1-Methylcyclopropene Alleviates Postharvest Chilling Injury of Snap Beans by Enhancing Antioxidant Defense System.

Research background: Chilling injury is a major disorder affecting the quality of tropical and subtropical vegetables during low temperature storage. Snap bean (Phaseolus vulgaris L.) is sensitive to chilling injury. The main purpose of the present study is to investigate the alleviating effects of 1-methylcyclopropene (1-MCP) on chilling injury of snap bean. In addition, the related mechanisms were also detected from the perspective of the changes of antioxidant defense system. Experimental approach: Snap beans were exposed to different volume fractions of 1-MCP. After 24 h of treatment, snap beans were stored at 4 °C for up to 14 days. Chilling injury index, electrolyte leakage, titratable acidity and total soluble solids were determined. Contents of chlorophyll, ascorbic acid and malondialdehyde were assessed. The total antioxidant capacity, Fe(II) ion chelating capacity, scavenging capacities on free radicals and activities of antioxidant enzymes were detected. Total phenol content and activities of related metabolic enzymes were also determined. Results and conclusions: 1-MCP treatment reduced chilling injury index, electrolyte leakage rate and malondialdehyde content of snap beans. The amounts of total soluble solids, titratable acid, ascorbic acid and total chlorophyll in 1-MCP-treated snap beans were significantly higher than those of control. The snap beans treated with 1-MCP showed stronger total antioxidant capacity and metal chelating activity. The 1-MCP treatment enhanced scavenging effects of snap beans on superoxide, hydroxyl and 1,1-diphenyl-2-trinitrophenylhydrazine radicals. The activities of peroxidase, ascorbate peroxidase, superoxide dismutase and catalase in 1-MCP-treated group were higher than of control. The treatment also enhanced the accumulation of phenolic compounds in snap beans by regulating the activities of phenol-metabolizing enzymes such as shikimate dehydrogenase, phenylalanine ammonia lyase enzyme, cinnamic acid 4-hydroxylase and polyphenol oxidase. In conclusion, with the mechanism that involves the activation of enzymatic and non-enzymatic antioxidant systems, 1-MCP has the ability to avoid chilling injury of snap bean. Novelty and scientific contribution: This study gives insights into whether 1-MCP can regulate postharvest cold resistance in vegetables by enhancing the enzymatic antioxidant system and inducing the accumulation of non-enzymatic antioxidants. Considering the results, 1-MCP treatment could be an effective method to alleviate postharvest chilling injury of snap beans during low temperature storage.

Protective effect of 2-deoxy-D-glucose on the brain tissue in rat cerebral ischemia-reperfusion models by inhibiting Caspase-apoptotic pathway.

We observed the effect of 2-deoxy-D-glucose (2-DG) on the brain tissue in rat cerebral ischemia-reperfusion (I/R) and explored its mechanism. After observing the effect of 2-DG on endoplasmic reticulum stress (ERS), rats were randomly divided into sham-operation group, I/R group and I/R+2-DG group (each group with 60 rats). I/R models were prepared by middle cerebral artery occlusion. In I/R+2-DG group, each rat was given intraperitoneal 2-DG of 100 mg/kg once a day for 7 days before brain ischemia. According to different time points (3h, 6h, 12h, 24h and 48h) after I/R, each group was divided into 5 subgroups (each subgroup with 12 rats). Nerve cell apoptosis, and the expressions of mRNA and protein of glucose regulated protein 78 (GRP78), cleaved-caspase-9 and cleaved-caspase-3 were determined with TUNEL, Western blotting and RT-PCR, respectively, in rat cerebral hippocampal CA1 area at each time point. TUNEL-positive cells were significantly less in I/R+2-DG group than in I/R group at each time point (all P<0.01). In I/R and I/R+2-DG groups, the expressions of mRNA and protein of GRP78 reached the maximum 12 h after I/R, and cleaved-caspase-9 and cleaved-caspase-3 reached the maximum 24 h after I/R. Compared with sham-operation group, the expressions of mRNA and protein of GRP78, cleaved-caspase-9 and cleaved-caspase-3 were all significantly increased (all P<0.01) in I/R and I/R+2-DG groups. However, the expressions of mRNA and protein of GRP78 were significantly higher in I/R+2-DG group than in I/R group (all P<0.05), but the expressions of mRNA and protein of cleaved-caspase-9 and cleaved-caspase-3 were all significantly lower in I/R+2-DG group than in I/R group (all P<0.05). We conclude that 2-DG has a neuroprotective effect on the brain tissue in rat cerebral ischemia-reperfusion models. The mechanism may be that 2-DG starts ERS followed by up-regulation of mRNA and protein of GRP78 and down-regulation of mRNA and protein of cleaved-caspase-9 and cleaved-caspase-3, which blocks the apoptotic pathway.

Lactobacilli reduce chemokine IL-8 production in response to TNF-α and Salmonella challenge of Caco-2 cells.

The probiotic properties of two selected lactobacilli strains were assessed. L. salivarius and L. plantarum displayed higher hydrophobicity (48% and 54%, resp.) and coaggregation ability with four pathogens (from 7.9% to 57.5%). L. salivarius and L. plantarum had good inhibitory effects on S. aureus (38.2% and 49.5%, resp.) attachment to Caco-2 cells. Live lactobacilli strains and their conditioned media effectively inhibited IL-8 production (<14.6 pg/mL) in TNF-α-induced Caco-2 cells. Antibiotic-treated and the sonicated lactobacilli also maintained inhibitory effects (IL-8 production from 5.0 to 36.3 pg/mL); however, the heat-treated lactobacilli lost their inhibitory effects (IL-8 production from 130.2 to 161.0 pg/mL). These results suggest that both the structural components and the soluble cellular content of lactobacilli have anti-inflammatory effects. We also found that pretreatment of Caco-2 cells with lactobacilli inhibited S. typhimurium-induced IL-8 production (<27.3 pg/mL). However, lactobacilli did not inhibit IL-8 production in Caco-2 cells pretreated with S. typhimurium. These results suggest that the tested lactobacilli strains are appropriate for preventing inflammatory diseases caused by enteric pathogens but not for therapy. In short, L. salivarius and L. plantarum are potential candidates for the development of microbial ecological agents and functional foods.