JNK1 ablation improves pancreatic β-cell mass and function in db/db diabetic mice without affecting insulin sensitivity and adipose tissue inflammation

Antimony induces mitochondria-dependent and ER stress-triggered apoptosis via the oxidative stress-activated JNK signaling pathway in pancreatic islet β-cells

Antimony (Sb), a silvery-white metal, is a heavy metal of particular prevalence that has the ability to result in adverse effects in humans through environmental exposure resulting from natural processes and human activities. Epidemiological studies have suggested that Sb has an association with the potential for diabetes mellitus (DM) development. However, the mechanisms by which Sb exerts toxicological effects on pancreatic islet β-cells are still not clear. In this investigation, Sb exposure significantly inhibited rat pancreatic islet β-cell-derived RIN-m5F cell viability and insulin secretion, while inducing mitochondria-dependent apoptotic signals, inclusive of increased apoptotic cell populations, caspase-3 activity, the expression of PARP and caspase-3/-7/-9, and mitochondrial dysfunction. RIN-m5F cells exposure to Sb also led to the triggering of endoplasmic reticulum (ER) stress via the induction of a number of vital molecules, including CHOP, XBP-1s, and caspase-12. In Sb-exposed RIN-m5F cells, 4-PBA pretreatment (an inhibitor of ER stress) significantly suppressed protein expression related to ER stress and events of an apoptotic nature. Furthermore, exposure to Sb resulted in the significant activation of AMPKα, ERK1/2, and JNK signaling, as well as reactive oxygen species (ROS) generation. Pretreatment with SP600125 (an inhibitor of JNK) and antioxidant NAC, but not PD98059 (an inhibitor of ERK) or compound C (an inhibitor of AMPK), effectively abrogated the cytotoxicity, ER stress responses, mitochondrial dysfunction, apoptotic events, insulin secretion inhibition, and JNK activation in Sb-exposed rat pancreatic islet β-cells. However, SP600125 did not prevent ROS generation, which was inhibited by the antioxidant NAC. Collectively, the results demonstrate exposure to Sb to exert β-cell cytotoxicity through oxidative stress-activated JNK signaling downstream-regulated mitochondria-dependent and ER stress-triggered cell apoptotic pathways, eventually resulting in the death of rat pancreatic islet β-cells.

Tubular IKKβ Deletion Alleviates Acute Ischemic Kidney Injury and Facilitates Tissue Regeneration

Acute kidney injury (AKI) is a common renal injury leading to relevant morbidity and mortality worldwide. Most of the clinical cases of AKI are caused by ischemia reperfusion (I/R) injury with renal ischemia injury followed by reperfusion injury and activation of the innate immune response converging to NF-ĸB pathway induction. Despite the clear role of NF-ĸB in inflammation, it has recently been acknowledged that NF-ĸB may impact other cell functions. To identify NF-ĸB function with respect to metabolism, vascular function and oxidative stress after I/R injury and to decipher in detail the underlying mechanism, we generated a transgenic mouse model with targeted deletion of IKKβ along the tubule and applied I/R injury followed by its analysis after 2 and 14 days after I/R injury. Tubular IKKβ deletion ameliorated renal function and reduced tissue damage. RNAseq data together with immunohistochemical, biochemical and morphometric analysis demonstrated an ameliorated vascular organization and mRNA expression profile for increased angiogenesis in mice with tubular IKKβ deletion at 2 days after I/R injury. RNAseq and protein analysis indicate an ameliorated metabolism, oxidative species handling and timely-adapted cell proliferation and apoptosis as well as reduced fibrosis in mice with tubular IKKβ deletion at 14 days after I/R injury. In conclusion, mice with tubular IKKβ deletion upon I/R injury display improved renal function and reduced tissue damage and fibrosis in association with improved vascularization, metabolism, reactive species disposal and fine-tuned cell proliferation.

Arctostaphylos uva-ursi L. leaves extract and its modified cysteine preparation for the management of insulin resistance: chemical analysis and bioactivity

Bearberry (Arctostaphylos uva-ursi L.) is a perennial plant of the heather family (Ericaceae). The leaves are dominated by arbutin, phenol carbonic acids flavonoids, saponins, etc. It was previously shown that the bearberry leaves extract reduced blood glucose level in healthy animals under glucose overload, so it need to be studied more detail. The aim of the study was to investigate the chemical composition and the effect of dry alcohol extract from bearberry leaves, which enriched with cysteine, on the rats pancreas under experimental dexamethasone-induced insulin resistance (IR). Arctostaphylos uva-ursi L. leaves extract and its modified cysteine preparation were obtained according to the developed method with 50% ethanol solution. Their phytochemical profile, hypoglycaemic and pancreatic protective effect were investigated. Phenologlycoside (arbutin), phenolic carboxylic acid (gallic acid), 5 flavonoids and 4 hydroxycinnamic acids were identified and quantified in the extracts by HPLC. Present data revealed that bearberry leaves alcoholic dry extract enriched with cysteine has a hypoglycaemic and pancreatic protective effect in treated animals under dexamethasone-induced IR model. Treatment improved hyperglycaemia, insulin resistance and beta cell reduction induced by dexamethasone injections.

Circular RNA PIP5K1A act as microRNA-552-3p sponge to regulates inflammation, oxidative damage in glucolipotoxicity-induced pancreatic INS-1 β-cells via Janus kinase 1

Elevated level of glucolipotoxicity induces the loss of pancreatic β-cells functions and plays an important role in the development of type 2 diabetes (T2DM). Previous studies have indicated the importance of developing therapies against T2DM, while circular RNA (circRNA) has gained attraction as a modulator of pancreatic β-cell function. In the present study role of circPIP5K1A in dysfunctional β cells and mouse pancreas was comprehensively analyzed. INS-1E, as it has close similarity with naïve pancreatic β-cells, and clinical samples of T2DM patients were used to investigate the effect of circPIP5K1A, miR-552-3p, and Janus kinase 1 (JAK1). While, INS-1E cells were exposed to PAHG conditions (0.5 mM palmitic acid and 28 mM glucose) as studies have suggested that increased level of fatty acid and glucose resulted in autophagy activation of pancreatic β-cells that leads to T2DM. Key player of JAK1-STAT3 pathway and the level of Reactive Oxygen Species, inflammatory factors, and insulin secretion was detected to analyze the of the active association of circPIP5K1A, miR-552-3p with JAK1pathway. Our study has revealed the elevated level ofcircPIP5K1A and JAK1, but reduced level of miR-552-3pin the serum of T2DM patients. Furthermore, we also found that reduced expression ofcircPIP5K1A leads to decreased rate of inflammation, oxidative damage and apoptosisinINS-1E cells induced by glucolipotoxicity. CircPIP5K1A was available to competitively combine with miR-552-3p, while whose direct target was JAK1. In conclusion, our study suggested a novel involvement of circPIP5K1A in a cross talk between miR5523p/JAK1/STAT3 pathways in β-cells as a new therapeutic target for T2DM.  

Establishment of a Reproducible Ischemic Stroke Model in Nestin-GFP Mice with High Survival Rates

An accumulation of evidence shows that endogenous neural stem/progenitor cells (NSPCs) are activated following brain injury such as that suffered during ischemic stroke. To understand the expression patterns of these cells, researchers have developed mice that express an NSPC marker, Nestin, which is detectable by specific reporters such as green fluorescent protein (GFP), i.e., Nestin-GFP mice. However, the genetic background of most transgenic mice, including Nestin-GFP mice, comes from the C57BL/6 strain. Because mice from this background strain have many cerebral arterial branches and collateral vessels, they are accompanied by several major problems including variable ischemic areas and high mortality when subjected to ischemic stroke by occluding the middle cerebral artery (MCA). In contrast, CB-17 wild-type mice are free from these problems. Therefore, with the aim of overcoming the aforementioned defects, we first crossed Nestin-GFP mice (C57BL/6 background) with CB-17 wild-type mice and then developed Nestin-GFP mice (CB-17 background) by further backcrossing the generated hybrid mice with CB-17 wild-type mice. Subsequently, we investigated the phenotypes of the established Nestin-GFP mice (CB-17 background) following MCA occlusion; these mice had fewer blood vessels around the MCA compared with the number of blood vessels in Nestin-GFP mice (C57BL/6 background). In addition, TTC staining showed that infarcted volume was variable in Nestin-GFP mice (C57BL/6 background) but highly reproducible in Nestin-GFP mice (CB-17 background). In a further investigation of mice survival rates up to 28 days after MCA occlusion, all Nestin-GFP mice (CB-17 background) survived the period, whereas Nestin-GFP mice (C57BL/6 background) frequently died within 1 week and exhibited a higher mortality rate. Immunohistochemistry analysis of Nestin-GFP mice (CB-17 background) showed that GFP⁺ cells were mainly obverted in not only conventional neurogenic areas, including the subventricular zone (SVZ), but also ischemic areas. In vitro, cells isolated from the ischemic areas and the SVZ formed GFP⁺ neurosphere-like cell clusters that gave rise to various neural lineages including neurons, astrocytes, and oligodendrocytes. However, microarray analysis of these cells and genetic mapping experiments by Nestin-CreERT2 Line4 mice crossed with yellow fluorescent protein (YFP) reporter mice (Nestin promoter-driven YFP-expressing mice) indicated that cells with NSPC activities in the ischemic areas and the SVZ had different characteristics and origins. These results show that the expression patterns and fate of GFP⁺ cells with NSPC activities can be precisely investigated over a long period in Nestin-GFP mice (CB-17 background), which is not necessarily possible with Nestin-GFP mice (C57BL/6 background). Thus, Nestin-GFP mice (CB-17 background) could become a useful tool with which to investigate the mechanism of neurogenesis via the aforementioned cells under pathological conditions such as following ischemic stroke.