Endoplasmic reticulum stress-dependent activation of TRB3-FoxO1 signaling pathway exacerbates hyperglycemic nephrotoxicity: Protection accorded by Naringenin.

Endoplasmic reticulum (ER) dysfunction contributes greatly to the pathophysiology of hyperglycemic nephrotoxicity. This study unravels the critical role of Tribbles 3 (TRB3)-Forkhead box O1 (FoxO1) signaling pathway during hyperglycemic renal toxicity. It also uncovers the novel role of Naringenin, a flavanone, in regulating ER stress in proximal tubular cells, NRK 52E, and kidneys of streptozotocin/nicotinamide induced experimental diabetic Wistar rats. Results demonstrate that expression of ER stress marker proteins including phosphorylated protein kinase ER like kinase (p-PERK), phosphorylated eukaryotic Initiation Factor 2α (p-eIF2α), X Box Binding Protein 1 spliced (XBP1s), Activating Transcription Factor 4 (ATF4) and C/EBP Homologous Protein (CHOP) were upregulated in diabetic kidneys indicating the activation of ER stress response due to nephrotoxicity. Treatment with Naringenin reduced the expression of TRB3, an ER stress-inducible pseudokinase, both in vitro and in vivo. Gene silencing of TRB3 enhanced Akt and FoxO1 phosphorylation and alleviated FoxO1 mediated apoptosis during hyperglycemic nephrotoxicity. Notably, TRB3 gene silencing effects were comparable to the response with Naringenin treatment. Prevention of nuclear colocalization of ATF4 and CHOP in Naringenin treated cells was evident. Naringenin also reduced insulin resistance, apoptosis and glycogen accumulation along with enhancement of glucose tolerance in diabetic rats. Prevention of ultrastructural aberrations in the ER of hyperglycemic renal cells by Naringenin confirmed its anti-ER stress effects. These findings affirm that activation of TRB3-FoxO1 signaling is critical in the pathogenesis of hyperglycemia-induced renal toxicity and protective effect of Naringenin via modulation of ER stress may be exploited as a novel approach for its management.

Naringenin alleviates hyperglycemia-induced renal toxicity by regulating activating transcription factor 4-C/EBP homologous protein mediated apoptosis.

Endoplasmic reticulum (ER) dysfunction plays a prominent role in the pathophysiology of diabetic nephropathy (DN). This study aimed to investigate the novel role of Naringenin (a flavanone mainly found in citrus fruits) in modulating ER stress in hyperglycemic NRK 52E cells and STZ/nicotinamide induced diabetes in Wistar rats. The results demonstrated that Naringenin supplementation downregulated the expression of ER stress marker proteins, including p-PERK, p-eIF2α, XBP1s, ATF4 and CHOP during hyperglycemic renal toxicity in vitro and in vivo. Naringenin abrogated hyperglycemia-induced ultrastructural changes in ER, evidencing its anti-ER stress effects. Interestingly, treatment of Naringenin prevented nuclear translocation of ATF4 and CHOP in hyperglycemic renal cells and diabetic kidneys. Naringenin prevented apoptosis in hyperglycemic renal cells and diabetic kidney tissues by downregulating expression of apoptotic marker proteins. Further, photomicrographs of TEM confirmed anti-apoptotic potential of Naringenin as it prevented membrane blebbing and formation of apoptotic bodies in hyperglycemic renal cells. Naringenin improved glucose tolerance, restored serum insulin level and reduced serum glucose level in diabetic rats evidencing its anti-hyperglycemic effects. Histopathological examination of kidney tissues also confirmed prevention of damage after 28 days of Naringenin treatment in diabetic rats. Additionally, Naringenin diminished oxidative stress and improved antioxidant defense response during hyperglycemic renal toxicity. Taken together, our study revealed a novel role of Naringenin in ameliorating ER stress during hyperglycemic renal toxicity along with prevention of apoptosis, cellular and tissue damage. The findings suggest that prevention of ER stress can be exploited as a novel approach for the management of hyperglycemic nephrotoxicity.

PHLPP1/Nrf2-Mdm2 axis induces renal apoptosis via influencing nucleo-cytoplasmic shuttling of FoxO1 during diabetic nephropathy.

Impaired PI3K/Akt signaling (insulin resistance) and poor glycemic control (hyperglycemia) are the major risk factors involved in the progression of diabetic nephropathy (DN). This study was designed to identify factors influencing cell survival during DN. We found that high glucose exposure in renal proximal tubular cells (NRK52E) upregulated PHLPP1, an Akt phosphatase (Ser473), causing suppression in Akt and IGF1ß phosphorylation leading to inhibition in insulin signaling pathway. Results demonstrate that sustained activation of PHLPP1 promoted nuclear retention of FoxO1 by preventing its ubiquitination via Mdm2, an Akt/ Nrf2-dependent E3 ligase. Thus, enhanced FoxO1 nuclear stability caused aberration in renal gluconeogenesis and activated apoptotic cascade. Conversely, gene silencing of PHLPP1-enhanced Nrf2 expression and attenuated FoxO1 regulated apoptosis compared to hyperglycemic cells. Mechanistic aspects of PHLPP1-Nrf2/FoxO1 signaling were further validated in STZ-nicotinamide-induced type 2 diabetic Wistar rats. Importantly, we observed via immunoblotting and dual immunocytochemical studies that treatment of Morin (2',3,4',5,7-Pentahydroxyflavone) during diabetes significantly augmented FoxO1 nuclear exclusion, resulting in its ubiquitination via Akt-Nrf2/Mdm2 pathway. Furthermore, lowering of PHLPP1 expression by Morin also prevented FoxO1/Mst1-mediated apoptotic signaling in vitro and in vivo. Morin treatment under the experimental conditions, effectively decreased blood glucose levels, ameliorated insulin resistance, alleviated oxidative stress and attenuated renal apoptosis in diabetic rats comparable to metformin thereby exhibiting tremendous potential against renal complications of diabetes. These novel results further acclaim that inhibition of PHLPP1/FoxO1-Mdm2 axis is critical in the pathogenesis of diabetic nephropathy.

Nano-fibrous scaffold with curcumin for anti-scar wound healing.

Open deep cuts and wounds often take a long time to heal and may cause infection and scar formation. A simple biomimetic electrospun nano-fibrous antimicrobial dressing material loaded with dual anti-oxidants has been developed to address this problem. A composite nano-fibrous material (PVP-Ce-Cur NF) comprising polyvinyl pyrrolidone (PVP), cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and curcumin was developed using the electrospinning technique. The surface characteristics of nanofibers were examined using standard analytical techniques. The antimicrobial activity was tested against Escherichia coli (gram -ve) and Staphylococcus aureus (gram +ve) bacterial species. The MTT assay using 3T6-Swiss albino fibroblast indicated that the nano-fibrous dressing material was hemocompatible and devoid of cytotoxicity. Direct application of the PVP-Ce-Cur NF dressing material on full-thickness circular excision wound in model wistar rats displayed complete healing and re-epithelialisation without any scar within 20 days. A well-regulated level of hydroxyproline, superoxide dismutase (SOD) and catalase in granulation tissues indicated PVP-Ce-Cur NF as a potential wound dressing material with the anti-scar property.

Antimicrobial biodegradable chitosan-based composite Nano-layers for food packaging.

Stable silver nanoparticles (AgNPs) of size 80 ± 11 nm produced by chitosan (CH) mediated green synthesis were blended with polyvinyl alcohol (PVA) to form electrospun fibrous composite nano-layers (FCNLs). The chitosan acted as the stabilising as well as an antimicrobial agent in combination with the AgNPs which were characterised using UV-visible spectrophotometry, dynamic light scattering (DLS) and scanning electron microscopy (SEM). The crystallinity and chemical nature of the electrospun composite was characterised by using X-ray diffraction (XRD) and FTIR spectroscopy, respectively, and its hydrophobicity was characterised by measuring the water contact angle. The electrospun composite showed effective antimicrobial activity against Listeria monocytogenes (gram +ve) and Escherichia coli (gram -ve) bacterial species. The electrospun composite, when tested as packaging material for meat, showed bio-activity and extended the meat shelf-life by one week. The electrospun nanocomposite is able to inhibit microbial degradation of packaged food and extend its keeping quality in an eco-friendly manner.

Differential Susceptibility of Catheter Biomaterials to Biofilm-Associated Infections and Their Remedy by Drug-Encapsulated Eudragit RL100 Nanoparticles.

Biofilms are the cause of major bacteriological infections in patients. The complex architecture of Escherichia coli (E. coli) biofilm attached to the surface of catheters has been studied and found to depend on the biomaterial's surface properties. The SEM micrographs and water contact angle analysis have revealed that the nature of the surface affects the growth and extent of E. coli biofilm formation. In vitro studies have revealed that the Gram-negative E. coli adherence to implanted biomaterials takes place in accordance with hydrophobicity, i.e., latex > silicone > polyurethane > stainless steel. Permanent removal of E. coli biofilm requires 50 to 200 times more gentamicin sulfate (G-S) than the minimum inhibitory concentration (MIC) to remove 90% of E. coli biofilm (MBIC90). Here, in vitro eradication of biofilm-associated infection on biomaterials has been done by Eudragit RL100 encapsulated gentamicin sulfate (E-G-S) nanoparticle of range 140 nm. It is 10-20 times more effective against E. coli biofilm-associated infections eradication than normal unentrapped G-S. Thus, Eudragit RL100 mediated drug delivery system provides a promising way to reduce the cost of treatment with a higher drug therapeutic index.

Biomimetic PCL-gelatin based nanofibers loaded with ciprofloxacin hydrochloride and quercetin: A potential antibacterial and anti-oxidant dressing material for accelerated healing of a full thickness wound.

An open wound is highly susceptible to microbial infection leading to elevated level of inflammatory response. For prompt healing, a wound requires a biomimetic dressing material with ideal hydrophilicity and tensile strength, possessing antimicrobial and antioxidant property. Although PCL-based nanofibers have sufficient tensile strength and biocompatibility, it lacks in terms of optimum hydrophilicity and biodegradation. Therefore, we fabricated a PCL-gelatin based electrospun nanofibers, enriched with quercetin and ciprofloxacin hydrochloride (CH). The average diameter of developed nanofibers was 725.943 ±â€¯201.965 nm, and devoid of chemical interaction between two drugs and polymers. CH and quercetin exhibited biphasic in-vitro release in phosphate buffer (pH 7.4). The in-vitro antibacterial and antioxidant property of scaffolds were evaluated by film-diffusion against Staphylococcus aureus and DPPH assay, respectively. The addition of gelatin along with CH and quercetin enhanced the hydrophilicity (contact angle = 48.8 ±â€¯2.95°) and biodegradation rate of the nanofibers. In-vitro biocompatibility of scaffold was examined by hemocompatibility and fibroblast viability using MTT assay. The results confirm the direct application of scaffold in the wounded area. Further, complete closure of full-thickness wound within 16 days, and regulation of hydroxyproline, SOD and catalase level in granulation tissues following treatment with scaffold, confirmed its application for accelerated wound healing.

Activation of PERK-eIF2α-ATF4 pathway contributes to diabetic hepatotoxicity: Attenuation of ER stress by Morin.

Hyperglycemia associated ER stress has been found as a critical contributor in the pathogenesis of type 2 diabetes mellitus. However, reports regarding molecular mechanisms involved are limited. This study was aimed to identify the role of ER stress in regulating hepatic glucose metabolism and its link with oxidative stress. Further, this study explores the novel role of Morin, a flavonol, in modulating ER stress in STZ/nicotinamide induced type 2 diabetic male Wistar rats. Results demonstrate that hyperglycemia induced ER stress in rats and significantly lowered the expression of glucose transporter proteins resulting in impaired glucose metabolism during diabetes. Morin was found to downregulate PERK-eIF2α-ATF4 pathway by interacting with PERK protein as confirmed through pull-down assay. Additionally, Morin maintained the reducing environment in ER and enhanced PDI activity compared to diabetic rats. Morin prevented cell death by suppressing the expression of PERK dependent pro-apoptotic proteins including ATF4 and CHOP. Findings from this study affirm the role of ER stress in hyperglycemia induced gluco-metabolic aberrations and liver injury as confirmed by ISRIB, a standard chemical ER stress inhibitor. Notably, Morin promoted deactivation of UPR sensors and upregulated PDI activity endorsing its anti-ER stress potential which may allow the development of new therapeutic avenues to target hyperglycemic hepatotoxicity.

Ciprofloxacin HCl and quercetin functionalized electrospun nanofiber membrane: fabrication and its evaluation in full thickness wound healing.

Microbial infection and oxidative damage of the fibroblast often results in prolonged and incomplete wound healing. Therefore, there is an increasing demand for a scaffold being effective to prevent any possible infection and neutralize excessively released free radicals. Herein, we designed a PCL-based nanofiber loaded with ciprofloxacin hydrochloride (CHL) and quercetin. Developed nanofiber showed the formation of smooth and continuous nanofiber with 101.59 ± 29.18 nm average diameter and entrapping the drugs in amorphous form without any possible physico-chemical interaction between drugs and excipient. High entrapment efficiency (CHL: 92.04% and Que: 94.32%) and prolonged in-vitro release (for 7 days) demonstrated the capability of scaffold to suppress any probable infection and oxidative damage, which was further confirmed by in-vitro antibacterial and antioxidant activity. The biocompatibility of scaffold for direct application to wound site was evaluated through hemocompatibility and cytocompatibility assay. The wound healing efficacies of nanofiber were assessed using full thickness wound model in rats, which displayed accelerated wound healing with complete re-epithelialization and improved collagen deposition within 16 days. In-vivo wound healing finding was further corroborated by SOD, catalase, and hydroxyproline assay. The current study validates the application of ciprofloxacin HCl and quercetin functionalized nanofiber as a potential wound dressing material.

Emerging role of Unfolded Protein Response (UPR) mediated proteotoxic apoptosis in diabetes.

Endoplasmic reticulum (ER) is a crucial single membrane organelle that acts as a quality control system for cellular proteins as it is intricately involved in their synthesis, folding and trafficking to the respective targets. Type 2 diabetes is characterized by enhanced blood glucose level that promotes insulin resistance and hampers cellular glucose metabolism. Hyperglycemia provokes mitochondrial ROS production and glycation of proteins which exert a tremendous load on ER for conventional refolding of misfolded/unfolded and nascent proteins that perturb ER homeostasis resulting in apoptotic cell death. Impairment in ER functions is suspected to be through specific ER membrane-bound proteins known as Unfolded Protein Response (UPR) sensor proteins. Conformational changes in these proteins induce oligomerization and cross-autophosphorylation which facilitate processes required for the restoration of ER homeostatic imbalance. Multiple studies have reported the involvement of UPR mediated autophagy and apoptotic pathways in the progression of metabolic disorders including diabetes, cardiac ischemia/reperfusion injury and hypoxia-mediated cell death. In this review, the involvement of UPR pathways in the progression of diabetes associated complications have been addressed, which underscores molecular crosstalks during neuropathy, nephropathy, hepatic injury and retinopathy. A better understanding of these molecular interventions may reveal advanced therapeutic approaches for preventing diabetic comorbidities. The article also highlights the importance of phytochemicals that are emerging as novel ER stress inhibitors and are being explored for targeted interaction in preventing cell death responses during diabetes.

Activation of GSK3ß/ß-TrCP axis via PHLPP1 exacerbates Nrf2 degradation leading to impairment in cell survival pathway during diabetic nephropathy.

NF-E2 p45-related factor 2 (Nrf2), is a major redox sensitive transcription factor that plays an essential role in regulating glucose metabolism. Inactivation of Nrf2 has been associated with diabetic complications however, mechanisms warranting Nrf2 suppression are incompletely understood. We hypothesized that PHLPP1 activates GSK3ß to induce ß-TrCP mediated Nrf2 phosphorylation and degradation. In vivo study was carried out in STZ-NA induced type 2 diabetic male Wistar rats. GSK3ß mediated Nrf2 ubiquitination was confirmed by administration of GSK3ß inhibitor (LiCl; 60 mg/kg bwt.) which rapidly enhanced Nrf2 protein levels in STZ-NA treated diabetic rats. In addition, high glucose (30 mM; 48 h) treated renal proximal tubular cells NRK52E showed decreased Nrf2 nuclear localization, enhanced oxidative stress and caspase3 activation. While specific inhibition with GSK3ß inhibitor SB216763 in vitro restored cellular homeostasis, glucose uptake and decreased apoptotic cell death. Immunoblotting and immunocytochemistry data demonstrated that aberrant renal glucose fluxes are associated with p53 mediated modulation in glucose transporter levels where expression of p53 is indirectly targeted through Nrf2 responsive MDM2 protein. Gene knockdown of PHLPP1 in NRK52E cells enhanced Nrf2-responsive antioxidant enzymes HO-1 and NQO-1 which suggested that PHLPP1 up-regulation during hyperglycemia lowers Nrf2 stability via GSK3ß activation. More significantly, GSK3ß inhibition enhanced Nrf2-ARE binding compared to diabetic rats, providing further confirmation for GSK3ß/ß-TrCP pathway in suppressing Nrf2 activation during diabetic renal injury. Taken together, our results indicate that PHLPP1 up-surged Nrf2 nuclear instability by promoting Nrf2/ß-TrCP association and its inhibition may be critical in the management of diabetic nephropathy.

PHLPP: a putative cellular target during insulin resistance and type 2 diabetes.

Progressive research in the past decade converges to the impact of PHLPP in regulating the cellular metabolism through PI3K/AKT inhibition. Aberrations in PKB/AKT signaling coordinates with impaired insulin secretion and insulin resistance, identified during T2D, obesity and cardiovascular disorders which brings in the relevance of PHLPPs in the metabolic paradigm. In this review, we discuss the impact of PHLPP isoforms in insulin signaling and its associated cellular events including mitochondrial dysfunction, DNA damage, autophagy and cell death. The article highlights the plausible molecular targets that share the role during insulin-resistant states, whose understanding can be extended into treatment responses to facilitate targeted drug discovery for T2D and allied metabolic syndromes.

Concurrent acetylation of FoxO1/3a and p53 due to sirtuins inhibition elicit Bim/PUMA mediated mitochondrial dysfunction and apoptosis in berberine-treated HepG2 cells.

Post-translational modifications i.e. phosphorylation and acetylation are pivotal requirements for proper functioning of eukaryotic proteins. The current study aimed to decode the impact of acetylation/deacetylation of non-histone targets i.e. FoxO1/3a and p53 of sirtuins (NAD(+) dependent enzymes with lysine deacetylase activity) in berberine treated human hepatoma cells. Berberine (100 µM) inhibited sirtuins significantly (P<0.05) at transcriptional level as well as at translational level. Combination of nicotinamide (sirtuin inhibitor) with berberine potentiated sirtuins inhibition and increased the expression of FoxO1/3a and phosphorylation of p53 tumor suppressor protein. As sirtuins deacetylate non-histone targets including FoxO1/3a and p53, berberine increased the acetylation load of FoxO1/3a and p53 proteins. Acetylated FoxO and p53 proteins transcriptionally activate BH3-only proteins Bim and PUMA (3.89 and 3.87 fold respectively, P<0.001), which are known as direct activator of pro-apoptotic Bcl-2 family protein Bax that culminated into mitochondria mediated activation of apoptotic cascade. Bim/PUMA knock-down showed no changes in sirtuins' expression while cytotoxicity induced by berberine and nicotinamide was curtailed up to 28.3% (P<0.001) and it restored pro/anti apoptotic protein ratio in HepG2 cells. Sirtuins inhibition was accompanied by decline in NAD(+)/NADH ratio, ATP generation, enhanced ROS production and decreased mitochondrial membrane potential. TEM analysis confirmed mitochondrial deterioration and cell damage. SRT-1720 (1-10 µM), a SIRT-1 activator, when pre-treated with berberine (25 µM), reversed sirtuins expression comparable to control and significantly restored the cell viability (P<0.05). Thus, our findings suggest that berberine mediated sirtuins inhibition resulting into FoxO1/3a and p53 acetylation followed by BH3-only protein Bim/PUMA activation may in part be responsible for mitochondria-mediated apoptosis.