An insight into role of amino acids as antioxidants via NRF2 activation.

Oxidative stress can affect the protein, lipids, and DNA of the cells and thus, play a crucial role in several pathophysiological conditions. It has already been established that oxidative stress has a close association with inflammation via nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway. Amino acids are notably the building block of proteins and constitute the major class of nitrogen-containing natural products of medicinal importance. They exhibit a broad spectrum of biological activities, including the ability to activate NRF2, a transcription factor that regulates endogenous antioxidant responses. Moreover, amino acids may act as synergistic antioxidants as part of our dietary supplementations. This has aroused research interest in the NRF2-inducing activity of amino acids. Interestingly, amino acids' activation of NRF2-Kelch-like ECH-associated protein 1 (KEAP1) signaling pathway exerts therapeutic effects in several diseases. Therefore, the present review will discuss the relationship between different amino acids and activation of NRF2-KEAP1 signaling pathway pinning their anti-inflammatory and antioxidant properties. We also discussed amino acids formulations and their applications as therapeutics. This will broaden the prospect of the therapeutic applications of amino acids in a myriad of inflammation and oxidative stress-related diseases. This will provide an insight for designing and developing new chemical entities as NRF2 activators.

Antinephrolithiatic and antioxidative efficacy of Dolichos biflorus seeds in a lithiasic rat model.

CONTEXT: Dolichos biflorus sensu auct non L. (Fabaceae) is widely used for the treatment of kidney stones, leucorrhoea, urinary disorders, and menstrual troubles, and is known for its antioxidant activity. OBJECTIVES: To evaluate the preventive effect of hydro-alcoholic extract of Dolichos biflorus seeds (DBE) in ethylene glycol induced nephrolithiasis. MATERIALS AND METHODS: In vitro antioxidative capacity of DBE was estimated in terms of reducing power, superoxide radical, 2,2- diphenyl-1-picrylhydrazyl radical, and nitric oxide scavenging activity. A validated HPLC method was used for standardization using quercetin as a marker. Adult female Wistar rats were administered with DBE (150 and 300 mg/kg body weight/day) along with ethylene glycol (0.75%, v/v) for 28 d. The various biochemical parameters were measured in urine, serum, and kidney followed by histochemistry. RESULTS: Ethylene glycol caused a significant increase in calcium, oxalate, phosphate, and total protein in urine as well as in kidney whereas decrease in calcium, sodium, and magnesium in serum was observed (p < 0.001). Ethylene glycol also caused a significant increase in lipid peroxidation and concurrent decrease in activities of antioxidant enzymes in kidney (p < 0.001). However, the seed extract of D. biflorus caused significant restoration of all these parameters (p < 0.001). Histopathological and histochemical studies also showed the reduced calcifications in kidney of seed extract treated rats. DISCUSSION AND CONCLUSION: These results indicated that seeds of D. biflorus have significant prophylactic effect in preventing the nephrolithiasis, which might be due to the antioxidant activity of the active compounds of the plant.

Isolation and prevention of calcium oxalate-induced apoptotic death and oxidative stress in MDCK cells by diosgenin.

Calcium oxalate monohydrate (COM) has been shown to be the most frequent constituent of kidney stones. The interactions of cells with COM crystals produce a variety of physiological and pathological changes including the development of oxidative stress, cellular injury and apoptosis. On the other hand, diosgenin, a steroidal sapogenin, is well known for its antioxidant activity. Therefore, the aim of this study was to evaluate whether diosgenin protects MDCK renal epithelial cells from COM-induced apoptotic death. Diosgenin was isolated from fruits of Solanum xanthocarpum by silica gel column chromatography. It was obtained in high yields (1.23%) and the purity was ascertained by HPTLC analysis. Characterization of diosgenin was done by mp, UV-visible spectrophotometry, elemental analysis, FT-IR, (1)H NMR and (13)C NMR analysis. Cells were co-incubated with COM (80µg/cm(2)) and diosgenin (2.5, 5, 7.5 and 10µg/mL) for 24h. It was found that diosgenin attenuated the apoptotic death induced by COM as measured in terms of cell viability, caspase -9/3 activities and DNA fragmentation percent. The inhibitory role of diosgenin on caspase -9/3 activities was also analyzed using molecular docking experiments, which showed interactions to their active sites by H-bonds. Diosgenin also attenuated the increase in lipid peroxidation and glutathione depletion induced by COM crystals. In conclusion, the preventive effect of diosgenin is associated to the inhibition of oxidative stress and caspases.

Antioxidative mechanism involved in the preventive efficacy of Bergenia ciliata rhizomes against experimental nephrolithiasis in rats.

CONTEXT: Bergenia ciliata Haw. (Saxifragaceae) is widely used in traditional medicines for renal disorders including kidney stones, inflammation and also well known for its antioxidant activity. Use of traditional herbs proved to be an important strategy for the management of kidney stones by modulating the oxidative stress imposed by calcium oxalate nephrolithiasis. OBJECTIVES: To evaluate the antinephrolithiatic and antioxidative activity of B. ciliata rhizomes as a preventive agent on ethylene glycol (EG)-induced nephrolithiasis. MATERIALS AND METHODS: The hydro-methanol extract (30:70, v/v) of B. ciliata rhizomes was orally administrated simultaneously at a dose of 150 and 300 mg/kg body weight/day, to adult female Wistar rats for 28 d along with EG (0.75%, v/v) in drinking water. The results were compared to a parallel study conducted with marketed polyherbal drug cystone under identical dosage conditions. The biochemical parameters were measured in urine, serum and kidney followed by histochemistry. A validated HPLC method was used for standardization using gallic acid as a marker. RESULTS: EG caused a significant increase in calcium, oxalate and phosphate levels in urine and kidney and concurrent decrease in calcium, sodium and magnesium in serum (p<0.001). EG also caused an increase in lipid peroxidation and a decrease in activities of antioxidative enzymes in kidney. Co-treatment with B. ciliata rhizomes extract caused restoration of all these parameters (p<0.001). Histochemical studies showed reduced calcifications with extract treatment. CONCLUSION: B. ciliata has a significant prophylactic effect in preventing the nephrolithiasis, which might be mediated through antioxidant activity of these active compounds.

Antibody epitopes on g protein-coupled receptors mapped with genetically encoded photoactivatable cross-linkers.

We developed a strategy for creating epitope maps of monoclonal antibodies (mAbs) that bind to G protein-coupled receptors (GPCRs) containing photo-cross-linkers. Using human CXC chemokine receptor 4 (CXCR4) as a model system, we genetically incorporated the photolabile unnatural amino acid p-azido-l-phenylalanine (azF) at various positions within extracellular loop 2 (EC2). We then mapped the interactions of the azF-CXCR4 variants with mAb 12G5 using targeted loss-of-function studies and photo-cross-linking in whole cells in a microplate-based format. We used a novel variation of a whole cell enzyme-linked immunosorbent assay to quantitate cross-linking efficiency. 12G5 cross-linked primarily to residues 184, 178, and 189 in EC2 of CXCR4. Mapping of the data to the crystal structure of CXCR4 showed a distinct mAb epitope footprint with the photo-cross-linked residues clustered around the loss-of-function sites. We also used the targeted photo-cross-linking approach to study the interaction of human CC chemokine receptor 5 (CCR5) with PRO 140, a humanized mAb that inhibits human immunodeficiency virus-1 cellular entry, and 2D7. The mAbs produced distinct cross-linking patterns on EC2 of CCR5. PRO 140 cross-linked primarily to residues 174 and 175 at the amino-terminal end of EC2, and 2D7 cross-linked mainly to residues 170, 176, and 184. These results were mapped to the recent crystal structure of CCR5 in complex with maraviroc, showing cross-linked residues at the tip of the maraviroc binding crevice formed by EC2. As a strategy for mapping mAb epitopes on GPCRs, our targeted photo-cross-linking method is complementary to loss-of-function mutagenesis results and should be especially useful for studying mAbs with discontinuous epitopes.

Inhibitory potential of traditional herbs on α-amylase activity.

CONTEXT: There has been enormous interest in the development of alternative medicines for the control of diabetes. Use of carbohydrate-hydrolyzing enzyme inhibitors proved to be an important strategy for the management of postprandial hyperglycemia by delaying the process of carbohydrate hydrolysis and absorption. OBJECTIVE: Three common traditional herbs, namely, stem bark of Terminalia arjuna (Combretaceae), seeds of Eugenia cumini (Myrtaceae), and leaves of Aegle marmelos (Rutaceae), were tested for their α-amylase inhibitory activities to establish antidiabetic potential. MATERIALS AND METHODS: The plant extracts (aqueous, 50%, and 100% methanol) obtained were subjected to an in vitro amylase inhibitory assay using starch as a substrate and pancreatic amylase as the enzyme. Statistical differences and linear regression analysis were performed using GraphPad prism 5 software. RESULTS: The 50% methanol extracts of T. arjuna, E. cumini, and A. marmelos at a concentrations 50-500 µg/mL showed maximum percentage inhibition on amylase activity with IC(50) values of 302 ± 0.55, 632 ± 0.21, and 503 ± 0.28 µg/mL, respectively. However, the 100% methanol extracts of all the three plants showed the least inhibitory activity. DISCUSSION AND CONCLUSION: The results show that T. arjuna > E. cumini > A. marmelos have excellent inhibitory activity and, therefore, might be effective in lowering postprandial hyperglycemia.

Bergenia ciliata extract prevents ethylene glycol induced histopathological changes in the kidney.

The present investigation is an attempt to evaluate the effect of Bergenia ciliata extract on kidney of ethylene glycol induced urolithiasis in adult female Wistar rats. The hydro-alcoholic extract of Bergenia ciliata/standard drug cystone were administrated simultaneously at a dose of 150 and 300 mg/kg body weight/day, p.o. along with ethylene glycol (0.75% v/v) for 28 days. Significant changes were observed in body weight and absolute organ weight of ethylene glycol treated rats. Also histopathological results showed disrupted renal parenchyma, degenerative changes in glomeruli and focal calcification in glomerulo-tubular structures in ethylene glycol treated animals. Administration of Bergenia ciliata extract/cystone along with ethylene glycol showed significant protective effect in body weight and organ weight with few stray areas of calcifications in glomeruli. Moreover, Bergenia ciliata extract shows higher renoprotective index than cystone at the same dose level.