Protein nitration promotes inducible nitric oxide synthase transcription mediated by NF-κB in high glucose-stimulated human lens epithelial cells

Molecular mechanisms of diabetic nephropathy: A narrative review

Diabetic nephropathy (DN) is the predominant secondary nephropathy resulting in global end-stage renal disease. It is attracting significant attention in both domestic and international research due to its widespread occurrence, fast advancement, and limited choices for prevention and treatment. The pathophysiology of this condition is intricate and involves multiple molecular and cellular pathways at various levels. This article provides a concise overview of the molecular processes involved in the development of DN. It discusses various factors, such as signaling pathways, cytokines, inflammatory responses, oxidative stress, cellular damage, autophagy, and epigenetics. The aim is to offer clinicians a valuable reference for DN's diagnosis, treatment, and intervention.

Epigenetic programing of cancer stemness by transcription factors-non-coding RNAs interactions

Cancer 'stemness' is fundamental to cancer existence. It defines the ability of cancer cells to indefinitely perpetuate as well as differentiate. Cancer stem cell populations within a growing tumor also help evade the inhibitory effects of chemo- as well as radiation-therapies, in addition to playing an important role in cancer metastases. NF-κB and STAT-3 are representative transcription factors (TFs) that have long been associated with cancer stemness, thus presenting as attractive targets for cancer therapy. The growing interest in non-coding RNAs (ncRNAs) in the recent years has provided further insight into the mechanisms by which TFs influence cancer stem cell characteristics. There is evidence for a direct regulation of TFs by ncRNAs, such as, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) as well as circular RNAs (circRNAs), and vice versa. Additionally, the TF-ncRNAs regulations are often indirect, involving ncRNA-target genes or the sponging of other ncRNA species by individual ncRNAs. The information is rapidly evolving and this review provides a comprehensive review of TF-ncRNAs interactions with implications on cancer stemness and in response to therapies. Such knowledge will help uncover the many levels of tight regulations that control cancer stemness, providing novel opportunities and targets for therapy in the process.

β-Hydroxybutyrate inhibits cardiac microvascular collagen 4 accumulation by attenuating oxidative stress in streptozotocin-induced diabetic rats and high glucose treated cells

Accumulation of collagen 4 (COL4) and thickened basement membrane are features of diabetic cardiac microvascular fibrosis that may be induced by oxidative stress. The ketone body β-hydroxybutyrate exhibits various cardiovascular protective effects, however its mechanism remains to be clarified. In the current study, the effects of β-hydroxybutyrate on cardiac microvascular fibrosis and COL4 accumulation were evaluated in streptozotocin-induced diabetic rats and in high glucose (HG) treated human cardiac microvascular endothelial cells (HCMECs). Generations of inducible nitric oxide synthase (iNOS) and copper-zinc superoxide dismutase (Cu/Zn-SOD), and the amount of nitrotyrosine (NT) were measured in vivo and in vitro. Ten weeks of β-hydroxybutyrate treatment (160, 200 and 240 mg/kg/d) attenuated cardiac microvascular fibrosis and inhibited cardiac COL4 generation and microvascular distribution in diabetic rats. Furthermore, β-hydroxybutyrate promoted cardiac Cu/Zn-SOD generation and reduced NT content, without reducing iNOS generation in diabetic rats. In HCMECs, stimulation with HG induced excess generation of COL4 via peroxynitrite. β-Hydroxybutyrate treatment (2, 4, 6 mM) attenuated HG-stimulated COL4 accumulation in a concentration-dependent manner. Similarly, 4 mM β-hydroxybutyrate promoted Cu/Zn-SOD generation and reduced NT content, without affecting excess iNOS generation in HG-stimulated HCMECs. In conclusion, this study showed that β-hydroxybutyrate promoted Cu/Zn-SOD generation, reduced peroxynitrite and inhibited cardiac microvascular COL4 accumulation in diabetes.

TRPM7 channels play a role in high glucose-induced endoplasmic reticulum stress and neuronal cell apoptosis

High-glucose (HG) levels and hyperglycemia associated with diabetes are known to cause neuronal damage. The detailed molecular mechanisms, however, remain to be elucidated. Here, we investigated the role of transient receptor potential melastatin 7 (TRPM7) channels in HG-mediated endoplasmic reticulum stress (ERS) and injury of NS20Y neuronal cells. The cells were incubated in the absence or presence of HG for 48 h. We found that mRNA and protein levels of TRPM7 and of ERS-associated proteins, such as C/EBP homologous protein (CHOP), 78-kDa glucose-regulated protein (GRP78), and inducible nitric-oxide synthase (iNOS), increased in HG-treated cells, along with significantly increased TRPM7-associated currents in these cells. Similar results were obtained in cerebral cortical tissue from an insulin-deficiency model of diabetic mice. Moreover, HG treatment of cells activated ERS-associated proapoptotic caspase activity and induced cellular injury. Interestingly, a NOS inhibitor, l-NAME, suppressed the HG-induced increase of TRPM7 expression and cellular injury. siRNA-mediated TRPM7 knockdown or chemical inhibition of TRPM7 activity also suppressed HG-induced ERS and decreased cleaved caspase-12/caspase-3 levels and cell injury. Of note, TRPM7 overexpression increased ERS and cell injury independently of its kinase activity. Taken together, our findings suggest that TRPM7 channel activities play a key role in HG-associated ERS and cytotoxicity through an apoptosis-inducing signaling cascade involving HG, iNOS, TRPM7, ERS proteins, and caspases.

C-peptide prevents SMAD3 binding to alpha promoters to inhibit collagen type IV synthesis

Activation of transforming growth factor β1 (TGFB1)/SMAD3 signaling may lead to additional synthesis of collagen type IV (COL4), which is a major contributor to extracellular matrix (ECM) accumulation in diabetic nephropathy (DN). C-peptide can attenuate fibrosis to have unique beneficial effects in DN. However, whether and how C-peptide affects TGFB1/SMAD3-activated COL4 synthesis is unclear. In this study, pathological changes, expression of COL4 a1-a5 chains (Col4a1-a5), COL4 distribution and protein and TGFB1 and SMAD3 protein were first assessed in a rat model of diabetes. Then, rat mesangial cells were treated with high glucose (HG) and/or C-peptide to investigate the underlying mechanism. Col4a1-a5 expression, COL4 protein and secretion, TGFB1 protein, SMAD3 nuclear translocation and binding of SMAD3 to its cognate sites in the promoters of Col4a1a2, Col4a3a4 and Col4a5 were measured. It was found that C-peptide attenuated glomerular pathological changes and suppressed renal Col4a1-a5 mRNA expression, COL4 protein content and TGFB1 protein content. C-peptide had a dose-dependent effect to inhibit Col4a1-a5 mRNA expression, COL4 protein content and secretion, in HG-stimulated mesangial cells. In addition, the HG-induced increase in TGFB1 protein content was significantly reduced by C-peptide. Although not apparently affecting SMAD3 nuclear translocation, C-peptide prevented SMAD3 from binding to its sites in the Col4a1a2, Col4a3a4 and Col4a5 promoters in HG-stimulated mesangial cells. In conclusion, C-peptide could prevent SMAD3 from binding to its sites in the Col4a1a2, Col4a3a4 and Col4a5 promoters, to inhibit COL4 generation. These results may provide a mechanism for the alleviation of fibrosis in DN by C-peptide.

C-peptide prevents NF-κB from recruiting p300 and binding to the inos promoter in diabetic nephropathy

C-peptide (CP) has demonstrated unique beneficial effects in diabetic nephropathy (DN), but whether and how CP regulates NF-κB and its coactivator, p300, to suppress inducible iNOS and antagonize DN are unknown. iNOS expression, NF-κB nuclear translocation, colocalization and binding of NF-κB to p300, binding of NF-κB to the inos promoter, and the bound NF-κB, p300, and histone 3 lysine 9 acetylation (H3K9ac) at binding sites were measured in high glucose-stimulated mesangial cells. We evaluated pathologic changes, iNOS expression, NF-κB, and p300 contents in diabetic rats. We found that CP inhibited iNOS expression and notably prevented colocalization and binding of NF-κB and p300. CP prevented NF-κB from binding to the inos promoter, especially at the distal site, and reduced bound NF-κB, p300, and H3K9ac. N-terminal plus middle fragment could mostly mimic the antagonizing effects of CP against the pathologic changes of DN and equally suppresses renal iNOS expression as CP. In conclusion, CP prevented NF-κB from recruiting p300 and binding to the inos promoter, and decreased H3K9ac at the binding sites to suppress iNOS expression and antagonize DN, with the effect region identified as N-terminal plus middle fragment.-Li, Y., Li, X., He, K., Li, B., Liu, K., Qi, J., Wang, H., Wang, Y., Luo, W. C-peptide prevents NF-κB from recruiting p300 and binding to the inos promoter in diabetic nephropathy.

C-peptide exhibits a late induction effect on matrix metallopeptidase-9 in high glucose-stimulated rat mesangial cells

Insufficient matrix metalloproteinase (MMP)-9 and MMP-2 is considered to be a contributor of extracellular matrix (ECM) accumulation in diabetic nephropathy (DN). C-peptide can reverse fibrosis, thus exerting a beneficial effect on DN. Whether C-peptide induces MMP-9 and MMP-2 to reverse ECM accumulation is not clear. In the present study, in order to determine ECM metabolism, rat mesangial cells were treated with high glucose (HG) and C-peptide intervention, then the early and late effects of C-peptide on HG-affected MMP-9 and MMP-2 were evaluated. Firstly, it was confirmed that HG mainly suppressed MMP-9 expression levels. Furthermore, C-peptide treatment induced MMP-9 expression at 6 h and suppressed it at 24 h, revealing the early dual effects of C-peptide on MMP-9 expression. Subsequently, significant increase in MMP-9 expression at 72, 96 and 120 h C-peptide treatment was observed. These changes in MMP-9 protein content confirmed its expression changes following late C-peptide treatment. Furthermore, at 96 and 120 h C-peptide treatment reversed the HG-inhibited MMP-9 secretion, further indicating the late induction effect of C-peptide on MMP-9. The present results demonstrated that C-peptide exerted a late induction effect on MMP-9 in HG-stimulated rat mesangial cells, which may be associated with the underlying mechanism of C-peptide's reversal effects on DN.

Ginsenoside exhibits concentration-dependent dual effects on HepG2 cell proliferation via regulation of c-Myc and HNF-4α

Although ginsenoside can generally promote cell proliferation, it is reported to have anti-proliferative effects in hepatocellular carcinoma (HCC). Whether ginsenoside has concentration-dependent effects on HCC cell proliferation have not been clarified. Transcription factors c-Myc and hepatocyte nuclear factor (HNF)-4α are the most important opposite controllers of HCC cell proliferation. Whether and how ginsenoside regulates c-Myc and HNF-4α as well as their recruitment of the co-activator p300 to exhibit its effects on HCC cell proliferation are pending. In this study, it was found that low concentration ginsenoside promoted HepG2 cell proliferation while high concentration ginsenoside exhibited anti-proliferation effect. For low concentration ginsenoside treatment, c-Myc was up-regulated and the binding of p300 to c-Myc was promoted with obvious co-localization to activate HepG2 cell proliferation. However, for high concentration ginsenoside treatment, besides c-Myc, HNF-4α was also up-regulated might to exhibit an alternative effect. Furthermore, in contrast to the weakened binding and co-localization of c-Myc and p300, the binding of p300 to HNF-4α was enhanced with distinct co-localization to inhibit HepG2 cell proliferation for high concentration ginsenoside treatment. The results manifested that ginsenoside with low and high concentrations may differentially regulate c-Myc and HNF-4α as well as their recruitments of p300, to exhibit concentration-dependent dual effects on HepG2 cell proliferation.

Effects of an Antimutagenic 1,4-Dihydropyridine AV-153 on Expression of Nitric Oxide Synthases and DNA Repair-related Enzymes and Genes in Kidneys of Rats with a Streptozotocin Model of Diabetes Mellitus

Development of complications of diabetes mellitus (DM), including diabetic nephropathy, is a complex multi-stage process, dependent on many factors including the modification of nitric oxide (NO) production and an impaired DNA repair. The goal of this work was to study in vivo effects of 1,4-dihydropyridine AV-153, known as antimutagen and DNA binder, on the expression of several genes and proteins involved in NO metabolism and DNA repair in the kidneys of rats with a streptozotocin (STZ)-induced model of DM. Transcription intensity was monitored by means of real-time RT-PCR and the expression of proteins by immunohistochemistry. Development of DM significantly induced PARP1 protein expression, while AV-153 (0.5 mg/kg) administration decreased it. AV-153 increased the expression of Parp1 gene in the kidneys of both intact and diabetic animals. Expression of H2afx mRNA and γH2AX histone protein, a marker of DNA breakage, was not changed in diabetic animals, but AV-153 up-regulated the expression of the gene without any impact on the protein expression. Development of DM was followed by a significant increase in iNOS enzyme expression, while AV-153 down-regulated the enzyme expression up to normal levels. iNos gene expression was also found to be increased in diabetic animals, but unlike the protein, the expression of mRNA was found to be enhanced by AV-153 administration. Expression of both eNOS protein and eNos gene in the kidneys was down-regulated, and the administration of AV-153 normalized the expression level. The effects of the compound in the kidneys of diabetic animals appear to be beneficial, as a trend for the normalization of expression of NO synthases is observed.

Developmental Stage-Specific Embryonic Induction of HepG2 Cell Differentiation

BACKGROUND

Although hepatocellular carcinoma cells can sometimes undergo differentiation in an embryonic microenvironment, the mechanism is poorly understood.

AIM

The developmental stage-specific embryonic induction of tumor cell differentiation was investigated.

METHODS

Both chick and mouse liver extracts and hepatoblast-enriched cells at different developmental stages were used to treat human hepatoma HepG2 cells, and the effects on the induction of differentiation were evaluated. The nuclear factors controlling differentiation, hepatocyte nuclear factor (HNF)-4α, HNF-1α, HNF-6 and upstream stimulatory factor-1 (USF-1), and the oncogene Myc and alpha-fetoprotein (AFP) were measured. HNF-4α RNA interference was used to verify the role of HNF-4α. Embryonic induction effects were further tested in vivo by injecting HepG2 tumor cells into immunodeficient nude mice.

RESULTS

The 9-11-days chick liver extracts and 13.5-14.5-days mouse hepatoblast-enriched cells could inhibit proliferation and induce differentiation of HepG2 cells, leading to either death or maturation to hepatocytes. The maturation of surviving HepG2 cells was confirmed by increases in the expressions of HNF-4α, HNF-1α, HNF-6, and USF-1, and decreases in Myc and AFP. The embryonic induction of HepG2 cell maturation could be attenuated by HNF-4α RNA interference. Furthermore, the 13.5-days mouse hepatoblast culture completely eliminated HepG2 tumors with inhibited Myc and induced HNF-4α, confirming this embryonic induction effect in vivo.

CONCLUSIONS

This study demonstrated that developmental stage-specific embryonic induction of HepG2 cell differentiation might help in understanding embryonic differentiation and oncogenesis.

Developmental Stage-Specific Hepatocytes Induce Maturation of HepG2 Cells by Rebuilding the Regulatory Circuit

On the basis of their characteristics, we presume that developmental stage-specific hepatocytes should have the ability to induce maturation of hepatoma cells. A regulatory circuit formed by hepatocyte nuclear factor (HNF)-4α, HNF-1α, HNF-6 and the upstream stimulatory factor (USF-1) play a key role in the maturation of embryonic hepatocytes; however, it is unclear whether the regulatory circuit mediates the embryonic induction of hepatoma cell maturation. In this study, 12.5-d to 15.5-d mouse embryonic hepatocytes or their medium were used to coculture or treat HepG2 cells, and the induced maturation was evaluated in vitro and in vivo. In the induced HepG2 cells, the components of the regulatory circuit were detected, their cross-regulation was evaluated and HNF-4α RNA interference was performed. We found that 13.5-d to 14.5-d embryonic hepatocytes could induce HepG2 cell maturation, demonstrated by morphological changes, increased maturation markers and decreased c-Myc and α-fetoprotein (AFP) in vitro. The majority of HepG2 tumors were eliminated by 13.5-d embryonic induction in vivo. All components of the regulatory circuit were upregulated and the binding of HNF-4α, HNF-1α, HNF-6 and USF-1 to their target sites was promoted to rebuild the regulatory circuit in the induced HepG2 cells. Moreover, RNA interference targeting HNF-4α, which is the core of the regulatory circuit, attenuated the induced maturation of HepG2 cells with downregulation of the regulatory circuit. These results revealed that developmental stage-specific hepatocytes could induce the maturation of HepG2 cells by rebuilding the regulatory circuit.

Dynamic localization and functional implications of C-peptide might for suppression of iNOS in high glucose-stimulated rat mesangial cells

Although C-peptide has unique beneficial effects on diabetic nephropathy (DN), its functional localization and molecular mechanism have not been fully clarified. Whether C-peptide exhibits its protective role through the regulation of inducible nitric oxide synthase (iNOS), a key enzyme in oxidative stress, is not clear. In this study, it was revealed that C-peptide could enter the nucleus of high glucose-stimulated mesangial cells, especially in a time-dependent manner by high glucose pretreatment, while no C-peptide was detected in low glucose-cultured mesangial cells. The dynamic functional localization of C-peptide might be the intrinsic cause of its unique beneficial effects for DN, which may provide a foundation for further clarification of its underlying mechanism. Our preliminarily data also shown C-peptide suppressed the iNOS expression. Taking together, these results revealed the dynamic functional localization of C-peptide by high glucose stimulation in rat mesangial cells, which might suppress expression of iNOS to exhibit its protective effects.