Glycated matrix up-regulates inflammatory signaling similarly to Porphyromonas gingivalis lipopolysaccharide.

BACKGROUND AND OBJECTIVE: Hyperglycemia and advanced glycation end-products (AGEs) have been hypothesized as the etiologic factors of diabetic periodontitis. The aim of this study was to clarify in greater detail the patterns of AGE-mediated periodontal inflammation under various physiological conditions. MATERIAL AND METHODS: The deposition of AGEs and expression of the receptor for AGEs (RAGE) were identified by immunohistochemistry in Sprague-Dawley rats with experimentally induced periodontitis or diabetes. Human periodontal ligament cells (PDLCs) and mesenchymal stem cells (MSCs) were cultured under simulated conditions of hyperglycemia, Porphyromonas gingivalis lipopolysaccharide (LPS) stimulation and matrix glycation. Cell viability and expression of toll-like receptors (TLRs), Rage, an inflammatory signaling initiator (nuclear factor kappa light chain enhancer of activator ß cells), an oxidative stressor (heme oxygenase-1) and collagen synthesis (type I and type IV) genes were evaluated. RESULTS: The deposition of AGEs and the expression of Rage were evident in the inflamed periodontal tissues in all rats and appeared to be enhanced in rats with diabetes. Matrix glycation augmented cytotoxicity, up-regulated RAGE and TLRs in both PDLCs and MSCs, and significantly activated downstream inflammatory signaling in MSCs. Oxidative stress was significantly increased under matrix glycation in both PDLCs and MSCs and was significantly increased at a high-glucose concentration in MSCs. A consistent decrease in expression of type I and type IV collagens was observed in MSCs, but a delayed reduction was noted in PDLCs. CONCLUSIONS: Matrix glycation modulated cell behavior to induce inflammation equivalent to that produced by incubation with P. gingivalis LPS. Periodontal inflammation also led to matrix glycation, thus demonstrating a definite interaction between diabetes and periodontitis.

Cellular behavior change of macrophage after exposure to nanoparticles.

Magnetic nanoparticles (MNPs) are few of the nanoparticles used clinically. When MNPs are delivered into human body, they are ingested by macrophages. We evaluated the cellular response of macrophage after MNPs loading. In face of stimulation by lipopolysaccharide, a strong stimulant derived from bacterial cell wall, MNPs loaded macrophage exhibited decreased phagocytic activity and decreased generation of cytokines such as TNF-alpha, IL-1beta whereas increased nitric oxide generation was noticed. Although these changes might decrease bactiericidal activity, it also alleviates the risk of senses, a life threatening phenomenon in infection patients. The finding has significant implications on nanoparticle based targeted drug delivery.

Effects of renal clearance on plasma concentrations of homovanillic acid. Methodologic cautions.

Recently, there has been considerable interest in plasma concentrations of homovanillic acid (HVA) in various psychiatric disorders. Homovanillic acid is a weak organic acid, and its excretion probably resembles that of other organic acids (eg, p-aminohippuric acid) that are actively secreted by the kidney. Alterations in renal plasma flow can affect clearance of organic acids, resulting in changes in plasma concentrations. In our study, concentrations of plasma HVA and urinary HVA (from 24-hour urine collections) were measured in 20 prepubescent boys who received 3 weeks of placebo, dextroamphetamine sulfate, and fenfluramine hydrochloride in a randomized, double-blind, counterbalanced study of the treatment of attention-deficit disorder. Plasma HVA concentrations were significantly lower during fenfluramine treatment than during amphetamine treatment. This difference, however, seemed to be caused by alterations in renal clearance of HVA rather than changes in production. Whole-body production of HVA, as indexed by total urinary HVA excretion, was unaffected by the different treatments, while renal clearance of HVA did differ significantly between amphetamine and fenfluramine treatment. It seems that alterations in renal clearance can affect plasma HVA concentrations, which should be taken into account when plasma HVA is studied.

The mechanisms of action of lithium. I. Effects on serotoninergic and noradrenergic systems in normal subjects.

The effects of 2 weeks of lithium carbonate administration at therapeutic plasma levels were examined in 11 normal volunteers. Serotoninergic function before and after lithium administration was assessed using low-dose intravenous clomipramine hydrochloride challenge, while urinary and plasma metabolites of norepinephrine (NE) were used to assess noradrenergic systems. Long-term lithium administration in normal subjects did not significantly or consistently enhance serotonin-mediated neuroendocrine responses but did increase measures related to neuronal release of NE. No statistically significant effects of lithium on prolactin, corticotropin, or cortisol responses to serotoninergic challenge could be detected. The probability of a type II error was assessed, and a doubling of prolactin level was unlikely to have been missed, although more modest increases (less than 75%) could have been overlooked. After 2 weeks of lithium administration, there were significant increases in 24-hour urinary excretion of NE, normetanephrine, and fractional NE release, compatible with increased neuronal release of NE and a lithium-induced subsensitivity in alpha 2-adrenergic receptor function. These changes were not statistically significant after 1 week of administration, suggesting that increased NE release is characteristic of long- rather than short-term lithium administration. Since previous reports have demonstrated enhanced prolactin responses after short- but not long-term lithium use, the present study points to temporal specificity in lithium's effects on both serotoninergic and noradrenergic function. Lithium's effects on NE release were consistent but small (a 16% increase), while its effects on serotoninergic responses were larger (a 50% increase in prolactin responses) but quite inconsistent, suggesting that neither of these systems is the primary site of action of lithium.

Monoamine neurotransmitter interactions and the prediction of antidepressant response.

Clinical studies of monoamine neurotransmitter function in depression have concentrated on individual monoamines without focusing on interactions between monoamine systems. Virtually all modern studies have found significant correlations between monoamine metabolite concentrations in cerebrospinal fluid (CSF). These correlations should in part reflect interactions between central monoamine systems. In the present analysis, CSF had been obtained from depressed patients before (n = 40) and after (n = 36) antidepressant treatment. The patients were grouped based on their response to treatment. Absolute concentrations of CSF monoamine metabolites (homovanillic acid, 5-hydroxyindoleacetic acid, and 3-methoxy-4-hydroxyphenylethyleneglycol) did not differ between the two groups before or after treatment. However, when correlations between metabolites were compared, nonresponders to treatment differed considerably from responders. In responders, as in previously described normal populations, all three metabolites correlated with one another before and after treatment, and treatment-induced changes in metabolite concentrations also correlated with one another. In contrast, metabolites in nonresponders did not correlate with one another before treatment, nor did treatment-induced changes correlate with one another in this group. Furthermore, correlations between treatment-induced changes in metabolites differed significantly between responders and nonresponders, and there was a trend for pretreatment correlations to differ as well. The lack of correlation between monoamine metabolites in nonresponders suggests that interactions between monoamine systems may be disrupted in these individuals. Using CSF metabolite correlations to study neurotransmitter interactions may have clinical relevance and yields information not available from examining neurotransmitters in isolation.

Guanine nucleotide-binding proteins in bipolar affective disorder. Effects of long-term lithium treatment.

BACKGROUND: This study examines recent suggestions from a number of investigators that signal-transducing guanine nucleotide-binding (G) proteins may be involved in the pathophysiology of bipolar affective disorder and may represent molecular targets for lithium's mood-stabilizing actions. METHODS: We used selective antibodies to quantitate the levels of the G protein alpha subunits that regulate adenylate cyclase activity (G alpha s and G alpha i2) and phosphoinositide turnover (G alpha q/11). We also quantitated levels of pertussis toxin-catalyzed phosphate 32-labeled adenosine diphosphate ([32P]ADP) ribosylation in platelet and leukocyte membranes from a group of 14 untreated (predominantly manic) patients with bipolar affective disorder, 20 lithium-treated euthymic patients with bipolar affective disorder, and 11 healthy controls. RESULTS: In both tissues, the immunolabeling of the 45-kd form of G alpha s was higher in the bipolar affective disorder group considered as a whole (treated or untreated) compared with controls, effects that reached statistical significance in the leukocyte membranes. There were no significant differences in the immunolabeling of G alpha i1/2, G alpha q/11, or pertussis toxin-catalyzed [32P]ADP ribosylation in either tissue in the untreated bipolar affective disorder group compared with controls. In both tissues, lithium-treated subjects demonstrated lower levels of G alpha q/11 and higher levels of pertussis toxin-catalyzed [32P]ADP-ribosylation, which reached significance in the platelet membranes. CONCLUSIONS: Our results are complementary to the previously reported findings of elevated G alpha s levels in postmortem brain tissue form patients with bipolar affective disorder and in mononuclear leukocytes obtained from depressed patients with bipolar (but not unipolar) affective disorder. The significantly higher levels of pertussis toxin-catalyzed [32P]ADP ribosylation in the subjects receiving long-term lithium-treatment replicates our findings in rat cortex and in healthy volunteers and adds to the growing body of evidence implicating G alpha i as a target of lithium's actions.

The mechanisms of action of lithium. II. Effects on adenylate cyclase activity and beta-adrenergic receptor binding in normal subjects.

As part of a study of the effects of lithium carbonate on neurochemical function in man, platelet and lymphocyte adenylate cyclase activity and lymphocyte beta-adrenergic receptor binding characteristics were determined before and after 2 weeks of lithium treatment in 10 normal volunteers. Lithium had differential effects on platelet and lymphocyte adenylate cyclase activity. In platelets, basal and stimulated (guanyl imidodiphosphate [Gpp[NH]p] or cesium fluoride) adenylate cyclase activity was significantly augmented by lithium treatment. By contrast, in lymphocytes, Gpp(NH)p- and cesium fluoride-stimulated adenylate cyclase activity was unaffected, while basal activity was decreased modestly after lithium. These results are consistent with preclinical studies that suggest that lithium's effects on adenylate cyclase activity are specific with respect to tissue and brain region and that lithium may interfere with guanine nucleotide binding (G) protein function. Lithium treatment significantly increased the ratio of low- to high-affinity dissociation constants for agonist displacement of antagonist binding to lymphocyte beta-adrenergic receptors (thought to reflect coupling between the beta-adrenergic receptor and stimulatory G protein). Lithium had significant effects on measures associated with signal transduction that might be contrasted to its more subtle effects on neuronal function (norepinephrine release) and neuroendocrine systems (responses to serotoninergic challenge) in these same subjects (reported in a companion article). Lithium's primary site of action may be on signal transduction mechanisms. These effects subsequently may be manifested in changes in neurotransmitter function that may be important to lithium's mood-stabilizing actions.

Cerebrospinal fluid and plasma monoamine metabolites and their relation to psychosis. Implications for regional brain dysfunction in schizophrenia.

The relationship between central (cerebrospinal fluid [CSF]) and peripheral (plasma) monoaminergic metabolites and psychotic symptoms was examined in 22 drug-free schizophrenic inpatients. The CSF homovanillic acid levels did not differ significantly between patients and normal controls (n = 33). The CSF homovanillic acid levels, however, were negatively correlated with ratings of psychosis and positive symptoms, and the CSF homovanillic acid and 5-hydroxyindoleacetic acid levels correlated negatively with individual deficit symptoms. Stepwise and hierarchical multiple-regression analysis revealed that among monoaminergic measures, only the CSF and plasma homovanillic acid levels contributed significantly to the total Brief Psychiatric Rating Scale and positive symptom variance with negative and positive partial correlations, respectively. Levels of CSF 3-methoxy-4-hydroxyphenylglycol, but not of CSF norepinephrine, were significantly elevated in the schizophrenic patients compared with controls, and plasma 3-methoxy-4-hydroxyphenylglycol levels were positively correlated with negative symptoms. We discuss the potential implications of these findings for a model of dopaminergic dysfunction in schizophrenia involving distinct cortical and subcortical contributions.

Monoamine neurotransmitter interactions in drug-free and neuroleptic-treated schizophrenics.

OBJECTIVE: To study recent suggestions by a number of investigators that interactions between monoamine neurotransmitter systems play an important role in schizophrenia. It has not been clear how hypotheses about interactions might be tested in clinical data. One means for indexing interactions between monoamine neurotransmitter systems may be to compare correlations between cerebrospinal fluid (CSF) monoamine metabolite (homovanillic acid [HVA], 5-hydroxyindoleacetic acid [5-HIAA], and 3-methoxy-4-hydroxyphenylglycol [MHPG]) or ratios of these metabolites (HVA/5-HIAA and HVA/MHPG). DESIGN: We compared these putative measures of monoamine neurotransmitter interaction in 50 drug-free patients with schizophrenia (hospitalized on an inpatient ward of a tertiary care hospital) and 33 normal controls and examined the effects of neuroleptic antipsychotic treatment on these measures in 41 patients (22 of whom had antecedent drug-free CSF data). RESULTS: Drug-free patients with schizophrenia had significantly smaller correlations between CSF monoamine metabolites than normal controls. Longer drug-free time was associated with even smaller correlations between metabolites, suggesting that the difference between controls and patients was not due to acute drug withdrawal. After treatment with neuroleptic antipsychotics there were significant increases in the HVA/5-HIAA and HVA/MHPG ratios, as well as increases in correlations between monoamine metabolites. After treatment, there were no significant differences in metabolite correlations between patients and controls. Metabolite ratios and correlations did not predict subsequent treatment response, but preliminary analyses demonstrated negative relationships between HVA/5-HIAA and HVA/MHPG ratios and Brief Psychiatric Rating Scale rating at that time. CONCLUSIONS: The present findings are consistent with and support hypotheses suggesting that interactions between monoamine systems are altered in schizophrenia and that antipsychotic treatment may affect the functional balance between different monoamine neurotransmitters (although one should keep in mind factors other than interactions between monoamine systems that affect metabolite correlations and ratios.

Is there paradoxical growth hormone response to thyrotropin-releasing hormone in depression?

Several investigators have reported a paradoxical growth hormone (GH) response to thyrotropin-releasing hormone (TRH) in depressed patients, but other studies have failed to confirm this. In the present study, the GH response to TRH was studied in depressed patients and normal subjects. The rate of paradoxical GH response to TRH in depression was no different than that observed in control subjects. This was the case whether the data was examined using mean values or using frequency of abnormal responses. Patients with blunted thyrotropin (TSH) responses did not differ in GH release from patients with normal TSH response. A variety of factors may have contributed to the earlier reports of a positive GH response to TRH, including the definition of paradoxical GH release and the fact that depressed patients exhibit more frequent spontaneous diurnal GH release than do normal subjects.

The effects of antidepressants on the cerebrospinal fluid homovanillic acid/5-hydroxyindoleacetic acid ratio.

Dopamine and serotonin systems are morphologically interconnected in the midbrain. Several studies have also demonstrated a functional relationship between these two monoamine systems. Concentrations of their metabolites, 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA), consistently correlate with one another in human cerebrospinal fluid. Previous studies of the effects of antidepressants on the dopamine and serotonin systems have focused on the two systems in isolation without considering the interactions between the two. One way of taking this interaction into account may be to form a ratio of dopamine and serotonin measures. The present study measured HVA and 5HIAA in cerebrospinal fluid of 31 patients with depression and 12 patients with Alzheimer's disease before and after treatment with a variety of antidepressant drugs. The ratio of HVA/5HIAA was able to discriminate much more powerfully between effects of different drugs than HVA or 5HIAA examined separately.

ECT in a depressed patient after craniotomy.

ECT was successfully administered to a depressed woman who had had a craniotomy and had postoperative seizures. For ECT after craniotomy, the authors recommend postneurosurgical stabilization, continuation of anticonvulsants if a seizure disorder is present, and proper electrode placement.

Munchausen syndrome, depression, and the dexamethasone suppression test.

The authors describe two patients with Munchausen syndrome who met DSM-III criteria for major depression. Both patients exhibited evidence of nonsuppression of serum cortisol by dexamethasone. Although many patients with Munchausen syndrome have been reported to be depressed, only a few have received a diagnosis of major depression. Because the physical and psychiatric symptoms of the Munchausen patient are so complex, clinical assessment may stop at a diagnosis of Munchausen syndrome, and major depression may be overlooked. A diagnosis of major depression should be considered in the evaluation of these patients; the dexamethasone suppression test may enhance clinical assessment.

The functional neuroanatomy of Tourette's syndrome: an FDG-PET study. I. Regional changes in cerebral glucose metabolism differentiating patients and controls.

Regional metabolic rates for glucose estimated using [18F]fluorodeoxyglucose positron-emission tomography were compared in 16 drug-free patients with Tourette's syndrome (TS) and 16 age- and sex-matched normal volunteers. Tourette's syndrome patients were characterized by decreased normalized metabolic rates in paralimbic and ventral prefrontal cortices, particularly in orbitofrontal, inferior insular, and parahippocampal regions. Similar decreases were observed in subcortical regions, including the ventral striatum (nucleus accumbens/ventromedial caudate) and in the midbrain. These changes were more robust and occurred with greater frequency in the left hemisphere. They were associated with concomitant bilateral increases in metabolic activity the supplementary motor, lateral premotor, and Rolandic cortices. Effects of prior exposure to neuroactive drugs did not account for these findings. These results suggest that an altered relationship between limbic-related regions of the cortex and striatum and cortical regions involved in the initiation of movement may play a role in the pathogenesis of this illness.

Predictors of clozapine response in schizophrenia.

The introduction of the atypical neuroleptic, clozapine, has had widespread influence not only on the treatment of the seriously mentally ill patient, but also on new drug development and on hypotheses of the pathophysiology of schizophrenia. While clozapine differs from traditional neuroleptics in its lack of extrapyramidal side effects (EPS), it also is distinct in its profile of neurotransmitter receptor affinities. In our work examining the clinical and biological effects of clozapine in patients with schizophrenia, we have identified the presence of EPS during typical neuroleptic treatment as a consistent predictor of subsequent good response to clozapine. Further, our data suggest that clozapine should not be reserved for the most chronically ill patients, but rather be utilized in patients with less chronic courses of schizophrenia. Biological predictors of clozapine response are consistent with dopaminergic, serotonergic, and noradrenergic facets to its mechanism of action.

Regulation of signal transduction pathways by mood-stabilizing agents: implications for the delayed onset of therapeutic efficacy.

A series of investigations were performed to elucidate the mechanisms of action of lithium, valproate, and carbamazepine. We have found that lithium exerts major effects on G proteins, most likely via a posttranslational process stabilizing the inactive heterotrimeric (alpha beta gamma) form of the protein. We also find that chronic lithium and valproate exert major, very similar effects on the PKC signaling pathway, with both drugs decreasing the levels of membrane-associated PKC alpha and epsilon, and have similar effects on the DNA binding activity of the transcription factor, AP-1. By contrast, we find that carbamazepine exerts major, direct inhibitory effect at the level of adenylyl cyclases. Overall, the results suggest that signal transduction pathways are targets for the actions of mood-stabilizing agents; given their key roles in the amplification and integration of signals in the central nervous system, these findings have clear implications not only for research into the etiology/pathophysiology of manic-depressive illness, but also for the development of innovative treatment strategies.

Dose-dependent effects of intravenous alprazolam on neuroendocrine, biochemical, cardiovascular, and behavioral parameters in humans.

Neuroendocrine, biochemical, cardiovascular, and behavioral parameters were assessed in seven normal volunteers for 2 h after intravenous administration of alprazolam (APZ). Three doses of APZ (0.003, 0.007, and 0.02 mg/kg) were administered to each subject in a random order with at least 4 days between infusions. Plasma growth hormone and sedation increased in a dose dependent manner after APZ, and there was a dose dependent change in the shape of the cortisol response to APZ. No dose-response relationships were evident for plasma ACTH and norepinephrine. These differences in dose-response relationships may reflect the involvement of multiple systems in controlling neuroendocrine, biochemical, and subjective responses to APZ infusion. The optimal dose of APZ needed to produce a neuroendocrine or behavioral change appears to differ depending on the parameter of interest.

Intravenous alprazolam challenge in normal subjects. Biochemical, cardiovascular, and behavioral effects.

Alprazolam, a novel benzodiazepine derivative is thought to be effective in the treatment of anxiety, panic, and depressive disorders. There is considerable interest in alprazolam's mechanism of action, particularly whether its profile of actions might resemble that of the alpha 2 adrenoreceptor agonist, clonidine. The present study assessed the biochemical, cardiovascular, and behavioral responses of healthy volunteers to acute intravenous infusions of alprazolam and placebo. Alprazolam reduced ACTH and cortisol while increasing growth hormone. There was a transient reduction in plasma norepinephrine and only modest effects on cardiovascular parameters. Subjects became quite sedated after intravenous alprazolam. This pharmacodynamic profile resembles that previously reported for traditional benzodiazepines, although alprazolam may be a more potent stimulator of growth hormone release. Alprazolam's effects on growth hormone resemble those of clonidine, but unlike clonidine, alprazolam has relatively little effect on plasma catecholamine and cardiovascular parameters. This suggests that alpha 2 mechanisms do not play a primary role in alprazolam's mode of action. Since alprazolam infusion affects three different measures (ACTH/cortisol, growth hormone, and plasma norepinephrine) thought to be dysregulated in depression, challenge with intravenous alprazolam may prove to be a useful "probe" in affective disorders.

Activation in young rats induced by LY134046, an inhibitor of phenylethanolamine N-methyltransferase.

LY134046, a potent, selective inhibitor of rat brain phenylethanolamine N-methyltransferase, was shown to increase activity in 18- and 19-day-old rats. The effects on day 25 were different, with LY134046 causing a decrease in activity. The effects of yohimbine, a selective antagonist of the alpha-2 adrenergic receptor, were markedly different from LY134046, causing a decrease in activity on day 19. These data suggest that epinephrine synthesis may play an inhibitory role in the regulation of activity in young rats.

Clinical investigation of monoamine neurotransmitter interactions.

Monoamine neurotransmitter systems are widely thought to be involved in the pathophysiology of affective disorders and schizophrenia and the mechanism of action of antidepressant and antipsychotic drugs. Previous clinical studies have focused on individual monoamine function in isolation, even though a large number of preclinical studies have demonstrated that monoamine neurotransmitter systems interact with one another. In the present paper, preclinical data on monoamine neurotransmitter interactions are reviewed, and two methods for examining monoamine neurotransmitter system interactions in clinical data are presented. One of the best replicated findings in biological psychiatry is that monoamine metabolites in CSF correlate with one another. The degree of correlation may be in part a measure of the degree of interaction between the parent monoamine neurotransmitter systems. Another approach to studying interactions is the use of HVA/5HIAA and HVA/MHPG ratios as an index of interactions between 5HT-DA and NE-DA. When these methods are applied in schizophrenia, patients are found to have decreased monoamine metabolite correlations compared to normal controls. Metabolite correlations increase significantly after antipsychotic treatment, and the HVA/5HIAA and HVA/MPHG ratios also increase, suggesting that neuroleptics may act in part by strengthening interactions between monoamines. BPRS ratings are negatively correlated with HVA/5HIAA and HVA/MHPG so that patients with higher ratios have fewer symptoms, particularly after treatment. These results provide direct experimental support for hypotheses suggesting that interactions between monoamine neurotransmitters are important in schizophrenia. Some of the effects of the atypical neuroleptic, clozapine, on metabolite correlations and ratios are also discussed.