Localization of metallothionein-I and -II in hypertrophic astrocytes in brain lesions of dogs

Clinical and imaging associations for non-ketotic hyperglycemic chorea: a case-control study

Background

The non-ketotic hyperglycemic chorea (NKHC) was a rare complication for patients with diabetes mellitus, but not been well studied. In the present research, we aimed to investigate the clinical and imaging characteristics of NKHC and explore the potential association.

Methods

We performed a case-control study with patients diagnosed as NKHC. The patients with group of NKHC were retrospectively recruited, while the matched group were set to screened patients with diabetes mellitus but no NKHC at a 1:3 ratio. The clinical and imaging data were collected for all the participants of the two groups. Firstly, Correlation analysis was conducted to test the difference of all the variables between the NKHC group and matched group. Then, the putative associated factors for NKHC were further identified.

Results

Eleven men and 9 women with NKHC and 60 matched participants were analyzed. The mean age of the NKHC group was 68.5 ± 14.9 years. Participants with NKHC were more likely to have a higher glycosylated hemoglobin (HbA1c) level (13 ± 2.82 vs. 10.57 ± 2.71, P<0.001), and a higher frequency of renal dysfunction (estimated glomerular filtration rates <60 ml/min/1.73m2) (55% vs. 20%, P=0.005). Logistic regression analyses showed that both higher HbA1c and renal dysfunction were significantly correlated with NKHC.

Conclusion

A higher value of HbA1c and renal dysfunction may be associated with the occurrence of NKHC.

Metallothionein I/II Expression and Metal Ion Levels in Correlation with Amyloid Beta Deposits in the Aged Feline Brain

Brain aging has been correlated with high metallothionein I-II (MT-I/II) expression, iron and zinc dyshomeostasis, and Aβ deposition in humans and experimental animals. In the present study, iron and zinc accumulation, the expression of MT-I/II and Aβ42, and their potential association with aging in the feline brain were assessed. Tissue sections from the temporal and frontal grey (GM) and white (WM) matter, hippocampus, thalamus, striatum, cerebellum, and dentate nucleus were examined histochemically for the presence of age-related histopathological lesions and iron deposits and distribution. We found, using a modified Perl's/DAB method, two types of iron plaques that showed age-dependent accumulation in the temporal GM and WM and the thalamus, along with the age-dependent increment in cerebellar-myelin-associated iron. We also demonstrated an age-dependent increase in MT-I/II immunoreactivity in the feline brain. In cats over 7 years old, Aβ immunoreactivity was detected in vessel walls and neuronal somata; extracellular Aβ deposits were also evident. Interestingly, Aβ-positive astrocytes were also observed in certain cases. ICP-MS analysis of brain content regarding iron and zinc concentrations showed no statistically significant association with age, but a mild increase in iron with age was noticed, while zinc levels were found to be higher in the Mature and Senior groups. Our findings reinforce the suggestion that cats could serve as a dependable natural animal model for brain aging and neurodegeneration; thus, they should be further investigated on the basis of metal ion concentration changes and their effects on aging.

DNA Damage in Nasal and Brain Tissues of Canines Exposed to Air Pollutants Is Associated with Evidence of Chronic Brain Inflammation and Neurodegeneration

Acute, subchronic, or chronic exposures to particulate matter (PM) and pollutant gases affect people in urban areas and those exposed to fires, disasters, and wars. Respiratory tract inflammation, production of mediators of inflammation capable of reaching the brain, systemic circulation of PM, and disruption of the nasal respiratory and olfactory barriers are likely in these populations. DNA damage is crucial in aging and in age-associated diseases such as Alzheimer's disease. We evaluated apurinic/apyrimidinic (AP) sites in nasal and brain genomic DNA, and explored by immunohistochemistry the expression of nuclear factor NF κB p65, inducible nitric oxide synthase (iNOS), cyclo-oxygenase 2 (COX2), metallothionein I and II, apolipoprotein E, amyloid precursor protein (APP), and beta-amyloid1-42 in healthy dogs naturally exposed to urban pollution in Mexico City. Nickel (Ni) and vanadium (V) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Forty mongrel dogs, ages 7 days—10 years were studied (14 controls from Tlaxcala and 26 exposed to urban pollution in South West Metropolitan Mexico City (SWMMC)). Nasal respiratory and olfactory epithelium were found to be early pollutant targets. Olfactory bulb and hippocampal AP sites were significantly higher in exposed than in control age matched animals. Ni and V were present in a gradient from olfactory mucosa > olfactory bulb > frontal cortex. Exposed dogs had (a) nuclear neuronal NF κB p65, (b) endothelial, glial and neuronal iNOS, (c) endothelial and glial COX2, (d) ApoE in neuronal, glial and vascular cells, and (e) APP and β amyloid1-42 in neurons, diffuse plaques (the earliest at age 11 months), and in subarachnoid blood vessels. Increased AP sites and the inflammatory and stress protein brain responses were early and significant in dogs exposed to urban pollution. Oil combustion PM-associated metals Ni and V were detected in the brain. There was an acceleration of Alzheimer's-type pathology in dogs chronically exposed to air pollutants. Respiratory tract inflammation and deteriorating olfactory and respiratory barriers may play a role in the observed neuropathology. These data suggest that Alzheimer's disease may be the sequela of air pollutant exposures and the resulting systemic inflammation.

Effect of astrocyte-targeted production of IL-6 on traumatic brain injury and its impact on the cortical transcriptome

Interleukin-6 (IL-6) is one of the key players in the response of the brain cortex to injury. We have described previously that astrocyte-driven production of IL-6 (GFAP-IL6) in transgenic mice, although causing spontaneous neuroinflammation and long term damage, is beneficial after an acute (freeze) injury in the cortex, increasing healing and decreasing oxidative stress and apoptosis. To determine the transcriptional basis for these responses here we analyzed the global gene expression profile of the cortex, at 0 (unlesioned), 1 or 4 days post lesion (dpl), in both GFAP-IL6 mice and their control littermates. GFAP-IL6 mice showed an increase in genes associated with the inflammatory response both at 1 dpl (Iftm1, Endod1) and 4 dpl (Gfap, C4b), decreased expression of proapoptotic genes (i.e. Gadd45b, Clic4, p21) as well as reduced expression of genes involved in the control of oxidative stress (Atf4). Furthermore, the presence of IL-6 altered the expression of genes involved in hemostasis (Vwf), cell migration and proliferation (Cap2), and synaptic activity (Vamp2). All these changes in gene expression could underlie the phenotype of the GFAP-IL6 mice after injury, but many other possible factors were also identified in this study, highlighting the utility of this approach for deciphering new pathways orchestrated by IL-6.

Marcação imunoistoquímica da expressão astrocitária de proteína glial fibrilar ácida e de vimentina no sistema nervoso central de cães com cinomose

Uma vez que muitos dos aspectos envolvidos na patogenia dos processos desmielinizantes do sistema nervoso central (SNC) são ainda pouco esclarecidos e que os astrócitos parecem estar envolvidos na mediação de tais processos, este estudo analisou morfologicamente a participação astrocitária na desmielinização do SNC por meio da marcação imunoistoquímica de duas proteínas dos filamentos intermediários astrocitários - a proteína glial fibrilar ácida (GFAP) e a vimentina (VIM) -, comparando amostras de cerebelo e de tronco encefálico de oito cães com cinomose e de dois cães normais, de diferentes raças e com idades entre um e quatro anos. Cortes histológicos dos tecidos foram submetidos à marcação pelo método indireto da avidina-biotina-peroxidase (ABC) e a reatividade astrocitária, observada em microscopia de luz, foi quantificada em um sistema computacional de análise de imagens. Observou-se, na maioria dos cortes de animais doentes, a presença de lesões degenerativas compatíveis com desmielinização. A marcação para a GFAP e para a VIM foi mais intensa nos animais com cinomose do que nos animais normais, especialmente nas regiões circunventriculares e nas adjacentes às áreas de degeneração tecidual. Não houve diferença significativa entre a imunomarcação (GFAP e VIM) dos animais com cinomose com e sem infiltração inflamatória da substância branca do cerebelo. O aumento da imunorreatividade dos astrócitos para a GFAP e a reexpressão de VIM nas áreas lesionais indicam o envolvimento astrocitário na resposta do tecido nervoso às lesões desmielinizantes induzidas pelo vírus da cinomose (CDV) no SNC.

Immunohistochemical and Ultrastructural Findings Related to the Blood–Brain Barrier in the Blood Vessels of the Cerebral White Matter in Aged Dogs

Immunohistochemical and ultrastructural analysis of canine brain tissue was performed to determine whether cerebral capillaries, which form the blood--brain barrier (BBB), display age-related morphological changes in the white matter (WM). A slight decrease in laminin immunolabelling was detected in the basement membranes (BMs) of capillaries in the WM of old dogs, as compared with that in the brains of young dogs. The Prussian blue DAB post-DAB enhancement method detected iron present in macrophages and astrocytes in the WM. Copper/zinc superoxide dismutase, MT-I and -II and MT-III immunoreactivity was detected mainly in reactive astrocytes in the WM of aged dogs. Ultrastructurally, collagen-like fibrils were detected to a variable degree in the spaces between the BMs of capillary endothelial cells and astrocytes in the WM of some aged dogs. These results suggest that age-related morphological changes in capillaries of the WM are associated with BBB dysfunction, leading to the exudation of serum constituents, including harmful substances (e.g., iron), thereby causing tissue damage by oxidative injury. These factors may play a role in the pathogenesis of severe degenerative changes in the WM of aged dogs.

Roles of the metallothionein family of proteins in the central nervous system

Metallothioneins (MTs) constitute a family of proteins characterized by a high heavy metal [Zn(II), Cu(I)] content and also by an unusual cysteine abundance. Mammalian MTs are comprised of four major isoforms designated MT-1 trough MT-4. MT-1 and MT-2 are expressed in most tissues including the brain, whereas MT-3 (also called growth inhibitory factor) and MT-4 are expressed predominantly in the central nervous system and in keratinizing epithelia, respectively. All MT isoforms have been implicated in disparate physiological functions, such as zinc and copper metabolism, protection against reactive oxygen species, or adaptation to stress. In the case of MT-3, an additional involvement of this isoform in neuromodulatory events and in the pathogenesis of Alzheimer's disease has also been suggested. It is essential to gain insight into how MTs are regulated in the brain in order to characterize MT functions, both in normal brain physiology, as well as in pathophysiological states. The focus of this review concerns the biology of the MT family in the context of their expression and functional roles in the central nervous system.

Astrocyte phenotype and prevention against oxidative damage in neurotoxicity

Astrocytes possess a potent array of protective systems. These are chiefly targeted against oxidised products and radicals, which are frequently present in increased amounts following exposure of nervous tissue to a range of toxic insults. Following exposure to the toxic chemicals astrocytes commonly respond by alteration in phenotype with upregulation of a large number of molecules, including those controlling the protective systems. This article summarizes evidence, largely obtained from in vitro studies, which supports the concept that some of the changes in astrocyte phenotype are associated with increased protection against the cytotoxicity caused by the oxidative damage that results from exposure to range of neurotoxicants.

Localization of metallothioneins-I & -II and -III in the brain of aged dog

Localization of metallothionein (MT) -I & -II and MT-III and its significance in the brain aging in dogs were examined using immunohistological and molecular pathological techniques. MT-I & -II immunohistochemistry showed positive staining in the hypertrophic astrocytes throughout the aged dog brains; these MT-I & -II immunoreactive astrocytes were predominant in the cerebral cortex and around the blood vessels in the brain. These findings dominated in the brain regions with severe age-related morphological changes. In situ hybridization using MT-I mRNA riboprobes also demonstrated signals for MT-I mRNA in these hypertrophic astrocytes. Immunohistochemistry using a guinea pig antiserum against a synthetic polypeptide of canine MT-III demonstrated positive MT-III immunoreactivity predominantly in neurons in the Zn-rich regions such as hippocampus and parahippocampus. The findings were supported by in situ hybridization using MT-III mRNA riboprobes. Both MT-III immunoreactivity and signals for MT-III mRNA were demonstrated in neurons in the brain regardless of the intensity of the age-related changes. These results suggest, first, MT-I & -II may be induced in relation to the progress of the age-related morphological changes in the brain, playing an important role in the protection of the brain tissue from the toxic insults responsible for the brain aging, and second, MT-III may play a role in maintenance of Zn-related essential functions of the brain.