Chronic homocysteine exposure causes changes in the intrinsic electrophysiological properties of cultured hippocampal neurons

Homocystinuria is an inborn error of metabolism characterized by plasma homocysteine levels up to 500μM, premature vascular events and mental retardation. Mild elevations of homocysteine plasma levels up to 25μM, which are common in the general population, are associated with vascular disease, cognitive impairment and neurodegeneration. Several mechanisms of homocysteine neurotoxicity have been investigated. However, information on putative effects of hyperhomocysteinemia on the electrophysiology of neurons is limited. To screen for such effects, we examined primary cultures of mouse hippocampal neurons with the whole-cell patch-clamp technique. Homocysteine was applied intracellularly (100μM), or cell cultures were incubated with 100μM homocysteine for 24h. Membrane voltage was measured in current-clamp mode, and action potential firing was induced with short and prolonged current injections. Single action potentials induced by short current injections (5ms) were not altered by acute application or incubation of homocysteine. When we elicited trains of action potentials with prolonged current injections (200ms), a broadening of action potentials during repetitive firing was observed in control neurons. This spike broadening was unaltered by acute application of homocysteine. However, it was significantly diminished when incubation with homocysteine was extended to 24h prior to recording. Furthermore, the number of action potentials elicited by low current injections was reduced after long-term incubation with homocysteine, but not by the acute application. After 24h of homocysteine incubation, the input resistance was reduced which might have contributed to the observed alterations in membrane excitability. We conclude that homocysteine exposure causes changes in the intrinsic electrophysiological properties of cultured hippocampal neurons as a mechanism of neurological symptoms of hyperhomocysteinemi

Autoimmune Myasthenia Gravis after Sternal Fracture

We report a 54-year-old woman who suffered a commotio cerebri, whiplash injury and a chest trauma with sternal fracture due to a high-velocity car accident. Two months later, she developed unilateral ptosis and blurred vision, which worsened during the day. Multiple diagnoses were suggested, ranging from thoracic outlet syndrome towards depression. Symptoms persisted and five years later, the patient consulted a neurologist. Laboratory analysis revealed significantly elevated levels of antibodies to acetylcholine receptors, and the diagnosis of myasthenia gravis was made. Speculatively, the damage of retrosternal thymic remnants due to a sternal fracture might have precipitated the condition or exacerbated subclinical disease

Haplotype analysis of the 5,10-methylenetetrahydrofolate reductase (MTHFR) c.1298A>C (E429A) polymorphism

BACKGROUND: The polymorphism 5,10-methylenetetrahydrofolate reductase (MTHFR) c.1298A>C is associated with various diseases. 45 DNA samples homozygous for the A allele and 40 DNA samples homozygous for the C allele were taken from healthy German subjects of white Caucasian origin to analyze the haplotype of the two MTHFR c.1298A>C alleles. Samples were genotyped for the polymorphism MTHFR c.677C>T and for the silent polymorphisms MTHFR c.129C>T, IVS2 533G>A, c.1068C>T and IVS10 262C>G. FINDINGS: Haplotype construction revealed that the C-allele of MTHFR c.1298A>C was more frequently observed in cis with c.129T, IVS2 533A, c.677C, c.1068T, and IVS10 262G than expected from a normal distribution. Estimation of the most recent common ancestor with the DMLE + 2.3 program resulted in an estimated age of approximately 36,660 years of the MTHFR c.1298C allele. CONCLUSION: Given that the era from 30,000 to 40,000 years ago is characterised by the spread of modern humans in Europe and that the prevalence of the MTHFR c.1298C allele is significantly higher in Central Europe in comparison to African populations, a selective advantage of MTHFR c.1298C could be assumed, e. g. by adaption to changes in the nutritional environment. The known founder ancestry of the T allele of MTHFR c.677C>T allele, together with the present data suggests that the MTHFR mutant alleles c.677T and 1298C arose from two independent ancestral alleles, that both confer a selective advantage

Genetic variants of methionine metabolism and X-ALD phenotype generation: results of a new study sample

X-linked adrenoleukodystrophy (X-ALD) is the most common inherited leukodystrophy. Nevertheless, no genotype-phenotype correlation has been established so far. Unidentified modifier genes or other cofactors are suspected to modulate phenotype and prognosis. We recently described polymorphisms of methionine metabolism as possible disease modifiers in X-ALD. To retest these findings, we analyzed 172 new DNA samples of X-ALD patients from different populations (France, Germany, USA, China) by genotyping eight genetic variants of methionine metabolism, including DHFR c.594+59del19bp, CBS c.844_855ins68, MTR c.2756A>G, MTHFR c.677C>T and c.1298A>C, MTRR c.60A>G, RFC1 c.80G>A, and Tc2 c.776C>G. We compared three X-ALD phenotypes: childhood-onset cerebral demyelinating inflammatory type (CCALD; n=82), adulthood onset with focal cerebral demyelination (ACALD; n=38), and adulthood onset without cerebral demyelination (AMN; n=52). The association of genotypes and phenotypes was analyzed with univariate two-sided Pearson's χ 2. In the comparison between AMN and CCALD, the G allele of Tc2 c.776C>G was associated with X-ALD phenotypes (χ 2=6.1; P=0.048). The prevalence of the GG genotype of Tc2 c.776C>G was higher in patients with CNS demyelination compared to those without CNS demyelination (χ 2=4.42; P=0.036). The GG genotype was also more frequent in CCALD compared to AMN (χ 2=4.7; P=0.031). The other polymorphisms did not show any significant associations in this study sample. Whereas the influence of other polymorphisms of methionine metabolism was not confirmed, the present study supports the previously made observation that the Tc2 genotype contributes to X-ALD phenotype generatio

Homocysteine plasma levels in patients treated with antiepileptic drugs depend on folate and vitamin B12 serum levels, but not on genetic variants of homocysteine metabolism

Background: Antiepileptic drugs (AEDs) are commonly used in the treatment of epilepsy, psychiatric diseases and pain disorders. Several of these drugs influence blood levels of folate and vitamin B12 and, consequently, homocysteine. This may be relevant for AED effects and side effects. However, not only folate and vitamin B12, but also genetic variants modify homocysteine metabolism. Here, we aimed to determine whether there is a pharmacogenetic interaction between folate, vitamin B12 and genetic variants and homocysteine plasma level in AED-treated patients. Methods: In this mono-center study, we measured homocysteine, folate and vitamin B12 plasma levels in a population of 498 AED-treated adult patients with epilepsy. In addition, we analyzed the genotypes of seven common genetic variants of homocysteine metabolism: methylenetetrahydrofolate reductase (MTHFR) c.677C>T and c.1298A>C, methionine synthase (MTR) c.2756A>G, dihydrofolate reductase (DHFR) c.594+59del19bp, cystathionine β-synthase (CBS) c.844_855ins68, transcobalamin 2 (TC2) c.776C>G and methionine synthase reductase (MTRR) c.66G>A. Results: On multivariate logistic regression, folate and vitamin B12 levels, but none of the genetic variants, were predictive for homocysteine levels. Conclusions: These data suggest that, in AED-treated patients, folate and vitamin B12 play important roles in the development of hyperhomocysteinemia, whereas genetic variants of homocysteine metabolism do not and thus do not contribute to the risk of developing hyperhomocysteinemia during AED treatmen

ACNU-based chemotherapy for recurrent glioma in the temozolomide era

No standard of care for patients with recurrent glioblastoma has been defined since temozolomide has become the treatment of choice for patients with newly diagnosed glioblastoma. This has renewed interest in the use of nitrosourea-based regimens for patients with progressive or recurrent disease. The most commonly used regimens are carmustine (BCNU) monotherapy or lomustine (CCNU) combined with procarbazine and vincristine (PCV). Here we report our institutional experience with nimustine (ACNU) alone (n=14) or in combination with other agents (n=18) in 32 patients with glioblastoma treated previously with temozolomide. There were no complete and two partial responses. The progression-free survival (PFS) rate at 6months was 20% and the survival rate at 12months 26%. Grade III or IV hematological toxicity was observed in 50% of all patients and led to interruption of treatment in 13% of patients. Non-hematological toxicity was moderate to severe and led to interruption of treatment in 9% of patients. Thus, in this cohort of patients pretreated with temozolomide, ACNU failed to induce a substantial stabilization of disease in recurrent glioblastoma, but caused a notable hematotoxicity. This study does not commend ACNU as a therapy of first choice for patients with recurrent glioblastomas pretreated with temozolomid

Methionine metabolism in an animal model of sepsis

Background: Sepsis is a disease with high incidence and lethality and is accompanied by profound metabolic disturbances. In mammalian methionine metabolism, S-adenosylmethionine (SAM) is produced, which is important in the synthesis of neurotransmitters and glutathione and as an anti-inflammatory agent. The degradation product and antagonist of SAM is S-adenosylhomocysteine (SAH). In this study, we investigated changes in methionine metabolism in a rodent model of sepsis. Methods: Sepsis was induced in male Wistar rats (n=21) by intraperitoneal injection of bacterial lipopolysaccharide (10mg/kg). Controls (n=18) received vehicle only. Blood was collected by cardiac puncture 24h later. Puncture of the suboccipital fossa was performed to collect cerebrospinal fluid (CSF). Methionine metabolites were measured using stable isotope dilution tandem mass spectrometry. Plasma total homocysteine and cysteine were measured by HPLC using fluorescence detection. Glutathione was assayed using a modified enzymatic microtiter plate assay. Results: We observed significantly higher plasma levels of SAM (p<0.001) and SAM/SAH ratio (p=0.004) in septic animals. In CSF, there was also a trend for higher levels of SAM in septic animals (p=0.067). Oxidative stress was reflected by an increase in the ratio of oxidized/reduced glutathione in septic animals (p=0.001). Conclusions: Sepsis is associated with an increase in SAM/SAH ratio in plasma and CSF in rodents. This indicates an altered methylation potential during sepsis, which may be relevant for sepsis-associated impairment of transmethylation reactions, circulation and defense against oxidative stress. If verified in humans, such findings could lead to novel strategies for supportive treatment of sepsis, as methionine metabolism can easily be manipulated by dietary strategies. Clin Chem Lab Med 2008;46:1398-40

Amyotrophic lateral sclerosis after embolization of cerebral arterioveneous malformations

Cerebral arterioveneous malformations (AVM) can cause neurological symptoms and carry a risk of hemorrhage. Therapeutic options to cure or reduce AVM include surgery, embolization, irradiation, and combinations thereof. Prompted by three index cases treated in our center, we studied whether AVM embolization is associated with an increased risk of subsequent amyotrophic lateral sclerosis (ALS). In a monocenter series, we retrospectively analyzed the new development of ALS in patients who had been treated with embolization of cerebral AVM from 1986 to 2010 (n=1,114). After a median follow-up of 11years (range, 0-25years) after first embolization, seven patients developed ALS with a median latency of 14years (range, 12-17years) and a median age of ALS onset of 38years (range, 28-52years). In all cases, the initial limb of ALS symptom onset was ipsilateral to the AVM. Five patients died within the follow-up period, with a range of 1-4years after the onset of ALS symptoms. The seven patients belonged to a subgroup of 34 patients who had in common a rare AVM architecture characterized by significant perinidal angiogenesis. All cases were partially treated by at least three embolization sessions. As there is no known association between AVM and ALS, AVM embolization must be taken into account to have contributed to the development of ALS in the seven patients with this rare AVM architecture. Searching for underlying mechanisms, we compared frozen serum samples that were available from four of the patients who developed ALS, from eight patients with AVM of other architecture, and less than three embolizations who did not develop ALS, and of 20 controls. The concentration of vascular endothelial growth factor (VEGF) in the serum was lowest in AVM patients who developed ALS (245±154pmol/l) and highest in controls (409±178pmol/l). Although this difference was not statistically significant in the small sample, it suggests that low VEGF production by AVM with significant angiogenesis, possibly due to multiple embolization procedures, might have contributed to ALS development. ALS should be considered as a late complication of multiple embolizations of cerebral AVM characterized by significant perinidal angiogenesis

Amyotrophic lateral sclerosis after embolization of cerebral arterioveneous malformations

Cerebral arterioveneous malformations (AVM) can cause neurological symptoms and carry a risk of hemorrhage. Therapeutic options to cure or reduce AVM include surgery, embolization, irradiation, and combinations thereof. Prompted by three index cases treated in our center, we studied whether AVM embolization is associated with an increased risk of subsequent amyotrophic lateral sclerosis (ALS). In a monocenter series, we retrospectively analyzed the new development of ALS in patients who had been treated with embolization of cerebral AVM from 1986 to 2010 (n = 1,114). After a median follow-up of 11 years (range, 0-25 years) after first embolization, seven patients developed ALS with a median latency of 14 years (range, 12-17 years) and a median age of ALS onset of 38 years (range, 28-52 years). In all cases, the initial limb of ALS symptom onset was ipsilateral to the AVM. Five patients died within the follow-up period, with a range of 1-4 years after the onset of ALS symptoms. The seven patients belonged to a subgroup of 34 patients who had in common a rare AVM architecture characterized by significant perinidal angiogenesis. All cases were partially treated by at least three embolization sessions. As there is no known association between AVM and ALS, AVM embolization must be taken into account to have contributed to the development of ALS in the seven patients with this rare AVM architecture. Searching for underlying mechanisms, we compared frozen serum samples that were available from four of the patients who developed ALS, from eight patients with AVM of other architecture, and less than three embolizations who did not develop ALS, and of 20 controls. The concentration of vascular endothelial growth factor (VEGF) in the serum was lowest in AVM patients who developed ALS (245 ± 154 pmol/l) and highest in controls (409 ± 178 pmol/l). Although this difference was not statistically significant in the small sample, it suggests that low VEGF production by AVM with significant angiogenesis, possibly due to multiple embolization procedures, might have contributed to ALS development. ALS should be considered as a late complication of multiple embolizations of cerebral AVM characterized by significant perinidal angiogenesis