Cultured human keratinocytes as a model for studying the dopamine metabolism in schizophrenia

The dopamine hypothesis is the major etiological hypothesis of schizophrenia which proposes that enhanced central nervous system dopaminergic activity is the causative factor for this disease. The hypothesis remains unproven despite decades of research. The major difficulty in studying the disease is due to the unavailability of a suitable animal model. Studies with human blood, cerebrospinal fluid or post-mortem brains lead only to inconclusive results, due to the effects of medication and other environmental factors. No extra-neuronal cells, with the exception of adrenal medulla, have been reported to contain a dopamine metabolic pathway. Literature evidence and our own study suggest that human keratinocytes express the enzymes to synthesize and degrade dopamine. We have compared the properties of tyrosine hydroxylase, the rate-limiting enzyme, from mouse striatum and from human skin keratinocytes cultured in vitro. Moreover we could also detect dopamine beta hydroxylase and catechol-o-methyl transferase in keratinocytes. We propose that human keratinocytes cultured in vitro can be used to study the relevance of dopamine metabolism to schizophrenia under controlled conditions avoiding the effects of medication and other environmental factors.

Increased serum IgE in schizophrenic patients who responded poorly to neuroleptic treatment

Total serum IgE and plasma Interleukin (IL)-4 have been determined in patients with schizophrenia, 26 neuroleptic-free, and 81 neuroleptic-treated, and in 46 healthy control subjects. The total serum IgE was significantly higher in the patients who responded poorly to neuroleptic treatment compared with the other four groups (F = 4.27, df = 4, 148, P < 0.003). No significant changes were found in plasma IL-4 levels between any of the five groups. It is possible that raised serum IgE levels may characterise a subgroup of schizophrenia.

Concentrations of homovanillic Acid and gonadal hormones in the serum of male schizophrenic patients

The concentrations of serum homovanillic acid (HVA), luteinizing liormone (LH), follicle-stimulating hormone (FSH) and testosterone (T) were examined in 20 male schizophrenic patients not taking neuroleptic drugs, 44 treated with neuroleptic drugs, and 15 male healthy control subjects. Kurskal-Wallis analysis of variance showed no significant difference among the three groups in serum HVA, FSH, LH or testosterone although high concentrations were found in tlte patients not taking neuroleptic drugs. There was a significant positive correlation between serum HVA and FSH in the patients not taking neuroleptics. The present results suggest that the change of gonadal hormones may be related to the pathogenesis of schizophrenia.