Cerebrospinal fluid somatostatin in West syndrome: changes in response to combined treatment with high-dose pyridoxal phosphate and low-dose corticotropin

Pyridoxal-5′-phosphate (MC-1), a vitamin B6 derivative, inhibits expressed P2X receptors

P2X receptors are cation-permeable ligand-gated ion channels that open in response to the binding of ATP. These receptors are present in many excitable cells, including neurons, striated muscle cells, epithelial cells, and leukocytes. They mediate fast excitatory neurotransmission in the central and peripheral nervous systems and are thought to be involved in neuropathic pain, inflammation, and cell damage following ischemia–reperfusion injuries. P2X receptors are thus a target for the development of new therapeutics to treat chronic pain and inflammation. In this study, we characterized the inhibition caused by pyridoxal-5′-phosphate, a natural metabolite of vitamin B6 (MC-1), of P2X2, P2X4, P2X7, and P2X2/3 receptors stably expressed in HEK293 cells using the patch-clamp technique in the whole-cell configuration. We also tested a new approach using VC6.1, a modified cameleon calcium-sensitive fluorescent protein, to characterize the inhibition of P2X2 and P2X2/3. MC-1 blocked these two P2X receptors, with an IC50 of 7 and 13 μmol/L, respectively. P2X2 exhibited the highest affinity for VC6.1, and the chimeric receptor P2X2/3, the lowest. The patch-clamp and imaging approaches gave similar results and indicated that VC6.1 may be useful for high throughput drug screening. Pyridoxal-5′-phosphate is an efficient P2X blocker and can be classified as a P2X antagonist.

Pyridoxal phosphate is better than pyridoxine for controlling idiopathic intractable epilepsy

AIM

To study the difference between pyridoxine (PN) and its active form, pyridoxal phosphate, (PLP) in control of idiopathic intractable epilepsy in children.

METHODS

Among 574 children with active epilepsy, 94 (aged 8 months to 15 years) were diagnosed with idiopathic intractable epilepsy for more than six months. All received intravenous PLP 10 mg/kg, then 10 mg/kg/day in four divided doses. If seizures recurred within 24 hours, another dose of 40 mg/kg was given, followed by 50 mg/kg/day in four divided doses. For those patients whose seizures were totally controlled, PLP was replaced by the same dose of oral PN. If the seizure recurred, intravenous PLP was infused followed by oral PLP 50 mg/kg/day.

RESULTS

Fifty seven patients had generalised seizures (of whom 13 had infantile spasms) and 37 had focal seizure. Eleven had dramatic and sustained responses to PLP; of these, five also responded to PN. Within six months of treatment with PLP or PN, five of the 11 patients were seizure free and had their previous antiepileptic medicine tapered off gradually. Two were controlled with pyridoxine and the other three needed PLP to maintain seizure freedom. The remaining six responders needed PLP exclusively for seizure control. Six of the 11 responders to PLP had infantile spasms (46%); four of them needed PLP exclusively. The other five responders were in the remaining 81 patients with other seizure type.

CONCLUSIONS

PLP could replace PN in the treatment of intractable childhood epilepsy, particularly in the treatment of infantile spasms.

Reduction of myocardial ischemic injury following coronary intervention (the MC-1 to Eliminate Necrosis and Damage trial)

Myocardial ischemic injury complicating acute myocardial infarction (AMI) and coronary revascularization procedures remains an unresolved clinical dilemma. In preclinical studies, treatment with pyridoxal-5'-phosphate monohydrate (MC-1), a vitamin B6 metabolite, has demonstrated cardioprotective effects. Sixty patients scheduled for elective percutaneous coronary intervention (PCI) who had clinically high-risk characteristics for ischemic complications were randomized to treatment with MC-1 or placebo in a 2:1 double-blinded fashion. The primary end point was defined as infarct size as measured by area under the curve creatine kinase MB (CK-MB) enzymes. Secondary end points included periprocedural ischemia as assessed by continuous electrocardiographic monitoring, 30-day major adverse cardiac events, and net clinical safety, which included liver function testing. The primary end point, median periprocedural CK-MB area under the curve, was reduced from 32.9 ng/ml in the placebo group to 18.6 ng/ml with MC-1 treatment (p = 0.038), reflecting a shift in the distribution of CK-MB. By categorical classification, the occurrence of 30-day nonfatal AMI did not differ between groups. There were no deaths, and 30-day composite adverse event rates were similar (17.9% MC-1 vs 15.0% placebo, p = 1.0). There were no significant differences in ischemia parameters per continuous electrocardiographic monitoring, and no safety issues were identified. In this phase II pilot study, treatment of high-risk patients who underwent PCI with MC-1 was associated with a decrease in the total amount of CK-MB released after PCI. These results support the evaluation of MC-1 in pivotal trials of patients at risk for developing myocardial ischemia, infarction, or reperfusion injury.

Pyridoxal phosphate-responsive epilepsy with resistance to pyridoxine

We present a female infant with seizures responsive to pyridoxal phosphate but that are resistant to pyridoxine. The mechanism by which pyridoxal phosphate controls seizures in this patient is unknown. Her seizures are perhaps not solely caused by pyridoxal phosphate deficiency. It is suggested that in addition to glutamic acid decarboxylase abnormality, the path from the absorption, transportation, phosphorylation, and oxidation of pyridoxine to pyridoxal phosphate in this patient might be defective. It should be considered whether pyridoxal phosphate can be the drug of choice instead of pyridoxine in treating patients suspected of pyridoxine-dependent epilepsy to reduce failure rate and further delay in seizure control.

Cerebrospinal fluid somatostatin levels in febrile seizures and epilepsy in children

We analysed the level of cerebrospinal fluid (CSF) somatostatin in children with febrile seizures and epilepsy. In the febrile seizure group (n = 23), the somatostatin level was 83.9 +/- 11.2 pg/ml, which was significantly higher than that of age-matched controls. CSF samples obtained within 3 h of the last seizure had higher somatostatin levels (106.1 +/- 12.4 pg/ml;n = 14) than did the CSF obtained after 3 h (49.4 +/- 15.6 pg/ml;n = 9). The mean somatostatin level in the epilepsy group was 35.3 +/- 4.3 pg/ml (n = 34), and was distributed as follows: 27.6 +/- 3.6 pg/ml in the idiopathic generalized epilepsy group (n = 16), 44.0 +/- 9.4 pg/ml in the symptomatic generalized epilepsy group (n = 13), and 37.2 +/- 10.1 pg/ml in the partial epilepsy group (n = 5). The levels in each group were significantly higher than those in age-matched controls. Somatostatin is a hypothalamic tetradecapeptide with excitatory effects on neurons in children with febrile seizures and epilepsy. The finding that patients with convulsive disease had elevated levels of CSF somatostatin suggests that somatostatin release is somehow related to seizure activity. It remains to be determined whether this is due to increased release from over-active excitatory neurons or leakage from damaged or anoxic neurons, secondary to seizure activity.