Astragalus polysaccharide alleviates angiotensin II-induced glomerular podocyte dysfunction by inhibiting the expression of RARRES1 and LCN2.

Podocyte loss is a predictor of kidney disease development, including diabetic nephropathy. Astragalus polysaccharide (APS) was considered a renoprotective drug, whereas the mechanisms operated by APS on podocyte dysfunction are rarely mentioned. This study aims at the mechanistic underlying of APS on angiotensin II (Ang II)-induced podocyte dysfunction. Mouse glomerular podocytes MPC5 were induced with Ang II, the morphologic changes were observed and nephrin, desmin and Wilms' tumour protein-1 (WT-1) levels were determined. The MPC5 cells were treated with APS (50, 100 and 200 µg/mL) and transduced with retinoic acid receptor responder protein 1 (RARRES1) overexpression vectors. The expression of RARRES1, lipocalin-2 (LCN2), nephrin and desmin was tested, MPC5 cell viability and apoptosis were evaluated, and the levels of an endocytotic receptor megalin, Bcl-2, Bax, interleukin (IL)-6, IL-1ß and tumour necrosis factor (TNF)-α were assessed. The binding of RARRES1 to LCN2 was predicted and verified. Mice were infused with Ang II to evaluate histopathological alterations and 24-h urinary albumin content. Ang II induction suppressed MPC5 cell viability, reduced the expression of nephrin, WT-1, megalin and Bcl-2, and augmented the expression of desmin, Bax, IL-6, IL-1ß and TNF-α, which were significantly nullified by APS treatment. RARRES1 interacted with LCN2, and APS treatment inhibited RARRES1 and LCN2 expression in a dose-dependent manner, thereby alleviating Ang II-induced podocyte dysfunction. Ang II infusion in mice facilitated pathological alterations in renal tissues and increased urinary albumin content, which were attenuated after APS treatment. Overall, APS treatment alleviated Ang II-induced podocyte dysfunction by inhibiting RARRES1/LCN2 expression and blocked kidney injury development in vivo.

Disparate roles of retinoid acid signaling molecules in kidney disease.

Retinoid acid (RA) is synthesized mainly in the liver and has multiple functions in development, cell differentiation and proliferation, and regulation of inflammation. RA has been used to treat multiple diseases, such as cancer and skin disorders. The kidney is a major organ for RA metabolism, which is altered in the diseased condition. RA is known to have renal-protective effects in multiple animal models of kidney disease. RA has been shown to ameliorate podocyte injury through induction of expression of differentiation markers and regeneration of podocytes from its progenitor cells in animal models of kidney disease. The effects of RA in podocytes are mediated mainly by activation of the cAMP/PKA pathway via RA receptor-α (RARα) and activation of its downstream transcription factor, Kruppel-like factor 15. Screening of RA signaling molecules in human kidney disease has revealed RAR responder protein 1 (RARRES1) as a risk gene for glomerular disease progression. RARRES1, a podocyte-specific growth arrest gene, is regulated by high doses of both RA and TNF-α. Mechanistically, RARRES1 is cleaved by matrix metalloproteinases to generate soluble RARRES1, which then induces podocyte apoptosis through interaction with intracellular RIO kinase 1. Therefore, a high dose of RA may induce podocyte toxicity through upregulation of RARRES1. Based on the current findings, to avoid potential side effects, we propose three strategies to develop future therapies of RA for glomerular disease: 1) develop RARα- and Kruppel-like factor 15-specific agonists, 2) use the combination of a low dose of RAR-α agonist with phosphodiesterase 4 inhibitors, and 3) use a combination of RARα agonist with RARRES1 inhibitors.NEW & NOTEWORTHY Retinoic acid (RA) exerts pleotropic cellular effects, including induction of cell differentiation while inhibiting proliferation and inflammation. These effects are mediated by both RA responsive element-dependent or -independent pathways. In kidneys, RA confers renoprotection by signaling through podocyte RA receptor (RAR)α and activation of cAMP/PKA/Kruppel-like factor 15 pathway to promote podocyte differentiation. Nevertheless, in kidney disease settings, RA can also promote podocyte apoptosis and loss through downstream expression of RAR responder protein 1, a recently described risk factor for glomerular disease progression. These disparate roles of RA underscore the complexity of its effects in kidney homeostasis and disease, and a need to target specific RA-mediated pathways for effective therapeutic treatments against kidney disease progression.

Tazarotene-induced Gene 1 Induces Melanoma Cell Death by Triggering Endoplasmic Reticulum Stress Response.

BACKGROUND: This study investigated the mechanism by which tazarotene-induced gene 1 (TIG1) inhibits melanoma cell growth. The main focus was to analyze downstream genes regulated by TIG1 in melanoma cells and its impact on cell growth. METHODS: The effects of TIG1 expression on cell viability and death were assessed using water-soluble tetrazolium 1 (WST-1) mitochondrial staining and lactate dehydrogenase release assays. RNA sequencing and Western blot analysis were employed to investigate the genes regulated by TIG1 in melanoma cells. Additionally, the correlation between TIG1 expression and its downstream genes was analyzed in a melanoma tissue array. RESULTS: TIG1 expression in melanoma cells was associated with decreased cell viability and increased cell death. RNA-sequencing (RNA-seq), quantitative reverse transcription PCR (reverse RT-QPCR), and immunoblots revealed that TIG1 expression induced the expression of Endoplasmic Reticulum (ER) stress response-related genes such as Homocysteine-responsive endoplasmic reticulum-resident ubiquitin-like domain member 1 (HERPUD1), Binding immunoglobulin protein (BIP), and DNA damage-inducible transcript 3 (DDIT3). Furthermore, analysis of the melanoma tissue array revealed a positive correlation between TIG1 expression and the expression of HERPUD1, BIP, and DDIT3. Additionally, attenuation of the ER stress response in melanoma cells weakened the impact of TIG1 on cell growth. CONCLUSIONS: TIG1 expression effectively hinders the growth of melanoma cells. TIG1 induces the upregulation of ER stress response-related genes, leading to an increase in caspase-3 activity and subsequent cell death. These findings suggest that the ability of retinoic acid to prevent melanoma formation may be associated with the anticancer effect of TIG1.

Secretome survey of human plexiform neurofibroma derived Schwann Cells reveals a secreted form of the RARRES1 protein.

To bring insights into neurofibroma biochemistry, a comprehensive secretome analysis was performed on cultured human primary Schwann cells isolated from surgically resected plexiform neurofibroma and from normal nerve tissue. Using a combination of SDS-PAGE and high precision LC-MS/MS, 907 proteins were confidently identified in the conditioned media of Schwann cell cultures combined. Label free proteome profiling revealed consistent release of high levels of 22 proteins by the four biological replicates of NF1 Schwann cell cultures relative to the two normal Schwann cell cultures. Inversely, 9 proteins displayed decreased levels in the conditioned media of NF1 relative to normal Schwann cells. The proteins with increased levels included proteins involved in cell growth, angiogenesis and complement pathway while proteins with decreased levels included those involved in cell adhesion, plasminogen pathway and extracellular matrix remodeling. Retinoic acid receptor responder protein-1 (RARRES1), previously described as an integral membrane tumor suppressor, was found exclusively secreted by NF1 Schwann cells but not by normal Schwann cells. All-trans retinoic acid modulated secretion of RARRES1 in a dose dependent manner. This study shows altered secretion of key proteins in NF1 derived Schwann cells. The potential implication of these proteins in neurofibroma biology is discussed.

Expression and clinicopathological correlations of retinoid acid receptor responder protein 1 in renal cell carcinomas.

AIM: To evaluate the expression and prognostic value of RARRES1 at protein level in renal cell carcinoma (RCC). MATERIALS & METHODS: Expression profile of RARRES1 was analyzed in 903 documented RCC followed by clinicopathological correlations and survival analysis. RESULTS: RARRES1 expression was seen in 72.5% of RCC. A stronger RARRES1 expression was seen in high grade compared with low grade RCC (p < 0.001). Logrank tests revealed shorter overall survival in RARRES1 positive RCC (p = 0.006) and in pT1/2 tumors with RARRES1 expression (p = 0.002). CONCLUSION: The variable expression profile in low and high grade RCC may reflect and confirm the differences of previous gene expression analysis. There was a significant prognostic value of RARRES1 expression in patients with RCC, especially in pT1/2 tumors.

Molecular evolution and expression profile of the chemerine encoding gene RARRES2 in baboon and chimpanzee

BACKGROUND: Chemerin, encoded by the retinoic acid receptor responder 2 (RARRES2) gene is an adipocytesecreted protein with autocrine/paracrine functions in adipose tissue, metabolism and inflammation with a recently described function in vascular tone regulation, liver, steatosis, etc. This molecule is believed to represent a critical endocrine signal linking obesity to diabetes. There are no data available regarding evolution of RARRES2 in non-human primates and great apes. Expression profile and orthology in RARRES2 genes are unknown aspects in the biology of this multigene family in primates. Thus; we attempt to describe expression profile and phylogenetic relationship as complementary knowledge in the function of this gene in primates. To do that, we performed A RT-PCR from different tissues obtained during necropsies. Also we tested the hypotheses of positive evolution, purifying selection, and neutrality. And finally a phylogenetic analysis was made between primates RARRES2 protein. RESULTS: RARRES2 transcripts were present in liver, lung, adipose tissue, ovary, pancreas, heart, hypothalamus and pituitary tissues. Expression in kidney and leukocytes were not detectable in either species. It was determined that the studied genes are orthologous. CONCLUSIONS: RARRES2 evolution fits the hypothesis of purifying selection. Expression profiles of the RARRES2 gene are similar in baboons and chimpanzees and are also phylogenetically related.