Effects of combined use of diallyl disulfide and N-acetyl-cysteine on acetaminophen hepatotoxicity in β-naphthoflavone-pretreated mice

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Trivalent methylated arsenical-induced phosphatidylserine exposure and apoptosis in platelets may lead to increased thrombus formation

Trivalent methylated metabolites of arsenic, monomethylarsonous acid (MMA^III) and dimethylarsinous acid (DMA^III), have been found highly reactive and toxic in various cells and in vivo animal models, suggesting their roles in the arsenic-associated toxicity. However, their effects on cardiovascular system including blood cells, one of the most important targets for arsenic toxicity, remain poorly understood. Here we found that MMA^III and DMA^III could induce procoagulant activity and apoptosis in platelets, which play key roles in the development of various cardiovascular diseases (CVDs) through excessive thrombus formation. In freshly isolated human platelets, treatment of MMA^III resulted in phosphatidylserine (PS) exposure, a hallmark of procoagulant activation, accompanied by distinctive apoptotic features including mitochondrial membrane potential disruption, cytochrome c release, and caspase-3 activation. These procoagulant activation and apoptotic features were found to be mediated by the depletion of protein thiol and intracellular ATP, and flippase inhibition by MMA^III, while the intracellular calcium increase or reactive oxygen species generation was not involved. Importantly, increased platelet procoagulant activity by MMA^III resulted in enhanced blood coagulation and excessive thrombus formation in a rat in vivo venous thrombosis model. DMA^III also induced PS-exposure with apoptotic features mediated by protein thiol depletion, which resulted in enhanced thrombin generation. In summary, we believe that this study provides an important evidence for the role of trivalent methylated arsenic metabolites in arsenic-associated CVDs, giving a novel insight into the role of platelet apoptosis in toxicant-induced cardiovascular toxicity.     

Comparison of N-acetylcysteine and mesna as uroprotectors with ifosfamide combination chemotherapy in refractory germ cell tumors

From January 1983 through August 1988, 318 consecutive patients with refractory germ cell neoplasms were treated with ifosfamide-containing combination chemotherapy. The patients received ifosfamide at 1.2 gm/m² day with cis-platin 20 mg/m² day for 5 days and etoposide 75 mg/m² day for 5 days or vinblastine 0.11 mg/kg on days 1 and 2 for each cycle. Of 277 evaluable patients, NAC was used as an uroprotector in the initial 86 patients while the latter 191 consecutive patients received mesna to reduce urothelial toxicity. Dosages of NAC was 2.0 gm po q 6 hr and for mesna 120 mg/m² IV push prior to ifosfamide and then 1200 mg/m²/day as continuous infusion of 5 consecutive days. All patients received 3.0 liters of normal saline per day. The number of courses of chemotherapy given in the two groups were similar. Twenty-four of the 86 patients (27.9%) receiving NAC developed hematuria (13 patients — grade 1, 4 patients — grade 2, and 7 patients — grade 3 toxicity). While 8 out of 191 (4.2%) mesna patients developed hematuria (6 — grade 1 and 2 — grade 3) (p<0.0001). The incidence of severity of renal toxicity was similar in the two groups. Ifosfamide dosage was reduced solely for urothelial toxicity in 11 patients receiving NAC compared with none of the patients receiving mesna (p<0.0001). Chemotherapy response was similar in the two groups. In conclusion, mesna provides better urothelial protection from ifosfamide-induced toxicity than NAC and allows better maintenance of the drug dosage.     

Inhibition of calcium-independent phospholipase A2 activates p38 MAPK signaling pathways during cytostasis in prostate cancer cells

The p38 mitogen-activated protein kinase (MAPK) signaling pathways activated during cytostasis induced by Ca²⁺-independent phospholipase A₂ (iPLA₂) inhibition in prostate cancer cells were investigated. iPLA₂ inhibition using siRNA, or the selective inhibitor bromoenol lactone (BEL) and it's enantiomers, decreased growth in LNCaP (p53 positive) and PC-3 (p53 negative) human prostate cancer cells. Decreased cell growth correlated to time- and concentration-dependent activation of the mitogen-activated protein kinase p38 in both cell lines. Inhibition of cytosolic iPLA₂β using S-BEL, induced significantly higher levels of P-p53, p53, p21 and P-p38 expression than inhibition of microsomal iPLA₂γ using R-BEL. Inhibition of p38 using SB202190 or SB203580 inhibited BEL-induced increases in P-p53 (ser15), p53 and p21, and altered the number of cells in G1 in LNCaP cells, and S-phase in PC-3 cells. BEL treatment also induced reactive species in PC-3 and LNCaP cells, which was partially reversed by pretreatment with N-acetyl-cysteine (NAC). NAC subsequently inhibited BEL-induced activation of p38 and p53 in LNCaP cells. In addition, treatment of cells with NAC partially reversed the effect of BEL on cell growth and preserved cell morphology. Collectively, these data demonstrate the novel findings that iPLA₂ inhibition activates p38 by inducing reactive species, and further suggest that this signaling kinase is involved in p53 activation, cell cycle arrest and cytostasis.     

Old age-associated enrichment of peripheral T regulatory cells and altered redox status in pulmonary tuberculosis patients

Aging influences the susceptibility and prognosis to various infectious diseases including tuberculosis (TB). Despite the impairment of T-cell function and immunity in older individuals, the mechanism for the higher incidence of TB in the elderly remains largely unknown. Here, we evaluated the age-associated immune alterations, particularly in effector and Treg responses in pulmonary TB patients. We also evaluated the impact of redox status and its modulation with N-acetyl-cysteine (NAC) in elderly TB. Higher frequency of Treg cells and reduced IFN-γ positive T cells were observed among older TB patients. The elevated number of Treg cells correlated tightly with bacillary load (i.e. disease severity); which declined significantly in response to successful anti-tubercular treatment. We could rescue Myobacterium tuberculosis-specific effector T cell (Th1) responses through various in vitro approaches, for example, Treg cell depletion and co-culture experiments, blocking experiments using antibodies against IL-10, TGF-β, and programmed death-1 (PD-1) as well as NAC supplementation. We report old age-associated enrichment of Treg cells and suppression of M. tuberculosis-specific effector T (Th1) cell immune responses. Monitoring these immune imbalances in older patients may assist in immune potentiation through selectively targeting Treg cells and/or optimizing redox status by NAC supplementation.     

Beneficial in vitro effect of N-acetyl-cysteine on oxidative stress and apoptosis

Chronic renal failure (CRF) is usually accompanied by abnormalities of both humoral and cellular immune response. The aim of the study was to investigate the influence of N-acetyl-cysteine (NAC) on intracellular oxidative stress and apoptosis rate of T lymphocytes in children with CRF. Twenty-two children (aged 4–16, mean 7.4) with CRF treated with dialysis were enrolled in the study. Intracellular reactive oxygen species (ROS) production was quantified by mean rhodamine 123 (RHO) fluorescence intensity with flow cytometry. Annexin V FITC was used for identifying apoptotic cells. Mean fluorescence intensity (MFI), which reflected intracellular oxidative stress in T lymphocytes, was increased in patients with CRF compared with the controls (CD3+: 31.58±11.58 vs 22.55±4.97, p =0.043; CD3+CD4+: 32.50±8.59 vs 27.75±12.76, NS; CD3+CD8+: 32.10±11.85 vs 20.77±4.89, p =0.012). Apoptotic T lymphocytes occurred more frequently in patients with CRF treated with hemodialysis (HD) (11.36±6.96%) than in the controls (6.14%±3.36%; p =0.025). After 24 h incubation with NAC MFI and apoptosis rate decreased significantly in all subpopulations of lymphocytes. NAC, as a strong antioxidant, has a favorable effect on intracellular oxidative stress and apoptosis rate of T lymphocytes in patients with CRF. A decreased apoptosis rate may have positive effect on functional abnormalities of T cells already found in patients with CRF.     

Short communication: Cause and prevention of mafosfamide-induced venous pain

An experimental rat model for the study of venous pain induced by 4-hydroxy-cyclophosphamide (4-OH-CP) derivatives was developed and validated. Using various metabolites and chemical variants of 4-OH-CP it was found that pain induction was independent from the compound's alkylating activity but possibly related to the spontaneous generation of minute amounts of acrolein from the 4-OH-CP molecule. Accordingly, the pain could be prevented by the addition of thiol compounds such as mesna or N-acetyl-cysteine.     

Subneurotoxic copper(II)-induced NF-κB-dependent microglial activation is associated with mitochondrial ROS

Microglia-mediated neuroinflammation and the associated neuronal damage play critical roles in the pathogenesis of neurodegenerative disorders. Evidence shows an elevated concentration of extracellular copper(II) in the brains of these disorders, which may contribute to neuronal death through direct neurotoxicity. Here we explored whether extracellular copper(II) triggers microglial activation. Primary rat microglia and murine microglial cell line BV-2 cells were cultured and treated with copper(II). The content of tumor necrosis factor-α (TNF-α) and nitric oxide in the medium was determined. Extracellular hydrogen peroxide was quantified by a fluorometric assay with Amplex Red. Mitochondrial superoxide was measured by MitoSOX oxidation. At subneurotoxic concentrations, copper(II) treatment induced a dose- and time-dependent release of TNF-α and nitric oxide from microglial cells, and caused an indirect, microglia-mediated neurotoxicity that was blocked by inhibition of TNF-α and nitric oxide production. Copper(II)-initiated microglial activation was accompanied with reduced IкB-α expression as well as phosphorylation and translocation of nuclear factor-κB (NF-κB) p65 and was blocked by NF-κB inhibitors (BAY11-7082 and SC-514). Moreover, copper(II) treatment evoked a rapid release of hydrogen peroxide from microglial cells, an effect that was not affected by NADPH oxidase inhibitors. N-acetyl-cysteine, a scavenger of reactive oxygen species (ROS), abrogated copper(II)-elicited microglial release of TNF-α and nitric oxide and subsequent neurotoxicity. Importantly, mitochondrial production of superoxide, paralleled to extracellular release of hydrogen peroxide, was induced after copper(II) stimulation. Our findings suggest that extracellular copper(II) at subneurotoxic concentrations could trigger NF-κB-dependent microglial activation and subsequent neurotoxicity. NADPH oxidase-independent, mitochondria-derived ROS may be involved in this activation.