Akt activation protects liver cells from apoptosis in rats during acute cold exposure

The role of NAD-dependent deacetylase sirtuin-2 in liver metabolic stress through regulating pyruvate kinase M2 ubiquitination

NAD-dependent deacetylase Sirt2 is involved in mammalian metabolic activities, matching energy demand with energy production and expenditure, and is relevant to a variety of metabolic diseases. Here, we constructed Sirt2 knockout and adeno-associated virus overexpression mice and found that deletion of hepatic Sirt2 accelerated primary obesity and insulin resistance in mice with concomitant hepatic metabolic dysfunction. However, the key targets of Sirt2 are unknown. We identified the M2 isoform of pyruvate kinase (PKM2) as a key Sirt2 target involved in glycolysis in metabolic stress. Through yeast two-hybrid and mass spectrometry combined with multi-omics analysis, we identified candidate acetylation modification targets of Sirt2 on PKM2 lysine 135 (K135). The Sirt2-mediated deacetylation-ubiquitination switch of PKM2 regulated the development of glycolysis. Here, we found that Sirt2 deficiency led to impaired glucose tolerance and insulin resistance and induced primary obesity. Sirt2 severely disrupted liver function in mice under metabolic stress, exacerbated the metabolic burden on the liver, and affected glucose metabolism. Sirt2 underwent acetylation modification of lysine 135 of PKM2 through a histidine 187 enzyme active site-dependent effect and reduced ubiquitination of the K48 ubiquitin chain of PKM2. Our findings reveal that the hepatic glucose metabolism links nutrient state to whole-body energetics through the rhythmic regulation of Sirt2.

Cold stress causes liver damage by inducing ferroptosis through the p38 MAPK/Drp1 pathway

Acute extreme cold exposure impairs human health and even causes hypothermia which threatens human life. Liver, as a hub in metabolism and thermogenesis, is vital for cold acclimatization. Although accumulating evidence has suggested that cold exposure can cause liver damage, the underlying mechanisms remain poorly understood. This study investigated the role and underlying mechanisms of ferroptosis in cold stress-induced liver damage. To evaluate the role of ferroptosis in cold stress-induced liver damage, rats were pretreated with ferroptosis inhibitor liproxstatin-1 (Lip-1) before exposed to -10 °C for 8 h. Core body temperature was recorded. The levels of ferroptosis-related indicators were examined with the corresponding assay kits or by western blotting. Hepatic pathological changes were analyzed by hematoxylin-eosin staining and ultrastructural observation. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured to assess liver function. Rats were also pretreated with p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 or Dynamin-related protein 1 (Drp1) inhibitor Mdivi-1 to determine the underlying mechanisms. We found that Lip-1 inhibited ferroptosis, attenuated hepatic pathological damages and blocked the increased ALT and AST levels in cold-exposed rats. Moreover, Mdivi-1 inhibited mitochondrial fission and suppressed ferroptosis. Furthermore, SB203580 and Mdivi-1 administration alleviated cold stress-induced liver injury. Our results suggested that cold stress caused liver damage partially by inducing ferroptosis through the p38 MAPK/Drp1 pathway. These findings might provide an effective preventive and therapeutic target for cold stress-induced liver injury.

O-GlcNAc / Akt pathway regulates glucose metabolism and reduces apoptosis in liver of piglets with acute cold stress

Cold stress is one of the serious factors restricting the development of animal husbandry in cold areas. Cold exposure can easily lead to cold stress, slow growth and even death of newborn animals. O-GlcNAcylation modification can act as type of "stress receptor" and"nutrition sensor" in a variety of stress responses, however, it is not clear how O-GlcNAcylation can regulate glucose metabolism in the liver of piglets under cold stress. In this study, piglets 21 days of age were exposed to 4 °C for 4 h or 8 h in a phytotron. Serum cortisol and other stress hormones were used to assess body status to establish a cold stress piglet model. The changes of glycogen in liver were detected by PAS. FDP and PA were also measured to study the glycolysis level of liver. To characterize potential mechanisms of O-GlcNAcylation on the livers of cold stress piglets, AKT, GSK3β, GS, PFKFB2, AS160 and their corresponding phosphorylation were determined by Western blotting. Results show O-GlcNAcylation increased and apoptosis levels increased in the liver following cold exposure during excessive CORT or metabolic dysfunction. It is suggested that the acute cold exposure of piglets induced a sequential change in the level of O-GlcNAcylation, which may be one of the factors mediating liver cell apoptosis and glucose metabolism regulation by the O-GlcNAc/AKT pathway. These findings provide new insight into the mechanisms of the cold stress response, which can facilitate the development of new strategies to combat the effects of hypothermia.

Changes in the Concentration of Purine and Pyridine as a Response to Single Whole-Body Cryostimulation

To our knowledge, this is the first study in which we provide evidence that a single whole-body cryostimulation treatment leads to changes associated with erythrocyte energy metabolism. These changes are beneficial from the point of view of cellular bioenergetics, because they are associated with an increase in ATP concentration and erythrocyte energy potential expressed by an increase in the ATP/ADP and ATP/AMP ratios and the value of adenylate energy charge (AEC). In addition, as affected by cryogenic temperatures, there is a decrease in the concentration of purine catabolism products, i.e., inosine and hypoxanthine in the blood.

Green synthesis of silver nanoparticles by Nigella sativa extract alleviates diabetic neuropathy through anti-inflammatory and antioxidant effects

Green synthesis of silver nanoparticles has gained great interest among scientists. In view of this data, we conducted this study to identify the ameliorative effect of green synthesis of silver nanoparticles using Nigella sativa extract in diabetic neuropathy induced experimentally. In this study, 50 adult male albino rats were used and they were randomly divided into five groups; the first group was the healthy control group, the second group were the diabetic neuropathy diabetic neuropathy induced, Groups (3-6) diabetic neuropathy induced group and treated with silver nanoparticles, Nigella sativa extract and green synthesized silver nanoparticles using Nigella sativa extract respectively. Biochemical parameters including diabetic, inflammatory and antioxidant biomarkers were evaluated. Brain histopathology was also performed. Results revealed substantial rise in glucose, AGE, aldose reductase with insulin reduction in diabetic neuropathy induced group as compared to healthy control. Also, inflammatory markers increased significantly in diabetic neuropathy induced group. A remarkable change in oxidative status was observed in the same group. Furthermore, significant decline in nitrotyrosin level was observed. Regarding gene expression, we found significant down regulation in brain TKr A accompanied by upregulation of nerve growth factor in diabetic neuropathy group comparing with healthy control. Several treatments for diabetic neuropathy remarkably ameliorate all the investigated biomarkers. Histological findings are greatly relied on for the results achieved in this study. Therefore, it can be established that green synthesis of silver nanoparticles in combination with Nigella sativa extract could be a newly neuroprotective agents against inflammation and oxidative stress characterizing diabetic neuropathy through their antidiabetic, anti-inflammatory and anti-oxidants effects.

Rno-miR-425-5p targets the DLST and SLC16A1 genes to reduce liver damage caused by excessive energy mobilization under cold stress

MicroRNAs (miRNAs) are a class of single-stranded non-coding small RNA molecules, which participate in the regulation of many physiological processes, and play a crucial role in cancer, metabolism and other processes. Rno-miR-425-5p has been shown to play a role in the response to cold stress. To explore the mechanism by which rno-miR-425-5p regulates the response to cold stress, we analysed the candidate target genes of rno-miR-425-5p. After verification in rat hepatocyte BRL cells and in rat liver tissue, we identified several target genes that were altered in expression in response to cold stress. In rat liver tissue, the expression of rno-miR-425-5p was significantly increased and the expression levels of target genes DLST and SLC16A1 were decreased under cold stress. The miRNA and mRNA levels were analysed by quantitative real-time PCR and the protein levels were detected by Western blot analysis. Combined with the results of bioinformatic analysis, we concluded that rno-miR-425-5p reduced the expression of DLST and SLC16A1, inhibiting energy release from the tricarboxylic acid cycle and preventing the liver from being injured by excessive energy mobilization.

Regulating glycolysis, the TLR4 signal pathway and expression of RBM3 in mouse liver in response to acute cold exposure

At low temperatures, the liver increases glucose utilization and expresses RNA-binding motif 3 (RBM3) to cope with cold exposure. In this study, the expression of heat shock protein 70 (HSP70), Toll-like receptor 4 (TLR4), bone marrow differentiation factor 88 (MYD88), and phosphorylated nuclear factor-κB (NF-κB) was consistent with fluctuations in insulin in fasted cold-exposed mice. We also found up-regulation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in acute cold exposure with a decrease in core body temperature. RBM3 transcription and translation were activated 2 h after cold exposure. The anti-apoptotic factor Bcl-2/Bax ratio also increased, while expression of apoptosis factors: cleaved caspase-3, cleaved poly(ADP-ribose)polymerase 1 (PARP-1) and cytochrome-c (Cyt-c) was unchanged. Liver glycogen was depleted after 2 h of cold exposure, and blood glucose decreased after 4 h. Glycogen synthase kinase 3β (GSK3β) phosphorylation continued to increase to promote hepatic glycogen synthesis. We found a high level of protein kinase B (AKT) phosphorylation after 6 h of cold exposure. In addition, we demonstrated that after cold exposure for 2 h, in the liver, continued phosphorylation of fructose-2,6-diphosphate (PFKFB2) and decreased accumulation of glycogen intermediates fructose-1,6-diphosphate (FDP) and pyruvic acid (PA). In summary, the liver responds to cold exposure through a number of different pathways, including activation of HSP70/TLR4 signaling pathways, up-regulation of RBM3 expression, and increased glycolysis and glycogen synthesis. We propose a possible signaling pathway in which regulation of RBM3 expression by the liver affects the AKT metabolic signaling pathway. Lay summary In response to changes in ambient temperature, mice regulate global metabolism and gene expression through hormones. This study focused on the effects of environmental hypothermia on molecular pathways of glucose metabolism in the liver, which is the important metabolic organ in mice. This provides a basis for further study of mice against cold exposure damage.

Effects of Cold-inducible RNA-binding Protein (CIRP) on Liver Glycolysis during Acute Cold Exposure in C57BL/6 Mice

Cold-inducible RNA-binding protein (CIRP) is a stress-responsive protein involved in several signal transduction pathways required for cellular function, which are associated with apoptosis and proliferation. The present study aimed to investigate the possible effects of CIRP-mediated regulation of glucose metabolism in the liver following acute cold exposure. The livers and serum of male C57BL/6 mice were collected following cold exposure at 4 °C for 0 h, 2 h, 4 h, and 6 h. Glucose metabolic markers and the expression of glucose metabolic-related proteins were detected in the liver. Acute cold exposure was found to increase the consumption of glycogen in the liver. Fructose-1,6-diphosphate (FDP) and pyruvic acid (PA) were found to show a brief increase followed by a sharp decrease during cold exposure. Anti-apoptotic protein (Bcl-2) expression was upregulated. CIRP protein expression displayed a sequential increase with prolonged acute cold exposure time. Acute cold exposure also increased the level of protein kinase B (AKT) phosphorylation, and activated the AKT-signaling pathway. Taken together, these findings indicate that acute cold exposure increased the expression of CIRP protein, which regulates mouse hepatic glucose metabolism and maintains hepatocyte energy balance through the AKT signaling pathway, thereby slowing the liver cell apoptosis caused by cold exposure.

Effects of Acute Cold Stress on Liver O-GlcNAcylation and Glycometabolism in Mice

Protein O-linked β-N-acetylglucosamine glycosylation (O-GlcNAcylation) regulates many biological processes. Studies have shown that O-GlcNAc modification levels can increase during acute stress and suggested that this may contribute to the survival of the cell. This study investigated the possible effects of O-GlcNAcylation that regulate glucose metabolism, apoptosis, and autophagy in the liver after acute cold stress. Male C57BL/6 mice were exposed to cold conditions (4 °C) for 0, 2, 4, and 6 h, then their livers were extracted and the expression of proteins involved in glucose metabolism, apoptosis, and autophagy was determined. It was found that acute cold stress increased global O-GlcNAcylation and protein kinase B (AKT) phosphorylation levels. This was accompanied by significantly increased activation levels of the glucose metabolism regulators 160 kDa AKT substrate (AS160), 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 2 (PFKFB2), and glycogen synthase kinase-3β (GSK3β). The levels of glycolytic intermediates, fructose-1,6-diphosphate (FDP) and pyruvic acid (PA), were found to show a brief increase followed by a sharp decrease. Additionally, adenosine triphosphate (ATP), as the main cellular energy source, had a sharp increase. Furthermore, the B-cell lymphoma 2(Bcl-2)/Bcl-2-associated X (Bax) ratio was found to increase, whereas cysteine-aspartic acid protease 3 (caspase-3) and light chain 3-II (LC3-II) levels were reduced after acute cold stress. Therefore, acute cold stress was found to increase O-GlcNAc modification levels, which may have resulted in the decrease of the essential processes of apoptosis and autophagy, promoting cell survival, while altering glycose transport, glycogen synthesis, and glycolysis in the liver.

miRNA-23a has effects to improve lung injury induced by sepsis in vitro and vivo study

AIM

The aim of this study is to explain the effects and mechanism of miRNA-23a in lung injury which were induced by sepsis in vitro and vivo.

METHODS

In the vitro study, The BEAS-2B cells were divided into 4 groups: NC, MC, miRNA and miRNA + PTEN agonist groups. The cell proliferation and apoptosis of difference groups were measured by MTT and flow cytometry, the relative proteins expression of difference groups were measured by WB assay. In the vivo study, the rats were also divided into 4 groups: NC, MC, miRNA and miRNA + PTEN agonist groups. The miRNA-23a expression of difference groups were evaluated by ISH in lung tissues of rats. The cell apoptosis of difference groups were evaluated by TUNEL assay in lung tissues; the relative proteins expression of difference groups were evaluated by IHC assay.

RESULTS

Compared with NC group, the cell apoptosis rate of MC groups were significantly increased in vitro and vivo studies (P ＜ 0.05, respectively). The relative proteins (PTEN, PI3K, AKT and P53) expressions of MC group were significantly differences (P ＜ 0.05, respectively) compared with those of NC groups in vitro and vivo studies. However, with miRNA-23a infection, the cell apoptosis of miRNA group were significantly suppressed compared with MC groups, and the relative proteins (PTEN, PI3K, AKT and P53) of miRNA group were also significantly differences compared with MC groups in vitro and vivo studies (P ＜ 0.05, respectively).

CONCLUSION

The miRNA-23a has improved lung injury induced by sepsis via PTEN/PI3K/AKT/P53 pathway in vitro and vivo studies.

Vibrio cholerae Cholix Toxin-Induced HepG2 Cell Death is Enhanced by Tumor Necrosis Factor-Alpha Through ROS and Intracellular Signal-Regulated Kinases

Cholix toxin (Cholix) from Vibrio cholerae is a potent virulence factor exhibiting ADP-ribosyltransferase activity on eukaryotic elongation factor 2 (eEF2) of host cells, resulting in the inhibition of protein synthesis. Administration of Cholix or its homologue Pseudomonas exotoxin A (PEA) to mice causes lethal hepatocyte damage. In this study, we demonstrate cytotoxicity of Cholix on human hepatocytes in the presence of tumor necrosis factor α (TNF-α), which has been reported to play a fatal role in PEA administered to mice. Compared with incubating HepG2 cells with Cholix alone, co-treatment with TNF-α and Cholix (TNF-α/Cholix) significantly enhanced the activation of caspases, cytochrome c release from mitochondria into cytoplasm, and poly-ADP-ribose polymerase (PARP) cleavage, while incubation with TNF-α alone or co-treatment with TNF-α/catalytically inactive Cholix did not. In the early stage of cell death, Cholix increased phosphorylation of mitogen-activated protein kinases (e.g., p38, ERK, JNK) and Akt, which was not affected by TNF-α alone. MAPK inhibitors (SP600125, SB20852, and U0126) suppressed PARP cleavage induced by TNF-α/Cholix. Protein kinase inhibitor Go6976 suppressed JNK phosphorylation and PARP cleavage by TNF-α/Cholix. In contrast, PKC activator PMA in the absence of TNF-α promoted Cholix-induced PARP cleavage. Reactive oxygen species (ROS) inhibitor, N-acetyl cysteine (NAC), suppressed TNF-α/Cholix-induced JNK and ERK phosphorylation, resulting in inhibition of PARP cleavage. These data suggest that ROS and JNK pathways are important mediators of TNF-α/Cholix-induced HepG2 cell death.

Identification of cold-responsive miRNAs in rats by deep sequencing

miRNA is an endogenously noncoding sRNA, which is involved in post-transcription gene expression regulation of growth, tumor development and stress survival. As a biological marker, miRNA has been used for the early diagnosis of diseases and the evaluation of some physiological state. We constructed two small RNA libraries with the serums of rats treated or not with cold conditions (4℃ for 12h) by deep sequencing, in order to understand the miRNAs' expressions of cold-exposed rats and find new cold-responsive biological markers. 485 conserved miRNAs and 287 novel miRNAs were identified in the two libraries by comparing to the known miRNAs of rat in miRBase 21.0 Differential expression analysis showed that 56 conserved miRNAs and 3 novel miRNAs were expressed differentially in low ambient temperature. The qRT-PCR results confirmed that rno-miR-151-3p, rno-miR-210-3p, rno-miR-425-5p, rno-miR-383-5p, rno-miR-92a-3p, rno-miR-98-5p and rno-miR-328a-3p decreased significantly in rats serums treated with cold exposure. The expressions of the 7 miRNAs changed significantly in cold-exposed rats' livers too. rno-miR-383-5p decreased significantly, but all the others increased significantly. Thus, the 7 miRNAs were considered as cold-responsive miRNAs of rat. 670 target genes of the 7 cold-responsive miRNAs were predicted. KEGG analysis showed that they were enriched in 28 pathways and most of them were enriched by metabolic pathway. Overall, the results of this study suggest an important role for selected miRNA's in the response to cold stress.

Antidiabetic assessment; in vivo study of gold and core-shell silver-gold nanoparticles on streptozotocin-induced diabetic rats

Recently, we have published a pioneering work on green biosynthesis and complete characterization of gold and core shell silver-gold nanoparticles (AuNPs and Ag@AuNPs). Herein, the so obtained nanoparticles are assessed for their antidiabetic activity in streptozotocin-induced diabetic rats. Thus, sixty-four male albino rats were divided into eight groups: control untreated; diabetic rats; diabetic rats received standard drug; diabetic rats received carrier only; diabetic rats received 0.5ml AuNPs; diabetic rats received 1ml AuNPs; diabetic rats received 0.5ml Ag@AuNPs and diabetic rats received 1ml Ag@AuNPs for twenty-one days. Results revealed that diabetic rats treated with AuNPs or Ag@AuNPs restored normal glucose level. In particular, Ag@AuNPs was found to significantly induce a reduction in blood glucose and restore both the high serum insulin level and glucokinase activity compared to the control normal rats. The results obtained disclose the effectual role of Ag@AuNPs in reducing the lipid profile, an anti-inflammatory effect in diabetic rats assessed using inflammatory markers IL-α and C-reactive protein (CRP). Histopathological examination of diabetic rats signifies distortion in the arrangement of cells around the central vein, inflammatory cells, pyknotic and apoptotic nuclei. Kidney of diabetic rat appears with vacuolation and pyknotic nuclei of some tubules. On the other hand, the liver of diabetic rat treated with Ag@AuNPs displayed normal hepatic cells with only few necrosis of hepatocytes. Ag@AuNPs restored the increased number of caspase-3 stained cells in the liver and kidney tissue in diabetic rats. In conclusion, Ag@AuNPs was observed to improve diabetic condition by limiting prolonged inflammation, suppressing oxidative stress and elevating the antioxidant defense system in diabetic rats which subsequently evoke the potential impact of AuNPs as a cost effective therapeutic cure in diabetic treatments and its complications.

Nrf2 deficiency promotes apoptosis and impairs PAX7/MyoD expression in aging skeletal muscle cells

Skeletal muscle redox homeostasis is transcriptionally regulated by nuclear erythroid-2-p45-related factor-2 (Nrf2). We recently demonstrated that age-associated stress impairs Nrf2-ARE (antioxidant-response element) transcriptional signaling. Here, we hypothesize that age-dependent decline or genetic ablation of Nrf2 leads to accelerated apoptosis and skeletal muscle degeneration. Under basal-physiological conditions, disruption of Nrf2 significantly downregulates antioxidants and causes oxidative stress. Surprisingly, Nrf2-null mice had enhanced antioxidant capacity identical to wild-type (WT) upon acute endurance exercise stress (AEES), suggesting activation of Nrf2-independent mechanisms (i.e., PGC1α) against oxidative stress. Analysis of prosurvival pathways in the basal state reveals decreased AKT levels, whereas p-p53, a repressor of AKT, was increased in Nrf2-null vs WT mice. Upon AEES, AKT and p-AKT levels were significantly (p < 0.001) increased (>10-fold) along with profound downregulation of p-p53 (p < 0.01) in Nrf2-null vs WT skeletal muscle, indicating the onset of prosurvival mechanisms to compensate for the loss of Nrf2 signaling. However, we found a decreased stem cell population (PAX7) and MyoD expression (differentiation) along with profound activation of ubiquitin and apoptotic pathways in Nrf2-null vs WT mice upon AEES, suggesting that compensatory prosurvival mechanisms failed to overcome the programmed cell death and degeneration in skeletal muscle. Further, the impaired regeneration was sustained in Nrf2-null vs WT mice after 1 week of post-AEES recovery. In an age-associated oxidative stress condition, ablation of Nrf2 results in induction of apoptosis and impaired muscle regeneration.