in the heart of the rats exercising 3 times/w is significantly higher than that of the rats exercising 6 times/w ( $P<0.05$ ); cardiomyocyte apoptosis AI value, Bcl-2, and Bax expressions of the control rats is the highest and significantly higher than those in the exercise group ( $P<0.05$ ); Bcl-2/Bax in the control rats is the lowest and is significantly lower than that in the exercise group ( $P<0.05$ ). The AI value, Bcl-2, and Bax expression of myocardial cell apoptosis in 3 times/w exercise rats are significantly higher than those in 6 times/w exercise rats ( $P<0.05$ ); Bcl-2/Bax of 3 times/w exercise rats is significantly lower than that in 6 times/w exercise rats ( $P<0.05$ ); by observing the rats that completed treadmill exercise, Akt2 protein of 3 times/w exercise rats and 6 times/w exercise rats is observed and analyzed. Compared with the control rats, the expressions of the two proteins are increased in 3 times/w exercise rats and 6 times/w exercise rats, and the upregulation in 6 times/w exercise rats is significantly increased and higher than that in 3 times/w exercise rats ( $P<0.05$ ). For aging rats, treadmill exercise can reduce the body Bcl-2 and Bax values, improve the mitochondrial DNA damage and myocardial cell telomerase activity in aging model rats, and slow down the aging process.

A synthetic retinoic acid receptor agonist Am80 ameliorates renal fibrosis via inducing the production of alpha-1-acid glycoprotein

Renal fibrosis is a major factor in the progression of chronic kidney disease and the final common pathway of kidney injury. Therefore, the effective therapies against renal fibrosis are urgently needed. The objective of this study was to investigate the effect of Am80, a synthetic retinoic acid receptor (RAR) agonist, in the treatment of renal interstitial fibrosis using unilateral ureteral obstruction (UUO) mice. The findings indicate that Am80 treatment suppressed renal fibrosis and inflammation to the same degree as the naturally-occuring retinoic acid, all-trans retinoic acid (atRA). But the adverse effect of body weight loss in Am80-treated mice was lower compared to the atRA treatment. The hepatic mRNA levels of alpha-1-acid glycoprotein (AGP), a downstream molecule of RAR agonist, was increased following administration of Am80 to healthy mice. In addition, increased AGP mRNA expression was also observed in HepG2 cells and THP-1-derived macrophages that had been treated with Am80. AGP-knockout mice exacerbated renal fibrosis, inflammation and macrophage infiltration in UUO mice, indicating endogenous AGP played an anti-fibrotic and anti-inflammatory role during the development of renal fibrosis. We also found that no anti-fibrotic effect of Am80 was observed in UUO-treated AGP-knockout mice whereas atRA treatment tended to show a partial anti-fibrotic effect. These collective findings suggest that Am80 protects against renal fibrosis via being involved in AGP function.

All-trans retinoic acid suppresses bone morphogenetic protein 4 in mouse diabetic nephropathy through a unique retinoic acid response element

Diabetic nephropathy (DN) causes mesangial matrix expansion, which results in glomerulosclerosis and renal failure. Collagen IV (COL4) is a major component of the mesangial matrix that is positively regulated by bone morphogenetic protein 4 (BMP4)/suppressor of mothers against decapentaplegic (Smad1) signaling. Because previous studies showed that retinoids treatment had a beneficial effect on kidney disease, we investigated the therapeutic potential of retinoids in DN, focusing especially on the regulatory mechanism of BMP4. Diabetes was induced with streptozotocin in 12-wk-old male Crl:CD1(ICR) mice, and, 1 mo later, we initiated intraperitoneal injection of all-trans retinoic acid (ATRA) three times weekly. Glomerular matrix expansion, which was associated with increased BMP4, phosphorylated Smad1, and COL4 expression, worsened in diabetic mice at 24 wk of age. ATRA administration alleviated DN and downregulated BMP4, phosopho-Smad1, and COL4. In cultured mouse mesangial cells, treatment with ATRA or a retinoic acid receptor-α (RARα) agonist significantly decreased BMP4 and COL4 expression. Genomic analysis suggested two putative retinoic acid response elements (RAREs) for the mouse Bmp4 gene. Chromatin immunoprecipitation analysis and reporter assays indicated a putative RARE of the Bmp4 gene, located 11,488-11,501 bp upstream of exon 1A and bound to RARα and retinoid X receptor (RXR), which suppressed BMP4 expression after ATRA addition. ATRA suppressed BMP4 via binding of a RARα/RXR heterodimer to a unique RARE, alleviating glomerular matrix expansion in diabetic mice. These findings provide a novel regulatory mechanism for treatment of DN.

Retinoic Acid Ameliorates Pancreatic Fibrosis and Inhibits the Activation of Pancreatic Stellate Cells in Mice with Experimental Chronic Pancreatitis via Suppressing the Wnt/β-Catenin Signaling Pathway

Pancreatic fibrosis, a prominent feature of chronic pancreatitis (CP), induces persistent and permanent damage in the pancreas. Pancreatic stellate cells (PSCs) provide a major source of extracellular matrix (ECM) deposition during pancreatic injury, and persistent activation of PSCs plays a vital role in the progression of pancreatic fibrosis. Retinoic acid (RA), a retinoid, has a broad range of biological functions, including regulation of cell differentiation and proliferation, attenuating progressive fibrosis of multiple organs. In the present study, we investigated the effects of RA on fibrosis in experimental CP and cultured PSCs. CP was induced in mice by repetitive cerulein injection in vivo, and mouse PSCs were isolated and activated in vitro. Suppression of pancreatic fibrosis upon administration of RA was confirmed based on reduction of histological damage, α-smooth muscle actin (α-SMA) expression and mRNA levels of β-catenin, platelet-derived growth factor (PDGF)-Rβ transforming growth factor (TGF)-βRII and collagen 1α1 in vivo. Wnt 2 and β-catenin protein levels were markedly down-regulated, while Axin 2 expression level was up-regulated in the presence of RA, both in vivo and in vitro. Nuclear translation of β-catenin was significantly decreased following RA treatment, compared with cerulein-induced CP in mice and activated PSCs. Furthermore, RA induced significant PSC apoptosis, inhibited proliferation, suppressed TCF/LEF-dependent transcriptional activity and ECM production of PSC via down-regulation of TGFβRII, PDGFRβ and collagen 1α1 in vitro. These results indicate a critical role of the Wnt/β-catenin signaling pathway in RA-induced effects on CP and PSC regulation and support the potential of RA as a suppressor of pancreatic fibrosis in mice.

Potential signal pathway between all-trans retinoic acid and LMX1B in hypoxia-induced renal tubular epithelial cell injury

All-trans retinoic acid (ATRA), an active metabolite of vitamin A, exerts various effects on physiological processes such as cell growth, differentiation, apoptosis and inflammation. LMX1B, a developmental LIM-homeodomain transcription factor, is widely expressed in vertebrate embryos, and it takes part in the development of diverse structures such as limbs, kidneys, eyes, brains, etc. Renal tubular epithelial cell culture was performed, and mRNA and protein expression of some factors were detected. We recently demonstrated that ATRA up-regulated the LMX1B, and down-regulated the transforming growth factor-β1, collagen IV and fibronectin in a hypoxia/reoxygenation (H-R) injury system in renal tubular epithelial cells (RTEC). In conclusion, ATRA acts as a positive regulator of LMX1B in H-R RTEC.

A urine metabonomics study of chronic renal failure and intervention effects of total aglycone extracts of Scutellaria baicalensis in 5/6 nephrectomy rats

This study was to clarify the pathogenesis of CRF and action mechanism of TAES.

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

BACKGROUND AND OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

LIM homeobox transcription factor 1B expression affects renal interstitial fibrosis and apoptosis in unilateral ureteral obstructed rats

LIM homeobox transcription factor 1B (LMX1B) is a transcription factor of the LIM homeodomain type and has been implicated in the development of diverse structures such as limbs, kidneys, eyes, and the brain. Furthermore, LMX1B has been implicated in nail-patella syndrome, which is predominantly characterized by malformation of limbs and nails, and in 30% of patients, nephropathy, including renal fibrosis, is observed. Since no reports were available that studied the link between LMX1B expression and renal interstitial fibrosis, we explored if LMX1B affects typical markers of fibrosis, e.g., extracellular matrix components, profibrotic factors, and apoptosis as the final detrimental consequence. We recently showed that LMX1B acts as a negative regulator of transforming growth factor-βl, collagen type III, fibronectin, cleaved caspase-3, and the cell apoptosis rate in a renal tubular epithelial cell system under hypoxic conditions. Here, we confirmed these results in unilateral ureteral obstructed rats. Furthermore, LMX1B was distinctly expressed throughout the glomerulus and tubule lining, including epithelial cells. Knockdown of LMX1B aggravated the expression of fibrosis markers, oxidative stress, and apoptosis compared with the already increased levels due to unilateral ureteral obstruction, whereas overexpression attenuated these effects. In conclusion, reduced LMX1B levels clearly represent a risk factor for renal fibrosis, whereas overexpression affords some level of protection. In general, LMX1B may be considered to be a negative regulator of the fibrosis index, transforming growth factor-βl, collagen type III, fibronectin, cleaved caspase-3, cell apoptosis, ROS, and malondialdehyde ( r = −0.756, −0.698, −0.921, −0.923, −0.843, −0.794, −0.883, and −0.825, all P < 0.01).

Role of high mobility group box 1 and its signaling pathways in renal diseases

The high mobility group box 1 (HMGB1) protein, a member of the high mobility group nuclear protein family and an endogenous ligand for TLR2/4 and RAGE (receptor for advanced glycation end products), is one of the most evolutionarily conserved proteins and it has recently emerged as an extracellular signaling factor with key roles in cell differentiation, proliferation and disease pathogenesis. The present data indicate that HMGB1 is one of most important proinflammatory cytokines, and plays an important role in renal diseases. The literatures were searched extensively and this review was performed to sum up the role of HMGB1 in renal diseases.

Association of prohibitin-1 and 2 with oxidative stress in rats with renal interstitial fibrosis

Prohibitins PHB1 and PHB2 are evolutionary conserved and pleiotropic proteins, which have been shown to be important factors in various cellular functions, including proliferation, tumour suppression, apoptosis, transcription, and mitochondrial protein folding. Recently, we demonstrated that down-regulation promoted renal interstitial fibrosis (RIF) in ureteral obstructed rats. Furthermore, the hypoxic conditions and oxidative stress have been implicated in obstruction-mediated renal disease. This study was performed to explore the association of PHBs with oxidative stress in a rat model of RIF. PHBs, the pro-fibrotic transforming growth factor-β1 (TGF-β1), and the extracellular matrix proteins collagen-IV (Col-IV) and fibronectin (FN) were evaluated, as were markers of oxidative stress [total reactive oxygen species (ROS), malondialdehyde (MDA)] and antioxidative capacity (superoxide dismutase, glutathione), and apoptosis. Our results showed a progressive increase in oxidative stress and concomitant decrease in antioxidants over a period of 4 weeks ureteral obstruction. Concomitantly, profibrotic components increased and PHB expression decreased. Overall, both PHBs were negatively correlated with the extent of observed fibrosis, TGF-β1, Col-IV, FN, ROS, MDA, and apoptosis.

Effect of Ginkgo biloba extract on the expressions of Cox-2 and GST-Pi in rats with hepatocellular carcinoma risk

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common and aggressive cancers worldwide, and the pathogenesis is complicated at present. There iare few effective therapeutic measures, and novel therapeutic strategies are urgently required to improve clinical outcome. Ginkgo biloba extract (EGb) is reported to have an anti-cancer activity.

OBJECTIVES

To explore the effect of EGb on expressions of cyclooxygenase-2 (Cox-2) and glutathione S-transferase Pi (GST-Pi) in the pathogenesis of HCC.

METHODS

120 Wistar rats were divided into three groups at random: normal control group (control group), HCC risk group without treatment (HCC risk group), HCC risk group treated with EGb (EGb group); n=40, respectively. The HCC risk in rat was induced by aflatoxin B1 injection. At the end of 13-week, 33-week, 53-week and 73-week, 10 rats in each group were killed and the relevant samples were collected.

RESULTS

The mRNA and protein expressions of Cox-2 and GST-Pi were measured by real-time reverse transcription polymerase chain reaction, immunohistochemical analysis and western-blot. When compared with those in the control group in 73-week, the mRNA and protein expressions of GST-Pi in EGb group were weaker than those in HCC risk group in 73-week. However, the mRNA and protein expressions of Cox-2 in HCC risk group were increased than that of control group, and there was no statistical difference for mRNA and protein expressions of Cox-2 between HCC risk group and EGb group.

CONCLUSION

EGb can regulate the expression of GST-Pi, but it does not seem to have an effect on Cox-2 expression in the liver of HCC risk rats.

The potential signal pathway between PAX2 and CD2AP in the renal interstitial fibrosis disease

Paired box gene 2 (PAX2) can regulate tissue development and cellular differentiation, and it is associated with renal diseases. CD2-associated protein (CD2AP) is an adaptor protein involving in a variety of physiological and disease processes. Renal interstitial fibrosis (RIF) is a hallmark of common progressive chronic diseases which lead to renal failure. This study was performed to investigate whether there was a potential signal pathway between PAX2 and CD2AP in RIF rats induced by unilateral ureteral obstruction (UUO). Eighty Wistar male rats were divided into two groups randomly: sham operation group (SHO) and model group subjected to UUO (GU), n = 40. The model was established by left ureteral ligation. Renal tissues were collected at 14 d and 28 d after surgery. RIF index, cell apoptosis index, protein expression of PAX2, CD2AP, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV), fibronectin (FN) in renal interstitium and renal tissue, and mRNA expression of PAX2, CD2AP, and TGF-β1 in renal tissue were detected. Compared with that in the SHO group, the PAX2 and CD2AP expressions (mRNA and protein) were significantly increased (p < 0.01). Protein expressions of TGF-β1, Col-IV, and FN, and RIF index or cell apoptosis index in the GU group were markedly elevated than those in the SHO group (all p < 0.01). PAX2 or CD2AP was positively correlated with TGF-β1, Col-IV, and FN, and RIF index or cell apoptosis index (all p < 0.05). Furthermore, PAX2 was positively correlated with CD2AP (p < 0.05). In conclusion, the expression of PAX2 or CD2AP was increased in RIF rats, and PAX2 was positively correlated with CD2AP. There might be a potential signaling pathway between PAX2 and CD2AP in RIF disease. Further research is needed to determine the association in RIF disease.

Hypoxia-induced collagen synthesis of human lung fibroblasts by activating the angiotensin system

The exact molecular mechanism that mediates hypoxia-induced pulmonary fibrosis needs to be further clarified. The aim of this study was to explore the effect and underlying mechanism of angiotensin II (Ang II) on collagen synthesis in hypoxic human lung fibroblast (HLF) cells. The HLF-1 cell line was used for in vitro studies. Angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) expression levels in human lung fibroblasts were analysed using real-time polymerase chain reaction (RT-PCR) after hypoxic treatment. Additionally, the collagen type I (Col-I), AT1R and nuclear factor κappaB (NF-κB) protein expression levels were detected using Western blot analysis, and NF-κB nuclear translocation was measured using immunofluorescence localization analysis. Ang II levels in HLF-1 cells were measured with an enzyme-linked immunosorbent assay (ELISA). We found that hypoxia increased Col-I mRNA and protein expression in HLF-1 cells, and this effect could be inhibited by an AT1R or AT2R inhibitor. The levels of NF-κB, RAS components and Ang II production in HLF-1 cells were significantly increased after the hypoxia exposure. Hypoxia or Ang II increased NF-κB-p50 protein expression in HLF-1 cells, and the special effect could be inhibited by telmisartan (TST), an AT1R inhibitor, and partially inhibited by PD123319, an AT2R inhibitor. Importantly, hypoxia-induced NF-κB nuclear translocation could be nearly completely inhibited by an AT1R or AT2R inhibitor. Furthermore pyrrolidine dithiocarbamate (PDTC), a NF-κB blocker, abolished the expression of hypoxia-induced AT1R and Col-I in HLF-1 cells. Our results indicate that Ang II-mediated NF-κB signalling via ATR is involved in hypoxia-induced collagen synthesis in human lung fibroblasts.

Prohibitin attenuates oxidative stress and extracellular matrix accumulation in renal interstitial fibrosis disease

Prohibitin is an evolutionary conserved and pleiotropic protein that has been implicated in various cellular functions, including proliferation, tumour suppression, apoptosis, transcription, and mitochondrial protein folding. Both prohibitin over- and under-expression have been implicated in various diseases and cell types. We recently demonstrated that prohibitin down-regulation results in increased renal interstitial fibrosis (RIF). Here we investigated the role of oxidative stress and prohibitin expression in RIF in unilateral ureteral obstructed rats. Lentivirus-based delivery vectors were used to knockdown or over-express prohibitin. Our results show that increased prohibitin expression was negatively correlated with the RIF index, reactive oxygen species, malon dialdehyde, transforming growth factor β1, collagen IV, fibronectin, and cell apoptosis index. In conclusion, we postulate that prohibitin acts as a positive regulator of mechanisms that counteract oxidative stress and extracellular matrix accumulation and therefore has an antioxidative effect.

IL-10 treatment is associated with prohibitin expression in the Crohn's disease intestinal fibrosis mouse model

Prohibitin, which can inhibit oxidative stress and mitochondrial dysfunction, has been shown to have significant anti-inflammatory activities. Here, we investigate the effects of altering prohibitin levels in affected tissues in the interleukin-10 knockout (IL-10KO) mouse model with intestinal fibrosis. The aim of this study is to investigate the effects of IL-10 on prohibitin and the role of prohibitin in intestinal fibrosis of murine colitis. After the mice were treated with IL-10, prohibitin expression and localization were evaluated in IL-10KO and wild-type (WT, 129/SvEv) mice. The colon tissue was then investigated and the potential pathogenic molecular mechanisms were further studied. Fluorescence-based quantitative polymerase chain reaction (FQ-PCR) and immunohistochemistry assays revealed a significant upregulation of prohibitin with IL-10 treatment. Furthermore, IL-10 decreases inflammatory cytokines and TGF-β1 in the IL-10KO model of Crohn's disease and demonstrates a promising trend in decreasing tissue fibrosis. In conclusion, we hypothesize that IL-10 treatment is associated with increased prohibitin and would decrease inflammation and fibrosis in an animal model of Crohn's disease. Interestingly, prohibitin may be a potential target for intestinal fibrosis associated with inflammatory bowel disease (IBD).

Signaling pathways of prohibitin and its role in diseases

Prohibitin (PHB), appearing to be a negative regulator of cell proliferation and to be a tumor suppressor, has been connected to diverse cellular functions including cell cycle control, senescence, apoptosis and the regulation of mitochondrial activities. It is a growth regulatory gene that has pleiotropic functions in the nucleus, mitochondria and cytoplasmic compartments. However, in different tissues/cells, the expression of PHB was different, such as that it was increased in most of the cancers, but its expression was reduced in kidney diseases. Signaling pathways might be very important in the pathogenesis of diseases. This review was performed to provide a relatively complete signaling pathways flowchart for PHB to the investigators who were interested in the roles of PHB in the pathogenesis of diseases. Here, we review the signal transduction pathways of PHB and its role in the pathogenesis of diseases.

The controversial role of retinoic acid in fibrotic diseases: analysis of involved signaling pathways

Fibrotic diseases, such as liver, pulmonary and renal fibrosis, are common end-stage conditions and represent a major global health problem. Furthermore, effective therapeutic measures are presently unavailable. Extracellular matrix accumulation is the most prominent characteristic in the pathogenesis of fibrotic disease. Retinoic acid, including all-trans retinoic acid, 9-cis and 13-cis retinoic acid, play important roles in various physiological processes, such as in embryonic development, reproduction, vision, cell growth, differentiation, apoptosis and inflammation. Present studies report that retinoic acid treatment may affect various processes involved in the onset and progression of fibrotic disease. However, the therapeutic effects of retinoic acid in such diseases remain controversial. Several reports indicate that retinoic acid positively affects the progression of fibrosis and alleviates the accumulation of the extracellular matrix, whereas other studies report the opposite; that retinoic acid exacerbates fibrosis and induces extracellular matrix accumulation. Signaling pathways might be an important influencing factor and differences in signaling events might be responsible for the contradictory role of retinoic acid in fibrotic diseases. Since there was no review available that investigated the role of retinoic acid and the signaling pathways involved, we retrospectively studied the literature and provide a comprehensive analysis of retinoic acid’s role in fibrotic diseases, and provide an overview of the signal transduction pathways involved in its pathogenesis.

Association of all-trans retinoic acid treatment with the renin-angiotensin aldosterone system expression in glomerulosclerosis rats

BACKGROUND AND OBJECTIVE

All-trans retinoic acid (ATRA), a promising therapeutic agent, has been confirmed in animal experiments as playing a protective role against renal diseases. The renin-angiotensin aldosterone system (RAAS) plays a key role in the pathogenesis of renal diseases, and RAAS inhibitors can prevent the progression of kidney diseases. In our previous study, we found that ATRA could play a protective role against glomerulosclerosis (GS) lesions in rats, and its effect was similar to RAAS inhibitors. However, whether ATRA treatment was associated with RAAS expression was not clear.

METHODS

Six-week-old male Wistar rats were divided into three groups: sham operation group (SHO), glomerulosclerosis model group without treatment (GS) and GS model group treated with ATRA (GA). At the end of 13 weeks, the relevant samples were collected and analyzed.

RESULTS

The mRNA and protein expression of angiotensin-converting enzyme 1 (ACE1) in the GS group was notably higher when compared with the SHO group. However, mRNA and protein expression of ACE1 in the ATRA treatment group was markedly down-regulated when compared with the GS group. Angiotensin-converting enzyme 2 (ACE2) expression (mRNA or protein) in the GS group was reduced compared with that in the SHO group, and ATRA markedly increased the mRNA and protein expression of ACE2 compared with the GS group. The levels of protein expression of angiotensin I and angiotensin II were significantly up-regulated in the GS group compared with those in the SHO group, and ATRA reduced their expression in the GA group when compared with the GS group.

CONCLUSION

ATRA is associated with RAAS expression in GS rats, but its detailed mechanism needs to be elucidated by further research.

Association of retinoic acid receptors with extracellular matrix accumulation in rats with renal interstitial fibrosis disease

The nuclear retinoic acid receptors (RARs) function as ligand-dependent transcriptional regulators and include three subtypes (RARα, RARβ and RARγ), which control the expression of specific gene subsets subsequent to ligand binding and to strictly controlled phosphorylation processes. Extracellular matrix (ECM) accumulation is the most important characteristic of renal interstitial fibrosis (RIF). This study was performed to investigate whether RARs were associated with ECM accumulation in the progression of RIF in rats. Eighty Wistar male rats were divided into a sham operation group (SHO) and a model group subjected to unilateral ureteral obstruction (GU) at random; n = 40, respectively. The RIF disease in GU group was established by left ureteral ligation. The renal tissues were collected at two weeks and four weeks after surgery. Protein expressions of RARα, RARβ, RARγ, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV) and fibronectin (FN) were detected using immunohistochemical analysis, and mRNA expressions of RARα, RARβ, RARγ and TGF-β1 in renal tissue were detected by real time reverse transcription polymerase chain reaction. RIF index in renal interstitium was also calculated. When compared with those in SHO group, expressions of RARα and RARβ (protein and mRNA) were markedly reduced in the GU group (each p < 0.01). There was no marked difference for the expression of RARγ (protein and mRNA) between the SHO group and the GU group. The expressions of TGF-β1, Col-IV, FN and the RIF index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of RARα/RARβ was negatively correlated with protein expression of TGF-β1, Col-IV or FN and the RIF index (all p < 0.01). In conclusion, the low expression of RARα/RARβ is associated with ECM accumulation in the progression of RIF in rats, suggesting that RARα/RARβ is a potentially therapeutic target for prevention of RIF.

Overexpressed C-type natriuretic peptide serves as an early compensatory response to counteract extracellular matrix remodeling in unilateral ureteral obstruction rats

Although the mechanism underlying C-type natriuretic peptide (CNP) beneficial effects is not entirely understood, modulating the expression of matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinases (TIMPs) may play an important role. The study presented herein was designed as a first demonstration of the regulative effects of CNP on MMPs/TIMPs expression in unilateral ureteral obstruction (UUO) rats. The continuous changes of CNP, MMP-2, MMP-9, TIMP-1, TIMP-2 and type IV collagen (Col-IV) expression were determined in the obstructed rat kidneys at 3 days, 1, 2, and 3 months post-UUO respectively. According to the real-time PCR analysis, CNP, MMP-2 and MMP-9 mRNA expression in the obstructed kidneys were significantly higher compared to every time corresponding SOR, and progressively decreased over time. In contrast, in the obstructed kidneys collected 2 and 3 months post-UUO, the higher TIMP-1 and TIMP-2 mRNA expression were observed in comparison to the corresponding SOR group. The above trends of CNP, MMP-2, MMP-9, TIMP-1, and TIMP-2 transcripts were confirmed by their protein expression based on immunohistochemistry and western blot, and finally contributed to the progressive elevated Col-IV expression in the obstructed kidneys throughout the entire study period. Overexpressed CNP may be an early compensatory response to counteract extracellular matrix remodeling in UUO rats.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.