Kinetics and mechanism of the chromic oxidation of myo-inositol

Effects of Dietary Inositol Supplementation on Growth, Digestive Performance, Antioxidant Capacity, and Body Composition of Golden Pompano (Trachinotus ovatus)

A 56-day culture experiment was performed to evaluate effects of inositol supplementation on growth, digestive performance, antioxidant capacity, and body composition of golden pompano (Trachinotus ovatus). Five experimental diets (D1, D2, D3, D4, and D5) supplemented with 0, 150, 300, 600, and 1,200 mg kg⁻¹ inositol were formulated, respectively. Triplicate groups of 300 fish with an initial weight of (18.78 ± 0.21 g) and 15 seawater cages were used in the feeding experiment. Results indicated that the final body weight (FBW), weight gain rate (WGR), specific growth ratio (SGR), and condition factor (CF) in fish fed with D3–D5 diets were significantly higher than those fed the D1 and D2 diets, and the highest values were detected in D3 diet treatment. The whole-body composition was not significantly affected by different experimental diets. Fish fed with D3-D5 diets showed higher activities of amylase (AMS), lipase (LPS), and superoxide dismutase (SOD), and significantly higher than those fed with D1 and D2 diets. In contrast, fish fed with D3–D5 diets showed lower MDA content and significantly lower than those fed with D1 and D2 diets. The mRNA level of glutathione reductase (GR) in fish fed with D3 and D4 diets was significantly higher than those fed with D1, D2, and D5 diets. Likewise, the mRNA level of catalase (CAT) significantly increased in the dietary inositol groups compared with the D1 group. In conclusion, the supplement of inositol not less than 300 mg kg⁻¹ in the diet is indispensable to maintain the rapid growth and promote antioxidative capacity of T. ovatus.

Dietary myo-inositol deficiency decreased the growth performances and impaired intestinal physical barrier function partly relating to nrf2, jnk, e2f4 and mlck signaling in young grass carp (Ctenopharyngodon idella)

In this study, we investigated the effects of dietary myo-inositol on the growth and intestinal physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp (221.83 ± 0.84 g) were fed six diets containing graded levels of myo-inositol (27.0, 137.9, 286.8, 438.6, 587.7 and 737.3 mg/kg) for 10 weeks. After the growth trial, fish were challenged with Aeromonas hydrophila for 14 days. The results indicated that compared with optimal myo-inositol levels, myo-inositol deficiency (27.0 mg/kg diet): (1) decreased glutathione (GSH) contents and antioxidant enzymes activities, and down-regulated the mRNA levels of antioxidant enzymes [not glutathione-S-transferase (gst) p1 and gstp2] and NF-E2-related factor 2 (nrf2), whereas up-regulated the reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC) contents, and the mRNA levels of Kelch-like-ECH-associated protein 1 (keap1) in three intestinal segments of young grass carp (P < 0.05). (2) Up-regulated cysteinyl aspartic acid-protease (caspase)-2, -3, -7, -8, -9, apoptotic protease activating factor-1 (apaf-1), Bcl2-associated X protein (bax), fas ligand (fasl), gen-activated protein kinase (p38mapk) and c-Jun N-terminal protein kinase (jnk) mRNA levels, whereas down-regulated B-cell lymphoma-2 (bcl-2), inhibitor of apoptosis proteins (iap) and myeloid cell leukemia-1 (mcl-1) mRNA levels in three intestinal segments of young grass carp (P < 0.05). (3) Down-regulated mRNA levels of cell cycle proteins cyclin b, cyclin d, cyclin e and E2F transcription factor 4 (e2f4) in three intestinal segments of young grass carp (P < 0.05). (4) Down-regulated the mRNA levels of zonula occludens (zo) 1, zo-2, occludin, claudin-b, -c, -f, -3c, -7a, -7b as well as -11, and up-regulated the mRNA levels of claudin-12, -15a (not -15b) and myosin light chain kinase (mlck) in three intestinal segments of young grass carp (P < 0.05). All above data indicated that dietary myo-inositol deficiency could damage physical barrier function in three intestinal segments of fish. Finally, the myo-inositol requirements based on the percent weight gain (PWG), reactive oxygen species (ROS) contents in the proximal intestine (PI), relative mRNA levels of caspase-2 (PI), cyclin b (MI) as well as claudin-b (PI) were estimated to be 276.7, 304.1, 327.9, 416.7 and 313.2 mg/kg diet, respectively.

Dietary myo-inositol modulates immunity through antioxidant activity and the Nrf2 and E2F4/cyclin signalling factors in the head kidney and spleen following infection of juvenile fish with Aeromonas hydrophila

This study was conducted to investigate the effects of the dietary vitamin myo-inositol (MI), on the immunity and structural integrity of the head kidney and spleen following infection of fish with the major freshwater pathogen bacterial Aeromonas hydrophila. The results demonstrated for the first time that MI deficiency depressed the lysozyme and acid phosphatase (ACP) activities and the complement 3 (C3) and C4 contents in the head kidney and spleen compared with the optimal MI levels, indicating that MI deficiency decreased the immunity of these important fish immune organs. The depression in immunity due to MI deficiency was partially related to oxidative damage [indicated by increases in the malondialdehyde (MDA) and protein carbonyl (PC) contents] that was in turn partially due to the decreased glutathione (GSH) content and the disturbances in antioxidant enzyme activities [total superoxide dismutase (T-SOD), CuZnSOD, MnSOD, catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)]. MI deficiency inhibited the antioxidant-related gene transcription [CuZnSOD, MnSOD, CAT, GPx1a, GR and NF-E2-related factor 2 (Nrf2)] in the head kidney and spleen following infection of the fish with A. hydrophila. The oxidative damage due to MI deficiency also resulted in the inhibition of proliferation-associated signalling (cyclin D1, cyclin A, cyclin E and E2F4). Thus, MI deficiency partially inhibited damage repair. Excessive MI exhibited negative effects that were similar to MI deficiency, whereas the optimal MI content reversed those indicators. These observations indicated that an MI deficiency or excess could cause depression of the immune system that might be partially related to oxidative damage, antioxidant disturbances, and the inhibition of the proliferation-associated signalling in the head kidney and spleen following infection of fish with A. hydrophila. Finally, the optimal MI levels were 660.7 (based on ACP) and 736.8 mg kg(-1) diet (based on MDA) in the head kidney and 770.5 (based on ACP) and 766.9 mg kg(-1) diet (based on MDA) in the spleen of juvenile Jian carp.

Redox and complexation chemistry of the CrVI/CrV-D-glucaric acid system

When an excess of uronic acid over Cr(VI) is used, the oxidation of D-glucaric acid (Glucar) by Cr(VI) yields D-arabinaric acid, CO2 and Cr(III)-Glucar complex as final redox products. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species. The reaction rate increases with [H(+)] and [substrate]. The experimental results indicated that Cr(IV) and Cr(V) are very reactive intermediates since their disappearance rates are much faster than Cr(VI). Cr(IV) and Cr(V) intermediates are involved in fast steps and do not accumulate in the redox reaction of the mixture Cr(VI)-Glucar. Kinetic studies show that the redox reaction between Glucar and Cr(VI) proceeds through a mechanism combining one- and two-electron pathways: Cr(VI) → Cr(IV) → Cr(II) and Cr(VI) → Cr(IV) → Cr(III). After the redox reaction, results show a slow hydrolysis of the Cr(III)-Glucar complex into [Cr(OH2)6](3+). The proposed mechanism is supported by the observation of free radicals, CrO2(2+) (superoxo-Cr(III) ion) and oxo-Cr(V)-Glucar species as reaction intermediates. The continuous-wave electron paramagnetic resonance, CW-EPR, spectra show that five-coordinate oxo-Cr(V) bischelates are formed at pH ≤ 4 with the aldaric acid bound to oxo-Cr(V) through the carboxylate and the α-OH group. A different oxo-Cr(V) species with Glucar was detected at pH 6.0. The high g(iso) value for the last species suggests a mixed coordination species, a five-coordinated oxo-Cr(V) bischelate with one molecule of Glucar acting as a bi-dentate ligand, using the 2-hydroxycarboxylate group, and a second molecule of Glucar with any vic-diolate sites. At pH 7.5 only a very weak EPR signal was observed, which may point to instability of these complexes. This behaviour contrasts with oxo-Cr(V)-uronic species, and must thus be related to the Glucar acyclic structure. In vitro, our studies on the chemistry of oxo-Cr(V)-Glucar complexes can provide information on the nature of the species that are likely to be stabilized in vivo.

Copper exposure induces oxidative injury, disturbs the antioxidant system and changes the Nrf2/ARE (CuZnSOD) signaling in the fish brain: protective effects of myo-inositol

The brain is the center of the nervous system in all vertebrates, and homeostasis of the brain is crucial for fish survival. Copper (Cu) is essential for normal cellular processes in most eukaryotic organisms but is toxic in excess. Although Cu is indicated as a potent neurotoxicant, information regarding its threat to fish brain and underlying mechanisms is still scarce. In accordance, the objective of this study was to assess the effects and the potential mechanism of Cu toxicity by evaluating brain oxidative status, the enzymatic and mRNA levels of antioxidant genes, as well as the Nrf2/ARE signaling in the brain of fish after Cu exposure. The protective effects of myo-inositol (MI) against subsequent Cu exposure were also investigated. The results indicate that induction of oxidative stress by Cu is shown by increases in brain ROS production, lipid peroxidation and protein oxidation, which are accompanied by depletions of antioxidants, including total superoxide dismutase (T-SOD), CuZnSOD, glutathione-S-transferase (GST) and glutathione reductase (GR) activities and glutathione (GSH) content. Cu exposure increased the catalase (CAT) and glutathione peroxidase (GPx) activities. Further molecular results showed that Cu exposure up-regulated CuZnSOD, GPx1a and GR mRNA levels, suggesting an adaptive mechanism against stress. Moreover, Cu exposure increased fish brain Nrf2 nuclear accumulation and increased its ability of binding to ARE (CuZnSOD), which supported the increased CuZnSOD mRNA levels. In addition, Cu exposure caused increases of the expression of the Nrf2, Maf G1 (rather than Maf G2 gene) and PKCd genes, suggesting that de novo synthesis of those factors is required for the protracted induction of such antioxidant genes. However, the modulation of Keap1a (rather than Keap1b) of fish brain under Cu exposure might be used to turn off of the signaling cascade and avoid harmful effects. Interestingly, pre-treatment of fish with MI prevented the fish brain from Cu-induced oxidative damages mainly by increasing the GSH content and CuZnSOD and GST activities. Summarily, this study indicates that although Cu stimulates adaptive increases in the expression of some antioxidant enzyme genes through Nrf2/ARE signaling, it also induces oxidation and the depletion of most of antioxidant enzyme activities and GSH content due to the increase of ROS production, and MI protects the fish brain against Cu toxicity.

Reduction of hypervalent chromium in acidic media by alginic acid

Selective oxidation of carboxylate groups present in alginic acid by Cr(VI) affords CO2, oxidized alginic acid, and Cr(III) as final products. The redox reaction afforded first-order kinetics in [alginic acid], [Cr(VI)], and [H(+)], at fixed ionic strength and temperature. Kinetic studies showed that the redox reaction proceeds through a mechanism which combines Cr(VI)→Cr(IV)→Cr(II) and Cr(VI)→Cr(IV)→Cr(III) pathways. The mechanism was supported by the observation of free radicals, CrO2(2+) and Cr(V) as reaction intermediates. The reduction of Cr(IV) and Cr(V) by alginic acid was independently studied and it was found to occur more than 10(3) times faster than alginic acid/Cr(VI) reaction, in acid media. At pH 1-3, oxo-chromate(V)-alginic acid species remain in solution during several hours at 15°C. The results showed that this abundant structural polysaccharide present on brown seaweeds is able to reduce Cr(VI/V/IV) or stabilize high-valent chromium depending on pH value.

In vitro interceptive and reparative effects of myo-inositol against copper-induced oxidative damage and antioxidant system disturbance in primary cultured fish enterocytes

Copper (Cu) is essential for normal cellular processes in most eukaryotic organisms but is toxic in excess. Our previous study reported that a nutrient antioxidant, myo-inositol (MI), can protect fish from Cu-induced oxidative injury; however, the mechanisms involved are not fully understood. Therefore, the present study aimed to analyze potential pathways. First, to investigate the hypothesis that MI protects enterocytes against Cu toxicity via the intercept pathway, enterocytes were treated with different concentrations of MI (0-75mg/L medium) in the presence of 6mg/L of Cu for 24h (Experiment 1). Next, we investigated the potential reparative role of MI after a Cu challenge (Experiment 2). The results of Experiment 1 indicated that cells exposed to Cu alone for 24h exhibited increases in lactate dehydrogenase release (LDH), malondialdehyde (MDA) formation and protein oxidation (P<0.05). Notably, a dose-dependent inhibitory effect on LDH release was observed with all doses of MI. Moreover, co-treatment with MI completely inhibited Cu-induced protein carbonyl (PC) formation. However, Cu-induced lipid peroxidation was not altered by MI co-treatment. Additionally, Cu exposure suppressed total-superoxide dismutase (T-SOD), CuZnSOD and catalase (CAT) activities, and these changes were completely blocked by co-treatment with sufficient MI concentrations. In contrast, cells exposed to Cu exhibited adaptive increases in reduced glutathione (GSH) content and the activities of anti-hydroxyl radical (AHR), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR). Interestingly, the Cu-stimulated increases in these antioxidants were blocked by co-treatment with sufficient MI concentrations. The results of Experiment 2 indicated that cell injury (LDH release), lipid peroxidation (MDA formation) and protein oxidation induced by Cu were reversed by subsequent MI treatment. Meanwhile, Cu-induced decreases in alkaline phosphatase (AKP), anti-superoxide anion (ASA), T-SOD and CuZnSOD activities were completely restored by subsequent MI treatment, while the reduced CAT activity was partially restored. However, MI rescues partially restored the adaptive increase in GPx activity induced by Cu, whereas the adaptive increase in reduced GSH content was completely reversed by 75mg/L of MI. However, subsequent MI treatments did not alter the induction of GST activity by Cu. In conclusion, we demonstrated for the first time that MI not only protected enterocytes from Cu-induced oxidative damage but also increased the repair activity in primary enterocytes after challenge with Cu. Moreover, MI-mediated increases in antioxidant enzyme activities contributed to lipid and protein oxidant repair.

Myo-inositol prevents copper-induced oxidative damage and changes in antioxidant capacity in various organs and the enterocytes of juvenile Jian carp (Cyprinus carpio var. Jian)

Although oxidative stress has been demonstrated to be involved in copper (Cu)-induced toxicity, information regarding the effect of antioxidants on Cu toxicity is still scarce. This study assessed the possible protective effects of myo-inositol (MI) against subsequent Cu exposure in juvenile Jian carp (Cyprinus carpio var. Jian) in vivo and in their enterocytes in vitro. First, oxidative stress was established by exposing fish to different concentrations of Cu (0-7.2 mg Cu/L water) for 4 days. Next, the protective effects of MI (administered as a dietary supplement for 60 days) against subsequent Cu exposure (0.6 mg Cu/L water for 4 days) were studied in fish. The third trial determined the effects of Cu exposure (0-6.0 mg Cu/L of medium for 24h) on enterocytes in vitro. Finally, enterocytes were pre-incubated with graded levels of MI (0-75 mg MI/L of medium) for 72 h and exposed to 6.0 mg Cu/L of medium for 24h. The results indicated that ≥ 0.6 mg Cu/L water could induce oxidative stress in fish (P<0.05). Cu exposure significantly induced increases in lipid peroxidation and protein oxidation in the gill, hepatopancreas and intestine in fish. However, these oxidative effects were prevented by MI pre-supplementation. MI also prevented the toxic effects of Cu on anti-superoxide anion (ASA), anti-hydroxyl radical (AHR), superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR) activities and glutathione (GSH) content in these organs. In vitro, enterocytes exposed to Cu displayed a dose-dependent injury. Moreover, cell viability, protein retention (PR), alkaline phosphatase, total-SOD (T-SOD) and Cu/ZnSOD activities were all depressed by Cu (P<0.05). Interestingly, the final experiment showed that MI pre-supplementation could block the toxic effects of Cu on the antioxidant system, and thus protect enterocytes from Cu-induced oxidative damage. All of these results indicated that the induction of key antioxidant defenses by MI pre-supplementation, including SOD, CAT, GPx, GST and GSH, may play an important role in the protection of fish against oxidative stress.

Detection and structural characterization of oxo-chromium(V)-sugar complexes by electron paramagnetic resonance

This article describes the detection and characterization of oxo-Cr(V)-saccharide coordination compounds, produced during chromic oxidation of carbohydrates by Cr(VI) and Cr(V), using electron paramagnetic resonance (EPR) spectroscopy. After an introduction into the main importance of chromium (bio)chemistry, and more specifically the oxo-chromium(V)-sugar complexes, a general overview is given of the current state-of-the-art EPR techniques. The next step reviews which types of EPR spectroscopy are currently applied to oxo-Cr(V) complexes, and what information about these systems can be gained from such experiments. The advantages and pitfalls of the different approaches are discussed, and it is shown that the potential of high-field and pulsed EPR techniques is as yet still largely unexploited in the field of oxo-Cr(V) complexes. Subsequently, the discussion focuses on the analysis of oxo-Cr(V) complexes of different types of sugars and the implications of the results in terms of understanding chromium (bio)chemistry.