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Mulberry Leaf Polysaccharides Attenuate Oxidative Stress Injury in Peripheral Blood Leukocytes by Regulating
Wenqiang Jiang1, Yan Lin2, Linjie Qian1
1Wuxi Fisheries College, Nanjing Agricultural University, Wuxi 214081, China.
Abstract:
The present study assessed the protective effects and underlying mechanisms of mulberry leaf polysaccharides (MLPs) against hydrogen peroxide (H2O2)-induced oxidative stress injury in the peripheral blood leukocytes (PBLs) of Megalobrama amblycephala. Five treatment groups were established in vitro: the NC group (PBLs incubated in an RPMI-1640 complete medium for 4 h), the HP group (PBLs incubated in an RPMI-1640 complete medium for 3 h, and then stimulated with 100 μM of H2O2 for 1 h), and the 50/100/200-MLP pre-treatment groups (PBLs were pre-treated with MLPs (50, 100, and 200 μg/mL) for 3 h, and then stimulated with 100 μM of H2O2 for 1 h). The results showed that MLP pre-treatment dose-dependently enhanced PBLs' antioxidant capacities. The 200 μg/mL MLP pre-treatment effectively protected the antioxidant system of PBLs from H2O2-induced oxidative damage by reducing the malondialdehyde content and lactic dehydrogenase cytotoxicity, and increasing catalase and superoxide dismutase activities (p < 0.05). The over-production of reactive oxygen species, depletion of nicotinamide adenine dinucleotide phosphate, and collapse of the mitochondrial membrane potential were significantly inhibited in the 200-MLP pre-treatment group (p < 0.05). The expressions of endoplasmic reticulum stress-related genes (forkhead box O1α (foxO1α), binding immunoglobulin protein (bip), activating transcription factor 6 (atf6), and C/EBP-homologous protein (chop)), Ca2+ transport-related genes (voltage-dependent anion-selective channel 1 (vdac1), mitofusin 2 (mfn2), and mitochondrial Ca2+ uniporter (mcu)), and interleukin 6 (il-6) and bcl2-associated x (bax) were significantly lower in the 200-MLP pre-treatment group than in the HP group (p < 0.05), which rebounded to normal levels in the NC group (p > 0.05). These results indicated that MLP pre-treatment attenuated H2O2-induced PBL oxidative damage in the M. amblycephala by inhibiting endoplasmic reticulum stress and maintaining mitochondrial function. These findings also support the possibility that MLPs can be exploited as a natural dietary supplement for M. amblycephala, as they protect against oxidative damage.
Insights
Mulberry leaf polysaccharides (MLPs) protect fish leukocytes from oxidative stress by enhancing antioxidant capacity and inhibiting endoplasmic reticulum stress. MLPs show promise as a natural dietary supplement for aquaculture.
Area of Science:
- Aquaculture and Fish Health
- Oxidative Stress Research
- Natural Product Chemistry
Background:
- Oxidative stress poses a significant threat to fish health and aquaculture productivity.
- Peripheral blood leukocytes (PBLs) are crucial in fish immune responses and susceptible to oxidative damage.
- Hydrogen peroxide (H₂O₂) is a common inducer of oxidative stress in biological systems.
Purpose of the Study:
- To investigate the protective effects of mulberry leaf polysaccharides (MLPs) against H₂O₂-induced oxidative stress in Megalobrama amblycephala PBLs.
- To elucidate the underlying mechanisms of MLP-mediated protection.
- To assess the potential of MLPs as a dietary supplement for fish.
Main Methods:
- In vitro incubation of Megalobrama amblycephala PBLs with varying concentrations of MLPs followed by H₂O₂ stimulation.
- Assessment of antioxidant enzyme activities (catalase, superoxide dismutase), malondialdehyde (MDA) content, and lactate dehydrogenase (LDH) cytotoxicity.
- Measurement of reactive oxygen species (ROS) production, nicotinamide adenine dinucleotide phosphate (NADPH) levels, and mitochondrial membrane potential.
- Analysis of gene expression related to endoplasmic reticulum (ER) stress, calcium transport, and apoptosis.
Main Results:
- MLP pre-treatment dose-dependently improved PBL antioxidant capacity, reducing MDA and LDH levels while increasing catalase and superoxide dismutase activities.
- MLPs significantly inhibited H₂O₂-induced ROS over-production, NADPH depletion, and mitochondrial membrane potential collapse.
- MLP pre-treatment down-regulated the expression of ER stress markers (foxO1α, bip, atf6, chop) and apoptosis-related genes (bax), while up-regulating mitochondrial function genes (vdac1, mfn2, mcu) and il-6.
- Gene expression levels in the 200 μg/mL MLP group returned to normal levels, similar to the control group.
Conclusions:
- MLPs effectively protect Megalobrama amblycephala PBLs against H₂O₂-induced oxidative stress.
- The protective mechanisms involve the inhibition of endoplasmic reticulum stress and maintenance of mitochondrial function.
- MLPs demonstrate potential as a natural dietary supplement to enhance fish health and resilience in aquaculture.
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