Sex-specific associations between Neutrophil Gelatinase-Associated Lipocalin (NGAL) and cognitive domains in late-life depression.

BACKGROUND: Although it is well established that late-life depression is associated with both systemic low-graded inflammation and cognitive impairment, the relation between inflammation and cognition in depressed older persons is still equivocal. The objective of this study is to examine the association between plasma Neutrophil Gelatinase-Associated Lipocalin (NGAL) concentrations and cognitive functioning in late-life depression, including the potentially moderating role of sex. METHODS: A total of 369 depressed older persons (≥60 years) from The Netherlands study of Depression in Older persons (NESDO) were included. Four cognitive domains, i.e. verbal memory, processing speed, interference control and attention were assessed with three cognitive tests (Stroop test, Wais Digit span test, and Rey's verbal learning test). Multiple linear regression analyses were applied with the four cognitive domains as dependent variables adjusted for confounders. RESULTS: The association between NGAL levels and specific cognitive domains were sex-specific. In women, higher NGAL levels were associated with impaired verbal memory and lower processing speed. In men, higher NGAL levels were associated with worse interference control. Higher NGAL levels were not associated with attention. No sex-specific associations of either high sensitivity C-reactive protein (hsCRP) or interleukin-6 (IL-6) with cognitive functioning were found. CONCLUSION: This study shows sex-specific association of NGAL with cognitive functioning in late-life depression.

Neutrophil gelatinase-associated lipocalin: a novel inflammatory marker associated with late-life depression.

OBJECTIVE: Systemic low graded inflammation has been identified as a possible biological pathway in late-life depression. Identification of inflammatory markers and their association with characteristics of depression is essential with the aim to improve diagnosis and therapeutic approaches. This study examines the determinants of plasma Neutrophil Gelatinase-Associated Lipocalin (NGAL), which is selectively triggered by TNFα receptor 1 signaling within the central nervous system, and its association with late-life depressive disorder. METHODS: Baseline data were obtained from a well-characterized prospective cohort study of 350 depressed and 129 non-depressed older persons (≥60years). Past 6month diagnosis of major depressive disorder (MDD) according to DSM-IV-TR criteria was assessed with the Composite International Diagnostic Interview (CIDI 2.0). Potential determinants of plasma NGAL included sociodemographic characteristics, lifestyle and psychiatric and physical comorbidity. RESULTS: Plasma NGAL concentrations were significantly associated with age, male gender, smoking and waist circumference. Adjusted for these determinants, depressed patients had significantly higher NGAL plasma levels compared to non-depressed comparison group. Depressed patients who did not meet full criteria for MDD in the month before sampling (partially remitted) had lower plasma NGAL levels compared with those who did. Subjects with a recurrent depression had higher plasma NGAL levels compared to those with a first episode. NGAL levels were neither related with specific symptom profiles of depression nor with antidepressant drug use. CONCLUSION: Adjusted for confounders, NGAL plasma levels are increased in depressed older persons, without any effect of antidepressant medication and age of onset.

Developmental docosahexaenoic and arachidonic acid supplementation improves adult learning and increases resistance against excitotoxicity in the brain.

Through metabolic imprinting mechanisms a number of bioactive molecules including polyunsaturated fatty acids affect brain functions in the developmental age and longer-lasting beneficial effects are expected. In this study pregnant rats were offered diets either containing no docosahexaenoic acid (DHA) and arachidonic acid (AA) (Placebo diet) or an excess amount of these long chain polyunsaturated fatty acids (LC-PUFA) (Supplement diet) up to the time of weaning. Bilateral N-methyl-D-aspartate (NMDA) induced neurodegeneration in the entorhinal cortex of offspring in the age of 4 months was used as a tool to investigate the neuroprotective property of the developmentally supplemented DHA and AA treatments. Hippocampus-dependent spatial learning was measured in Morris water maze and the extent of neuronal lesion in the injected brain area was evaluated. Under baseline condition, in intact or sham-lesioned rats, the Morris water maze performance was superior in the supplemented group compared to the placebo controls. NMDA-lesion in the entorhinal cortex area decreased spatial learning in the supplement-treated rats while insignificantly diminished it in the placebo controls. The same supplementation attenuated the lesion size induced by the NMDA injection into the entorhinal and ventral hippocampal areas. We concluded that LC-PUFA supplementation during fetal and early postnatal development results in long-term enhancement of spatial learning ability of the offspring and offers resistance against excitotoxic brain lesion which lasts up to the adult age.

Spumiform basement membrane aberrations in the microvasculature of the midbrain periaqueductal gray region in hamster: rostro-caudal pathogenesis?

Spumiform basement membrane degeneration (sbmd) is a specific kind of aberration present in the capillaries of the midbrain periaqueductal gray (PAG) region of the senescent hamster. These capillaries, separated by the ependymal cell layer, are bordering the Sylvian cerebral aqueduct. The aqueduct, connecting the 3rd and 4th ventricle, may be crucial for local homeostatic as well as general autonomic functions of the PAG. Local pressure effects of the flowing and pulsating cerebrospinal fluid on the PAG-vasculature are probably different for the rostral 'entrance' and the caudal 'exit' of the aqueduct. In view of the different functions of the various divisions of the PAG, the frequency and extent of the aberrations in the rostral, intermediate and caudal dl/vlPAG-microvasculature could shed some light on the causal factors involved in the regional distribution of the particular microvascular aberrations found in the PAG during aging. In the present study we investigated the ultrastructure of capillaries in dorsal and ventral subdivisions of anterior and posterior regions of the PAG of young and old female Syrian hamsters. Sbmds were classified into four stages of spumiform severity and for each stage the frequency was determined in the rostral PAG, at two levels in the intermediate PAG and in a dorsal and a ventral part of the caudal PAG. Results of our quantitative studies showed that in aged hamster PAG various stages of sbmd were present in 91.6 ± 0.6% of all capillaries. No clear evidence was found for regional differentiation between rostral, intermediate and caudal parts of the PAG. Next to sbmd, capillary split basement membrane (sbm) and vacuolization were common features at all five PAG locations. 84.3 ± 2.3% of all screened PAG capillaries displayed sbm. In agreement with our previous findings, several other types of microvascular aberrations were observed in addition to general aspects of aging and some ependymal structural peculiarities. We conclude that the presence of various forms of sbmds in the PAG of senescent hamsters is a phenomenon that appears to be specific to the PAG region, but causal factors for this type of capillary degeneration remain unclear. Sbmds in the PAG may have serious consequences not only for blood-brain barrier functioning, but also for vascular perfusion and blood supply with eventually serious consequences for adequate regulation of the autonomic and motor control functions of the PAG region.

Chronic but not acute foot-shock stress leads to temporary suppression of cell proliferation in rat hippocampus.

Stressful experiences, especially when prolonged and severe are associated with psychopathology and impaired neuronal plasticity. Among other effects on the brain, stress has been shown to negatively regulate hippocampal neurogenesis, and this effect is considered to be exerted via glucocorticoids. Here, we sought to determine the temporal dynamics of changes in hippocampal neurogenesis after acute and chronic exposure to foot-shock stress. Rats subjected to a foot-shock procedure showed strong activation of the hypothalamic-pituitary-adrenal (HPA) axis, even after exposure to daily stress for 3 weeks. Despite a robust release of corticosterone, acute foot-shock stress did not affect the rate of hippocampal cell proliferation. In contrast, exposure to foot-shock stress daily for 3 weeks led to reduced cell proliferation 2 hours after the stress procedure. Interestingly, this stress-induced effect did not persist and was no longer detected 24 hours later. Also, while chronic foot-shock stress had no impact on survival of hippocampal cells that were born before the stress procedure, it led to a decreased number of doublecortin-positive granule neurons that were born during the chronic stress period. Thus, whereas a strong activation of the HPA axis during acute foot-shock stress is not sufficient to reduce hippocampal cell proliferation, repeated exposure to stressful stimuli for prolonged period of time ultimately results in dysregulated neurogenesis. In sum, this study supports the notion that chronic stress may lead to cumulative changes in the brain that are not seen after acute stress. Such changes may indicate compromised brain plasticity and increased vulnerability to neuropathology.

Early transient presence of implanted bone marrow stem cells reduces lesion size after cerebral ischaemia in adult rats.

AIMS: Previous studies on the therapeutic time window for intravascular administration of bone marrow stem cells (BMSCs) after stroke have shown that early intervention (from 3 h after onset) in the middle cerebral artery occlusion (MCAO) rat model is the most effective approach to reduce ischaemic lesion size. We have confirmed these observations but noticed that 2 weeks after transplantation, almost none of the grafted BMSCs could be detected in or around the lesion. The present experiments aimed to assess the fate and kinetics of intravascularly injected BMSCs shortly after administration in correlation to the development of the ischaemic lesion after MCAO. METHODS: We administered a syngeneic suspension of complete (haematopoietic and mesenchymal) BMSCs via the carotid artery to rats at 2 h after MCAO onset. We examined the distribution and tissue location of BMSCs within the first 24 h after arterial administration by perfusion-fixating rats and performing immunohistochemical analysis at different time points. RESULTS: The vast majority (>95%) of BMSCs appeared to become trapped in the spleen shortly after injection. Six hours after implantation, together with the appearance of activated microglia, the first BMSCs could be detected in and around the lesion; their number gradually increased during the first 12 h after implantation but started to decrease at 24 h. The implanted BMSCs were surrounded by activated and phagocytotic microglia. CONCLUSION: Our results show that ischaemic lesion size reduction can already be achieved by the early transient presence at the lesion site of intravascularly implanted BMSCs, possibly mediated via activated microglia.

Effects of Vinpocetine on mitochondrial function and neuroprotection in primary cortical neurons.

Vinpocetine (ethyl apovincaminate), a synthetic derivative of the Vinca minor alkaloid vincamine, is widely used for the treatment of cerebrovascular-related diseases. One of the proposed mechanisms underlying its action is to protect against the cytotoxic effects of glutamate overexposure. Glutamate excitotoxicity leads to the disregulation of mitochondrial function and neuronal metabolism. As Vinpocetine has a binding affinity to the peripheral-type benzodiazepine receptor (PBR) involved in the mitochondrial transition pore complex, we investigated whether neuroprotection can be at least partially due to Vinpocetine's effects on PBRs. Neuroprotective effects of PK11195 and Ro5-4864, two drugs with selective and high affinity to PBR, were compared to Vinpocetine in glutamate excitotoxicity assays on primary cortical neuronal cultures. Vinpocetine exerted a neuroprotective action in a 1-50microM concentration range while PK11195 and Ro5-4864 were only slightly neuroprotective, especially in high (>25microM) concentrations. Combined pretreatment of neuronal cultures with Vinpocetine and PK11195 or Ro5-4864 showed increased neuroprotection in a dose-dependent manner, indicating that the different drugs may have different targets. To test this hypothesis, mitochondrial membrane potential (MMP) of cultured neurons was measured by flow cytometry. 25microM Vinpocetine reduced the decrease of mitochondrial inner membrane potential induced by glutamate exposure, but Ro5-4864 in itself was found to be more potent to block glutamate-evoked changes in MMP. Combination of Ro5-4864 and Vinpocetine treatment was found to be even more effective. In summary, the present results indicate that the neuroprotective action of vinpocetine in culture can not be explained by its effect on neuronal PBRs alone and that additional drug targets are involved.

A review of the neuroprotective properties of the 5-HT1A receptor agonist repinotan HCl (BAYx3702) in ischemic stroke.

Repinotan HCl (repinotan, BAYx3702), a highly selective 5-HT1A receptor agonist with a good record of safety was found to have pronounced neuroprotective effects in experimental models that mimic various aspects of brain injury. Repinotan caused strong, dose-dependent infarct reductions in permanent middle cerebral artery occlusion, transient middle cerebral artery occlusion, and traumatic brain injury paradigms. The specific 5-HT1A receptor antagonist WAY 100635 blocked these effects, indicating that the neuroprotective properties of repinotan are mediated through the 5-HT1A receptor. The proposed neuroprotective mechanisms of repinotan are thought to be the result of neuronal hyperpolarization via the activation of G protein-coupled inwardly rectifying K+ channels upon binding to both pre- and post-synaptic 5-HT1A receptors. Hyperpolarization results in inhibition of neuron firing and reduction of glutamate release. These mechanisms, leading to protection of neurons against overexcitation, could explain the neuroprotective efficacy of repinotan per se, but not necessarily the efficacy by delayed administration. The therapeutic time window of repinotan appeared to be at least 5 h in in vivo animal models, but may be even longer at higher doses of the drug. Experimental studies indicate that repinotan affects various mechanisms involved in the pathogenesis of brain injury. In addition to the direct effect of repinotan on neuronal hyperpolarization and suppression of glutamate release this compound affects the death-inhibiting protein Bcl-2, serotonergic glial growth factor S-100beta and Nerve Growth Factor. It also suppresses the activity of caspase-3 through MAPK and PKCalpha; this effect may contribute to its neuroprotective efficacy. The dose- and time-dependent neuroprotective efficacy of repinotan indicates that the drug is a promising candidate for prevention of secondary brain damage in brain-injured patients suffering from acute ischemic stroke. Unfortunately, however, the first, randomized, double blind, placebo-controlled clinical trial did not demonstrate the efficacy of repinotan in acute ischemic stroke.

Neuroprotective effect of developmental docosahexaenoic acid supplement against excitotoxic brain damage in infant rats.

Long-chain polyunsaturated fatty acid (LC-PUFA) composition of neural membranes is a key factor for brain development, in chemical communication of neurons and probably also their survival in response to injury. Viability of cholinergic neurons was tested during brain development following dietary supplementation of fish oil LC-PUFAs (docosahexaenoic acid [DHA], eicosapentaenoic acid, arachidonic acid) in the food of mother rats. Excitotoxic injury was introduced by N-methyl-D,L-aspartate (NMDA) injection into the cholinergic nucleus basalis magnocellularis of 14-day-old rats. The degree of loss of cholinergic cell bodies, and the extend of axonal and dendritic disintegration were measured following immunocytochemical staining of cell bodies and dendrites for choline acetyltransferase and p75 low-affinity neurotrophin receptor and by histochemical staining of acetylcholinesterase-positive fibres in the parietal neocortex. The impact of different feeding regimens on fatty acid composition of neural membrane phospholipids was also assayed at 12 days of age. Supplementation of LC-PUFAs resulted in a resistance against NMDA-induced excitotoxic degeneration of cholinergic neurones in the infant rats. More cholinergic cells survived, the dendritic involution of surviving neurons in the penumbra region decreased, and the degeneration of axons at the superficial layers of parietal neocortex also attenuated after supplementing LC-PUFAs. A marked increment in DHA content in all types of phospholipids was obtained in the forebrain neuronal membrane fraction of supplemented rats. It is concluded that fish oil LC-PUFAs, first of all DHA, is responsible for the neuroprotective action on developing cholinergic neurons against glutamate cytotoxicity.

Chronic excess of corticosterone increases serotonergic fibre degeneration in aged rats.

Evidence is presented for the potentiating role of corticosterone on axonal degeneration of serotonergic neurones during ageing. Aged rats, 24 months old, were implanted subcutaneously with 2 x 100 mg pellets of corticosterone. Serotonergic and cholinergic (ChAT- and NADPHd-positive) fibre degenerations in the anteroventral thalamic nucleus (AVT) were measured 2 months after corticosterone implantation. Numbers of immunoreactive serotonergic raphe and mesolimbic cholinergic neurones were also quantified. Basal plasma corticosterone and adrenocorticotropin (ACTH) concentrations were assayed at 2, 4, 6, and 8 weeks after implantation in the plasma and at 1, 2, 4 and 6 weeks in urine. The degree of serotonergic fibre aberrations in the AVT increased significantly after corticosterone exposure, while that of ChAT-positive and NADPHd-stained axon aberrations showed a modest but nonsignificant increase. A positive correlation between the magnitudes of serotonergic and cholinergic fibre aberrations appeared in the AVT, but only in the corticosterone-treated rats. The number of serotonin immunopositive neurones in the raphe nuclei after corticosterone decreased marginally, while that of mesopontine ChAT-positive neurones was not influenced. Measurements of basal plasma corticosterone and ACTH, as well as urine corticosterone, revealed that the steroid implantation increased the plasma corticosterone level for at least 4 weeks and decreased ACTH level for at least 6 weeks. By the week 8, the pituitary-adrenal function was apparently restored. However, at sacrifice, both the weight of adrenal glands and that of thymus remained reduced, indicating the long-lasting effects of corticosterone on target tissues. It is concluded that the raphe serotonergic neurones and their projecting fibres are sensitive to corticosterone excess in aged rats and become more vulnerable to degeneration processes than under normal ageing conditions. Cholinergic neurones of brainstem origin, which also express massive NADPHd activity, are more resistant against corticosterone, but their axon degeneration correlates to serotonergic fibre degeneration.

Cutaneous lymphatic amyloid deposits in "Hungarian-type" familial transthyretin amyloidosis: a case report.

Multiple transthyretin (TTR) mutations have recently been identified and implicated in the development of familial systemic amyloidoses, but early diagnosis of these disorders is still largely unresolved. We investigated the presence and tissue distribution of TTR-derived amyloid in skin biopsies of a 59-year-old woman carrying the "Hungarian-type" mutation of TTR (Asp18Gly). Clinical symptoms involved severe central nervous system dysfunction without signs of polyneuropathy, also referred to as the "central form" of TTR-related systemic amyloidosis. Skin biopsy was also evaluated as a tool in order to diagnose this type of TTR amyloidosis. Biopsy samples were collected from the infra-axillary region. Light microscopy using Congo red and polarized light was used to diagnose amyloid deposits. Subsequently, electron microscopic analysis was performed to correlate the amyloid deposits with vicinal dermal structures. The amyloid class was determined by means of immunocytochemistry. TTR amyloid was primarily localized to lymphatic microvessels in the present case, whereas arterioles were devoid of TTR amyloid deposits. In addition, the well-known association of TTR amyloid with neural structures along the erector pilorum and around the sebaceous and serosal (sweat) glands was also evident. Electron microscopic analysis of amyloid deposits revealed characteristic amyloid fibrils that were irregular in shape, and exhibited a heterogeneous density and a random deposition pattern. Immunocytochemistry confirmed the cutaneous accumulation of TTR amyloid. In conclusion, amyloid deposits were abundantly present in the skin of a patient with "Hungarian-type" TTR amyloidosis; skin biopsy seems to be appropriate for the diagnosis of this disorder. We showed that besides the erector pilorum, sweat glands and nerve terminals, lymphatic microvessels are also severely infiltrated by TTR amyloid. Whether these pathological alterations can exclusively be found in "Hungarian-type" TTR amyloidosis should still be investigated. If such changes are not specific for the Asp18Gly mutation, they may be considered as diagnostic markers for "central" TTR amyloid disorders.

17beta-estradiol enhances cortical cholinergic innervation and preserves synaptic density following excitotoxic lesions to the rat nucleus basalis magnocellularis.

Estradiol exerts beneficial effects on neurodegenerative disorders associated with the decline of cognitive performance. The present study was designed to further investigate the effect of 17beta-estradiol on learning and memory, and to evaluate its neuroprotective action on cholinergic cells of the nucleus basalis magnocellularis, a neural substrate of cognitive performance. Female rats were ovariectomized at an age of 6 months. Three weeks later they received injections of either a mid-physiological dose of 17beta-estradiol or vehicle (oil), every other day for 2 weeks. The effect of estradiol on cognitive performance was tested in two associative learning paradigms. In the two-way active shock avoidance task estradiol-replaced animals learned significantly faster, while in the passive shock avoidance test no differences were observed between the experimental groups. Subsequent unilateral infusion of N-methyl-D-aspartate in the nucleus basalis magnocellularis resulted in a significant loss of cholinergic neurons concomitant with the loss of their fibers invading the somatosensory cortex. Estradiol treatment did not affect the total number of choline-acetyltransferase-immunoreactive neurons and their coexpression of the p75 low-affinity neurotrophin receptor either contralateral or ipsilateral to the lesion. In contrast, cholinergic fiber densities in estradiol-treated animals were greater both in the contralateral and ipsilateral somatosensory cortices as was detected by quantitative choline-acetyltransferase and vesicular acetylcholine transporter immunocytochemistry. However, estradiol treatment did not affect the lesion-induced relative percentage loss of cholinergic fibers. A significant decline of synaptophysin immunoreactivity paralleled the cholinergic damage in the somatosensory cortex of oil-treated animals, whereas an almost complete preservation of synaptic density was determined in estradiol-treated rats. Our results indicate that estradiol treatment enhances the cortical cholinergic innervation but has no rescuing effect on cholinergic nerve cells in the basal forebrain against excitotoxic damage. Nevertheless, estradiol may restore or maintain synaptic density in the cerebral cortex following cholinergic fiber loss. This estradiol effect may outweigh the lack of cellular protection on cholinergic cells at the functional level.

Impaired Learning and Abnormal Open-field Behaviours of Rats After Early Postnatal Anoxia and the Beneficial Effect of the Calcium Antagonist Nimodipine.

Perinatal anoxia/hypoxia is considered a serious risk factor for normal brain development. Anoxia induced by repeated asphyxia at 2 and 4 days after birth resulted in a transient hyperactivity in the small open-field, and a behavioural depression in adult open-field activity of male Wistar rats. The same treatment impaired adult learning behaviour in pole-jumping conditioned avoidance and appetitively motivated hole-board test situations. The calcium entry blocker nimodipine (in doses of 3 and 10 mg/kg) prevented the anoxia-induced changes in orientation motility in the open-field tests and almost fully antagonized the learning deficit in the hole-board test. The behavioural deficit seen during acquisition of the pole-jumping conditioned avoidance response was ameliorated to a lesser degree. The results indicate that the maintenance of calcium homeostasis during the early postnatal phase of brain development is crucial to prevent anoxia-induced behavioural abnormalities.