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Resistance to the current Androgen Receptor Signaling Inhibitor (ARSI) therapies has led to higher incidences of therapy-induced neuroendocrine-like prostate cancer (t-NEPC). This highly aggressive subtype with predominant small-cell-like characteristics is resistant to taxane chemotherapies and has a dismal overall survival. t-NEPCs are mostly treated with platinum-based drugs with a combination of etoposide or taxane and have less selectivity and high systemic toxicity, which often limit their clinical potential. During t-NEPC transformation, adenocarcinomas lose their luminal features and adopt neuro-basal characteristics. Whether the adaptive neuronal characteristics of t-NEPC are responsible for such taxane resistance remains unknown. Pathway analysis from patient gene-expression databases indicates that t-NEPC upregulates various neuronal pathways associated with enhanced cellular networks. To identify transcription factor(s) (TF) that could be important for promoting the gene expression for neuronal characters in t-NEPC, we performed ATAC-Seq, acetylated-histone ChIP-seq, and RNA-seq in our NE-like cell line models and analyzed the promoters of transcriptionally active and significantly enriched neuroendocrine-like (NE-like) cancer-specific genes. Our results indicate that Pax5 could be an important transcription factor for neuronal gene expression and specific to t-NEPC. Pathway analysis revealed that Pax5 expression is involved in axonal guidance, neurotransmitter regulation, and neuronal adhesion, which are critical for strong cellular communications. Further results suggest that depletion of Pax5 disrupts neurite-mediated cellular communication in NE-like cells and reduces surface growth factor receptor activation, thereby, sensitizing them to docetaxel therapies. Moreover, t-NEPC-specific hydroxymethylation of Pax5 promoter CpG islands favors Pbx1 binding to induce Pax5 expression. Based on our study, we concluded that continuous exposure to ARSI therapies leads to epigenetic modifications and Pax5 activation in t-NEPC, which promotes the expression of genes necessary to adopt taxane-resistant NE-like cancer. Thus, targeting the Pax5 axis can be beneficial for reverting their taxane sensitivity.
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Docetaxel , Resistencia a Medicamentos Antineoplásicos , Fator de Transcrição PAX5 , Neoplasias da Próstata , Humanos , Masculino , Docetaxel/farmacologia , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/genética , Neoplasias da Próstata/patologia , Neoplasias da Próstata/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Linhagem Celular Tumoral , Fator de Transcrição PAX5/metabolismo , Fator de Transcrição PAX5/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Antineoplásicos/farmacologia , Carcinoma Neuroendócrino/metabolismo , Carcinoma Neuroendócrino/tratamento farmacológico , Carcinoma Neuroendócrino/patologia , Carcinoma Neuroendócrino/genética , Regiões Promotoras Genéticas/genética , Receptores Androgênicos/metabolismo , Receptores Androgênicos/genéticaRESUMO
Prostate cancer, one of the most frequently diagnosed cancers in men, leads to significant mortality worldwide. Its study is important due to the complexity and diversity in its progression, highlighting the urgent need for improved therapeutic strategies. This chapter probes into the genetic and epigenetic factors influencing prostate cancer progression, underscoring the importance of understanding the disease's molecular fundamentals for the development of targeted therapies. It specifically reviews the role of key genetic mutations in genes such as Androgen Receptor, TP53, SPOP, FOXA1 and PTEN which are crucial for the disease onset and a progression. Furthermore, it examines the impact of epigenetic modifications, including DNA methylation and histone modification, which contribute to the cancer's progression by affecting gene expression and cellular behavior. Further, in this chapter we delve into the underlying signaling mechanism, the advancements in targeting genetic and epigenetic alterations in prostate cancer. These findings have revealed promising targets for therapeutic advancements, aiming to understand and identify promising avenues for future therapies. This chapter improves our current understanding of prostate cancer genetic and epigenetic landscape, emphasizing the necessity of advancing our knowledge to refine and expand treatment options for prostate cancer patients.
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Epigênese Genética , Neoplasias da Próstata , Humanos , Masculino , Neoplasias da Próstata/genética , Neoplasias da Próstata/patologia , Epigênese Genética/genética , Metilação de DNA/genética , Regulação Neoplásica da Expressão GênicaRESUMO
Various substances possessing radiation scavenging properties, known as radioprotectors, play a crucial role in shielding organisms from the harmful effects of ionizing radiation (IR) by preventing cellular damage caused by free radicals. Initially, synthetic radioprotectors were developed using thiol synthetic compounds. However, among these, only amifostine (WR-2721) underwent clinical testing as a radioprotector. Various composites with different chemical structures other than thiol compounds were also investigated. However, synthetic radioprotectors are known to be associated with severe side effects, which lead to an inclination towards natural substances. Plants and natural products have emerged as promising sources of radioprotectors, renowned for their non-toxic nature across a broad range of doses and their cost-effectiveness. Radioprotectors are employed in diverse pharmaceutical approaches to mitigate the toxicities induced by radiation. The present review encompasses a detailed account of various synthetic and naturally occurring compounds possessing radioprotective properties, and different investigations related to their radioprotective action, ranging from free radicals scavenging to gene therapy, have also been precisely covered. Numerous radioprotectors have different mechanisms of action, and have proven benefits of naturally occurring compounds over chemically synthesized ones.
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Thyroid hormones (TH) are vital for brain functions, while TH deficiency, i.e. hypothyroidism, induces neurological impairment in children and adults. Cerebellar neuronal apoptosis and motor deficits are crucial events in hypothyroidism; however, the underlying mechanism is less-known. Using a methimazole-treated hypothyroidism rat model, we investigated cerebellar autophagy, growth factor, and apoptotic mechanisms that participate in motor functions. We first identified that methimazole up-regulated cerebellar autophagy, marked by enhanced LC3B-II, Beclin-1, ATG7, ATG5-12, p-AMPKα/AMPKα, and p62 degradation as well as reduced p-AKT/AKT, p-mTOR/mTOR, and p-ULK1/ULK1 in developing and young adult rats. We probed upstream effectors of this abnormal autophagy and detected a methimazole-induced reduction in cerebellar phospho-epidermal growth factor receptor (p-EGFR)/EGFR and heparin-binding EGF-like growth factor (HB-EGF). Here, while a thyroxine-induced TH replenishment alleviated autophagy process and restored HB-EGF/EGFR, HB-EGF treatment regulated AKT-mTOR and autophagy signaling in the cerebellum. Moreover, neurons of the rat cerebellum demonstrated this reduced HB-EGF-dependent increased autophagy in hypothyroidism. We further checked whether the above events were related to cerebellar neuronal apoptosis and motor functions. We detected that comparable to thyroxine, treatment with HB-EGF or autophagy inhibitor, 3-MA, reduced methimazole-induced decrease in Nissl staining and increase in c-Caspase-3 and TUNEL-+ve apoptotic count of cerebellar neurons. Additionally, 3-MA, HB-EGF, and thyroxine attenuated the methimazole-induced diminution in riding time on rota-rod and grip strength for the motor performance of rats. Overall, our study enlightens HB-EGF/EGFR-dependent autophagy mechanism as a key to cerebellar neuronal loss and functional impairments in developmental hypothyroidism, which may be inhibited by HB-EGF and 3-MA treatments, like thyroxine.
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Hipotireoidismo , Proteínas Proto-Oncogênicas c-akt , Animais , Ratos , Autofagia , Cerebelo/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Receptores ErbB/metabolismo , Fator de Crescimento Semelhante a EGF de Ligação à Heparina/metabolismo , Hipotireoidismo/induzido quimicamente , Metimazol/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Tiroxina , Serina-Treonina Quinases TOR/metabolismoRESUMO
Resistance to the current Androgen Receptor Signaling Inhibitor (ARSI) therapies has led to higher incidences of therapy-induced neuroendocrine-like prostate cancer (t-NEPC). This highly aggressive subtype with predominant small cell-like characteristics is resistant to taxane chemotherapies and has a dismal overall survival. t-NEPCs are mostly treated with platinum-based drugs with a combination of etoposide or taxane and have less selectivity and high systemic toxicity, which often limit their clinical potential. During t-NEPC transformation, adenocarcinomas lose their luminal features and adopt neuro-basal characteristics. Whether the adaptive neuronal characteristics of t-NEPC are responsible for such taxane resistance remains unknown. Pathway analysis from patient gene-expression databases indicates that t-NEPC upregulates various neuronal pathways associated with enhanced cellular networks. To identify transcription factor(s) (TF) that could be important for promoting the gene expression for neuronal characters in t-NEPC, we performed ATAC-Seq, acetylated-histone ChIP-seq, and RNA-seq in our NE-like cell line models and analyzed the promoters of transcriptionally active and significantly enriched neuroendocrine-like (NE-like) cancer-specific genes. Our results indicate that Pax5 could be an important transcription factor for neuronal gene expression and specific to t-NEPC. Pathway analysis revealed that Pax5 expression is involved in axonal guidance, neurotransmitter regulation, and neuronal adhesion, which are critical for strong cellular communications. Further results suggest that depletion of Pax5 disrupts cellular interaction in NE-like cells and reduces surface growth factor receptor activation, thereby, sensitizing them to taxane therapies. Moreover, t-NEPC specific hydroxymethylation of Pax5 promoter CpG islands favors Pbx1 binding to induce Pax5 expression. Based on our study, we concluded that continuous exposure to ARSI therapies leads to epigenetic modifications and Pax5 activation in t-NEPC, which promotes the expression of genes necessary to adopt taxane-resistant NE-like cancer. Thus, targeting the Pax5 axis can be beneficial for reverting their taxane sensitivity.
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CONTEXT: Posterior reversible encephalopathy syndrome (PRES) is a clinical-radiological entity characterized by acute neurological symptoms with reversible subcortical vasogenic brain edema. One of the most common risk factors is pre-eclampsia/eclampsia. AIMS: This study aimed to compare the clinical and radiological characteristics of PRES with those without PRES in patients with pre-eclampsia/eclampsia and attempts to find independent predictors of PRES. METHODS AND MATERIALS: This was a single-center, retrospective study. Fifty-three female patients admitted to the Department of Obstetrics & Gynaecology, AIIMS Rishikesh between 2018 and 2021 with severe pre-eclampsia/eclampsia were included. Brain imaging was done to confirm the diagnosis of PRES. Baseline characteristics between patients whose imaging was suggestive and not suggestive of PRES were compared. RESULTS: Fifty-three patients with pre-eclampsia/eclampsia were included in the analysis. The median age and period of gestation of the study population were 28 (range 19-37) years and 36.6 (range 24.2-41.5) weeks respectively. Twelve patients (22.6%) had eclampsia, and 41 (87.4%) had pre-eclampsia of which 28 (52.8%) had severe pre-eclampsia. Twelve patients were diagnosed with PRES. Patients with PRES were significantly younger with a median age of 23 [range 20-30 vs 29 (range 19-37; p = 0.005) years], and more likely to be primiparous (91.7% vs 36.6%; p < 0.001) compared to those without PRES. PRES was significantly more common in patients with eclampsia. Of 12 patients with eclampsia, nine (75%) had evidence of PRES. The maternal and fetal outcome, however, was similar in both groups. Patients with PRES were more likely to have poor sensorium compared to those without PRES (83.3% vs 5.3%; p < 0.01). Eclampsia was found in the independent predictor of PRES (odds ratio, OR 20.9; 95% confidence interval, CI 3.0-147.0, p = 0.02). CONCLUSIONS: In this study, patients with PRES were younger and significantly more likely to be primiparous and have eclampsia compared to those without PRES. Headache followed by seizures and altered sensorium were the most common clinical manifestations and subcortical white matter hyperintensities involving fronto-parieto-occipital lobes were the most common radiological finding. Eclampsia emerged as an independent risk factor for PRES.
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Neuroendocrine (NE)-like tumors secrete various signaling molecules to establish paracrine communication within the tumor milieu and to create a therapy-resistant environment. It is important to identify molecular mediators that regulate this secretory phenotype in NE-like cancer. The current study highlights the importance of a cell surface molecule, Neuropilin-2 (NRP2), for the secretory function of NE-like prostate cancer (PCa). Our analysis on different patient cohorts suggests that NRP2 is high in NE-like PCa. We have developed cell line models to investigate NRP2's role in NE-like PCa. Our bioinformatics, mass spectrometry, cytokine array, and other supporting experiments reveal that NRP2 regulates robust secretory phenotype in NE-like PCa and controls the secretion of factors promoting cancer cell survival. Depletion of NRP2 reduces the secretion of these factors and makes resistant cancer cells sensitive to chemotherapy in vitro and in vivo. Therefore, targeting NRP2 can revert cellular secretion and sensitize PCa cells toward therapy.
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Neuropilina-2 , Neoplasias da Próstata , Linhagem Celular Tumoral , Humanos , Masculino , Neuropilina-2/metabolismo , Fenótipo , Próstata/metabolismo , Neoplasias da Próstata/genética , Transdução de Sinais/fisiologiaRESUMO
Neuropilins (NRPs) are transmembrane proteins involved in vascular and nervous system development by regulating angiogenesis and axon guidance cues. Several published reports have established their role in tumorigenesis. NRPs are detectable in tumor cells of several cancer types and participate in cancer progression. NRP2 is also expressed in endothelial and immune cells in the tumor microenvironment and promotes functions such as lymphangiogenesis and immune suppression important for cancer progression. In this review, we have taken a comprehensive approach to discussing various aspects of NRP2-signaling in cancer, including its regulation, functional significance in cancer progression, and how we could utilize our current knowledge to advance the studies and target NRP2 to develop effective cancer therapies.
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Neoplasias , Neuropilina-2 , Transdução de Sinais , Humanos , Neoplasias/metabolismo , Neoplasias/patologia , Neovascularização Patológica , Neuropilina-2/metabolismo , Neuropilinas/metabolismo , Microambiente TumoralRESUMO
Thyroid hormone (TH) is essential for brain development, and hypothyroidism induces cognitive deficits in children and young adults. However, the participating mechanisms remain less explored. Here, we examined the molecular mechanism, hypothesizing the involvement of a deregulated autophagy and apoptosis pathway in hippocampal neurons that regulate cognitive functions. Therefore, we used a rat model of developmental hypothyroidism, generated through methimazole treatment from gestation until young adulthood. We detected that methimazole stimulated the autophagy mechanism, characterized by increased LC3B-II, Beclin-1, ATG7, and ATG5-12 conjugate and decreased p-mTOR/mTOR and p-ULK1/ULK1 autophagy regulators in the hippocampus of developing and young adult rats. This methimazole-induced hippocampal autophagy could be inhibited by thyroxine treatment. Subsequently, probing the upstream mediators of autophagy revealed an increased hippocampal neuroinflammation, marked by upregulated interleukin (IL)-1alpha and beta and activated microglial marker, Iba1, promoting neuronal IL-1 receptor-1 expression. Hence, IL-1R-antagonist (IL-1Ra), which reduced hippocampal neuronal IL-1R1, also inhibited the enhanced autophagy in hypothyroid rats. We then linked these events with hypothyroidism-induced apoptosis and loss of hippocampal neurons, where we observed that like thyroxine, IL-1Ra and autophagy inhibitor, 3-methyladenine, reduced the cleaved caspase-3 and TUNEL-stained apoptotic neurons and enhanced Nissl-stained neuronal count in methimazole-treated rats. We further related these molecular results with cognition through Y-maze and passive avoidance tests, demonstrating an IL-1Ra and 3-methyladenine-mediated improvement in learning-memory performances of the hypothyroid rats. Taken together, our study enlightens the critical role of neuroinflammation-dependent autophagy mechanism in TH-regulated hippocampal functions, disrupted in developmental hypothyroidism.
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Apoptose , Autofagia , Disfunção Cognitiva/etiologia , Hipocampo/patologia , Hipotireoidismo/complicações , Hipotireoidismo/patologia , Interleucina-1/metabolismo , Neurônios/patologia , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Disfunção Cognitiva/patologia , Disfunção Cognitiva/fisiopatologia , Hipocampo/metabolismo , Hipocampo/fisiopatologia , Hipotireoidismo/sangue , Hipotireoidismo/fisiopatologia , Inflamação/patologia , Memória/efeitos dos fármacos , Metimazol/farmacologia , Microglia/efeitos dos fármacos , Microglia/patologia , Proteínas Associadas aos Microtúbulos/metabolismo , Modelos Biológicos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação/efeitos dos fármacos , Ratos Wistar , Serina-Treonina Quinases TOR/metabolismo , Tiroxina/sangue , Tri-Iodotironina/sangueRESUMO
The original version of this article unfortunately contained mistakes. The authors noticed that Fig. 1C (cortex), 1D (hippocampus), 4A (cortex), 4B (cortex) and the beta actin Western blot of Supplement 2A in the original article had errors.
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The original version of this article unfortunately contained mistake on Fig. 3A.
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The anti-diabetic drug and peroxisome proliferator-activated receptor-gamma (PPARγ) agonist, rosiglitazone, alters astrocyte activation; however, its mechanism remains less-known. We hypothesized participation of epidermal growth factor receptor (EGFR), known to control astrocyte reactivity. We first detected that rosiglitazone promoted glial fibrillary acidic protein (GFAP) expression in primary astrocytes as well as the mouse cerebral cortex, associated with increased EGFR activation. Screening for EGFR ligands revealed a rosiglitazone-mediated increase of heparin-binding epidermal growth factor (HB-EGF) in astrocytes, resulting in HB-EGF release into culture medium and mouse cerebrospinal fluid too. Treatment with HB-EGF-siRNA and EGFR inhibitors showed that the rosiglitazone-induced HB-EGF and p-EFGR were interdependent, which participated in GFAP increase. Interestingly, we observed that rosiglitazone could induce cellular and secreted-HB-EGF in neurons also, contributing toward the activated EGFR-induced GFAP in astrocytes. Probing whether these effects of rosiglitazone were PPARγ-linked, revealed potential PPARγ-responsive elements within HB-EGF gene. Moreover, gel-shift, site-directed mutagenesis, chromatin-immunoprecipitation and luciferase-reporter assays demonstrated a PPARγ-dependent HB-EGF transactivation. Subsequently, we examined effects of rosiglitazone in a high-fat diet-fed diabetes mouse model, and supporting observations in the normal cortical cells, identified a rosiglitazone-induced GFAP, astrocyte and neuronal HB-EGF and secreted-HB-EGF in the cerebral cortex of diabetic mice. Moreover, assessing relevance of increased HB-EGF and GFAP revealed an anti-apoptotic role of rosiglitazone in the cerebral cortex, supported by a GFAP-siRNA as well as HB-EGF-siRNA-mediated increase in cleaved-caspase 3 and 9 levels in the rosiglitazone-treated astrocyte-neuron coculture. Overall, our study indicates that rosiglitazone may protect the brain, via a PPARγ-dependent HB-EGF/EGFR signaling and increased GFAP.
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Astrócitos/efeitos dos fármacos , Hipoglicemiantes/farmacologia , Neurônios/efeitos dos fármacos , Rosiglitazona/farmacologia , Transdução de Sinais/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Astrócitos/metabolismo , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Dieta Hiperlipídica , Proteína Glial Fibrilar Ácida/biossíntese , Fator de Crescimento Semelhante a EGF de Ligação à Heparina/biossíntese , Hipoglicemiantes/efeitos adversos , Camundongos , Neurônios/metabolismo , PPAR gama/efeitos dos fármacos , PPAR gama/metabolismo , Regulação para CimaRESUMO
Recent studies showed that neuronal surface protein CD200 plays a key role in the regulation of neuroinflammation. Previously, we showed that arsenic (0.38 mg/kg body weight) exposure induces microglial activation and consequently IL-6/TNF-α secretion. This result indicated the possibility of alteration in the expression of CD200. Therefore, the present study was focused on checking arsenic-induced alteration in CD200 expression and revealing the underlying mechanism. Male BALB/c mice were exposed to arsenic (vehicle, 0.038 and 0.38 mg/kg body weight) for 60 days, and the expression level of CD200 was found to be decreased which was rescued by minocycline (33 mg/kg body weight) co-administration. Higher CD68 staining, increased level of IL-6/TNF-α, as well as higher level of IFNγ, were observed in in vivo arsenic-exposed groups. Interestingly, in vitro arsenic exposure could not increase IL-6/TNF-α level in the culture supernatant, whereas, supplementation of IFNγ could mimic the in vivo results. However, arsenic could not induce IFNγ production from brain endothelial cells, microglia, and astrocytes, thereby suggesting the entry of IFNγ through the impaired blood-brain barrier. Evans blue fluorescence in the brain confirms altered blood-brain barrier permeability although no changes were observed in the expression level of tight junction proteins (claudin-5 and occludin). Finally, intracerebral injection of anti-IFNγ neutralizing antibody in arsenic-exposed brain reduced microglia activation (IL-6 and TNF-α and CD68 expression) and subsequently rescued CD200 level. Taken together, the study showed that arsenic-mediated compromised blood-brain barrier is a major driving force to induce microglial IL-6 and TNF-α production through serum IFNγ leading to CD200 downregulation.
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Antígenos CD/metabolismo , Barreira Hematoencefálica/efeitos dos fármacos , Citocinas/farmacologia , Microglia/efeitos dos fármacos , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Barreira Hematoencefálica/metabolismo , Citocinas/metabolismo , Regulação para Baixo/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Masculino , Camundongos Endogâmicos BALB C , Microglia/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismoRESUMO
We previously demonstrated that arsenic, cadmium, and lead mixture at environmentally relevant doses induces astrocyte apoptosis in the developing brain. Here, we investigated the mechanism and contribution of each metal in inducing the apoptosis. We hypothesized participation of transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), reported to affect astrocyte survival. We treated cultured rat astrocytes with single metals and their combinations and performed apoptosis assay and measured PPARγ expression levels. We found that cadmium demonstrated maximum increase in PPARγ as well as apoptosis, followed by arsenic and then lead. Interestingly, we observed that the metals mimicked PPARγ agonist, troglitazone, and enhanced PPARγ-transcriptional activity. Co-treatment with PPARγ-siRNA or PPARγ-antagonist, GW9662, suppressed the astrocyte apoptosis, suggesting a prominent participation of PPARγ in metal(s)-induced astrocyte loss. We explored PPARγ-transcriptional activity and identify its target gene in apoptosis, performed in silico screening. We spotted PPARγ-response elements (PPREs) within poly(ADP-ribose) polymerase (PARP) gene, and through gel-shift assay verified metal(s)-mediated increased PPARγ binding to PARP-PPREs. Chromatin-immunoprecipitation and luciferase-reporter assays followed by real-time PCR and Western blotting proved PPRE-mediated PARP expression, where cadmium contributed most and lead least, and the effects of metal mixture were comparable with troglitazone. Eventually, dose-dependent increased cleaved-PARP/PARP ratio confirmed astrocyte apoptosis. Additionally, we found that PPARγ and PARP expressions were c-Jun N-terminal kinases and cyclin-dependent kinase5-dependent. In vivo treatment of developing rats with the metals corroborated enhanced PPARγ-dependent PARP and astrocyte apoptosis, where yet again cadmium contributed most. Overall, our study enlightens a novel PPARγ-dependent mechanism of As-, Cd-, and Pb-induced astrocyte apoptosis.
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Arsênio/toxicidade , Encéfalo/efeitos dos fármacos , Cádmio/toxicidade , Chumbo/toxicidade , PPAR gama/agonistas , Poli(ADP-Ribose) Polimerases , Troglitazona/toxicidade , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Apoptose/fisiologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Sequência de Bases , Encéfalo/metabolismo , Células Cultivadas , Regulação da Expressão Gênica , PPAR gama/biossíntese , PPAR gama/genética , PPAR gama/metabolismo , Poli(ADP-Ribose) Polimerases/biossíntese , Poli(ADP-Ribose) Polimerases/genética , Ratos , Ratos WistarRESUMO
We earlier reported that exposure to arsenic at concentrations in ground water of India attenuated glial fibrillary acidic protein (GFAP) during brain development. Here, we validated the effects and explored mechanism in cultured astrocytes and developing rat brain. We hypothesized participation of epidermal growth factor receptor (EGFR), known to regulate GFAP. We found that arsenic inactivated EGFR, marked by reduced phospho-EGFR in astrocytes. Screening EGFR ligands revealed an arsenic-mediated attenuation in cellular and secreted-Heparin-binding EGF-like growth factor (HB-EGF). Furthermore, we observed that recombinant-HB-EGF cotreatment with arsenic blocked reduction in HB-EGF, secreted-HB-EGF and phospho-EGFR, which could be reversed by EGFR-inhibitor, gefitinib, suggesting that arsenic attenuated an HB-EGF/EGFR loop in astrocytes. This reduced HB-EGF/EGFR was essentially responsible for arsenic-induced astrocyte damage, obvious from a recombinant-HB-EGF-mediated recovery in GFAP levels and astrocyte morphology and reduction in astrocyte apoptosis, and the reverse by gefitinib. We found that arsenic also suppressed neuronal HB-EGF levels, which additionally contributed towards astrocyte damage. Exploring the pathways downstream of reduced HB-EGFR/EGFR revealed that an upregulated matrix metalloproteinase 9 (MMP9) within the astrocytes ultimately led to apoptosis and GFAP loss. Astrocytes and MMPs are known to regulate the blood-brain barrier (BBB) integrity, and hence we examined the effects of arsenic on BBB. We detected an arsenic-mediated increased BBB permeability, which could be blocked by recombinant-HB-EGF and MMP9 inhibitor, SB-3CT. Thus, our study indicates that via reduced astrocyte and neuronal HB-EGF signaling, arsenic may induce MMP9 levels and GFAP loss in astrocytes, which might adversely affect BBB integrity of the developing rat brain.
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Arsenitos/toxicidade , Astrócitos/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Receptores ErbB/metabolismo , Fator de Crescimento Semelhante a EGF de Ligação à Heparina/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Compostos de Sódio/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Astrócitos/metabolismo , Astrócitos/patologia , Encéfalo/embriologia , Encéfalo/metabolismo , Feminino , Exposição Materna , Organogênese/efeitos dos fármacos , Gravidez , Cultura Primária de Células , Ratos Wistar , Transdução de SinaisRESUMO
Arsenic promotes hippocampal neuronal damage inducing cognitive impairments. However, mechanism arbitrating arsenic-mediated cognitive deficits remains less-known. Here, we identified that chronic exposure to environmentally relevant doses of arsenic increased apoptosis, characterized by caspase-3 activation, poly(ADP-ribose) polymerase cleavage and Terminal deoxynucleotidyl transferase dUTP nick-end labeling of rat hippocampal neurons, marked by NeuN. Investigating apoptotic mechanism through invivo and invitro studies revealed that arsenic promoted bone morphogenetic protein-2 (BMP2) expression, supported by increased BMP-receptor2 (BMPR2) and p-Smad1/5 in hippocampal neurons. BMP2-silencing and treatment with BMP antagonist, noggin, attenuated the arsenic-induced apoptosis and loss in hippocampal neurons. We then investigated whether BMP2/Smad signaling stimulated neuronal apoptosis independently or required other intermediate pathways. We hypothesized participation of brain-derived neurotrophic factor (BDNF) that promotes neuronal survival. We identified an arsenic-mediated attenuation of BDNF-dependent TrkB signaling, and observed that co-treatment with recombinant-BDNF reinstated BDNF/TrkB and reduced neuronal apoptosis. To probe whether BMP2/Smad and BDNF/TrkB pathways could be linked, we co-treated arsenic with noggin or recombinant BDNF. We detected a noggin-mediated restored BDNF/TrkB, while recombinant-BDNF failed to affect BMP2/Smad signaling. In addition, we found that TrkB-inhibitor, K252a, nullified noggin-induced protection, proving the necessity of a downstream reduced BDNF/TrKB signaling for BMP2/Smad-mediated apoptosis in arsenic-treated neurons. We further related our observations with cognitive performances, and detected noggin-mediated restoration of transfer latency time and learning-memory ability for passive avoidance and Y-Maze tests respectively in arsenic-treated rats. Overall, our study proves that arsenic promotes hippocampal neuronal apoptosis through an up-regulated BMP2/Smad-dependent attenuation of BDNF/TrkB pathway, inducing cognitive deficits.
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Apoptose/efeitos dos fármacos , Arsênio/toxicidade , Proteína Morfogenética Óssea 2/metabolismo , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Transtornos Cognitivos/induzido quimicamente , Hipocampo/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Receptor trkB/metabolismo , Transdução de Sinais , Proteínas Smad/metabolismo , Animais , Células Cultivadas , Feminino , Hipocampo/patologia , Neurônios/patologia , Gravidez , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo Real , Regulação para CimaRESUMO
The astrocyte marker, glial fibrillary acidic protein (GFAP), has essential functions in the brain, but may trigger astroglial scarring when expressed in excess. Docosahexaenoic acid (DHA) is an n-3 fatty acid that is protective during brain development. However, the effect of DHA on GFAP levels of developing brain remains unexplored. Here, we detected that treating developing rats with DHA-enriched fish-oil caused dose-dependent GFAP augmentation. We investigated the mechanism promoting GFAP, hypothesizing the participation of fatty acid-binding protein-7 (FABP7), known to bind DHA. We identified that DHA stimulated FABP7 expression in astrocytes, and FABP7-silencing suppressed DHA-induced GFAP, indicating FABP7-mediated GFAP increase. Further investigation proved FABP7 expression to be phosphatidylinositide 3-kinases (PI3K)/AKT and nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARγ)-dependent. We found that PI3K/AKT activated PPARγ that triggered FABP7 expression via PPARγ-responsive elements within its gene. Towards identifying FABP7-downstream pathways, we considered our previous report that demonstrated cyclin-dependent kinase-5 (CDK5)-PPARγ-protein-protein complex to suppress GFAP. We found that the DHA-induced FABP7 underwent protein-protein interaction with PPARγ, which impeded CDK5-PPARγ formation. Hence, it appeared that enhanced FABP7-PPARγ in lieu of CDK5-PPARγ resulted in increased GFAP. PI3K/AKT not only stimulated formation of FABP7-PPARγ protein-protein complex, but also up-regulated a FABP7-independent MAP-kinase-phosphatase-3 pathway that inactivated CDK5 and hence attenuated CDK5-PPARγ. Overall, our data reveal that via the proximal PI3K/AKT, DHA induces FABP7-PPARγ, through genomic and non-genomic mechanisms, and MAP-kinase-phosphatase-3 that converged at attenuated CDK5-PPARγ and therefore, enhanced GFAP. Accordingly, our study demonstrates a DHA-mediated astroglial hyperactivation, pointing toward a probable injurious role of DHA in brain development.
Assuntos
Astrócitos/metabolismo , Ácidos Docosa-Hexaenoicos/farmacologia , Fosfatase 6 de Especificidade Dupla/biossíntese , Proteína 7 de Ligação a Ácidos Graxos/biossíntese , Proteína Glial Fibrilar Ácida/biossíntese , Proteína Oncogênica v-akt/biossíntese , PPAR gama/biossíntese , Animais , Astrócitos/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Células Cultivadas , Relação Dose-Resposta a Droga , Feminino , Masculino , Ligação Proteica/fisiologia , Ratos , Ratos Wistar , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologiaRESUMO
Pesticide exposure is recognized as a risk factor for Alzheimer's disease (AD). We investigated early signs of AD-like pathology upon exposure to a pyrethroid pesticide, cypermethrin, reported to impair neurodevelopment. We treated weanling rats with cypermethrin (10 and 25 mg/kg) and detected dose-dependent increase in the key proteins of AD, amyloid beta (Aß), and phospho-tau, in frontal cortex and hippocampus as early as postnatal day 45. Upregulation of Aß pathway involved an increase in amyloid precursor protein (APP) and its pro-amyloidogenic processing through beta-secretase (BACE) and gamma-secretase. Tau pathway entailed elevation in tau and glycogen-synthase kinase-3-beta (GSK3ß)-dependent, phospho-tau. GSK3ß emerged as a molecular link between the two pathways, evident from reduction in phospho-tau as well as BACE upon treating GSK3ß inhibitor, lithium chloride. Exploring the mechanism revealed an attenuated heparin-binding epidermal growth factor (HB-EGF) signaling and downstream astrogliosis-mediated neuroinflammation to be responsible for inducing Aß and phospho-tau. Cypermethrin caused a proximal reduction in HB-EGF, which promoted astrocytic nuclear factor kappa B signaling and astroglial activation close to Aß and phospho-tau. Glial activation stimulated generation of interleukin-1 (IL-1), which upregulated GSK3ß, and APP and tau as well, resulting in co-localization of Aß and phospho-tau with IL-1 receptor. Intracerebral insertion of exogenous HB-EGF restored its own signaling and suppressed neuroinflammation and thereby Aß and phospho-tau in cypermethrin-exposed rats, proving a central role of reduced HB-EGF signaling in cypermethrin-mediated neurodegeneration. Furthermore, cypermethrin stimulated cognitive impairments, which could be prevented by exogenous HB-EGF. Our data demonstrate that cypermethrin induces premature upregulation of GSK3ß-dependent Aß and tau pathways, where HB-EGF signaling and neuroinflammation serve as essential regulators.