Amelioration of glomerulosclerosis with all-trans retinoic acid is linked to decreased plasminogen activator inhibitor-1 and α-smooth muscle actin

A New Prospect for the Treatment of Nephrotic Syndrome Based on Network Pharmacology Analysis

Network pharmacology is an emerging field which is currently capturing interest in drug discovery and development. Chronic kidney conditions have become a threat globally due to its associated lifelong therapies. Nephrotic syndrome (NS) is a common glomerular disease that is seen in paediatric and adult population with characteristic manifestation of proteinuria, oedema, hypoalbuminemia, and hyperlipidemia. It involves podocyte damage with tubulointerstitial fibrosis and glomerulosclerosis. Till date there has been no specific treatment available for this condition that provides complete remission. Repurposing of drugs can thus be a potential strategy for the treatment of NS. Recently, epigenetic mechanisms were identified that promote progression of many renal diseases. Therefore, in the present study, we investigated two epigenetic drugs valproic acid (VPA) and all-trans retinoic acid (ATRA). Epigenetic drugs act by binging about changes in gene expression without altering the DNA sequence. The changes include DNA methylation or histone modifications. The targets for the two drugs ATRA and VPA were collated from ChEMBL and Binding DB. All the genes associated with NS were collected from DisGeNET and KEGG database. Interacting proteins for the target genes were acquired from STRING database. The genes were then subjected to gene ontology and pathway enrichment analysis using a functional enrichment software tool. A drug-target and drug-potential target-protein interaction network was constructed using the Cytoscape software. Our results revealed that the two drugs VPA and ATRA had 65 common targets that contributed to kidney diseases. Out of which, 25 targets were specifically NS associated. Further, our work exhibited that ATRA and VPA were synergistically involved in pathways of inflammation, renal fibrosis, glomerulosclerosis and possibly mitochondrial biogenesis and endoplasmic reticulum stress. We thus propose a synergistic potential of the two drugs for treating chronic kidney diseases, specifically NS. The outcomes will undoubtedly invigorate further preclinical and clinical explorative studies. We identify network pharmacology as an initial inherent approach in identifying drug candidates for repurposing and synergism.

An exploratory review of Potential Adjunct Therapies for the Treatment of Coronavirus Infections

Objective

The purpose of this exploratory review c, including vitamin D, zinc, vitamin A, elderberry (S nigra), garlic (A sativum), licorice (G glabra), stinging nettle (U dioica), N-acetylcysteine, quercetin and selenium as potential adjunct therapies for the treatment of coronavirus infections.

Methods

A search of PubMed was performed for articles published from 2005 to 2021. Key words searched were zinc, vitamin A, vitamin D, Sambucus nigra, Allium sativum, Glycyrrhiza glabra, Urtica dioica, N-Acetylcysteine, quercetin, selenium and coronavirus.

Results

There were 47 articles selected for this review. Findings included that vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra, U dioica, N-acetylcysteine, quercetin and selenium have been shown to produce anti-inflammatory, immunostimulatory or antiviral effects that may enhance the actions of standard therapeutics for the treatment of CoV infections. We found only research articles related to the effects of vitamin D, zinc, G glabra, quercetin and selenium against COVID-19.

Conclusion

We identified non-pharmaceutical supplements (Vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra and U dioica) which may have potential to provide support for those with coronavirus infections. However, rigorous clinical studies need to be performed before any clinical recommendations can be made at this time.

Concomitant inhibition of hedgehog signalling and activation of retinoid receptors abolishes bleomycin-induced lung fibrosis

Pulmonary fibrosis is a devastating disease with unknown treatment. All-trans retinoic acid (ATRA) attenuates bleomycin-induced lung fibrosis by different mechanistic pathways. However, the role of retinoid receptors in lung fibrosis is still unclear. Forskolin (FSK), a potent inhibitor for the revolutionary hedgehog (Hh) signalling pathway, has a promising antifibrotic effect on other organs such as the liver. This study investigates the interplay between the retinoid receptors modulation and the Hh signalling pathway in bleomycin (BLM)-induced pulmonary fibrosis. Rats were randomised and administrated a single dose of 7.5 mg/kg of BLM alone and with ATRA, FSK and both of them. The effects of FSK and ATRA on lung functions, oxidative stress markers (malondialdehyde [MDA], glutathione [GSH], superoxide dismutase [SOD] and catalase [CAT]), retinoid markers (retinoic acid receptors [RAR] and rexinoid X receptors [RXR]) and Hh signalling markers (patched homolog 1 [Ptch-1], Smoothened [Smo] and glioblastoma-2 [Gli-2]) were assessed. In single therapies, ATRA and FSK ameliorated BLM-induced lung fibrosis. On the contrary, a combination of both drugs synergistically reversed the effect of BLM-induced lung fibrosis, as indicated by the enhancement of lung functions and the decrease of the α-smooth muscle actin (α-SMA) expression and collagen deposition. Additionally, FSK and ATRA ameliorated oxidative stress and inflammation, reduced transforming growth factor β1 (TGF-β1) levels and reversed the effect of BLM on the mRNA expression of Ptch-1, Smo and Gli-2. FSK inhibited the Hh pathway and also activated protein kinase A (PKA) that is, in part, involved in phosphorylation of RAR/RXR heterodimer (a key step in retinoid receptor activation). The present results suggest that a combination of FSK and ATRA has a promising therapeutic value for lung fibrosis management.

Pharmacological inhibition of autophagy by 3-MA attenuates hyperuricemic nephropathy

Autophagy has been identified as a cellular process of bulk degradation of cytoplasmic components and its persistent activation is critically involved in the renal damage induced by ureteral obstruction. However, the role and underlying mechanisms of autophagy in hyperuricemic nephropathy (HN) remain unknown. In the present study, we observed that inhibition of autophagy by 3-methyladenine (3-MA) abolished uric acid-induced differentiation of renal fibroblasts to myofibroblasts and activation of transforming growth factor-β1 (TGF-β1), epidermal growth factor receptor (EGFR), and Wnt signaling pathways in cultured renal interstitial fibroblasts. Treatment with 3-MA also abrogated the development of HN in vivo as evidenced by improving renal function, preserving renal tissue architecture, reducing the number of autophagic vacuoles, and decreasing microalbuminuria. Moreover, 3-MA was effective in attenuating renal deposition of extracellular matrix (ECM) proteins and expression of α-smooth muscle actin (α-SMA) and reducing renal epithelial cells arrested at the G₂/M phase of cell cycle. Injury to the kidney resulted in increased expression of TGF-β1 and TGFβ receptor I, phosphorylation of Smad3 and TGF-β-activated kinase 1 (TAK1), and activation of multiple cell signaling pathways associated with renal fibrogenesis, including Wnt, Notch, EGFR, and nuclear factor-κB (NF-κB). 3-MA treatment remarkably inhibited all these responses. In addition, 3-MA effectively suppressed infiltration of macrophages and lymphocytes as well as release of multiple profibrogenic cytokines/chemokines in the injured kidney. Collectively, these findings indicate that hyperuricemia-induced autophagy is critically involved in the activation of renal fibroblasts and development of renal fibrosis and suggest that inhibition of autophagy may represent a potential therapeutic strategy for HN.

Inhibition of HDAC enhances STAT acetylation, blocks NF-κB, and suppresses the renal inflammation and fibrosis in Npr1 haplotype male mice

Guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) plays a critical role in the regulation of blood pressure and fluid volume homeostasis. Mice lacking functional Npr1 (coding for GC-A/NPRA) exhibit hypertension and congestive heart failure. However, the underlying mechanisms remain largely less clear. The objective of the present study was to determine the physiological efficacy and impact of all-trans-retinoic acid (ATRA) and sodium butyrate (NaBu) in ameliorating the renal fibrosis, inflammation, and hypertension in Npr1 gene-disrupted haplotype (1-copy; +/-) mice (50% expression levels of NPRA). Both ATRA and NaBu, either alone or in combination, decreased the elevated levels of renal proinflammatory and profibrotic cytokines and lowered blood pressure in Npr1^+/- mice compared with untreated controls. The treatment with ATRA-NaBu facilitated the dissociation of histone deacetylase (HDAC) 1 and 2 from signal transducer and activator of transcription 1 (STAT1) and enhanced its acetylation in the kidneys of Npr1^+/- mice. The acetylated STAT1 formed a complex with nuclear factor-κB (NF-κB) p65, thereby inhibiting its DNA-binding activity and downstream proinflammatory and profibrotic signaling cascades. The present results demonstrate that the treatment of the haplotype Npr1^+/- mice with ATRA-NaBu significantly lowered blood pressure and reduced the renal inflammation and fibrosis involving the interactive roles of HDAC, NF-κB (p65), and STAT1. The current findings will help in developing the molecular therapeutic targets and new treatment strategies for hypertension and renal dysfunction in humans.

An in vitro model for the pro-fibrotic effects of retinoids: mechanisms of action

BACKGROUND AND PURPOSE

Retinoids, including all-trans retinoic acid (tRA), have dose-dependent pro-fibrotic effects in experimental kidney diseases. To understand and eventually prevent such adverse effects, it is important to establish relevant in vitro models and unravel their mechanisms.

EXPERIMENTAL APPROACH

Fibrogenic effects of retinoids were assessed in NRK-49F renal fibroblasts using picro-Sirius red staining for collagens and quantified by spectrophotometric analysis of the eluted stain. Other methods included RT-qPCR, immunoassays and matrix metalloproteinase (MMP) activity assays.

KEY RESULTS

With or without TGF-β1, tRA was dose-dependently pro-fibrotic, notably increasing collagen accumulation. tRA and TGF-β1 additively suppressed expression of mRNA for MMP2, 3 and 13 and suppressed MMP activity. tRA, in the presence of TGF-β1, induced plasminogen activator inhibitor-1 (PAI-1) mRNA and they additively induced PAI-1 protein expression. A PAI-1 inhibitor, a pan-retinoic acid receptor (RAR) antagonist and a pan-retinoid X receptor (RXR) antagonist each partially prevented the pro-fibrotic effect of tRA. The dose-dependent pro-fibrotic effects of a pan-RXR agonist were similar to those of tRA. A pan-RAR agonist showed weaker, less dose-dependent pro-fibrotic effects and the pro-fibrotic effects of RARα and RARβ-selective agonists were even smaller. An RARγ-selective agonist did not affect fibrogenesis.

CONCLUSIONS AND IMPLICATIONS

An in vitro model for the pro-fibrotic effects of retinoids was established in NRK-49F cells. It was associated with reduced MMP activity and increased PAI-1 expression, and was probably mediated by RXR and RAR. To avoid or antagonize the pro-fibrotic activity of tRA, further studies on RAR isotype-selective agonists and PAI-1 inhibitors might be of value.

Selective renal vasoconstriction, exaggerated natriuresis and excretion rates of exosomic proteins in essential hypertension

AIM

In essential hypertension (EH), the regulation of renal sodium excretion is aberrant. We hypothesized that in mild EH, (i) abnormal dynamics of plasma renin concentration (PRC) and atrial natriuretic peptide (ANP) are responsible for the exaggerated natriuresis, and (ii) exosomic protein patterns reflect the renal tubular abnormality involved in the dysregulation of sodium excretion.

METHODS

After 2-week drug washout and 4-day diet, systemic and renal hemodynamics, cardio-renal hormones, glomerular filtration and renal excretion were studied in male patients during saline loading (SL). Excretion rates of exosome-related urinary proteins including apical membrane transporters were determined by proteomics-based methods.

RESULTS

In patients, baseline renal vascular conductance was reduced (-44%, P < 0.001), but non-renal vascular conductances were normal while PRC was reduced and ANP elevated (both P < 0.01). SL induced exaggerated natriuresis and reduced PRC (P < 0.01), at normal suppression rate. SL increased arterial pressure in patients (+11 mmHg, P < 0.001), but not in controls; however, during time control, patients showed identical increases (+10 mmHg, P < 0.005) apparently dissociating arterial pressure from natriuresis. At baseline, excretion rates of 438 proteins ranged from 0.07 to 49.8 pmol (mmol creatinine)(-1); 12 proteins were found in all subjects, and 21 proteins were found in two or more patients, but not in controls. In patients, the excretion rate of retinoic acid-induced gene 2 protein was reduced, and excretion rates of other proteins showed increased variances compatible with pathophysiological and clinical applicability.

CONCLUSION

Essential hypertension patients exhibit selective renal vasoconstriction and individually varying excretion rates of several exosome-related proteins. Hormonal changes, rather than arterial pressure, seem to cause exaggeration of natriuresis.

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.

All-trans retinoic acid displays multiple effects on the growth, lipogenesis and adipokine gene expression of AML-I preadipocyte cell line

Adipose tissue is a potential site of retinoic acid (RA) action, but its physiological significance remains to be clarified. We have examined the effect of all-trans retinoic acid (ATRA) on growth and differentiation of preadipocytes, and on adipokine gene expression in mature adipocytes using human preadipocyte cell model, AML-I. Both ATRA and 9-cis RA induced growth arrest in AML-I preadipocyte at between 50 and 100 µM, which was accompanied by apoptosis. Western blotting showed a loss of NF-κB, Bcl-2 and p-Akt, and the accumulation of Bad and Akt in cytoplasm of ATRA-treated AML-I preadipocytes. Exposure of AML-I to ATRA or 9-cis RA increased intracellular lipid accumulation in a time-dependent manner compared to vehicle-treated cells. Expression of fatty acid synthase (FAS) and peroxisome proliferator-activated receptor-γ (PPAR-γ) proteins was increased in ATRA-treated cells. Thus, both ATRA and 9-cis RA promoted differentiation, inhibited proliferation and induced apoptosis in AML-I preadipocytes. ATRA also modulated adipokine expression by increasing the mRNA level of adipocytokines (adiponectin, leptin and LPL), and by inhibiting PAI-1 mRNA expression in mature AML-I adipocytes. The data suggest that ATRA exerts a wide range of effects--growth arrest, apoptosis, lipogenesis and modulation of adipokine gene expression--during the maturation of preadipocytes into adipocytes.

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.

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

This study was performed to investigate the association of prohibitin with renal interstitial fibrosis (RIF) lesion and to explore the association of all-trans retinoic acid (ATRA) treatment with prohibitin expression in RIF rats. Rats were divided into three groups: the sham operation group (SHO), the model group subjected to unilateral ureteral obstruction (UUO), and the model group treated with ATRA (GA). Renal tissues were collected at 14 and 28 days after surgery, and the relevant indicators were detected. In comparison with the SHO group, the RIF index in the UUO group was markedly elevated (p < 0.01), and the RIF index in the GA group was alleviated compared with that in the UUO group (p < 0.01). Compared with the SHO group, the expression of prohibitin (protein or mRNA) in the UUO group was significantly reduced (each p < 0.01). Prohibitin expression in the GA group was markedly increased when compared with that in the UUO (p < 0.01). The expression of TGF-β1 (protein and mRNA), protein expressions of Col-IV, fibronectin, α-SMA and cleaved Caspase-3, ROS generation and cell apoptosis index in the UUO group were markedly higher than those in the SHO group (all p < 0.01), and their expressions in the GA group were markedly down-regulated compared to those in the UUO group (all p < 0.01, respectively). The protein expression of prohibitin was negatively correlated with the RIF index, protein expression of TGF-β1, Col-IV, fibronectin, α-SMA or cleaved Caspase-3, ROS generation and the cell apoptosis index (each p < 0.01). In conclusion, lower expression of prohibitin is associated with the RIF, and ATRA treatment is associated with increased prohibitin, which can prevent the progression of RIF.

Proteome analysis of laser microdissected glomeruli from formalin-fixed paraffin-embedded kidneys of autopsies of diabetic patients: nephronectin is associated with the development of diabetic glomerulosclerosis

BACKGROUND

To date, little proteomic information has been available from the glomeruli of diabetic patients, possibly due to the clinical limitations of renal biopsy in diabetic patients and insufficient quantities of such specimens for proteome analysis. The purpose of the present study was to identify altered protein expression profiles in diabetic glomeruli using formalin-fixed paraffin-embedded (FFPE) kidney tissues from diabetic patients.

METHODS

Glomeruli were laser microdissected from FFPE autopsy kidney tissues from 10 patients with diabetic nephropathy and 10 non-diabetic control patients and underwent proteome analysis using QSTAR Elite liquid chromatography with tandem mass spectrometry and iTRAQ technology. Immunohistochemical analysis was performed on 93 autopsy samples from diabetic patients with and without nephropathy (n = 45 and n = 48, respectively).

RESULTS

Thirty-one renal and urological disease-related proteins displayed a differential abundance in glomerular samples from patients with diabetic nephropathy compared with non-diabetic control patients. Among them, we found that nephronectin, which functions in the assembly of extracellular matrix, showed clearly positive immunoreactivity in diabetic glomeruli. The numerical fraction of nephronectin-positive glomerular cross sections was increased significantly in diabetic patients with nephropathy compared to those without nephropathy (32.1 ± 31.5 versus 4.14 ± 5.65%, P < 0.0001). Furthermore, there was a significant positive correlation between this numerical fraction of nephronectin-positive glomerular cross sections and the glomerular sclerosis index (ρ = 0.881, P < 0.0001, n = 93).

CONCLUSION

The present study demonstrated, for the first time, that nephronectin may be associated with the development of diabetic glomerulosclerosis and that proteome analysis with FFPE kidney tissues from diabetic patients with nephropathy is useful in understanding diabetic nephropathy.

All-trans retinoic acid regulates the expression of apolipoprotein E in rats with glomerulosclerosis induced by Adriamycin

Apolipoprotein E (apoE) is an important plasma protein in cholesterol homeostasis and plays a key role in the progression of glomerulosclerosis (GS). We conducted this investigation to explore whether all-trans retinoic acid (ATRA) could regulate the apoE expression in the pathological process of GS. 120 Wistar rats were divided into three groups at random: sham operation group (SHO), glomerulosclerosis model group without treatment (GS), GS model group treated with ATRA (GA); n=40, respectively. The disease of GS in rat was established by uninephrectomy and adriamycin (5mg/kg) injection. At the end of 9 and 13 weeks, 20 rats in each group were killed and the relevant samples were collected. 24-hour urine total protein (24UTP), 24-hour urine excretion for albumin (24Ualb), serum total protein (TP) and serum albumin (Alb), blood urea nitrogen (BUN), serum creatinine (Scr), total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), serum and urine apoE and glomerulosclerosis index (GSI) were measured. The protein expressions of collagen IV (Col-IV), fibronectin (FN) and apoE in glomeruli were determined by immunohistochemistry. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR) was used to detect the expression of apoE mRNA in kidney. TP and Alb in GA group in 9/13-week were increased than those of GS group, however, the differences were not statistically significant. Compared with group GS at 9/13 weeks, values of 24UTP, 24Ualb, BUN, Scr, TC, TG, HDL, LDL, serum and urine apoE, and GSI in GA group that were significantly reduced, and protein expressions of Col-IV, FN and apoE in glomeruli and expression of apoE mRNA in renal tissue were significantly down-regulated by ATRA (P<0.01). In conclusion, ATRA can regulate the expression of apoE, reduce the accumulation of extracellular matrix (ECM) and step down the progression of GS.