A bovine milk-derived peptide ameliorates alloxan-injured pancreatic ß cells through IRS2/PI3K/Akt signaling.

BACKGROUND AND AIMS: Lacto-ghrestatin is abovine milk-derived peptide with the sequence of LIVTQTMKG, named LGP9 here. This study aimed to investigate protective effects of LGP9 on diabetic ß cells in vivo and in vitro. METHODS AND RESULTS: Type-1-diabetic (T1D) mice were generated by alloxan (ALX; 50 mg/kg, i.v.) and received a four-week treatment schedule of LGP9 at 0.3 mg/kg and 1 mg/kg. Related biochemical parameters were analyzed, and the protein expression was evaluated by Western blotting. The results showed that LGP9 decreased body weight, water consumption and blood glucose, improved oxygen stress and upregulated IRS2/PI3K/Akt signaling in the pancreas of T1D mice. To further investigate the mechanism of LGP9 on the preventive effect of the pancreas, Rin-m5f cells were treated with 15 mM alloxan and followed with LGP9 at 30 µM and 90 µM. The results indicated that LGP9 rebalanced oxygen stress levels, increased cell proliferation, decreased cell apoptosis and activated IRS2/PI3K/Akt signaling. CONCLUSION: LGP9 ameliorated alloxan-injured pancreatic ß cells through IRS2/PI3K/Akt signaling. The finding provides important help for the research and development of LGP9 in therapeutics of diabetes.

Phycocyanin Inhibits Tumorigenic Potential of Pancreatic Cancer Cells: Role of Apoptosis and Autophagy.

Pancreatic adenocarcinoma (PDA) is one of the most lethal human malignancies, and unresponsive to current chemotherapies. Here we investigate the therapeutic potential of phycocyanin as an anti-PDA agent in vivo and in vitro. Phycocyanin, a natural product purified from Spirulina, effectively inhibits the pancreatic cancer cell proliferation in vitro and xenograft tumor growth in vivo. Phycocyanin induces G2/M cell cycle arrest, apoptotic and autophagic cell death in PANC-1 cells. Inhibition of autophagy by targeting Beclin 1 using siRNA significantly suppresses cell growth inhibition and death induced by phycocyanin, whereas inhibition of both autophagy and apoptosis rescues phycocyanin-mediated cell death. Mechanistically, cell death induced by phycocyanin is the result of cross-talk among the MAPK, Akt/mTOR/p70S6K and NF-κB pathways. Phycocyanin is able to induce apoptosis of PANC-1 cell by activating p38 and JNK signaling pathways while inhibiting Erk pathway. On the other hand, phycocyanin promotes autophagic cell death by inhibiting PI3/Akt/mTOR signaling pathways. Furthermore, phycocyanin promotes the activation and nuclear translocation of NF-κB, which plays an important role in balancing phycocyanin-mediated apoptosis and autosis. In conclusion, our studies demonstrate that phycocyanin exerts anti-pancreatic cancer activity by inducing apoptotic and autophagic cell death, thereby identifying phycocyanin as a promising anti-pancreatic cancer agent.

Phycocyanin ameliorates alloxan-induced diabetes mellitus in mice: Involved in insulin signaling pathway and GK expression.

The therapeutic potential and molecular mechanism of phycocyanin from Spirulina on alloxan-induced diabetes mice was investigated. In the experiment, 4-week treatment of phycocyanin at the dose of 100 and 200 mg/kg body weight in alloxan-induced diabetes mice resulted in improved metrics in comparison with alloxan-induced diabetes group. These metrics include blood glucose levels, glycosylated serum protein (GSP), glycosylated hemoglobin (GHb) and fasting serum insulin (FINS) levels. As its molecular mode of action, phycocyanin leads to the increase of IRS-1 tyrosine phosphorylation and the decrease of IRS-1 serine phosphorylation, also accompany with increased level of Akt phosphorylation on Ser473 in the liver and pancreas in diabetic mice. In addition, phycocyanin treatment enhanced the glucokinase (GK) level in the liver and pancreas, and the glucokinase regulatory protein (GKRP) level in the liver in diabetic mice. The results suggest that phycocyanin ameliorates alloxan-induced diabetes mellitus in mice by activating insulin signaling pathway and GK expression in pancreas and liver in diabetic mice.

Effects of phycocyanin on INS-1 pancreatic ß-cell mediated by PI3K/Akt/FoxO1 signaling pathway.

The level of methylglyoxal (MG), which is a side-product of metabolic pathways, particularly in glycolysis, is elevated in diabetes. Notably, the accumulation of MG causes a series of pathological changes. Phycocyanin (PC) has been demonstrated to show insulin-sensitizing effect, however, the underlying molecular mechanism remains elusive. The aim of this study was to investigate the protective effects of PC on INS-1 rat insulinoma ß-cell against MG-induced cell dysfunction, as well as the underlying mechanisms. PC was preliminarily verified to time-dependently activate PI3-kinase (PI3K) pathway, but the PI3K-specific inhibitor Wortmannin blocked the effect of PC. Glucose-stimulated insulin secretion (GSIS) was impaired in MG-treated INS-1 cells. Furthermore, MG induced dephosphorylation of Akt and FoxO1, resulting in nuclear localization and transactivation of FoxO1. Nevertheless, these effects were all effectively attenuated by PC. The ameliorated insulin secretion was related to the changes of FoxO1 mediated by PC, which demonstrated by RNA interference. And, the dosage used in the above experiments did not affect ß-cell viability and apoptosis, although long-term MG induced cell apoptosis and mitochondrial dysfunction. In conclusion, PC was capable to protect INS-1 pancreatic ß-cell against MG-induced cell dysfunction through modulating PI3K/Akt pathway and the downstream FoxO1.

Molecular mechanisms of exopolysaccharide from Aphanothece halaphytica (EPSAH) induced apoptosis in HeLa cells.

The present study aims to investigate the pharmacological effect of the exopolysaccharides from Aphanothece halophytica GR02 (EPSAH) on the HeLa human cervical cancer cell line. HeLa cells were cultured in RPMI-1640-10% FBS medium containing with or without different concentrations of EPSAH. Cell viability was assessed by methylthiazol tetrazolium (MTT) assay. Cell apoptosis was elevated with Wright-Giemsa staining, AO/EB double staining, and DNA fragmentation assay. Apoptosis-associated molecules from cultured HeLa cells were quantified using Western blot analysis. Our results suggest that EPASH induces apoptosis in HeLa cells by targeting a master unfolded protein response (UPR) regulator Grp78. Grp78 further promotes the expression of CHOP and downregulates expression of survivin, which leads to activate mitochondria-mediated downstream molecules and p53-survivin pathway, resulting in caspase-3 activation and causing apoptosis. These findings provide important clues for further evaluating the potential potency of EPSAH for use in cancer therapy.

Antidiabetic potential of phycocyanin: effects on KKAy mice.

CONTEXT: Phycocyanin (PC) has been proven to have many therapeutic properties, but its effects on diabetes have not been investigated. OBJECTIVE: Antidiabetic activity of PC isolated from Spirulina platensis was evaluated in this study. MATERIALS AND METHODS: Oral administration of PC (100 mg/kg, once per day for 3 weeks) on KKAy mice were investigated by monitoring the changes in body weight, food intake, fasting plasma glucose level, 24 h random blood glucose levels, oral glucose tolerance tests (OGTTs), glycosylated serum protein (GSP), fasting serum insulin (FINS), glycogen, triglyceride (TG), total cholesterol (TC), total antioxidative capability (T-AOC) and malondialdehyde (MDA). Histopathological changes in the pancreas were also examined with hematoxylin-eosin staining. RESULTS: Administration of PC significantly decreased the body weight, fasting plasma glucose, 24 h random blood glucose levels, FINS and GSP levels, TG and TC content in serum and livers, MDA content in livers (p < 0.05 or p < 0.01). On the other hand, glucose tolerance to glucose administration, T-AOC, and the content of glycogen in liver and muscle were enhanced following PC treatment (p < 0.05 or p < 0.01). Histopathological results showed that PC administration suppressed the abnormal enlargement of islets observed in the pancreas of KKAy mice. DISCUSSION AND CONCLUSION: The antidiabetic effect of PC on KKAy mice is most likely due to its ability to enhance insulin sensitivity, amelioration of insulin resistance of peripheral target tissues and regulation of glucolipide metabolism. Therefore, PC may have a potential clinical utility in combating type-2 diabetes.

Preventive effect of phycocyanin from Spirulina platensis on alloxan-injured mice.

The preventive effect of phycocyanin (obtained from Spirulina platensis) on alloxan-injured mice is investigated. Oral administration of phycocyanin was started two weeks before an alloxan injury and continued until four weeks later. Tests resulted in the following positive results of oral phycocyanin administration on alloxan-injured mice: decrease fasting blood glucose and glycosylated serum protein (GSP); maintain total antioxidative capability (T-AOC); avert malondialdehyde (MDA) formation in the liver, kidney, and pancreas; decrease total cholesterol (TC) level and triglycerides (TG) level in serum and liver; increase the levels of hepatic glycogen level; maintain glucokinase (GK) expression in the liver and decrease p53 expression in the pancreas at mRNA level. The histological observations also supported the above results. Acute toxicity study further shows that phycocyanin is relatively safe. These results led to the conclusion that phycocyanin has significant preventive effect on alloxan-injured mice. The inhibition of p53 pathway could be one of the mechanisms that led to the protection of pancreatic islets from alloxan injury. We also proposed that GK expression that functions to promote liver glycogen synthesis could be the reason for reduced blood glucose level. The encouraging results are the first step in studying the potential of phycocyanin as a clinical measure in preventing diabetes.

Phycocyanin may suppress D-galactose-induced human lens epithelial cell apoptosis through mitochondrial and unfolded protein response pathways.

Apoptosis of lens epithelial cell (LEC) plays an important role in cataract formation, and its prevention may be one of the therapeutic strategies in treating cataract. This study used human lens epithelial cell (hLEC) line SRA01/04 to investigate the protective effect and mechanism of phycocyanin on glactose-induced apoptosis in hLEC. hLECs were cultured in D/F(12)-10% FBS medium containing 125mM d-galactose with or without phycocyanin. Cell viability was assessed by methylthiazol tetrazolium (MTT) assay. Cell apoptosis was elevated with Wright-Giemsa staining, AO/EB double staining, and DNA fragmentation assay. Mitochondrial apoptosis-associated molecules and unfolded protein response-associated molecules from cultured SRA01/04 cells were quantified using protein blot analysis. The results demonstrated that phycocyanin suppressed SRA01/04 cells' morphologic changes and apoptosis induced by d-galactose, inhibited the expression and activation of caspase 3, alternated the Bax/Bcl-2 ratio, and down-regulated the level of p53, GRP78, and CHOP in d-galactose-treated SRA01/04 cells. These results suggest that phycocyanin might suppress d-galactose-induced hLEC apoptosis through two pathways: mitochondrial pathway, involving p53 and Bcl-2 family protein expression, and unfolded protein response pathway, involving GRP78 and CHOP expression.

Protective effect of C-phycocyanin against carbon tetrachloride-induced hepatocyte damage in vitro and in vivo.

This study focused on the hepatoprotective activity of C-phycocyanin (C-PC) against carbon tetrachloride-induced hepatocyte damage in vitro and in vivo. In in vitro study, human hepatocyte cell line L02 was used. C-PC showed its capability to reverse CCl(4)-induced L02 cells viability loss, alanine transaminase (ALT) leakage and morphological changes. C-PC also showed the following positive effects: prevent the CCl(4)-induced overproduction of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA); prevent changes in superoxide dismutase (SOD) activity; and reduce glutathione (GSH) level. In vivo, C-PC showed its capability to decrease serum ALT and aspartate transaminase (AST) levels in CCl(4)-induced liver damage in mice. The histological observations supported the results obtained from serum enzymes assays. C-PC also showed the following effects in mice liver: prevent the CCl(4)-induced MDA formation and GSH depletion; prevent SOD and glutathione peroxidase (GSH-Px) activity; and prevent the elevation of transforming growth factor-beta1 (TGF-beta1) and hepatocyte growth factor (HGF) mRNAs. Both the in vitro and in vivo results suggested that C-PC was useful in protecting against CCl(4)-induced hepatocyte damage. One of the mechanisms is believed to be through C-PCs scavenging ability to protect the hepatocytes from free radicals damage induced by CCl(4). In addition, C-PC may be able to block inflammatory infiltration through its anti-inflammatory activities by inhibiting TGF-beta1 and HGF expression.