Organophosphates modulate tissue transglutaminase activity in differentiated C6 neural cells.

OBJECTIVE: The organophosphate compounds chlorpyrifos (O, O-diethyl O-[3,5,6-trichloro-2-pyridinyl] phosphorothioate, CPF) and phenyl saligenin phosphate (PSP) have been widely implicated in developmental neurotoxicity and neurodegeneration. However, the underlying mechanism remains unclear. Transglutaminase (TG)2 is a calcium ion (Ca2+)-dependent enzyme with an important role in neuronal cell outgrowth and differentiation and in neurotoxin activity and is modulated by organophosphates. MATERIALS AND METHODS: We studied TG2 activity modulation by CPO and PSP during differentiation in C6 glioma cells. We studied the effects of CPO or PSP treatment with or without the TG2 inhibitor Z-DON and identified potential TG2 protein substrates via mass spectrometry. RESULTS: PSP and CPO did not affect cell viability but affected TG2 activity in differentiating cells. Our results indicate that the organophosphate-induced amine incorporation activity of TG2 may have a direct effect on neuronal outgrowth, differentiation, and cell survival by modifying several essential microtubule proteins, including tubulin. Inhibiting TG2 reduced neurite length but not cell survival. CONCLUSIONS: TG2 inhibitors can protect against organophosphate-induced neuropathy and could be used for developing novel therapeutic strategies for treating brain cancer and neurodegenerative disorders.

CMF and MET treatment induce cognitive impairment through upregulation of IL-1α in rat brain.

OBJECTIVE: Cyclophosphamide (CYP), methotrexate (MTX) and 5-fluorouracil (5-FU) (CMF) are chemotherapeutic agents known to cause acute and long-term cognitive impairment in cancer patients. Cognitive function is regulated mainly by neuronal circuitry in the brain, especially the cortex and hippocampus as well as other components of the limbic area. Neuroinflammation mediated by proinflammatory cytokines is a well-known cause of cognitive impairment. Our previous study showed that metformin induced cognitive impairment and neuroinflammation in CMF-treated rats. Understanding the effects and mechanisms of CMF and MET treatment on chemotherapy-related cognitive impairment and the relationship with neuroinflammation may help prevent some of the adverse effects of this type of chemotherapy in cancer patients. MATERIALS AND METHODS: Rats were divided into four groups: control (normal saline), CMF (50 mg/kg CYP, 2 mg/kg MTX, 50 mg/kg 5-FU; two doses administered by intraperitoneal injection over two weeks), MET (2.5 mg/ml - oral administration daily), and CMF+MET group. IL-1α, IRS-1, Akt-a and TNF-α levels in brain tissues were measured by ELISA and data were analyzed by one-way ANOVA test followed by Tukey's test. RESULTS: Compared with the control group, IL-1α levels were significantly increased in the CMF+MET group, whereas there were no significant differences in the MET and CMF groups. On the other hand, IRS-1, TNF-α and Akt-a expression and mitochondrial complex 1 activity indicated that systemic CMF and MET treatment did not change the expression of these proteins in the brain compared to the control group. CONCLUSIONS: Our results indicate that cognitive function is impaired by the administration of two doses of CMF and MET over a period of two weeks as a result of IL-1α overexpression in the brain.