Biopterin synthesis defect. Treatment with L-dopa and 5-hydroxytryptophan compared with therapy with a tetrahydropterin.

We have identified a generalized deficiency of monoamine neurotransmitters in a patient with a defect in biopterin synthesis. Neurotransmitter precursors (L-3,4-dihydroxyphenylalanine [L-dopa]; 5-hydroxytryptophan [5-HTP] and a tetrahydropterin [6-methyltetrahydropterin (6MPH4)] were investigated for their ability to normalize monoamine neurotransmitter metabolism. Before treatment, the concentrations of dopamine (DA), norepinephrine, epinephrine, and six monoamine metabolites were very low or undetectable in plasma, cerebrospinal fluid, or urine. L-Dopa and 5-HTP replacement was begun at age 7 mo. This therapy generally corrected the deficiency of monoamines and their metabolites, and improved neurological development until the age of 25 mo. Despite these benefits, the intermittent administration of L-dopa could not produce a stable improvement of acute neurological function or DA metabolism. In the 3 h after L-dopa administration, plasma DA and the motor activity and alertness of the patient rose and fell in parallel. Doses of L-dopa that were clinically optimal produced normal plasma levels of norepinephrine and epinephrine, but excessive concentrations of DA and its metabolites. Furthermore, the clinical and biochemical effects of L-dopa were inhibited by phenylalanine and 5-HTP, respectively, demonstrating that these amino acids have antagonistic pharmacological effects. Physiological correction of the monoamine deficit and the hyperphenylalaninemia of this disorder was attempted at age 35 mo using high doses (8-38 mg/kg per d) of 6MPH4. 6MPH4, a synthetic analogue of tetrahydrobiopterin, controlled the hyperphenylalaninemia. Significant concentrations of 6MPH4 were obtained in the cerebrospinal fluid; no neurological improvement or stimulation of monoamine synthesis in the central nervous system was detected. These findings indicate the complexity in replacement therapy with L-dopa and 5-HTP, but suggest that this treatment may be partially effective in biopterin-deficient patients who are unresponsive to high doses of tetrahydropterins.

Total and free plasma tryptophan levels in patients with affective disorders: effects of a peripheral decarboxylase inhibitor.

Previous reports of decreased cerebrospinal fluid tryptophan levels and decreased free plasma tryptophan levels, as well as a reduction in the volume of distribution of tryptophan, suggest that alterations in the disposition of plasma tryptophan may occur in depressives. We examined the disposition of plasma tryptophan in ten normal controls and ten depressed patients. These measures were made on two drug-free baseline days and on two days when the subjects had been receiving the peripheral decarboxylase inhibitor, carbidopa, which inhibits tryptophan metabolism via extracerebral indoleamine pathways.

Increased phospholipid breakdown in schizophrenia. Evidence for the involvement of a calcium-independent phospholipase A2.

BACKGROUND: Magnetic resonance spectroscopy studies have suggested above-normal turnover of membrane phospholipids in brains of patients with schizophrenia. One possible explanation for these findings is increased activity of the phospholipid-catabolizing enzyme phospholipase A2 (PLA2). However, attempts to demonstrate higher PLA2 activity in the serum of subjects with schizophrenia have led to conflicting results. We hypothesized that this was due to serum PLA2 activity consisting of a family of different enzymes, with each group of investigators measuring activity of different PLA2 forms. DESIGN: Activity of PLA2 in serum samples obtained from 24 individuals with schizophrenia was compared with serum obtained from 33 age- and sex-matched control subjects, using both fluorometric and radiometric assays with different substrates. Each method had previously yielded conflicting results concerning the status of the enzyme in schizophrenia. RESULTS: With the fluorometric assay, serum PLA2 activity in individuals with schizophrenia was markedly increased by 49% compared with control subjects (P < .001). In contrast, radiometric assay of the same serum samples resulted in PLA2 activity not significantly different between patients and control subjects. Further investigations demonstrated that, whereas the radiometric assay measured activity of a calcium-dependent enzyme, the fluorometric assay detected a calcium-insensitive enzyme possessing an acid-neutral pH optimum. CONCLUSIONS: Increased calcium-independent PLA2 activity was seen in the serum of patients with schizophrenia. This change, if present also in the brain, may well explain the increased levels of phosphodiesters observed using magnetic resonance spectroscopy and therefore may contribute to the pathophysiological features of the disorder.

CNS monoamine metabolism in bipolar affective disorder. Evaluation using a peripheral decarboxylase inhibitor.

Carbidopa, a decarboxylase inhibitor that does not cross the blood-brain barrier, inhibits the peripheral synthesis of nor-adrenaline, serotonin, and tryptamine. By reducing the peripheral component of end-products of these amines in urine, a more accurate assessment of central nervous system (CNS) amine metabolism is provided. Urinary 5-hydroxyindoleacetic acid (5-HIAA), tryptamine, and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured over ten days in ten normal controls and eight bipolar depressives. After a three-day baseline period, carbidopa, 100 mg three times a day, was given for seven days. While the patients tended to excrete less MHPG in the baseline period, these differences became somewhat larger, and statistically significant when peripheral contributions were reduced with carbidopa. While carbidopa resulted in striking inhibition of tryptamine excretion, and smaller decreases in the excretion of 5-HIAA and MHPG, evidently from storage pools, there were no significant differences in degree of inhibition between patients and controls. Absolute values of 5-HIAA and tryptamine were similar for both groups, during the baseline and again with carbidopa. These results after carbidopa are compatible with a central catecholaminergic deficit in bipolar depressives and the use of urinary MHPG as an index of CNS catecholamine function.

Effect of carbidopa on prolactin, growth hormone and cortisol secretion in man.

Serum prolactin, growth hormone and cortisol levels were examined in normal volunteers following administration of carbidopa, a peripheral decarboxylase inhibitor. 24-hour urinary tryptamine levels dropped markedly indicating that inhibition of decarboxylase was effective. Prolactin levels rose while growth hormone and cortisol remained unchanged. Since the tuberoinfundibular dopamine nerve terminals lie outside the blood brain barrier, this study suggests that these neurons are involved in prolactin but not in growth hormone or cortisol regulation. Findings are compatible with two alternate hypotheses--either that dopamine is a physiologic prolactin inhibiting factor (PIF) or that tuberoinfundibular dopamine neurons regulate the release of PIF.

Lithium regulation of aldolase A expression in the rat frontal cortex: identification by differential display.

BACKGROUND: Substantial evidence indicates that lithium may exert its therapeutic effects through progressive adaptive changes at the level of gene expression; however, the study of lithium-regulated genes has been primarily undertaken with the "candidate gene" approach based on a specific testable hypothesis. The aim of our study was to identify lithium-regulated genes that would not be predicted a priori by the candidate gene approach. METHODS: Differential display polymerase chain reaction was used to isolate and identify messenger RNAs (mRNAs) that are differentially expressed in the frontal cortex of rats given lithium for 5 weeks to achieve plasma lithium concentrations of 0.6 to 0.9 mmol/L. RESULTS: A putative lithium-regulated complementary DNA fragment (LRG1) was identified. Northern blot analysis revealed that 5 weeks of lithium treatment, but not 1 week, significantly reduced LRG1 mRNA levels. LRG1 mRNA levels were similarly reduced by 5 weeks of carbamazepine, but not valproate administration. Sequence analysis and search of the GenBank database revealed that LRG1 is analogous to the sequence of the gene for rat aldolase A. CONCLUSIONS: These results demonstrate that chronic administration of lithium, but not short-term administration, down regulates the levels of aldolase A mRNA, suggesting this effect may play a role in mediating the therapeutic action of this agent.

Reduced brain 5-HT and elevated NE turnover and metabolites in bipolar affective disorder.

Levels of norepinephrine (NE), serotonin (5-HT), dopamine (DA), and their major metabolites were determined in postmortem brain obtained from nine subjects with antemortem histories meeting DSM-III-R criteria for bipolar affective disorder. Compared with controls, no statistically significant differences were found in mean levels of NE, 5-HT, or DA in any brain area of bipolar subjects. NE turnover as estimated by the ratio of the major NE metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) to NE was increased in frontal (+107%), temporal (+103%), and occipital (+64%) cortex and thalamus (+83%). Significant decreases were found in the major 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA), in frontal (-54%) and parietal cortex (-64%), and in 5-HIAA/5-HT ratio in temporal cortex (-55%), with a trend for decreases in both measures in caudate nucleus. In addition, levels of the major DA metabolite, homovanillic acid (HVA) were significantly decreased (-46%) in parietal cortex and HVA/DA ratios were significantly reduced (-66%) in occipital cortex obtained from bipolar compared to control subjects. Our data, taken together with previous findings regarding monoamines in postmortem brain of depressed and suicide subjects, suggest that decreased 5-HT metabolite levels and turnover may be common to all mood disorders. Increased cortical NE turnover, however, may be a more important component in the pathophysiology of bipolar disorder.

Effects of chronic lithium and carbamazepine treatment on G-protein subunit expression in rat cerebral cortex.

Although lithium and carbamazepine (CBZ) are effective in the treatment of bipolar affective disorder, their mechanism of action is still unknown. Recent evidence suggests that lithium and CBZ might exert their therapeutic effects by modulating the function of guanosine triphosphate (GTP)-regulatory (G) proteins associated with central nervous system second messenger systems. In the present study, we showed that chronic lithium administration decreases G alpha s, G alpha i1, and G alpha i2 messenger RNA (mRNA) abundance by 25%-30% in rat cerebral cortex. However, the levels of G alpha s, G alpha i1, and G alpha i2 mRNA were unaffected by chronic CBZ treatment. The effects of lithium on G alpha s, G alpha i1, and G alpha i2 mRNA levels appear to be selective, as the mRNA levels of G alpha o, G alpha x, G beta 1, G beta 2, and G beta 3 subunits remained unchanged. Two days after terminating chronic lithium treatment, changes in G alpha s, G alpha i1, and G alpha i2 mRNA levels were not demonstrable. Short-term administration of lithium (2 days), however, reduced only the G alpha i2 mRNA levels. Surprisingly, there was no significant difference in the amount of immunologically detectable G alpha s-s, G alpha s-1, G alpha i(1 + 2), G alpha 0, and G beta (1 + 2) in the cortex of rats chronically treated with lithium or CBZ, compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

The niacin challenge test: clinical manifestation of altered transmembrane signal transduction in schizophrenia?

Several lines of evidence implicate altered phospholipid-dependent signal transduction (PDST) in the pathophysiology of schizophrenia. Niacin induces vasodilation through mechanisms requiring intact PDST. Thus, an altered response to a challenge dose of niacin may reflect disturbances in these signalling processes in this disorder. In the present study, niacin-induced vasodilation was estimated quantitatively in schizophrenic and comparison bipolar affective disorder and healthy subjects using thermocouple sensors to measure the change in skin temperature relative to core body and ambient room temperature. Twelve (42.9%) of 28 schizophrenic subjects did not vasodilate in response to a 200-mg niacin challenge dose, whereas only 1 of 18 (6%) bipolar disorder subjects and none of 28 controls showed impaired response (Fisher's Exact Test, p < .0001). These findings support the notion that the schizophrenic syndromes are biochemically heterogeneous and suggest the existence of a subgroup of schizophrenic subjects in whom phospholipid-dependent signalling responses may be impaired.

Increased G alpha q/11 immunoreactivity in postmortem occipital cortex from patients with bipolar affective disorder.

As disturbances in guanine nucleotide binding (G) protein-coupled phosphoinositide second messenger systems have been implicated in bipolar disorder, we examined whether the abundance of G alpha q/11 and phospholipase C (PLC)-beta 1 two key transducing proteins in this signaling pathway, are altered in this disorder. Compared with the controls, immunoreactive levels of G alpha q/11 were significantly elevated by 62% (p = .047) in occipital cortex of bipolar subjects. A similar increase (52%) in the PLC-beta 1 immunolabeling was also found in the occipital cortex of the bipolar subjects, but only reached marginal statistical significance (p = .07). In contrast, frontal and temporal cortex G alpha q/11 or PLC-beta 1 immunolabeling did not differ between bipolar and control subjects. Cerebral cortical immunoreactive levels of G beta 1 or G beta 2, included as a negative control, were not different between comparison groups. These findings support and extend earlier observations suggesting that disturbances in G protein-coupled second messenger signaling pathways may play an important role in the pathophysiology of bipolar affective disorder.

Associated disturbances in calcium homeostasis and G protein-mediated cAMP signaling in bipolar I disorder.

BACKGROUND: Evidence of extensive cross-talk between calcium (Ca(2+))- and cAMP-mediated signaling systems suggests that previously reported abnormalities in Ca(2+) homeostasis in bipolar I (BP-I) patients may be linked to disturbances in the function of G proteins that mediate cAMP signaling. METHODS: To test this hypothesis, the beta-adrenergic agonist, isoproterenol, and the G protein activator, sodium fluoride (NaF), were used to stimulate cAMP production in B lymphoblasts from healthy and BP-I subjects phenotyped on basal intracellular calcium concentration ([Ca(2+)](B)). cAMP was measured by radioimmunoassay and [Ca(2+)](B) by ratiometric fluorometry with fura-2. RESULTS: Isoproterenol- (10 microM) stimulated cAMP formation was lower in intact B lymphoblasts from BP-I patients with high [Ca(2+)](B) (>/= 2 SD above the mean concentration of healthy subjects) compared with patients having normal B lymphoblast [Ca(2+)](B) and with healthy subjects. Although basal and NaF-stimulated cAMP production was greater in B lymphoblast membranes from male BP-I patients with high versus normal [Ca(2+)](B), there were no differences in the percent stimulation. This suggests the differences in NaF response resulted from higher basal adenylyl cyclase activity. CONCLUSIONS: These findings suggest that trait-dependent disturbances in processes regulating beta-adrenergic receptor sensitivity and G protein-mediated cAMP signaling occur in conjunction with altered Ca(2+) homeostasis in those BP-I patients with high B lymphoblast [Ca(2+)](B).

Altered TRPC7 gene expression in bipolar-I disorder.

BACKGROUND: As altered storage-operated calcium (Ca(2+)) entry (SOCE) may affect Ca(2+) homeostasis in bipolar disorder (BD), we determined whether changes occur in the expression of TRPC7 and SERCA2s, proteins implicated or known to be involved in SOCE, in B lymphoblast cell lines (BLCLs) from BD-I patients and comparison subjects. METHODS: mRNA levels were determined in BLCL lysates from BD-I, BD-II, and major depressive disorder patients, and healthy subjects by comparative reverse transcriptase-polymerase chain reaction, and BLCL basal intracellular Ca(2+) concentration ([Ca(2+)]B) was determined by ratiometric spectrophotometry using Fura-2, in aliquots of the same cell lines, at 13-16 passages in culture. RESULTS: TRPC7 mRNA levels were significantly lower in BLCLs from BD-I patients with high BLCL [Ca(2+)]B compared with those showing normal [Ca(2+)]B (-33%, p =.017) and with BD-II patients (-48%, p =.003), major depressive disorder patients (-47%, p =.049) and healthy subjects (-33%, p =.038). [Ca(2+)]B also correlated inversely with TRPC7 mRNA levels in BLCLs from the BD-I group as a whole (r = -.35, p =.027). CONCLUSIONS: Reduced TRPC7 gene expression may be a trait associated with pathophysiological disturbances of Ca(2+) homeostasis in a subgroup of BD-I patients.

Inositol 1,4,5-trisphosphate receptor in developing and senescent rat cerebellum.

Numerous process associated with intracellular calcium homeostasis have previously been found to vary with age. To determine whether the binding sites for the calcium-mobilizing second messenger, inositol 1,4,5-trisphosphate (InsP3), also displays such variation, [3H]InsP3 binding was investigated in cerebellar or cerebral cortical membranes prepared from rats at different ages from birth up to 24 months of age. In the cerebellum, the InsP3 receptor density was very low during the first week after birth, increased markedly between days 8 and 28 and then reached an apparent plateau between 28 to 56 days of age. The InsP3 receptor binding affinity was comparable at different developmental stages. No age-related differences were found in InsP3 receptor density or affinity in the cerebral cortex of 3-, 6-, 9-, 12-, and 24-month-old rats. In the cerebellum, InsP3 receptor density but not affinity was significantly reduced in 24-month-old compared only to 3-month-old animals. Our data suggest that the changes in InsP3 receptor binding during early development might reflect the growth and maturation of neurons containing these receptors (i.e., Purkinje cells). Furthermore, the age-dependent reduction in InsP3 receptor density, together with the recent report of senescent changes in protein kinase C activity, indicate that disruption of phosphoinositide second messenger system may be of importance to the impairment of neuronal responsiveness and behavioral deficits observed with aging.

The nonlinear kinetics of desipramine and 2-hydroxydesipramine in plasma.

Plasma levels of desipramine (DMI) and the unconjugated form of its principal metabolite 2-hydroxydesipramine (OH-D) were measured under steady-state conditions in nine depressed inpatients during treatment with 75 mg DMI every 12 hr and after at least 1 wk of an increased dose of DMI (after steady state). When DMI dosage was raised after an initial steady state had been reached, the rise in plasma DMI level was proportionately greater than the increase in dosage, suggesting saturation of DMI elimination pathways. Levels of OH-D rose in proportion to dose, suggesting saturation of DMI elimination by 2-hydroxylation could not explain DMI plasma level changes. In contrast, there were no dose-dependent effects on the disposition of amitriptyline or its metabolite nortriptyline in subjects receiving the same amitriptyline dose.

Depression: new evidence in support of biological differentiation.

The authors studied monoamine metabolism in patients with bipolar (manic-depressive) and unipolar depressive illness and in normal control subjects under strict dietary conditions before and during administration of carbidopa, a peripheral decarboxylase inhibitor. They found that unipolar depressed patients excreted higher amounts of 3-methoxy-4-hydroxyphenylglycol (MHPG) and 5-hydroxyindoleacetic acid (5-HIAA) in the drug-free period and while receiving carbidopa and significantly less tryptamine only after carbidopa administration. Plasma tryptophan levels differed in the three groups. The authors state that their research design reveals changes in serotonin and nonrepinephrine metabolism in unipolar depressed subjects that distinguish this group from normal and bipolar depressed subjects, suggesting a reduced CNS uptake of tryptophan in unipolar depression.

High intracellular calcium concentrations in transformed lymphoblasts from subjects with bipolar I disorder.

OBJECTIVE: Higher basal concentrations of intracellular calcium Ca2+ in platelets and lymphocytes from subjects with bipolar affective disorder than in unipolar depressed and healthy subjects implicate abnormal intracellular Ca2+ signaling in bipolar disorder. The purpose of this study was to clarify whether these intracellular Ca2+ abnormalities are trait related. METHOD: Basal Ca2+ concentration was measured by using ratiometric fluorescence assay with fura-2 for T lymphocytes and Epstein-Barr-virus-immortalized B lymphoblasts from physically healthy subjects with DSM-IV diagnoses of bipolar mood disorder (bipolar I, N = 28; bipolar II, N = 11) or major depressive disorder (N = 14), mixed psychiatric patients with non-mood disorders (N = 14), and health subjects (N = 20). Phytohemagglutinin-stimulated (10 micrograms/ml) intracellular Ca2+ levels were also determined in T lymphocytes. RESULTS: The basal Ca2+ concentration was significantly higher in the B lymphoblasts from patients with bipolar I disorder, but not bipolar II disorder or major depression, than in healthy subjects or psychiatric patients with nonmood disorders. There was a significant interaction between gender and diagnosis in the effect on basal Ca2+ levels in T lymphocytes. Contrasts of diagnoses within gender revealed significantly higher basal Ca2+ concentrations in T lymphocytes in male bipolar I patients, but not mean with bipolar II disorder or major depression, than in healthy male comparison subjects. Phytohemagglutinin-stimulated Ca2+ concentrations did not differ among groups, but the percent differences from basal Ca2+ levels were lower in bipolar I and depressed patients than in healthy subjects. CONCLUSIONS: These findings support the occurrence of abnormal calcium homeostasis in bipolar disorder and suggest that trait-dependent factors account, at least partly, for the higher basal lymphocyte Ca2+ concentration in bipolar I subjects.

Mononuclear leukocyte levels of G proteins in depressed patients with bipolar disorder or major depressive disorder.

Stimulatory (Gs) and inhibitory (G(i)) guanine nucleotide binding protein alpha subunit levels were measured in mononuclear leukocytes from 22 drug-free depressed patients (eight with bipolar disorder, 14 with major depressive disorder) and a comparison group of 17 age- and sex-matched healthy subjects. The levels of Gs alpha and G(i) alpha were significantly higher (160% and 114%, respectively) in the bipolar patients, but not the patients with major depressive disorder, than in the healthy subjects. These data add to the evidence for abnormalities in G protein levels and function in the pathophysiology of bipolar disorder.

Obesity and precursor availability affect urinary catecholamine metabolite production in women.

The effect of obesity and tyrosine (tyr) supplements on catecholamine metabolism in 12 normal weight and nine obese adult women was studied. Protein intake was maintained at 1.4 g protein/kg fat-free mass daily for 4 days with tyr added (0.26 g/kg fat-free mass) to the liquid diet on the last 2 days. In the 12 normal subjects, but not the obese, base-line urinary excretion of the norepinephrine metabolite, 3-methoxy-4-hydroxy phenylethyleneglycol was related to body fat whereas excretion of the norepinephrine metabolite vanilmandelic acid was related to fat-free mass and to total energy intake. Normal subjects responded to tyr with elevations in plasma tyr/neutral amino acid, plasma 3-methoxy-4-hydroxy phenylethyleneglycol, urinary vanilmandelic acid, and homovanillic acid, a dopamine metabolite, but not the norepinephrine metabolite, dihydroxy phenylethyleneglycol. The obese showed no increase in plasma or urinary 3-methoxy-4-hydroxy phenylethyleneglycol during tyr supplementation, although vanilmandelic acid and homovanillic acid increased. We conclude that urinary catecholamine metabolite production is related to body composition and to tyr intake in normal weight women. These relationships however, are altered in the obese, suggesting an association of obesity with abnormal catecholamine metabolism.

The effect of a peripheral decarboxylase inhibitor (carbidopa) on monoamine and neuroendocrine function in man.

Carbidopa, a selective extracerebral decarboxylase inhibitor, was given to 10 normal volunteers to determine its effects on endogenous catecholamine, indoleamine, and endocrine function. Tryptamine, which is largely extracerebral in origin, was inhibited markedly (80 percent) by the carbidopa; 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenolglycol (MHPG) excretion also were inhibited by the drug but not to the same degree as tryptamine. These differential results may be due partly to the higher central nervous system origin of the 5-HIAA and MHPG but also to a peripheral "stores" effect. In addition, carbidopa resulted in significant increases in plasma prolactin and a small but significant decrease in plasma glucagon.

Molecular cloning of a novel isoform of diphosphoinositol polyphosphate phosphohydrolase: a potential target of lithium therapy.

The mechanisms underlying the therapeutic effects of lithium are largely unknown but may involve progressive adaptive alterations at the level of gene expression. Using differential display PCR, we identify a novel cDNA fragment, the expression of which was increased in the rat frontal cortex after 5 weeks of lithium administration. A full-length cDNA (2954-nt) was cloned by arrayed cDNA library screening, and sequencing of the clone revealed an open reading frame of 537-bp encoding a 179-residue protein. Amino acid sequence comparisons revealed that our clone is a member of the Nudix hydrolase family, with the highest percentage of homology (95%) being with a subtype of human diphosphoinositol polyphosphate phosphohydrolase, hDIPP2. Northern blot analysis revealed that chronic lithium treatment significantly increased rDIPP2 mRNA levels in frontal cortex, but not in hippocampus, midbrain, and cerebellum. The effect of lithium on rDIPP2 mRNA expression was not shared by two other anticonvulsant mood stabilizers, carbamazepine and valproate. Time-course studies showed that 1-week of lithium had no effect on rDIPP2 mRNA abundance in the frontal cortex. Our results suggest that DIPP2 may represent a biologically relevant target of lithium therapy, further supporting the notion that abnormalities in inositol phosphate metabolism may be significant in the pathophysiology and pharmacotherapy of bipolar disorder.