J. Steven Richardson

Autopsy samples of Alzheimer's cortex show increased peroxidation in vitro.

Abstract: The formation of thiobarbituric acid‐reactive products was measured as an index of peroxidation by oxygen free radicals in homogenates of frontal cortex and cerebellum from brains taken at autopsy and verified histologically as being Alzheimers (n = 6) or normal (n = 6). Compared with controls, basal peroxidation is significantly higher in Alzheimers cortex, and this difference is also evident in the presence of exogenous iron. Peroxidation in cerebellum and levels of total glutathione, RNA, and DNA in cortex and cerebellum do not differ significantly between Alzheimers brain and controls. Iron‐induced peroxidation in cortex is reduced by the lazaroid U‐74500A, with calculated IC50 values that are significantly higher in Alzheimers samples (10 μM) than in controls (2.5 μM). These observations suggest that cerebral cortex from Alzheimers patients differs from controls with respect to in vitro peroxidation.

Method for the rapid determination of norepinephrine, dopamine, and serotonin in the same brain region.

A method is presented for the fluorometric analysis of norepinephrine dopamine and serotonin. This procedure is a combination of an unpublished catecholamine assay developed by Hogans and of the o-phthaldialdehyde serotonin reaction reported by Maickel and Miller [9]. This procedure should greatly facilitate the correlation of neurotransmitter levels in brain regions with changes in behavior produced by experimental manipulations.

Free Radicals in the Genesis of Alzheimer's Diseasea

As part of an ongoing investigation of the role of oxygen free radicals in Alzheimers disease (AD), the formation of peroxidation products, the activities of free radical defense enzymes, and the level of total iron were determined in autopsy brain tissue from donors with AD and from age‐matched non‐demented donors. Calcium uptake was also investigated in mitochondria harvested from fibroblasts grown in tissue culture from skin samples taken from brain donors.

Animal models of depression: Parallels and correlates to severe depression in humans

Drugs with antidepressant properties in patients with severe depression also have various behavioral and neurochemical effects in animals. This has given rise to numerous animal models that have been suggested to be valid for research into the neurobiology of depression and the neurochemical mechanisms of the antidepressant drugs. However, considerable evidence from many avenues of research indicates that severe depression is a biochemical disorder that develops in those individuals with some predisposing neurochemical vulnerability. Although the predisposing biochemical abnormality has not been identified, it may be related to the neurochemical mechanisms that regulate impulse traffic in various neural systems and maintain the homeostatic balance of neural activity within the brain. Therefore, the appropriate animal model for severe depression should have some disruption of neural functioning that is returned to normal by the chronic administration of antidepressant drugs. Of the numerous animal models of depression that have been presented in the literature, only the rat with olfactory bulb lesions meets this requirement. The behavioral and endocrine abnormalities induced by the olfactory bulb lesions are reversed by chronic (but not acute) treatment with antidepressants of various classes. Of the existing animal models of severe depression, the olfactory bulbectomy model holds the most promise for elucidating the neurobiology of depression and the neurochemistry of antidepressant drugs.

Dose-related effects of chronic antidepressants on neuroprotective proteins BDNF, Bcl-2 and Cu/Zn-SOD in rat hippocampus.

It has been proposed that antidepressants have neuroprotective effects on hippocampal neurons. To further test this hypothesis, brain-derived neurotrophic factor (BDNF), B cell lymphoma protein-2 (Bcl-2), and copper–zinc superoxide dismutase (Cu/Zn-SOD) were examined immunohistochemically in hippocampal neurons of Sprague–Dawley rats following daily treatment with 5 or 10 mg/kg of amitriptyline or venlafaxine for 21 days. At 5 mg/kg, both amitriptyline and venlafaxine increased the intensity of BDNF immunostaining in hippocampal pyramidal neurons, and the intensity of Bcl-2 immunostaining in hippocampal mossy fibers, but did not alter the Cu/Zn-SOD immunoreactivity. The high dose of venlafaxine, however, decreased the intensity of BDNF immunostaining in all subareas of the hippocampus and increased the intensity of Cu/Zn-SOD immunostaining in the dentate granular cell layer. The high dose of amitriptyline increased the intensity of Cu/Zn-SOD immunostaining, but did not affect the immunoreactivity of Bcl-2 or BDNF. These findings suggest that the chronic administration of amitriptyline or venlafaxine at 5 mg/kg, but not 10 mg/kg, may be neuroprotective to hippocampal neurons. These dose-related effects of antidepressant drugs on hippocampal neurons may have relevance to disparate findings in the field.

Quetiapine attenuates the immobilization stress-induced decrease of brain-derived neurotrophic factor expression in rat hippocampus

Quetiapine is a new atypical antipsychotic drug widely used in the treatment of schizophrenia and other psychotic disorders. This study examined the influence of quetiapine on the decrease of brain-derived neurotrophic factor (BDNF) expression, induced by chronic immobilization stress, in the hippocampus of the rat. Pretreatment with 10 mg/kg of quetiapine markedly attenuated the stress-induced decrease in levels of BDNF protein, as determined by Western blot analyses, and the reduction of BDNF immunoreactivity, in hippocampal pyramidal and dentate granular neurons. These results suggest that the chronic administration of quetiapine could be neuroprotective to hippocampal neurons in schizophrenia and this effect may be related to its antipsychotic effect in patients with schizophrenia.

Olanzapine protects PC12 cells from oxidative stress induced by hydrogen peroxide.

Neuroanatomical studies suggest that neuronal atrophy and destruction occur over the course of many years in neurodegenerative conditions such as schizophrenia and Alzheimers disease. In schizophrenia, early intervention with atypical neuroleptics such as olanzapine has been shown to prevent development of some of the more serious and debilitating symptoms in many patients. The mechanisms whereby olanzapine slows or prevents symptom progression in schizophrenia remain unclear. A previous study found that olanzapine increased mRNA for the copper/zinc isoform of the superoxide dismutase enzyme (SOD‐1). We investigated the effects of olanzapine in PC12 cells exposed to hydrogen peroxide. We measured cell viability, observed evidence of necrosis and apoptosis, checked the SOD‐1 mRNA by Northern blot analyses, and determined SOD‐1 enzyme activity. We found that: 1) the decrease in cell viability induced by hydrogen peroxide was attenuated in PC12 cells pretreated with olanzapine; 2) olanzapine increased SOD enzyme activity in PC12 cells; 3) inhibiting SOD activity with diethyldithiocarbamic acid prevented the cytoprotective actions of olanzapine; and 4) the decrease in SOD‐1 mRNA level induced by hydrogen peroxide was blocked by pretreatment with olanzapine. These data indicate that the neuroprotective action of olanzapine includes the upregulation of SOD.

Actions of neurotoxic β-amyloid on calcium homeostasis and viability of PC12 cells are blocked by antioxidants but not by calcium channel antagonists

Abstract: The fragment of β‐amyloid comprised of amino acids 25–35 induces a rapid, concentration‐dependent increase in cytosolic free calcium levels in suspensions of PC12 neuronal cells. This action of β‐amyloid 25–35 is not altered by pretreatment with the calcium channel blockers nifedipine or cobalt, with the depleter of intracellular calcium stores cyclopiazonic acid, or with the phospholipase C inhibitor neomycin. However, the effects of β‐amyloid 25–35 on cytosolic free calcium are absent in calcium‐free buffer and are blocked by the antioxidant lazaroid U‐83836E and by vitamin E. β‐Amyloid 25–35 is also neurotoxic and produces a concentration‐dependent reduction in the viability of PC12 cells in culture. The neurotoxic action of β‐amyloid is blocked by U‐83836E and vitamin E but not by nifedipine or cobalt. These data indicate that both the disruption of calcium homeostasis and the reduction of cell viability produced by β‐amyloid in PC12 cells are mediated by free radical‐based processes.

Atypical antipsychotics attenuate neurotoxicity of β-amyloid(25–35) by modulating Bax and Bcl-Xl/s expression and localization

We have demonstrated recently that atypical antipsychotics possess neuroprotective actions in H2O2‐mediated and serum‐withdrawal models of cell death. In the present study, we compared the ability of atypical and typical antipsychotics to protect against an insult mediated by Aβ(25–35), an apoptogenic fragment of the Alzheimers disease‐related β‐amyloid (Aβ) peptide. Treatment of PC12 cell cultures with Aβ(25–35) did not significantly alter total cellular expression levels of Bax, a proapoptotic Bcl‐2 family member, or levels of Bcl‐XL, an antiapoptotic analogue. Treatment with Aβ(25–35), however, did result in mitochondrial translocation of Bax, which effectively increased the mitochondrial ratio of Bax to Bcl‐XL. This relative increase in proapoptotic molecules was reduced by pretreatment with atypical (quetiapine and olanzapine) and typical (haloperidol) antipsychotics. We also observed a selective increase in proapoptotic Bcl‐XS immunodetection in haloperidol‐treated cells, which was evident particularly in the mitochondrial compartment. This increase in proapoptotic molecules may account for the lower neuroprotective potential of haloperidol, as determined by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium (MTT) reduction assay. The disparate neuroprotective effects of atypical and typical antipsychotics/neuroleptics may be due to their respective abilities to regulate pro‐ and anti‐apoptotic protein translocation and expression.

Mitochondria from Alzheimer's fibroblasts show decreased uptake of calcium and increased sensitivity to free radicals.

Many of the biological abnormalities seen in samples of the brain and other tissues from patients with Alzheimers disease, are consistent with an excessive action of oxygenic free radicals. Mitochondria from fibroblasts grown in tissue culture from skin samples taken at autopsy from patients with histologically confirmed Alzheimers disease, take up significantly less calcium than do fibroblast mitochondria from age matched non-demented controls. Following exposure to oxygenic free radicals generated by adding ferrous ions to the incubation mixture, calcium uptake is increased to a greater extent in Alzheimers mitochondria than in controls. At the doses used, pretreatment with the lazaroid antioxidant drug U-74500A, or with the iron chelator deferoxamine, prevents the free radical induced increase in calcium uptake by control mitochondria, but provides only partial protection for Alzheimers mitochondria. These observations suggest that Alzheimers fibroblast mitochondria have impaired calcium transport processes and show increased sensitivity to oxygenic free radicals.