Regional-specific changes in rat brain BDNF in a model of methamphetamine abuse.

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays key roles in neuronal protection and synaptic plasticity. Changes in BDNF are associated with various pathological conditions, including methamphetamine (meth) addiction, although the effects of meth on BDNF expression are not always consistent. We have previously demonstrated region-specific effects of a chronic meth regime on BDNF methylation and expression in the rat brain. This study aims to determine the effect of chronic meth administration on the expression of BDNF protein using immunohistochemistry in the rat frontal cortex and hippocampus. Novel object recognition (NOR) as a measure of cognitive function was also determined. Male Sprague Dawley rats were administered a chronic escalating dose (0.1-4 mg/kg over 14 days) (ED) of meth or vehicle; a subgroup of animals receiving meth were also given an acute "binge" (4x6mg) dose on the final day before NOR testing. The results showed that hippocampal CA1 BDNF protein was significantly increased by 72 % above control values in the ED-binge rats, while other hippocampal regions and frontal cortex were not significantly affected. Meth-administered animals also demonstrated deficits in NOR after 24 h delay. No significant effect of the additional binge dose on BDNF protein or NOR findings was apparent. This finding is consistent with our previous results of reduced DNA methylation and increased expression of the BDNF gene in this region. The hippocampal BDNF increase may reflect an initial increase in a protective factor produced in response to elevated glutamate release resulting in neurodegenerative excitotoxicity.

A solid lipid particle formulation of long pepper extract reduces pain and astrocyte activation in a rat model of neuropathic pain.

OBJECTIVES: To investigate the effects of solid lipid microparticle (SLM) creams containing a long pepper extract (LPE) or piperine on neuropathy-related pain and the expression of glial fibrillary acidic protein (GFAP) as a measure of astrogliosis. METHODS: Neuropathic pain in male Spraque Dawley rats was induced by sciatic nerve ligation (SNL) and followed by treatment with LPE-SLM, piperine-SLM, capsaicin or vehicle creams. The pain score was assessed by thermal hyperalgesia test. The GFAP expression in the spinal cord was determined by immunohistochemistry. RESULTS: Pain scores were significantly increased after SNL and decreased when treated by LPE-SLM. The number of GFAP immunopositive cells was significantly increased in the SNL rats. Treated by LPE-SLM and capsaicin creams resulted in a significant reduction of the number of GFAP immunopositive cells. The LPE-SLM treated rats showed greater effects than the piperine and capsaicin preparations. CONCLUSIONS: The LPE-SLM cream has a potential effect on pain attenuation via a decrease of spinal astrocyte activation-related mechanism. The LPE in SLM preparation could provide an alternative therapeutic strategy for treating neuropathic pain.

Changes of BDNF exon IV DNA methylation are associated with methamphetamine dependence.

Aim: We investigated DNA methylation of BDNF in methamphetamine (METH) dependence in humans and an animal model. Materials & methods:BDNF methylation at exon IV was determined by pyrosequencing of blood DNA from METH-dependent and control subjects, and from rat brain following an escalating dose of METH or vehicle. Bdnf expression was determined in rat brain. Results:BDNF methylation was increased in human METH dependence, greatest in subjects with psychosis and in prefrontal cortex of METH-administered rats; rat hippocampus showed reduced Bdnf methylation and increased gene expression. Conclusion:BDNF methylation is abnormal in human METH dependence, especially METH-dependent psychosis, and in METH-administered rats. This may influence BDNF expression and contribute to the neurotoxic effects of METH exposure.

Lay abstract The effects of methamphetamine (METH), an addictive psychostimulant drug, on changes of DNA methylation of an important regulator of neuronal survival, BDNF, were examined in blood of METH-dependent patients and in the brain of METH-administered rats. BDNF methylation was increased in patients and in the prefrontal cortex of METH-administered rats, while rat hippocampus showed a reduction of Bdnf methylation, with an equivalent increase in gene expression. The methylation increases in humans were greatest in those with a METH-induced psychosis. Although a relationship between Bdnf methylation and its expression has not been proven, changes of BDNF DNA methylation are associated with METH dependence, especially METH-dependent psychosis, suggesting that METH neurotoxicity may relate to the effects of changes in BDNF methylation.

Early-life stress effects on BDNF DNA methylation in first-episode psychosis and in rats reared in isolation.

Stressful events during early-life are risk factors for psychiatric disorders. Brain-derived neurotrophic factor (BDNF) is implicated in psychosis pathophysiology and deficits in BDNF mRNA in animal models of psychiatric disease are reported. DNA methylation can control gene expression and may be influenced by environmental factors such as early-life stress. We investigated BDNF methylation in first-episode psychosis (FEP) patients (n = 58), their unaffected siblings (n = 29) and community-based controls (n = 59), each of whom completed the Childhood Trauma Questionnaire (CTQ); BDNF methylation was also tested in male Wistar rats housed isolated or grouped from weaning. DNA was extracted from human blood and rat brain (prefrontal cortex and hippocampus), bisulphite-converted and the methylation of equivalent sequences within BDNF exon IV determined by pyrosequencing. BDNF methylation did not differ significantly between diagnostic groups; however, individuals who had experienced trauma presented higher levels of methylation. We found association between the mean BDNF methylation and total CTQ score in FEP, as well as between individual CpG sites and subtypes of trauma. No significant correlations were found for controls or siblings with child trauma. These results were independent of age, gender, body mass index, BDNF genotype or LINE-1, a measure of global methylation, which showed no significant association with trauma. Isolation rearing resulted in increased BDNF methylation in both brain regions compared to group-housed animals, a correlate of previously reported changes in gene expression. Our results suggest that childhood maltreatment may result in increased BDNF methylation, providing a mechanism underlying the association between early-life stress and psychosis.

Pharmacogenetics of drug dependence: Polymorphisms of genes involved in glutamate neurotransmission.

Multiple studies provide evidence to support dysfunction of glutamate neurotransmission in the pathogenesis of drug dependence. Pharmacogenetic investigation of glutamate-related genes has provided further support for the involvement of this neurotransmitter in the risk of, and consequences of, drug abuse and dependence. This paper aims to provide a brief review of these association studies. Findings involving single nucleotide polymorphisms (SNPs) in glutamate receptor genes (GRIN, GRIA) and glutamate transporter genes (SLC1A, SLC17A) are reviewed as potential risk factors. As yet a clear perspective of the functional consequences and interactions of the various reported findings is lacking.

Genetic variation of GRIA3 gene is associated with vulnerability to methamphetamine dependence and its associated psychosis.

Methamphetamine (METH) is an addictive psychostimulant drug commonly leading to schizophrenia-like psychotic symptoms. Disturbances in glutamatergic neurotransmission have been proposed as neurobiological mechanisms and the α-amino-3 hydroxy-5 methyl-4 isoxazole propionic acid (AMPA) glutamate receptor has been implicated in these processes. Moreover, genetic variants in GRIAs, genes encoding AMPA receptor subunits, have been observed in association with both drug dependence and psychosis. We hypothesized that variation of GRIA genes may be associated with METH dependence and METH-induced psychosis. Genotyping of GRIA1 rs1428920, GRIA2 rs3813296, GRIA3 rs3761554, rs502434 and rs989638 was performed in 102 male Thai controls and 100 METH-dependent subjects (53 with METH-dependent psychosis). We observed no evidence of association with METH dependence and METH-dependent psychosis in the GRIA1 and GRIA2 polymorphisms, nor with single polymorphisms rs3761554 and rs989638 in GRIA3. An association of GRIA3 rs502434 was identified with both METH dependence and METH-dependent psychosis, although this did not withstand correction for multiple testing. Combining the analysis of this site with the previously-demonstrated association with BDNF rs6265 resulted in a highly significant effect. These preliminary findings indicate that genetic variability in GRIA3 may interact with a functional BDNF polymorphism to provide a strong risk factor for the development of METH dependence in the Thai population.

BDNF (Val66Met) genetic polymorphism is associated with vulnerability for methamphetamine dependence.

AIM: Association of the brain-derived neurotrophic factor (BDNF) genetic polymorphism rs6265 (Val66Met) with methamphetamine (METH) dependence and METH-induced psychosis was investigated in the Thai population. MATERIALS & METHODS: The rs6265 genotype was determined in 100 male METH-dependent subjects and 102 controls using a real-time PCR high-resolution melt (RT-PCR-HRM) assay. RESULTS: The rs6265 genotype demonstrated significant differences in distribution between METH-dependent subjects and controls in which the frequency of GG genotype versus A-allele carriers was associated with METH dependence. Moreover, a significant effect of genotype on the occurrence of psychosis was found, with a lower frequency of GG genotype associated with METH-induced psychosis. CONCLUSION: The present findings indicate that rs6265 is associated with METH dependence in the Thai population, with the GG genotype greater in METH-dependent subjects but reducing the emergence of METH-dependent psychosis.