Pyrroloquinoline quinone modulates mitochondrial quantity and function in mice

When pyrroloquinoline quinone (PQQ) is added to an amino acid-based, but otherwise nutritionally complete basal diet, it improves growth-related variables in young mice. We examined PQQ and mitochondrial function based on observations that PQQ deficiency results in elevated plasma glucose concentrations in young mice, and PQQ addition stimulates mitochondrial complex 1 activity in vitro. PQQ-deficient weanling mice had a 20-30% reduction in the relative amount of mitochondria in liver; lower respiratory control ratios, and lower respiratory quotients than PQQ-supplemented mice (2 mg PQQ/kg diet). In mice from dams fed a conventional laboratory diet, but switched at weaning to the basal diet, plasma glucose, Ala, Gly, and Ser concentrations were elevated at 4 wk (PQQ- vs. PQQ+), but not at 8 wk. The relative mitochondrial content (ratio of mtDNA to nuclear DNA) also tended (P<0.18) to be lower (PQQ- vs. PQQ+) at 4 wk, but not at 8 wk. PQQ also counters the mitochondrial complex 1 inhibitor, diphenylene iodonium (DPI). Mice were gavaged with 0, 0.4, or 4 microg PQQ/g body weight (BW) daily for 14 d. At each PQQ level, DPI was injected (i.p.) at 0, 0.4, 0.8, or 1.6 microg DPI/g BW. The PQQ-deficient mice exposed to 0.4 or 4.0 microg DPI/g lost weight and had lower plasma glucose levels than PQQ-supplemented mice (P<0.05). In addition, fibroblasts took up (3)H-PQQ added to cell cultures, and cultured hepatocytes maintained mitochondrial PQQ concentrations similar to those observed in vivo. Collectively, these results indicate that dietary PQQ can influence mitochondrial amount and function, particularly in perinatal and weanling mice.

Neuroprotection by pyrroloquinoline quinone (PQQ) in reversible middle cerebral artery occlusion in the adult rat

Pyrroloquinoline quinone (PQQ) is a naturally occurring redox cofactor that acts as an essential nutrient, antioxidant, and redox modulator. It has previously been reported to reduce infarct size in 7-day-old rat pups with an in vivo cerebral hypoxia/ischemia model (Jensen et al., 1994). In this study, we tested whether improvement is found in both behavioral measures of protection and by histological measures of infarcted tissue at 72 h after reversible middle cerebral artery occlusion (rMCAo) in adult rats. Two-hour rMCAo was induced in adult rats using the intraluminal suture technique. PQQ (10, 3, and 1 mg/kg) was given once by intravenous injection at the initiation, or 3 h after the initiation, of 2 h rMCAo. Neurobehavioral deficits were evaluated daily for 3 days followed by infarct volumes measurements by 2,3,5-triphenyltetrazolium chloride (TTC) staining. PQQ at 10 mg/kg infused at the initiation, or 3 h after the initiation, of rMCAo was effective in reducing cerebral infarct volumes measured 72 h later. At 3 h after ischemia, a dose of 3 mg/kg significantly reduced infarct volume compared to vehicle-treated animals, but 1 mg/kg was ineffective. Neurobehavioral scores were also significantly better in the PQQ-treated group compared to the vehicle controls when PQQ was given at 10 and 3 mg/kg, but not at 1 mg/kg. Thus, PQQ is neuroprotective when given as a single administration at least 3 h after initiation of rMCAo. These data indicate that PQQ may be a useful neuroprotectant in stroke therapy.

Pyrroloquinoline quinone (PQQ) prevents fibril formation of α-synuclein

Pyrroloquinoline quinone (PQQ) is a noncovalently bound cofactor in the bacterial oxidative metabolism of alcohols. PQQ also exists in plants and animals. Due to its inherent chemical feature, namely its free-radical scavenging properties, PQQ has been drawing attention from both the nutritional and the pharmacological viewpoint. alpha-Synuclein, a causative factor of Parkinson's disease (PD), has the propensity to oligomerize and form fibrils, and this tendency may play a crucial role in its toxicity. We show that PQQ prevents the amyloid fibril formation and aggregation of alpha-synuclein in vitro in a PQQ-concentration-dependent manner. Moreover, PQQ forms a conjugate with alpha-synuclein, and this PQQ-conjugated alpha-synuclein is also able to prevent alpha-synuclein amyloid fibril formation. This is the first study to demonstrate the characteristics of PQQ as an anti-amyloid fibril-forming reagent. Agents that prevent the formation of amyloid fibrils might allow a novel therapeutic approach to PD. Therefore, together with further pharmacological approaches, PQQ is a candidate for future anti-PD reagent compounds.

Pyrroloquinoline quinone is a potent neuroprotective nutrient against 6-hydroxydopamine-induced neurotoxicity

Pyrroloquinoline quinone (PQQ), which is an essential nutrient, has been shown to act as an antioxidant. Reactive oxygen species (ROS) are thought to be responsible for neurotoxicity caused by the neurotoxin 6-hydroxydopamine (6-OHDA). In this study, we investigated the ability of PQQ to protect against 6-OHDA-induced neurotoxicity using human neuroblastoma SH-SY5Y. When SH-SY5Y cells were exposed to 6-OHDA in the presence of PQQ, PQQ prevented 6-OHDA-induced cell death and DNA fragmentation. Flow cytometry analysis using the ROS-sensitive fluorescence probe, dihydroethidium, revealed that PQQ reduced elevation of 6-OHDA-induced intracellular ROS. In contrast to PQQ, antioxidant vitamins, ascorbic acid and alpha-tocopherol, had no protective effect. Moreover, we showed that PQQ effectively scavenged superoxide, compared to the antioxidant vitamins. Therefore, our results suggest the protective effect of PQQ on 6-OHDA-induced neurotoxicity is involved, at least in part, in its function as a scavenger of ROS, especially superoxide.

Effects of dietary pyrroloquinoline quinone disodium supplementation on inflammatory responses, oxidative stress, and intestinal morphology in broiler chickens challenged with lipopolysaccharide

This study was conducted to investigate the effects of pyrroloquinoline quinone disodium (PQQ·Na2) on inflammatory responses, oxidative stress, and intestinal morphology of broiler chickens challenged with lipopolysaccharide (LPS). A 2 × 2 factorial arrangement in a complete randomized design experiment was used to study the effect of dietary PQQ·Na2 (0 or 1 mg/kg) on broiler chickens with or without a challenge with LPS. A total of two hundred eighty-eight 1-day-old Arbor Acre broiler chickens were randomly assigned to 4 treatments with 6 replicate cages of 12 birds per cage. All experimental broilers were injected intraperitoneally with 0.5 mg/kg body weight of either Escherichia coli LPS or sterile saline at 16, 18, and 20 d of age. Results showed that injecting LPS significantly increased the concentrations of interleukin-1beta (IL-1β) in serum of birds on day 20 and day 21. Meanwhile, LPS injection increased (P < 0.05) the relative mRNA expression of interleukin-6 (IL-6) in the duodenal mucosa of broilers on day 21. However, dietary supplementation with PQQ·Na2 decreased (P < 0.05) the concentration of IL-6 in serum of birds on day 20 and the levels of IL-1β, IL-6, and interleukin-10 (IL-10) in serum of broiler chickens on day 21. Besides, supplementation of PQQ·Na2 within diet decreased (P < 0.05) the mRNA expressions of IL-1β and IL-10 in the duodenal mucosa of birds on day 20. Relative to saline injection, the activity of glutathione peroxidase (GSH-Px) in serum and the activities of total superoxide dismutase (T-SOD) and catalase (CAT) in liver were found to be lower (P < 0.05) in broilers after LPS challenge on day 21. However, birds fed with PQQ·Na2 showed higher (P < 0.05) GSH-Px activity in serum and higher (P < 0.05) T-SOD activities in liver on day 21 and day 42. Pyrroloquinoline quinone disodium also significantly attenuated the LPS-induced decreases in villus height to crypt depth ratio in the duodenum of broilers. In conclusion, dietary PQQ·Na2 supplementation significantly exerted protective effects on inflammation damage and oxidant stress of broilers under LPS challenge by regulating the expression of inflammatory cytokines (IL-1β, IL-6, and IL-10) and activities of antioxidant enzymes (GSH-Px, T-SOD, and CAT). Moreover, dietary PQQ·Na2 supplementation significantly ameliorated the LPS-impaired intestinal morphology in broilers. Therefore, it has been considered that PQQ·Na2 can be used as a potential feed additive in broiler production.

Pyrroloquinoline quinone (PQQ) decreases myocardial infarct size and improves cardiac function in rat models of ischemia and ischemia/reperfusion

As pyrroloquinoline quinone (PQQ) is a redox cofactor in mammals, we asked if it is cardioprotective. Rats were subjected to 2 h of left anterior descending (LAD) coronary artery ligation without reperfusion (model 1, ischemia). In model 2 (ischemia/reperfusion), rats were subjected to 17 or 30 min of LAD occlusion and 2 h of reperfusion. PQQ (15-20 mg/kg) was given i.p., either 30 min before LAD occlusion (Pretreatment) or i.v. at the onset of reperfusion (Treatment). In model 1, PQQ reduced infarct size (10.0 +/- 1.5 vs 19.1 +/- 2.1%, P < 0.01). In model 2, either PQQ Pretreatment or Treatment also reduced infarct size (18.4 +/- 2.3 and 25.6 +/- 3.5% vs 38.1 +/- 2.6%, P < 0.01). PQQ resulted in higher LV developed pressure and LV (+)dP/dt after 1-2 h of reperfusion (P < 0.05), and fewer ventricular fibrillation episodes. PQQ dose (5-20 mg/kg) was inversely related to infarct size. PQQ reduced myocardial tissue levels of malondialdehyde (MDA), an indicator of lipid peroxidation (316 +/- 88 vs 99 +/- 14 nmol/g, P < 0.01). PQQ given either as Pretreatment or as Treatment at the onset of reperfusion is highly effective in reducing infarct size and improving cardiac function in a dose-related manner in rat models of ischemia and ischemia/reperfusion. The optimal dose in this study, which exhibited neither renal nor hepatic toxicity, was 15 mg/kg, but lower doses may also be efficacious. We conclude that PQQ, which appears to act as a free radical scavenger in ischemic myocardium, is a highly effective cardioprotective agent.

Biochemistry: is pyrroloquinoline quinone a vitamin?

The announcement by Kasahara and Kato of pyrroloquinoline quinone (PQQ) as a 'new' vitamin has received considerable attention. We have since attempted to reproduce the findings on which their conclusion is based, namely that defects in lysine metabolism occur in PQQ-deprived rodents. However, we find that the activity of alpha-aminoadipic acid-delta-semialdehyde (AAS) dehydrogenase in liver and plasma levels of alpha-aminoadipic acid (AAA), both of which act as indicators of lysine degradation in mammals, are not affected by changes in PQQ dietary status. Our results call into question the identification of PQQ as a new vitamin.

Pyrroloquinoline quinone nutritional status alters lysine metabolism and modulates mitochondrial DNA content in the mouse and rat

Pyrroloquinoline quinone (PQQ) added to purified diets devoid of PQQ improves indices of perinatal development in rats and mice. Herein, PQQ nutritional status and lysine metabolism are described, prompted by a report that PQQ functions as a vitamin-like enzymatic cofactor important in lysine metabolism (Nature 422 [2003] 832). Alternatively, we propose that PQQ influences lysine metabolism, but by mechanisms that more likely involve changes in mitochondrial content. PQQ deprivation in both rats and mice resulted in a decrease in mitochondrial content. In rats, alpha-aminoadipic acid (alphaAA), which is derived from alpha-aminoadipic semialdehyde (alphaAAS) and made from lysine in mitochondria, and the plasma levels of amino acids known to be oxidized in mitochondria (e.g., Thr, Ser, and Gly) were correlated with changes in the liver mitochondrial content of PQQ-deprived rats, but not PQQ-supplemented rats. In contrast, the levels of NAD dependent alpha-aminoadipate-delta-semialdehyde dehydrogenase (AASDH), a cytosolic enzyme important to alphaAA production from alphaAAS, was not influenced by PQQ dietary status. Moreover, the levels of U26 mRNA were not significantly changed even when diets differed markedly in PQQ and dietary lysine content. U26 mRNA levels were measured, because of U26's proposed, albeit questionable role as a PQQ-dependent enzyme involved in alphaAA formation.

Genetic or pharmacological activation of the Drosophila PGC-1α ortholog spargel rescues the disease phenotypes of genetic models of Parkinson's disease

Despite intensive research, the etiology of Parkinson's disease (PD) remains poorly understood and the disease remains incurable. However, compelling evidence gathered over decades of research strongly support a role for mitochondrial dysfunction in PD pathogenesis. Related to this, PGC-1α, a key regulator of mitochondrial biogenesis, has recently been proposed to be an attractive target for intervention in PD. Here, we showed that silencing of expression of the Drosophila PGC-1α ortholog spargel results in PD-related phenotypes in flies and also seem to negate the effects of AMPK activation, which we have previously demonstrated to be neuroprotective, that is, AMPK-mediated neuroprotection appears to require PGC-1α. Importantly, we further showed that genetic or pharmacological activation of the Drosophila PGC-1α ortholog spargel is sufficient to rescue the disease phenotypes of Parkin and LRRK2 genetic fly models of PD, thus supporting the proposed use of PGC-1α-related strategies for neuroprotection in PD.

Pyrroloquinoline quinone stimulates epithelial cell proliferation by activating epidermal growth factor receptor through redox cycling

Pyrroloquinoline quinone (PQQ), a redox cofactor for bacterial dehydrogenases, has been implicated to be an important nutrient in mammals functioning as a potent growth factor. However, the underlying molecular mechanisms have not been elucidated. The present study revealed that PQQ induces the activation (tyrosine autophosphorylation) of epidermal growth factor receptor (EGFR) and its downstream signaling in a ligand-independent manner, leading to increased cellular proliferation in an epithelial cell line A431. PQQ inhibited protein tyrosine phosphatase 1B (PTP1B), which negatively regulates the EGFR signaling by tyrosine dephosphorylation, to oxidatively modify the catalytic cysteine through its redox cycling activity to generate H(2)O(2). PQQ-inducible intracellular ROS production and EGFR activation were significantly suppressed by the pre-treatment with antioxidants. The intracellular redox state regulates the EGFR signaling through the redox-sensitive catalytic cysteine of PTP1B and modulates cell proliferation. Our data suggest that PQQ may stimulate epithelial cell proliferation by activating EGFR by oxidation and subsequent inactivation of PTP1B via its redox cycling. Our results provide novel insight into the mechanisms by which PQQ may function as a growth factor to contribute to mammalian growth.

Pyrroloquinoline Quinone Resists Denervation-Induced Skeletal Muscle Atrophy by Activating PGC-1α and Integrating Mitochondrial Electron Transport Chain Complexes

Denervation-mediated skeletal muscle atrophy results from the loss of electric stimulation and leads to protein degradation, which is critically regulated by the well-confirmed transcriptional co-activator peroxisome proliferator co-activator 1 alpha (PGC-1α). No adequate treatments of muscle wasting are available. Pyrroloquinoline quinone (PQQ), a naturally occurring antioxidant component with multiple functions including mitochondrial modulation, demonstrates the ability to protect against muscle dysfunction. However, it remains unclear whether PQQ enhances PGC-1α activation and resists skeletal muscle atrophy in mice subjected to a denervation operation. This work investigates the expression of PGC-1α and mitochondrial function in the skeletal muscle of denervated mice administered PQQ. The C57BL6/J mouse was subjected to a hindlimb sciatic axotomy. A PQQ-containing ALZET® osmotic pump (equivalent to 4.5 mg/day/kg b.w.) was implanted subcutaneously into the right lower abdomen of the mouse. In the time course study, the mouse was sacrificed and the gastrocnemius muscle was prepared for further myopathological staining, energy metabolism analysis, western blotting, and real-time quantitative PCR studies. We observed that PQQ administration abolished the denervation-induced decrease in muscle mass and reduced mitochondrial activities, as evidenced by the reduced fiber size and the decreased expression of cytochrome c oxidase and NADH-tetrazolium reductase. Bioenergetic analysis demonstrated that PQQ reprogrammed the denervation-induced increase in the mitochondrial oxygen consumption rate (OCR) and led to an increase in the extracellular acidification rate (ECAR), a measurement of the glycolytic metabolism. The protein levels of PGC-1α and the electron transport chain (ETC) complexes were also increased by treatment with PQQ. Furthermore, PQQ administration highly enhanced the expression of oxidative fibers and maintained the type II glycolytic fibers. This pre-clinical in vivo study suggests that PQQ may provide a potent therapeutic benefit for the treatment of denervation-induced atrophy by activating PGC-1α and maintaining the mitochondrial ETC complex in skeletal muscles.

Protective effect of pyrroloquinoline quinone against Abeta-induced neurotoxicity in human neuroblastoma SH-SY5Y cells

The neurotoxicity of aggregated beta-amyloid (Abeta) has been implicated as a critical cause in the pathogenesis of Alzheimer's disease (AD). It can cause neurotoxicity in AD by evoking a cascade of oxidative damage-dependent apoptosis to neurons. In the present study, we for the first time investigated the protective effect of pyrroloquinoline quinone (PQQ), an anionic, water soluble compound that acts as a redox cofactor of bacterial dehydrogenases, on Abeta-induced SH-SY5Y cytotoxicity. Abeta(25-35) significantly reduced cell viability, increased the number of apoptotic-like cells, and increased ROS production. All of these phenotypes induced by Abeta(25-35) were markedly reversed by PQQ. PQQ pretreatment recovered cells from Abeta(25-35)-induced cell death, prevented Abeta(25-35)-induced apoptosis, and decreased ROS production. PQQ strikingly decreased Bax/Bcl-2 ratio, and suppressed the cleavage of caspase-3. These results indicated that PQQ could protect SH-SY5Y cells against beta-amyloid induced neurotoxicity.

Pyrroloquinoline quinone (PQQ) alleviated sepsis-induced acute liver injury, inflammation, oxidative stress and cell apoptosis by downregulating CUL3 expression

PQQ has anti-inflammatory and anti-oxidant effects. PQQ can relieve high glucose-induced renal cell damage by suppressing Keap1 expression. Keap1 can interact with CUL3. Upregulation of CUL3 facilitates the apoptosis of LPS-induced podocytes. Based on knowledge above, this current work was designed to explore the role of PQQ in sepsis and determine the molecular function of CUL3 in the pathogenesis of sepsis. Rats received CLP surgery to establish sepsis models in vivo. Kupffer cells were pretreated with PQQ (10, 50 and 100 nmol/L) for 2 h and then treated with 100 ng/mL LPS for 24 h, simulating sepsis-induced acute liver injury in vitro. H&E staining was performed to evaluate liver injury of SD rats. Levels of inflammatory factors and oxidative stress markers were detected to assess inflammatory response and oxidative stress. Moreover, TUNEL staining, flow cytometric analysis and western blot were applied to determine cell apoptosis. It was confirmed that PQQ treatment relieved acute liver injury, inflammatory and oxidative stress damage and apoptosis of liver tissue cells in sepsis rats. In addition, PQQ therapy could alleviate inflammation, oxidative stress and apoptosis in LPS-induced Kupffer cells. Notably, LPS stimulation enhanced CUL3 expression and PQQ repressed CUL3 expression in Kupffer cells suffered from LPS. Overall, CUL3 overexpression weakened the remission effects of PQQ on LPS-induced inflammatory and oxidative damage and apoptosis of Kupffer cells. Mechanistically, PQQ treatment may mitigate sepsis-induced acute liver injury through downregulating CUL3 expression.

Enhanced rat sciatic nerve regeneration through silicon tubes filled with pyrroloquinoline quinone

Pyrroloquinoline quinone (PQQ) is an antioxidant that also stimulates nerve growth factor (NGF) synthesis and secretion. In an earlier pilot study in our laboratory, Schwann cell growth was accelerated, and NGF mRNA expression and NGF secretion were promoted. The present study was designed to explore the possible nerve-inducing effect of PQQ on a nerve tube model over a 1-cm segmental deficit. An 8-mm sciatic nerve deficit was created in a rat model and bridged by a 1-cm silicone tube. Then,10 mul of 0.03 mmol/l PQQ were perfused into the silicone chamber in the PQQ group. The same volume of normal saline was delivered in the control group. Each animal underwent functional observation (SFI) at 2-week intervals and electrophysiological studies at 4-week intervals for 12 weeks. Histological and morphometrical analyses were performed at the end of the experiment, 12 weeks after tube implantation. Using a digital image-analysis system, thickness of the myelin sheath was measured, and total numbers of regenerated axons were counted. There was a significant difference in SFI, electrophysiological index (motor-nerve conduct velocity and amplitude of activity potential), and morphometrical results (regenerated axon number and thickness of myelin sheath) in nerve regeneration between the PQQ group and controls (P < 0.05). More mature, high-density, newly regenerated nerve was observed in the PQQ group. We conclude that PQQ is a potent enhancer for the regeneration of peripheral nerves.

Pyrroloquinoline-quinone suppresses liver fibrogenesis in mice

Liver fibrosis represents the consequences of a sustained wound healing response to chronic liver injuries, and its progression toward cirrhosis is the major cause of liver-related morbidity and mortality worldwide. However, anti-fibrotic treatment remains an unconquered area for drug development. Accumulating evidence indicate that oxidative stress plays a critical role in liver fibrogenesis. In this study, we found that PQQ, a natural anti-oxidant present in a wide variety of human foods, exerted potent anti-fibrotic and ROS-scavenging activity in Balb/C mouse models of liver fibrosis. The antioxidant activity of PQQ was involved in the modulation of multiple steps during liver fibrogenesis, including chronic liver injury, hepatic inflammation, as well as activation of hepatic stellate cells and production of extracellular matrix. PQQ also suppressed the up-regulation of RACK1 in activated HSCs in vivo and in vitro. Our data suggest that PQQ suppresses oxidative stress and liver fibrogenesis in mice, and provide rationale for the clinical application of PQQ in the prevention and treatment of liver fibrosis.

Pyrroloquinoline quinine ameliorates doxorubicin-induced autophagy-dependent apoptosis via lysosomal-mitochondrial axis in vascular endothelial cells

The cardiotoxicity of doxorubicin (DOX) limits its clinical use in the treatment of a variety of solid tumors and malignant hematologic disease. However, the mechanism by which it causes cardiotoxicity is not fully understood. Apoptosis has been regarded as one of mechanisms underlying the cardiotoxic effects of DOX. In our study, we found that treatment of human umbilical vein endothelial cells (HUVECs) with DOX induced autophagy and apoptosis in a dose- and time-dependent manner. Treatment with DOX induced autophagy at earlier time (3 h), then lysosomal membrane permeabilization (LMP) altered after treatment for 12 h which followed by the release of cathepsin D (CTSD). Lysosome-associated membrane proteins-1 and -2 (LAMP1 and LAMP2) were decreased in DOX-treated cells. Additionally, DOX induced the collapse of mitochondrial transmembrane potential, reduction of translocase of the outer mitochondrial membrane-20 (TOM-20), and release of cytochrome c. Furthermore, autophagy inhibitor 3-MA relieved DOX-induced apoptosis as assessed by the expression of cleaved caspase-3, cleaved caspase-9 and TUNEL assay. CTSD inhibitor, pepstatin A, upregulated TOM-20 and suppressed the mitochondria release of cytochrome c as well as apoptosis under DOX stress. Pyrroloquinoline quinine (PQQ), a new B vitamin, ameliorated aforementioned phenomenon. In conclusion, our results suggested that DOX-induced apoptosis was autophagy-dependent via lysosomal-mitochondrial axis. PQQ had an ability to protect cell from autophagy-dependent apoptosis induced by DOX via lysosomal-mitochondrial axis to some extent. This study provided new mechanistic insight toward understanding the pathogenesis of DOX-induced cardiotoxicity and the protection effect of PQQ.

Protective Effect of Pyrroloquinoline Quinone (PQQ) in Rat Model of Intracerebral Hemorrhage

Pyrroloquinoline quinone (PQQ) has invoked considerable interest because of its presence in foods, antioxidant properties, cofactor of dehydrogenase, and amine oxidase. Protective roles of PQQ in central nervous system diseases, such as experimental stroke and spinal cord injury models have been emerged. However, it is unclear whether intracerebral hemorrhage (ICH), as an acute devastating disease, can also benefit from PQQ in experimental conditions. Herein, we examined the possible effect of PQQ on neuronal functions following ICH in the adult rats. The results showed that rats pretreated with PQQ at 10 mg/kg effectively improved the locomotor functions, alleviated the hematoma volumes, and reduced the expansion of brain edema after ICH. Also, pretreated rats with PQQ obviously reduced the production of reactive oxygen species after ICH, probably due to its antioxidant properties. Further, we found that, Bcl-2/Bax, the important indicator of oxidative stress insult in mitochondria after ICH, exhibited increasing ratio in PQQ-pretreated groups. Moreover, activated caspase-3, the apoptotic executor, showed coincident alleviation in PQQ groups after ICH. Collectively, we speculated that PQQ might be an effective and potential neuroprotectant in clinical therapy for ICH.

PQQ-dependent alcohol dehydrogenase (QEDH) of Pseudomonas aeruginosa is involved in catabolism of acyclic terpenes

Growth of Pseudomonas aeruginosa on acyclic terpene alcohols such as geraniol depends on the presence of the atuRABCDEFGH gene cluster and a functional acyclic terpene utilisation (Atu) pathway. The proteins encoded by the atu gene cluster are necessary but not sufficient for growth on acyclic terpenes. Comparative 2-dimensional polyacrylamide gel electrophoresis of soluble P. aeruginosa proteins revealed the presence of an additional spot (besides Atu proteins) that is specifically expressed in geraniol cells but is absent in isovalerate-grown cells. The spot was identified as PA1982 gene product a pyrroloquinoline quinone (PQQ) dependent ethanol oxidoreductase (QEDH). Inactivation of PA1982 by insertion mutagenesis resulted in inability of the mutant to utilise ethanol and in reduced growth on geraniol. Growth on ethanol was restored by transferring an intact copy of the PA1982 gene into the mutant. The PA1982 gene product was purified from recombinant Escherichia coli and revealed PQQ-dependent oxidoreductase activity with a variety of substrates including acyclic terpene derivates at comparable V(max)-values. Our results show that QEDH participates in oxidation of acyclic terpene derivates in addition to the well-known function in ethanol metabolism.

Pyrroloquinoline quinone alleviates natural aging-related osteoporosis via a novel MCM3-Keap1-Nrf2 axis-mediated stress response and Fbn1 upregulation

Age-related osteoporosis is associated with increased oxidative stress and cellular senescence. Pyrroloquinoline quinone (PQQ) is a water-soluble vitamin-like compound that has strong antioxidant capacity; however, the effect and underlying mechanism of PQQ on aging-related osteoporosis remain unclear. The purpose of this study was to investigate whether dietary PQQ supplementation can prevent osteoporosis caused by natural aging, and the potential mechanism underlying PQQ antioxidant activity. Here, we found that when 6-month-old or 12-month-old wild-type mice were supplemented with PQQ for 12 months or 6 months, respectively, PQQ could prevent age-related osteoporosis in mice by inhibiting osteoclastic bone resorption and stimulating osteoblastic bone formation. Mechanistically, pharmmapper screening and molecular docking studies revealed that PQQ appears to bind to MCM3 and reduces its ubiquitination-mediated degradation; stabilized MCM3 then competes with Nrf2 for binding to Keap1, thus activating Nrf2-antioxidant response element (ARE) signaling. PQQ-induced Nrf2 activation inhibited bone resorption through increasing stress response capacity and transcriptionally upregulating fibrillin-1 (Fbn1), thus reducing Rankl production in osteoblast-lineage cells and decreasing osteoclast activation; as well, bone formation was stimulated by inhibiting osteoblastic DNA damage and osteocyte senescence. Furthermore, Nrf2 knockout significantly blunted the inhibitory effects of PQQ on oxidative stress, on increased osteoclast activity and on the development of aging-related osteoporosis. This study reveals the underlying mechanism of PQQ's strong antioxidant capacity and provides evidence for PQQ as a potential agent for clinical prevention and treatment of natural aging-induced osteoporosis.

Pyrroloquinoline quinone ameliorates liver injury in mice induced by cyclophosphamide

The current study aimed to investigate the potential ameliorative effects of pyrroloquinoline quinone (PQQ) on cyclophosphamide (CTX)-induced liver injury in mice. The liver injury model was established by injecting mice with CTX (80 mg/kg/day). Liver function indices, antioxidant enzyme activities, and inflammatory cytokines were evaluated. In addition, protein expression levels of the nuclear factor E2-related factor 2 (Nrf2) and nuclear factor kappa-B (NF-κB) pathways in the liver tissues were determined using western blot. The results indicated that PQQ decreased the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and the malondialdehyde (MDA), interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) levels in the liver tissues. Moreover, PQQ enhanced the activities of oxidative stress markers to alleviate CTX induced oxidative stress. Furthermore, the expression levels of heme oxygenase-1 (HO-1), glutamate-cysteine ligase modifier subunit (GCLM), and NAD(P)H quinone oxidoreductase 1 (NQO1) were significantly increased, and the expression levels of NF-κB p50, NF-κB p65, and inhibitor of NF-κB kinase alpha (IKKα) were significantly decreased after PQQ administration, suggesting that PQQ alleviated CTX-induced liver injury via activating the Nrf2-mediated antioxidant response pathway, and inhibiting the NF-κB-mediated inflammation pathway. Therefore, PQQ can be potentially used as a dietary supplement or functional foods for alleviating the CTX-induced liver injury.

Pyrroloquinoline quinone promotes human mesenchymal stem cell-derived mitochondria to improve premature ovarian insufficiency in mice through the SIRT1/ATM/p53 pathway

BACKGROUND

DNA damage and oxidative stress induced by chemotherapy are important factors in the onset of premature ovarian insufficiency (POI). Studies have shown that mitochondria derived from mesenchymal stem cells (MSC-Mito) are beneficial for age-related diseases, but their efficacy alone is limited. Pyrroloquinoline quinone (PQQ) is a potent antioxidant with significant antiaging and fertility enhancement effects. This study aimed to investigate the therapeutic effect of MSC-Mito in combination with PQQ on POI and the underlying mechanisms involved.

METHODS

A POI animal model was established in C57BL/6J mice by cyclophosphamide and busulfan. The effects of MSC-Mito and PQQ administration on the estrous cycle, ovarian pathological damage, sex hormone secretion, and oxidative stress in mice were evaluated using methods such as vaginal smears and ELISAs. Western blotting and immunohistochemistry were used to assess the expression of SIRT1, PGC-1α, and ATM/p53 pathway proteins in ovarian tissues. A cell model was constructed using KGN cells treated with phosphoramide mustard to investigate DNA damage and apoptosis through comet assays and flow cytometry. SIRT1 siRNA was transfected into KGN cells to further explore the role of the SIRT1/ATM/p53 pathway in combination therapy with MSC-Mito and PQQ for POI.

RESULTS

The combined treatment of MSC-Mito and PQQ significantly restored ovarian function and antioxidant capacity in mice with POI. This treatment also reduced the loss of follicles at various stages, improving the disrupted estrous cycle. In vitro experiments demonstrated that PQQ facilitated the proliferation of MitoTracker-labelled MSC-Mito, synergistically restoring mitochondrial function and inhibiting oxidative stress in combination with MSC-Mito. Both in vivo and in vitro, the combination of MSC-Mito and PQQ increased mitochondrial biogenesis mediated by SIRT1 and PGC-1α while inhibiting the activation of ATM and p53, consequently reducing DNA damage-mediated cell apoptosis. Furthermore, pretreatment of KGN cells with SIRT1 siRNA reversed nearly all the aforementioned changes induced by the combined treatment.

CONCLUSIONS

Our research findings indicate that PQQ facilitates MSC-Mito proliferation and, in combination with MSC-Mito, ameliorates chemotherapy-induced POI through the SIRT1/ATM/p53 signaling pathway.

The mechanism of pyrroloquinoline quinone influencing the fracture healing process of estrogen-deficient mice by inhibiting oxidative stress

It is reported that oxidative stress plays a detrimental role in the process of bone fracture healing. And pyrroloquinoline quinone (PQQ) is used as antioxidant. However, there is no report about whether PQQ supplementation can promote fracture healing by eliminating oxidative stress. To investigate the protective effect of PQQ on fracture healing, open mid-diaphyseal femur fractures model were created in sham, ovariectomized (OVX) mice and PQQ-treated OVX mice. Our results confirmed that PQQ played a preventive and protective role in OVX-induced delay of bone fracture healing by inhibiting oxidative stress, subsequently promoting osteoblastic bone formation and inhibiting osteoclastic bone resorption. The findings of this study not only revealed the mechanism of PQQ supplementation in promoting fracture healing, but also provide experimental and theoretical basis for the clinical application of PQQ in the treatment of bone fracture.

Pyrroloquinoline Quinone Administration Alleviates Allergic Airway Inflammation in Mice by Regulating the JAK-STAT Signaling Pathway

The current asthma therapies are inadequate for many patients with severe asthma. Pyrroloquinoline quinone (PQQ) is a naturally-occurring redox cofactor and nutrient that can exert a multitude of physiological effects, including anti-inflammatory and antioxidative effects. We sought to explore the effects of PQQ on allergic airway inflammation and reveal the underlying mechanisms. In vitro, the effects of PQQ on the secretion of epithelial-derived cytokines by house dust mite- (HDM-) incubated 16-HBE cells and on the differentiation potential of CD4+ T cells were investigated. In vivo, PQQ was administered to mice with ovalbumin- (OVA-) induced asthma, and lung pathology and inflammatory cell infiltration were assessed. The changes in T cell subsets and signal transducers and activators of transcription (STATs) were evaluated by flow cytometry. Pretreatment with PQQ significantly decreased HDM-stimulated thymic stromal lymphopoietin (TSLP) production in a dose-dependent manner in 16-HBE cells and inhibited Th2 cell differentiation in vitro. Treatment with PQQ significantly reduced bronchoalveolar lavage fluid (BALF) inflammatory cell counts in the OVA-induced mouse model. PQQ administration also changed the secretion of IFN-γ and IL-4 as well as the percentages of Th1, Th2, Th17, and Treg cells in the peripheral blood and lung tissues, along with inhibition the phosphorylation of STAT1, STAT3, and STAT6 while promoting that of STAT4 in allergic airway inflammation model mice. PQQ can alleviate allergic airway inflammation in mice by improving the immune microenvironment and regulating the JAK-STAT signaling pathway. Our findings suggest that PQQ has great potential as a novel therapeutic agent for inflammatory diseases, including asthma.

Oral pyrroloquinoline quinone (PQQ) during pregnancy increases cardiomyocyte endowment in spontaneous IUGR guinea pigs

BACKGROUND

Intrauterine growth restriction (IUGR) exerts a negative impact on developing cardiomyocytes and emerging evidence suggests activation of oxidative stress pathways plays a key role in this altered development. Here, we provided pregnant guinea pig sows with PQQ, an aromatic tricyclic o-quinone that functions as a redox cofactor antioxidant, during the last half of gestation as a potential antioxidant intervention for IUGR-associated cardiomyopathy.

METHODS

Pregnant guinea pig sows were randomly assigned to receive PQQ or placebo at mid gestation and fetuses were identified as spontaneous IUGR (spIUGR) or normal growth (NG) near term yielding four cohorts: NG ± PQQ and spIUGR ± PQQ. Cross sections of fetal left and right ventricles were prepared and cardiomyocyte number, collagen deposition, proliferation (Ki67) and apoptosis (TUNEL) were analyzed.

RESULTS

Cardiomyocyte endowment was reduced in spIUGR fetal hearts when compared to NG; however, PQQ exerted a positive effect on cardiomyocyte number in spIUGR hearts. Cardiomyocytes undergoing proliferation and apoptosis were more common in spIUGR ventricles when compared with NG animals, which was significantly reduced with PQQ supplementation. Similarly, collagen deposition was increased in spIUGR ventricles and was partially rescued in PQQ-treated spIUGR animals.

CONCLUSION

The negative influence of spIUGR on cardiomyocyte number, apoptosis, and collagen deposition during parturition can be suppressed by antenatal administration of PQQ to pregnant sows. These data identify a novel therapeutic intervention for irreversible spIUGR-associated cardiomyopathy.

Pyrroloquinoline quinone inhibits PCSK9-NLRP3 mediated pyroptosis of Leydig cells in obese mice

Abnormal lipid metabolism and chronic low-grade inflammation are the main traits of obesity. Especially, the molecular mechanism of concomitant deficiency in steroidogenesis-associated enzymes related to testosterone (T) synthesis of obesity dominated a decline in male fertility is still poorly understood. Here, we found that in vivo, supplementation of pyrroloquinoline quinone (PQQ) efficaciously ameliorated the abnormal lipid metabolism and testicular spermatogenic function from high-fat-diet (HFD)-induced obese mice. Moreover, the transcriptome analysis of the liver and testicular showed that PQQ supplementation not only inhibited the high expression of proprotein convertase subtilisin/Kexin type 9 (PCSK9) but also weakened the NOD-like receptor family pyrin domain containing 3 (NLRP3)-mediated pyroptosis, which both played a negative role in T synthesis of Leydig Cells (LCs). Eventually, the function and the pyroptosis of LCs cultured with palmitic acid in vitro were simultaneously benefited by suppressing the expression of NLRP3 or PCSK9 respectively, as well the parallel effects of PQQ were affirmed. Collectively, our data revealed that PQQ supplementation is a feasible approach to protect T synthesis from PCSK9-NLRP3 crosstalk-induced LCs' pyroptosis in obese men.