[Study on the effect of diallyl sulfide on peripheral nerve injury in n-hexane intoxicated rats]

Objective: To investigate the antagonistic effect of diallyl sulfide (DAS) against peripheral nerve injury induced by n-hexane in rats. Methods: A total of 68 adult male Wistar rats were selected, among which 50 were randomly selected and divided into blank control group, DAS control group (100 mg/kg·bw) , n-hexane model group, low-dose DAS intervention group (50 mg/kg·bw) , and high-dose DAS intervention group (100 mg/kg·bw) . A rat model of peripheral nerve injury was established by n-hexane exposure, and the rats were treated with DAS at different doses. The changes in pyrrole adducts and behavior were observed, a metabolic analysis was performed for serum pyrrole adducts, and the intervention effect was evaluated. The remaining 18 rats were randomly assigned to the n-hexane model group, the low-dose DAS intervention group, and the high-dose DAS intervention group, with 6 rats in each group, as satellite groups used for the toxicokinetic analysis of serum pyrrole adducts. Results: Compared with the blank control group, the n-hexane model group and low-and high-dose DAS intervention groups had a significant reduction in body weight since week 2 (P<0.01) . Compared with the n-hexane model group at the end of the experiment at week 7, the high-dose DAS intervention group had a significantly higher body weight (P<0.05) , while there was no significant difference in body weight between the n-hexane model group and the low-dose DAS intervention group (P>0.05) . The n-hexane model group developed gait abnormality at week 2 of poisoning, while the low-and high-dose DAS intervention groups developed gait abnormality at weeks 3 and 5 of poisoning, respectively. At the end of the experiment, the n-hexane model group and the low-and high-dose DAS intervention groups had a significantly higher gait score than the blank control group (P<0.01) . At the end of the experiment, the n-hexane model group and the low-dose DAS intervention group had significantly shorter latency in rotarod test than the blank control group (P<0.01) , while there was no significant difference in latency between the DAS control group and the high-dose DAS intervention group (P>0.05) . Compared with the n-hexane model group, the low-and high-dose DAS intervention groups had a significant increase in latency in rotarod test (P<0.01) . Compared with blank control group, the n-hexane model group and the low-dose DAS intervention group had a significant increase in mean nerve conduction velocity (P<0.01) , while there was no significant difference between the blank control group and the DAS control group or high-dose DAS intervention group (P>0.05) , and compared with the n-hexane model group, the low-and high-dose DAS intervention groups had a significant increase in nerve conduction velocity (P<0.01) . Compared with the blank control group at the end of the experiment at week 7, the n-hexane model group and the low-and high-dose DAS intervention groups had significant increases in the concentration of pyrrole adducts in serum, urine, and hair (P<0.01) , while there was no significant difference between the blank control group and the DAS control group (P>0.05) , and the high-dose DAS intervention group had a significantly lower concentration of pyrrole adducts in serum, urine, and hair than the low-dose DAS intervention group (P<0.05) . Serum pyrrole adducts reached the peak level at 9-12 hours and then started to decrease. Compared with the n-hexane model group, the high-and low-dose DAS intervention groups had a significantly shorter half-life period of serum pyrrole adducts (P<0.01) . Compared with the n-hexane model group, the high-and low-dose DAS intervention groups had a significant reduction in the area under the curve of serum pyrrole adducts (P<0.05) . Conclusion: DAS can antagonize peripheral nerve injury induced by n-hexane.

[Study on the determination of pyrrole adduct content in hair samples]

Objective: To find out a method to determine the pyrrole adducts in the hairs. Methods: Collected the hair from common people and rats, defatted after completely washed, steeped the hair in different concentration of 2, 5-hexandione to build hair model containing pyrrole adducts; dissolved the hair and determined the concentration of pyrrole adducts. Results: (1) . The combination of 0.72 mol/L of sodium hydrate and 2% tyrisin could dissolve the hair, and the digestion liquid could react with the Ehrlich's reagent showing fuchsia color; (2) . The color could maintain longer after adding more ethanol; (3) . More pyrrole adducts would be produced by the increasing the concentration of 2, 5-dihexandione (P<0.01) ; (4) . Concentration of pyrrole adducts in n-hexane treated hair showed no difference compared with control (P>0.05) . Conclusion: the method could be used to determine the concentration of pyrrole adducts in hair exposed to n-hexane.

Diallyl trisulfide attenuated n-hexane induced neurotoxicity in rats by modulating P450 enzymes

Chronic exposure to n-hexane can induce serious nerve system impairments without effective preventive medicines. Diallyl trisulfide (DATS) is a garlic-derived organosulfur compound, which has been demonstrated to have many beneficial effects. The current study was designed to evaluate whether DATS could restrain n-hexane induced neurotoxicity in rats and to explore the underlying mechanisms. Rats were treated with n-hexane (3 g/kg, p.o.) and different doses of DATS (10, 20 and 30 mg/kg, p.o.) for 8 weeks. Behavioral assessment showed that DATS could inhibit n-hexane induced neurotoxicity, demonstrated by the improvement of the grip strength and decline of gait scores. Toxicokinetic analysis revealed that the C_max and AUC_0-t of 2,5-hexanedione (product of n-hexane metabolic activation) and 2,5-hexanedione protein adducts in serum were significantly declined in DATS-treated rats, and the levels of pyrrole adducts in tissues were significantly reduced. Furthermore, DATS activated CYP1A1 and inhibited n-hexane induced increased expression and activity of CYP2E1 and CYP2B1. Collectively, these findings indicated that DATS protected the rats from n-hexane-induced neurotoxicity, which might be attributed to the modulation of P450 enzymes by DATS.

Mass spectrometry-based proteomics of oxidative stress: Identification of 4-hydroxy-2-nonenal (HNE) adducts of amino acids using lysozyme and bovine serum albumin as model proteins

Modification of proteins by 4-hydroxy-2-nonenal (HNE), a reactive by-product of ω6 polyunsaturated fatty acid oxidation, on specific amino acid residues is considered a biomarker for oxidative stress, as occurs in many metabolic, hereditary, and age-related diseases. HNE modification of amino acids can occur either via Michael addition or by formation of Schiff-base adducts. These modifications typically occur on cysteine (Cys), histidine (His), and/or lysine (Lys) residues, resulting in an increase of 156 Da (Michael addition) or 138 Da (Schiff-base adducts), respectively, in the mass of the residue. Here, we employed biochemical and mass spectrometry (MS) approaches to determine the MS "signatures" of HNE-modified amino acids, using lysozyme and BSA as model proteins. Using direct infusion of unmodified and HNE-modified lysozyme into an electrospray quadrupole time-of-flight mass spectrometer, we were able to detect up to seven HNE modifications per molecule of lysozyme. Using nanoLC-MS/MS, we found that, in addition to N-terminal amino acids, Cys, His, and Lys residues, HNE modification of arginine (Arg), threonine (Thr), tryptophan (Trp), and histidine (His) residues can also occur. These sensitive and specific methods can be applied to the study of oxidative stress to evaluate HNE modification of proteins in complex mixtures from cells and tissues under diseased versus normal conditions.