Asymmetric dimethylarginine (ADMA) treatment induces apoptosis in cultured rat mesangial cells via endoplasmic reticulum stress activation

Renal fibrosis in type 2 cardiorenal syndrome: An update on mechanisms and therapeutic opportunities

Cardiorenal syndrome (CRS) is a state of coexisting heart failure and renal insufficiency in which acute or chronic dysfunction of the heart or kidney lead to acute or chronic dysfunction of the other organ.It was found that renal fibrosis is an important pathological process in the progression of type 2 CRS to end-stage renal disease, and progressive renal impairment accelerates the deterioration of cardiac function and significantly increases the hospitalization and mortality rates of patients. Previous studies have found that Hemodynamic Aiteration, RAAS Overactivation, SNS Dysfunction, Endothelial Dysfunction and Imbalance of natriuretic peptide system contribute to the development of renal disease in the decompensated phase of heart failure, but the exact mechanisms is not clear. Therefore, in this review, we focus on the molecular pathways involved in the development of renal fibrosis due to heart failure and identify the canonical and non-canonical TGF-β signaling pathways and hypoxia-sensing pathways, oxidative stress, endoplasmic reticulum stress, pro-inflammatory cytokines and chemokines as important triggers and regulators of fibrosis development, and summarize the therapeutic approaches for the above signaling pathways, including SB-525334 Sfrp1, DKK1, IMC, rosarostat, 4-PBA, etc. In addition, some potential natural drugs for this disease are also summarized, including SQD4S2, Wogonin, Astragaloside, etc.

Asymmetric Dimethylarginine (ADMA) in Pediatric Renal Diseases: From Pathophysiological Phenomenon to Clinical Biomarker and Beyond

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, inhibits NO synthesis and contributes to the pathogenesis of many human diseases. In adults, ADMA has been identified as a biomarker for chronic kidney disease (CKD) progression and cardiovascular risk. However, little attention is given to translating the adult experience into the pediatric clinical setting. In the current review, we summarize circulating and urinary ADMA reported thus far in clinical studies relating to kidney disease in children and adolescents, as well as systematize the knowledge on pathophysiological role of ADMA in the kidneys. The aim of this review is also to show the various analytical methods for measuring ADMA and the issues tht need to be addressed before transforming to clinical practice in pediatric medicine. The last task is to suggest that ADMA may not only be suitable as a diagnostic or prognostic biomarker, but also a promising therapeutic strategy to treat pediatric kidney disease in the future.

Endoplasmic Reticulum Stress in Diabetic Nephrology: Regulation, Pathological Role, and Therapeutic Potential

Recent progress has been made in understanding the roles and mechanisms of endoplasmic reticulum (ER) stress in the development and pathogenesis of diabetic nephropathy (DN). Hyperglycemia induces ER stress and apoptosis in renal cells. The induction of ER stress can be cytoprotective or cytotoxic. Experimental treatment of animals with ER stress inhibitors alleviated renal damage. Considering these findings, the normalization of ER stress by pharmacological agents is a promising approach to prevent or arrest DN progression. The current article reviews the mechanisms, roles, and therapeutic aspects of these findings.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

Non-functioning adrenal incidentalomas may increase toxic metabolites

BACKGROUND

Non-functioning adrenal incidentaloma (NFAI) is a frequent diagnosis with increasing radiological tests. The emerging shreds of evidence showed that they might have negative cardiometabolic effects. The study aimed to investigate whether the toxic metabolites, asymmetric dimethylarginine (ADMA) levels, were altered in NFAI patients.

METHODS

We included 43 NFAI patients and 41 controls with similar ages and body mass indices in the study. We compared plasma ADMA levels of both groups and noted the radiological features of NFAIs.

RESULTS

The ADMA levels were significantly higher in NFAI patients than in the control group (307.04 ng/ml, range 81.89-577.7 ng/ml vs 192.54 ng/ml, range 70.61-440.26 ng/ml, p = 0.001). Nevertheless, we could not reach a significant correlation between ADMA levels and mass size.

CONCLUSION

The ADMA is known as a toxin and is increased in NFAI patients. NFAIs may not be innocent and may be considered a potential risk for the body. Further investigations were needed for more explanations.

A Multi-Platform Metabolomics Approach Identifies Urinary Metabolite Signatures That Differentiate Ketotic From Healthy Dairy Cows

Ketosis and subclinical ketosis are widespread among dairy cows especially after calving. Etiopathology of ketosis has been related to negative energy balance. The objective of this study was to investigate metabolite fingerprints in the urine of pre-ketotic, ketotic, and post-ketotic cows to identify potential metabolite alterations that can be used in the future to identify susceptible cows for ketosis and metabolic pathways involved in the development of disease. In this study, NMR, DI/LC-MS/MS, and GC-MS-based metabolomics were used to analyze urine samples from 6 cows diagnosed with ketosis and 20 healthy control (CON) cows at -8 and -4 weeks prepartum, the week (+1 to +3) of ketosis diagnosis, and at +4 and +8 weeks after parturition. Univariate and multivariate analyses were used to screen metabolite panels that can identify cows at their pre-ketotic stage. A total of 54, 42, 48, 16, and 31 differential metabolites between the ketotic and CON cows were identified at -8 and -4 weeks prepartum, ketosis week, and at +4, and +8 weeks postpartum, respectively. Variable importance in projection (VIP) plots ranked the most significant differential metabolites, which differentiated ketotic cows from the CON ones. Additionally, several metabolic pathways that are related to ketosis were identified. Moreover, two promising metabolite panels were identified which clearly separated ketotic from CON cows with excellent level of sensitivity and specificity. Overall, multiple urinary metabolite alterations were identified in pre-ketotic, ketotic, and post-ketotic cows. The metabolite panels identified need to be validated in the future in a larger cohort of animals.

PRMT1 mediates RANKL-induced osteoclastogenesis and contributes to bone loss in ovariectomized mice

Protein arginine methylation is a novel form of posttranslational modification mediated by protein arginine methyltransferase (PRMTs). PRMT1, a major isoform of the PRMT family, is responsible for various biological functions, including cellular differentiation. Although the important function that PRMT1 plays in various tissues is being increasingly recognized, its role in receptor activation of NF-κB ligand (RANKL)-induced osteoclastogenesis or osteoporosis has not yet been described. Here, we show that PRMT1 is essential for RANKL-induced osteoclastogenesis in vitro and for bone loss in vivo. RANKL treatment increased the expression of PRMT1 and its nuclear localization in bone marrow-derived macrophages (BMDMs) in a c-Jun N-terminal kinase (JNK)-dependent manner. Silencing PRMT1 attenuated RANKL-induced osteoclastogenesis by decreasing tartrate-resistant acid phosphatase (TRAP)-positive cells and inhibiting F-actin ring formation and bone resorption, which was confirmed in a separate experiment using haploinsufficient cells from PRMT1^+/- mice. Our results also revealed that PRMT1 regulates the transcription activity of NF-κB by directly interacting with it in RANKL-treated BMDMs. An in vivo study showed that the haploinsufficiency of PRMT1 reduced the enzyme activity of TRAP and increased the bone mineral density in the metaphysis of ovariectomized (OVX) mice. Finally, treatment with estrogen (E2) downregulated the RANKL-induced expression of PRMT1, suggesting that estrogen may exert an inhibitory effect on osteoclastogenesis by suppressing PRMT1 expression. Our results suggest that PRMT1 plays an important role in the progression of osteoporosis and that it might be a good therapeutic target for postmenopausal osteoporosis.

A protein that helps trigger bone loss in postmenopausal osteoporosis could be a potential therapeutic target. After the menopause, decreases in estrogen hormone levels can lead to bone diseases including osteoporosis. Osteoporosis occurs when the bone remodeling process breaks down, and bone resorption by cells called osteoclasts outweighs bone formation. In a mouse model of postmenopausal osteoporosis, Jong-Hwan Park at Chonnam National University, Gwangju, South Korea and co-workers identified key players in the progression of the disease. The team focused on factors influencing the RANKL protein, a known controller of bone remodeling. They found that RANKL triggers the formation of osteoclasts via interaction with another protein, PRMT1. Suppression of PRMT1 by estrogen appears to inhibit excessive osteoclast formation, suggesting it could be a potential therapeutic target for treating osteoporosis.

Asymmetric dimethylarginine downregulates sarco/endoplasmic reticulum calcium‑ATPase 3 and induces endoplasmic reticulum stress in human umbilical vein endothelial cells

Cardiovascular disease is the leading cause of mortality in patients with chronic kidney disease. Endothelial cell injury and apoptosis may promote atherosclerosis and cardiovascular disease. The present study investigated the potential mechanisms of asymmetric dimethylarginine (ADMA)‑induced apoptosis in human umbilical vein endothelial cells (HUVECs). It was demonstrated that ADMA decreased B‑cell lymphoma‑2 expression and increased cleaved‑caspase‑3 expression. Furthermore, terminal deoxynucleotidyl transferase (TdT)‑mediated‑digoxigenin‑11‑dUTP nick end labeling results indicated that ADMA induced apoptosis in HUVECs. These results suggest a potential mechanism of ADMA‑induced endothelial cell injury. It was also verified that ADMA induced the expression of phosphorylated protein kinase RNA‑like ER kinase, inositol requiring enzyme‑1, C/EBP homologous protein and glucose‑regulated protein, indicating activation of the endoplasmic reticulum (ER) stress response. Impaired function of sarco/endoplasmic reticulum calcium‑ATPase (SERCA) is considered a major contributor to ER stress. It was demonstrated that ADMA induced a significant downregulation of SERCA3, however not SERCA2b. Overall, the results indicated that ADMA induced apoptosis in HUVECs, and that this effect was closely associated with induction of ER stress and decreased SERCA3 expression.

Targeted inhibition of endoplasmic reticulum stress: New hope for renal fibrosis (Review)

Chronic kidney disease (CKD) has a very high mortality rate and remains a global health challenge. Inhibiting renal fibrosis is one of the most promising therapeutic strategies for CKD. Recent studies have indicated that endoplasmic reticulum stress (ERS) serves an active role in the development of acute and chronic kidney disease, especially with regards to renal fibrosis. In the current review, the authors summarize the latest understanding of the role of ERS during the onset of renal fibrosis. ERS promotes renal fibrosis through multiple signaling pathways, such as transforming growth factor-β, epithelial-mesenchymal transition and oxidative stress. In addition, ERS also causes podocyte damage, leading to increased proteinuria and the development of renal fibrosis in rat models. In conclusion, targeted inhibition of ERS may become a promising therapeutic strategy for renal fibrosis.

Regulation of c-Jun N-Terminal Protein Kinase (JNK) Pathway in Apoptosis of Endothelial Outgrowth Cells Induced by Asymmetric Dimethylarginine

BACKGROUND Endothelial outgrowth cells (EOCs) are terminal endothelial progenitor cells (EPCs). Asymmetric dimethylarginine (ADMA) has been identified as a novel risk factor for cardiovascular diseases. Our aim in the present study was to investigate the effect of regulation of asymmetric dimethylarginine (ADMA) on EOCs apoptosis and to explore the underlining mechanisms of c-Jun N-terminal protein kinase (JNK) pathway in the process. MATERIAL AND METHODS EOCs were harvested from umbilical cord blood and obtained by using density gradient centrifugation and adhesive culture methods. Endothelial characteristics were identified by immunohistochemistry and fluorescence staining. EOCs were treated with different concentrations of ADMA and detected by flow cytometry. After JNK specific inhibitor (SP600125) was added, EOCs apoptosis protein expressions were measured by Western blot analysis. Proliferation, migration, and vascularization were detected by CCK-8 assay, wound healing assay, and tube-like formation assay, respectively. RESULTS EOCs were successfully extracted from umbilical cord blood and different concentrations of ADMA aggravated EOCs apoptosis. ADMA distinctly activates the phosphorylation activity of JNK. Supplementation of JNK-specific inhibitor (SP600125) decreased expression of Bax and cleaved caspase 3/9, and alleviated ADMA-induced apoptosis. SP600125 also promoted angiogenesis viability. CONCLUSIONS The JNK pathway participates in the apoptosis-promoting process of EOCs, and targeted inhibition of the JNK pathway can alleviate ADMA-induced injury, which I s the potential underlying mechanism of vascular endothelium injury in ischemic stroke.

Toxic Dimethylarginines: Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA)

Asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) are toxic, non-proteinogenic amino acids formed by post-translational modification and are uremic toxins that inhibit nitric oxide (NO) production and play multifunctional roles in many human diseases. Both ADMA and SDMA have emerged as strong predictors of cardiovascular events and death in a range of illnesses. Major progress has been made in research on ADMA-lowering therapies in animal studies; however, further studies are required to fill the translational gap between animal models and clinical trials in order to treat human diseases related to elevated ADMA/SDMA levels. Here, we review the reported impacts of ADMA and SDMA on human health and disease, focusing on the synthesis and metabolism of ADMA and SDMA; the pathophysiological roles of these dimethylarginines; clinical conditions and animal models associated with elevated ADMA and SDMA levels; and potential therapies against ADMA and SDMA. There is currently no specific pharmacological therapy for lowering the levels and counteracting the deleterious effects of ADMA and SDMA. A better understanding of the mechanisms underlying the impact of ADMA and SDMA on a wide range of human diseases is essential to the development of specific therapies against diseases related to ADMA and SDMA.