Antioxidant and pro-oxidant properties of pyrroloquinoline quinone (PQQ): implications for its function in biological systems

Pyrroloquinoline quinone (PQQ) is a novel redox cofactor recently found in human milk. It has been reported to function as an essential nutrient, antioxidant and redox modulator in cell culture experiments and in animal models of human diseases. As mitochondria are particularly susceptible to oxidative damage we studied the antioxidant properties of PQQ in isolated rat liver mitochondria. PQQ was an effective antioxidant protecting mitochondria against oxidative stress-induced lipid peroxidation, protein carbonyl formation and inactivation of the mitochondrial respiratory chain. In contrast, PQQ caused extensive cell death to cells in culture. This surprising effect was inhibited by catalase, and was shown to be due to the generation of hydrogen peroxide during the autoxidation of PQQ in culture medium. We conclude that the reactivities of PQQ are dependent on its environment and that it can act as an antioxidant or a pro-oxidant in different biological systems.     

吡咯喹啉醌对NMDA诱发大鼠海马神经元损伤的影响

目的探讨吡咯喹啉醌（PQQ）对N-甲基-D-天冬氨酸（NMDA）诱发海马神经元损伤的影响。方法体外原代培养新生大鼠海马神经元，毒性剂量的NMDA诱致海马神经元损伤，预加PQQ，镜下观察神经元的形态变化，琼脂糖凝胶电泳观察细胞的死亡情况，激光共聚焦显微镜观察细胞内Ca^2＋浓度的变化。结果体外培养8d的海马神经用0．1mmol／LNMDA处理后，细胞内Ca^2＋快速增加，细胞以坏死和凋亡两种形式死亡，细胞的存活率降低；预先给予PQQ可明显减少细胞内Ca^2＋的增加，减少细胞死亡。结论PQQ对NMDA诱发的海马神经元损伤具有保护作用。     

吡咯喹啉醌对损伤周围神经的促恢复作用

目的：探讨吡咯喹啉醌(pyrroloquinoline quinone,PQQ)对周围神经损伤后神经功能恢复的影响及对神经所支配肌肉脂质过氧化反应的作用。方法：18只SD鼠随机分入治疗组(9只)与损伤对照组(9只)。所有动物均实施手术造成坐骨神经SeddonⅡ类损伤,治疗组腹腔注射PQQ,对照组给于等体积生理盐水。各组动物于术后3周测定坐骨神经功能指数(SFI)、运动神经传导速度(MCV)及趾长伸肌丙二醛(MDA)和超氧化物歧化酶(SOD)的含量。结果：治疗组SFI优于对照组,MCV快于对照组;治疗组趾长伸肌组织中MDA显著低于对照组,而SOD含量显著高于对照组。结论：PQQ能有效促进坐骨神经功能恢复。     

Pyrroloquinoline quinone delays inflammaging induced by TNF-α through the p16/p21 and Jagged1 signalling pathways

Previous studies on the longevity effect of pyrroloquinoline quinine (PQQ) on nematode worms have revealed that PQQ can enhance the antioxidant capacity of nematode worms, thus extending the lifespan of the worms. The induction and development of cellular senescence are closely connected with inflammatory reactions. The aim of this study was to determine the effect of PQQ and ageing factors on senescent cells. To this end, we cultivated human embryonic lung fibroblasts in nutrient solution with or without tumour necrosis factor-alpha (TNF-α) to establish an inflammaging model in vitro. The cells were preincubated with or without PQQ to determine if PQQ had any anti-inflammaging effect. More senescent cells were detected with the addition of TNF-α than without (P < .01). The ratio of senescent cells to non-senescent cells in the TNF-α group was greater than that in the control group (P < .01). When cells were preincubated with PQQ prior to TNF-α treatment, there were fewer senescent cells than those in the control group, which was not pretreated with PQQ (P < .05). The same tendency was noted with regard to p21, p16, and Jagged1. In summary, we used TNF-α, a well-known pro-inflammatory cytokine associated with inflammaging, to establish an in vitro inflammaging model and provided evidence that PQQ delays TNF-α –induced cellular senescence and has anti-inflammaging properties.     

The protective effect of pyrroloquinoline quinone and its derivatives against carbon tetrachloride-induced liver injury of rats

Pyrroloquinoline quinone (PQQ) and its derivative, oxazo pyrroloquinoline (OPQ-G), protected rats from experimental liver injury induced by carbon tetrachloride (CCl₄) in vivo. This effect was observed after an intraperitoneal injection of 5 mg/kg PQQ or OPQ-G, which was given twice, 10 min and 1 h before CCl₄ administration. Pyrroloquinoline quinone protected primary cultured rat hepatocytes from CCl₄ toxicity in vitro. This protection was most effective at a concentration of 3 μmol/L PQQ. Pyrroloquinoline quinone derivatives (oxazo pyrroloquinoline, methyl-thioethyl oxazo pyrroloquinoline and PQQ-allylester) also protected the hepatocytes from CCl₄ toxicity. Pyrroloquinoline quinone and its derivatives inhibited the lucigenin-enhanced chemiluminescence from isolated hepatocytes initiated by CCl₄. These results suggest that eliminating free radicals is one of the protective mechanisms of PQQ and its derivatives against CCl₄-induced liver injury.     

Acute and subchronic toxicity studies of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ™) in rats

The potential use of pyrroloquinoline quinone disodium salt (BioPQQ™), as a supplemental food ingredient, was evaluated in a range of oral toxicity studies in rats including an acute study, a 14-day preliminary and a 28-day repeated-dose study, and a 13-week subchronic study. The median lethal dose of BioPQQ™ was shown to be 1000–2000 mg/kg body weight (bw) in male and 500–1000 mg/kg bw in female rats. In the 14-day study, high doses of BioPQQ™ resulted in increases in relative kidney weights with associated histopathology in female rats only, while a follow-up 28-day study in female animals resulted in increases in urinary protein and crystals. These findings were reversible, and resolved during the recovery period. In the 13-week study, a number of clinical chemistry findings and histopathological changes were noted, which were deemed to be of no toxicological significance, as the levels were within the historical control range, were not dose-dependent, occurred at a similar frequency in control groups, or only occurred in the control group. Based on these findings, a no-observed-adverse-effect level of 100 mg/kg bw/day was determined for BioPQQ™ in rats, the highest dose tested in the 13-week study.     

吡咯喹啉醌对UVA诱导人皮肤成纤维细胞衰老的保护作用及机制研究

目的:研究吡咯喹啉醌(pyrroloquinoline quinine,PQQ)对UVA诱导人皮肤成纤维细胞衰老的保护作用及其机制?方法:体外使用6孔板培养人皮肤成纤维细胞(human skin fibroblasts,HSF),予以9 J/cm2照射,照射前后实验组加入80 ng/ml的8-甲氧基补骨脂(8-methoxypsoralan,8-MOP)和浓度为50?100?200 ng/ml的PQQ?UVA照射72 h后,对细胞进行衰老β-半乳糖苷酶染色?JC-1染色荧光显微镜检测线粒体膜电位变化?JC-1染色流式细胞仪检测线粒体膜去极化状况?real-time PCR检测衰老相关基因mmp1?mmp3的表达?结果:低剂量PQQ(50 ng/ml)实验组β-半乳糖苷酶染色呈阴性,JC-1染色后低剂量PQQ(50 ng/ml)实验组细胞线粒体膜电位改变的趋势有回转,JC-1染色后流式细胞仪检测PQQ对UVA诱导的衰老细胞线粒体去极化有保护作用,而且低剂量PQQ(50 ng/ml)实验组衰老相关基因mmp1?mmp3的表达也有明显降低?结论:吡咯喹啉醌对由UVA诱导的人皮肤成纤维细胞衰老有保护作用,而且这一作用可能是通过线粒体途径发挥作用的?     

吡咯喹啉醌对肝纤维化大鼠作用的初步研究

目的通过大鼠肝纤维化模型,研究吡咯喹啉醌(PQQ)对肝纤维化防治及其抗氧化能力。方法采用40%四氯化碳花生油溶液制备大鼠肝纤维化模型。观察PQQ对肝纤维化大鼠血清和肝组织中总抗氧化能力(T-AOC)、过氧化物歧化酶(SOD)、丙二醛(MDA)的影响。大鼠肝组织切片HE染色进行病理分析,V-G胶原染色估计肝组织胶原相对含量。结果 PQQ能显著增加纤维化大鼠血清及肝组织中SOD、T-AOC的水平,降低MDA含量,并能减轻肝脏胶原纤维增生程度。结论 PQQ具有较好的抗肝纤维化作用,作用机制与增强机体抗氧化水平有关。     

Pyrroloquinoline quinone protects mouse brain endothelial cells from high glucose-induced damage in vitro

Aim:

To investigate the effects of pyrroloquinoline quinone (PQQ), an oxidoreductase cofactor, on high glucose-induced mouse endothelial cell damage in vitro.

Methods:

Mouse brain microvascular endothelial bEND.3 cells were exposed to different glucose concentrations (5.56, 25 and 40 mmol/L) for 24 or 48 h. The cell viability was examined using MTT assay. Flow cytometry was used to analyze the apoptosis and ROS levels in the cells. MitoTracker Green staining was used to examine the mitochondria numbers in the cells. Western blot analysis was used to analyze the expression of HIF-1α and the proteins in JNK pathway.

Results:

Treatment of bEND.3 cells with high glucose significantly decreased the cell viability, while addition of PQQ (1 and 10 μmol/L) reversed the high glucose-induced cell damage in a concentration-dependent manner. Furthermore, PQQ (100 μmol/L) significantly suppressed the high glucose-induced apoptosis and ROS production in the cells. PQQ significantly reversed the high glucose-induced reduction in both the mitochondrial membrane potential and mitochondria number in the cells. The high glucose treatment significantly increased the expression of HIF-1α and JNK phosphorylation in the cells, and addition of PQQ led to a further increase of HIF-1α level and a decrease of JNK phosphorylation. Addition of JNK inhibitor SP600125 (10 μmol/L) also significantly suppressed high glucose-induced apoptosis and JNK phosphorylation in bEND.3 cells.

Conclusion:

PQQ protects mouse brain endothelial cells from high glucose damage in vitro by suppressing intracellular ROS and apoptosis via inhibiting JNK signaling pathway.