Lina Ji

Elevated Immune Response in the Brain of Autistic Patients

UNLABELLED This study determined immune activities in the brain of ASD patients and matched normal subjects by examining cytokines in the brain tissue. Our results showed that proinflammatory cytokines (TNF-alpha, IL-6 and GM-CSF), Th1 cytokine (IFN-gamma) and chemokine (IL-8) were significantly increased in the brains of ASD patients compared with the controls. However the Th2 cytokines (IL-4, IL-5 and IL-10) showed no significant difference. The Th1/Th2 ratio was also significantly increased in ASD patients. CONCLUSION ASD patients displayed an increased innate and adaptive immune response through the Th1 pathway, suggesting that localized brain inflammation and autoimmune disorder may be involved in the pathogenesis of ASD.

Anti-amyloidogenic, anti-oxidant and anti-apoptotic role of gelsolin in Alzheimer's disease.

Fibrillar amyloid beta-protein (Aβ) is a major component of amyloid plaques in the brains of individuals with Alzheimer’s disease (AD) and of adults with Down syndrome (DS). Gelsolin, a cytoskeletal protein, is present both intracellularly (cytoplasmic form) and extracellularly (secretory form in biological fluids). These two forms of gelsolin differ from each other in length and in cysteinyl thiol groups. Previous studies from our and other groups have identified the anti-amyloidogenic role of gelsolin in AD. Our studies showed that both plasma and cytosolic gelsolin bind to Aβ, and that gelsolin inhibits the fibrillization of Aβ and solubilizes preformed fibrils of Aβ. Other studies have shown that peripheral administration of plasma gelsolin or transgene expression of plasma gelsolin can reduce amyloid load in the transgenic mouse model of AD. Our recent studies showed that gelsolin expression increases in cells in response to oxidative stress. Oxidative damage is considered a major feature in the pathophysiology of AD. Aβ not only can induce oxidative stress, but also its generation is increased as a result of oxidative stress. In this article, we review evidence of gelsolin as an anti-amyloidogenic agent that can reduce amyloid load by acting as an inhibitor of Aβ fibrillization, and as an antioxidant and anti-apoptotic protein.

Cytoplasmic gelsolin in pheochromocytoma-12 cells forms a complex with amyloid beta-protein

Gelsolin exists as secretory (plasma) and cytoplasmic forms. We have reported that plasma gelsolin binds to amyloid &bgr;-protein (A&bgr;), and inhibits its fibrillization. Others reported that peripheral administration or transgene expression of plasma gelsolin reduces amyloid load in transgenic mouse models of Alzheimers disease. Here, we report that the expression of cytoplasmic gelsolin in pheochromocytoma-12 cells increases after treatment with hydrogen peroxide. When synthetic A&bgr; was fortified with cell lysate, cytoplasmic gelsolin co-immunoprecipitated with A&bgr;. The results suggest that cytoplasmic gelsolin forms a complex with A&bgr; in a manner like plasma form, and it may also regulate A&bgr; fibrillization. This report indicates that structural differences between plasma and cytoplasmic gelsolin do not play a key role in their complex formation with A&bgr;.

Gelsolin is Proteolytically Cleaved in the Brains of Individuals with Alzheimer's Disease

Gelsolin, a multifunctional actin-binding protein, forms a complex with amyloid-beta protein and reduces the amyloid load in the transgenic mouse model of Alzheimers disease (AD). Gelsolin consists of six homologous domains, which have specific affinities for phosphatidylinositol 4, 5-bisphosphate, calcium, and actin. During apoptosis, gelsolin is cleaved by the caspase-3 resulting in a 48 kDa carboxyl-terminal fragment (gelsolin-CTF). We report here that gelsolin is significantly cleaved in the frontal cortex of individuals with AD as compared to age-matched controls. A positive correlation was observed between the appearance of gelsolin-CTF in frontal cortex and severity of AD. Gelsolin-CTF was also observed in apoptotic SH-SY5Y cells induced by H2O2 or calcium ionophore A23187. In addition, lipid peroxidation was increased in the frontal cortex of AD suggesting that oxidative stress occurs in AD brain. Taken together, these results suggest that there may be a link among oxidative stress, neuronal apoptosis, and gelsolin cleavage in AD.

Brain Region–Specific Decrease in the Activity and Expression of Protein Kinase A in the Frontal Cortex of Regressive Autism

Autism is a severe neurodevelopmental disorder that is characterized by impaired language, communication, and social skills. In regressive autism, affected children first show signs of normal social and language development but eventually lose these skills and develop autistic behavior. Protein kinases are essential in G-protein-coupled, receptor-mediated signal transduction and are involved in neuronal functions, gene expression, memory, and cell differentiation. We studied the activity and expression of protein kinase A (PKA), a cyclic AMP–dependent protein kinase, in postmortem brain tissue samples from the frontal, temporal, parietal, and occipital cortices, and the cerebellum of individuals with regressive autism; autistic subjects without a clinical history of regression; and age-matched developmentally normal control subjects. The activity of PKA and the expression of PKA (C-α), a catalytic subunit of PKA, were significantly decreased in the frontal cortex of individuals with regressive autism compared to control subjects and individuals with non-regressive autism. Such changes were not observed in the cerebellum, or the cortices from the temporal, parietal, and occipital regions of the brain in subjects with regressive autism. In addition, there was no significant difference in PKA activity or expression of PKA (C-α) between non-regressive autism and control groups. These results suggest that regression in autism may be associated, in part, with decreased PKA-mediated phosphorylation of proteins and abnormalities in cellular signaling.

Upregulation of Cytoplasmic Gelsolin, an Amyloid-β-Binding Protein, Under Oxidative Stress Conditions: Involvement of Protein Kinase C

We have previously reported that gelsolin, an actin binding protein, regulates the fibrillization of amyloid-beta protein. We report here that the expression of cytoplasmic gelsolin (cgelsolin) was upregulated in a concentration-dependent manner when SH-SY5Y, PC-12, and HEK-293 cells were subjected to oxidative stress by treatment with hydrogen peroxide (H(2)O(2). Further studies were done to elucidate the mechanism involved in the regulation of c-gelsolin expression in cells. Pretreatment of cells with cycloheximide (an inhibitor of protein synthesis) resulted in significant inhibition of H(2)O(2)induced c-gelsolin expression, suggesting the possible de novo synthesis of c-gelsolin in cells. Staurosporine, a potent inhibitor of a variety of protein kinases including protein kinase C (PKC), also blocked the H(2)O(2)induced expression of cgelsolin. However, both H(2)O(2) and staurosporine activated the mitogen-activated protein kinases (MAPKs), i.e., c-Jun N-terminal kinase, P38, and extracellular signal-regulated kinase. Pretreatment of cells with Calphostin C, an inhibitor of PKC, blocked the upregulation of cgelsolin induced by H(2)O(2), while specific inhibitors of MAPKs had no effect on c-gelsolin expression, suggesting that MAPKs may not be involved in H(2)O(2)mediated upregulation of cgelsolin. On the other hand, phorbol-12-myristate-13-acetate, an activator of PKC, induced the expression of c-gelsolin. Our studies indicate that c-gelsolin is upregulated in cells under oxidative stress, and PKC is involved in its upregulation. It is suggested that activators of PKC that induce gelsolin expression may have therapeutic significance in Alzheimers disease.

Reduced Activity of Protein Kinase C in the Frontal Cortex of Subjects with Regressive Autism: Relationship with Developmental Abnormalities

Autism is a neurodevelopmental disorder with unknown etiology. In some cases, typically developing children regress into clinical symptoms of autism, a condition known as regressive autism. Protein kinases are essential for G-protein-coupled receptor-mediated signal transduction, and are involved in neuronal functions, gene expression, memory, and cell differentiation. Recently, we reported decreased activity of protein kinase A (PKA) in the frontal cortex of subjects with regressive autism. In the present study, we analyzed the activity of protein kinase C (PKC) in the cerebellum and different regions of cerebral cortex from subjects with regressive autism, autistic subjects without clinical history of regression, and age-matched control subjects. In the frontal cortex of subjects with regressive autism, PKC activity was significantly decreased by 57.1% as compared to age-matched control subjects (p = 0.0085), and by 65.8% as compared to non-regressed autistic subjects (p = 0.0048). PKC activity was unaffected in the temporal, parietal and occipital cortices, and in the cerebellum in both autism groups, i.e., regressive and non-regressed autism as compared to control subjects. These results suggest brain region-specific alteration of PKC activity in the frontal cortex of subjects with regressive autism. Further studies showed a negative correlation between PKC activity and restrictive, repetitive and stereotyped pattern of behavior (r= -0.084, p = 0.0363) in autistic individuals, suggesting involvement of PKC in behavioral abnormalities in autism. These findings suggest that regression in autism may be attributed, in part, to alterations in G-protein-coupled receptor-mediated signal transduction involving PKA and PKC in the frontal cortex.

Relationship Between Proteolytically Cleaved Gelsolin and Levels of Amyloid-β Protein in the Brains of Down Syndrome Subjects

Gelsolin plays an important role in the fibrillogenesis of amyloid-β (Aβ). It binds to Aβ and inhibits its fibrillization. Gelsolin also gets proteolytically cleaved under apoptotic conditions. We recently reported a correlation between proteolytic product of gelsolin (carboxyl-terminal fragment of gelsolin, gelsolin-CTF) and severity of Alzheimers disease. In this study, we report that gelsolin is cleaved in the brains of adult individuals (age, 43-63 years) with Down syndrome (DS), and that levels of gelsolin-CTF are significantly increased in the frontal cortex of adult DS subjects as compared to age-matched control subjects. Gelsolin-CTF was not observed in frontal cortex of young DS (age 0.5-23 years) and age-matched control subjects. In addition, the levels of both soluble and total Aβ40 and Aβ42 were significantly increased in the frontal cortex of adult DS patients as compared to age-matched control subjects. A positive relationship was observed between gelsolin-CTF in frontal cortex of DS, and the levels of soluble Aβ40 (r2= 0.7820, p < 0.01) and Aβ42 (r2 = 0.8179, p < 0.01). Experiments with recombinant full-length gelsolin and its N-terminal and C-terminal fragments showed that similar to gelsolin, proteolytic fragments of gelsolin can also interact with soluble synthetic Aβ. The post-translational modification of gelsolin proteins may not be essential as these proteins (overexpressed in Escherichia coli) were able to form complexes with Aβ. These results suggest that there may be a relationship between proteolytic cleavage of gelsolin and increased Aβ in the brain. Since soluble non-fibrillar forms of Aβ are neurotoxic, they may be involved in apoptosis and proteolysis of gelsolin.

Gelsolin levels are increased in the brain as a function of age during normal development in children that are further increased in Down syndrome.

Neuronal dysfunctions in several neurodegenerative diseases such as Down syndrome (DS) have been linked to oxidative stress. In this study, we observed that lipid peroxidation, a marker of oxidative stress, is significantly increased in the frontal cortex of brains of individuals with DS as compared with control subjects. We report here that gelsolin levels are increased in the frontal cortex of individuals with DS as compared with controls during early developmental ages (5 to 13 y). Interestingly, the levels of gelsolin in the frontal cortex were increased as a function of age in both DS and control subjects. Because cytoplasmic gelsolin has 5 free thiol groups (cysteine), and its levels are increased in response to oxidative stress, we propose that gelsolin may serve as an antioxidant protein.

Calcium Induces Expression of Cytoplasmic Gelsolin in SH-SY5Y and HEK-293 Cells

Gelsolin plays an important role in the regulation of amyloid beta-protein fibrillogenesis. We report here that calcium ionophore A23187 induces the expression of cytoplasmic gelsolin (c-gelsolin), and that protein kinase C (PKC) is involved in the up-regulation of c-gelsolin. In the presence of calcium, both SH-SY5Y and HEK-293 cells upon treatment with A23187 showed an increase in c-gelsolin expression in a concentration-dependent manner. Calcium-mediated up-regulation of c-gelsolin was inhibited by cycloheximide (a general inhibitor of protein synthesis). When cells were pretreated with staurosporine (an inhibitor of a variety of protein kinases including PKC), the up-regulation of c-gelsolin induced by A23187 was inhibited. Calphostin C, an inhibitor of PKC, blocked the up-regulation of c-gelsolin induced by A23187, while inhibitors of mitogen-activated protein kinases had no effect on c-gelsolin expression. In addition, phorbol-12-myristate-13-acetate, an activator of PKC, up-regulated c-gelsolin expression. These results suggest that calcium mediates up-regulation of c-gelsolin in a PKC-dependent manner.