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Nerve growth factor (NGF) was the first neurotrophin described. This neurotrophin contributes to organogenesis by promoting sensory innervation and angiogenesis in the endocrine and immune systems. Neuronal and non-neuronal cells produce and secrete NGF, and several cell types throughout the body express the high-affinity neurotrophin receptor TrkA and the low-affinity receptor p75NTR. NGF is essential for glucose-stimulated insulin secretion and the complete development of pancreatic islets. Plus, this factor is involved in regulating lipolysis and thermogenesis in adipose tissue. Immune cells produce and respond to NGF, modulating their inflammatory phenotype and the secretion of cytokines, contributing to insulin resistance and metabolic homeostasis. This neurotrophin regulates the synthesis of gonadal steroid hormones, which ultimately participate in the metabolic homeostasis of other tissues. Therefore, we propose that this neurotrophin's imbalance in concentrations and signaling during metabolic syndrome contribute to its pathophysiology. In the present work, we describe the multiple roles of NGF in immunoendocrine organs that are important in metabolic homeostasis and related to the pathophysiology of metabolic syndrome.

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Nerve growth factor (NGF) and its high-affinity receptor TRKA are overexpressed in epithelial ovarian cancer (EOC) displaying a crucial role in the disease progression. Otherwise, NGF interacts with its low-affinity receptor P75, activating pro-apoptotic pathways. In neurons, P75 could be cleaved by metalloproteinases (α and γ-secretases), leading to a decrease in P75 signaling. Therefore, this study aimed to evaluate whether the shedding of P75 occurs in EOC cells and whether NGF/TRKA could promote the cleavage of the P75 receptor. The immunodetection of the α-secretase, ADAM17, TRKA, P75, and P75 fragments was assessed by immunohisto/cytochemistry and Western blot in biopsies and ovarian cell lines. The TRKA and secretases' inhibition was performed using specific inhibitors. The results show that P75 immunodetection decreased during EOC progression and was negatively correlated with the presence of TRKA in EOC biopsies. NGF/TRKA increases ADAM17 levels and the fragments of P75 in ovarian cells. This effect is abolished when cells are previously treated with ADAM17, γ-secretase, and TRKA inhibitors. These results indicate that NGF/TRKA promotes the shedding of P75, involving the activation of secretases such as ADAM17. Since ADAM17 has been proposed as a screening marker for early detection of EOC, our results contribute to understanding better the role of ADAM17 and NGF/TRKA in EOC pathogenesis, which includes the NGF/TRKA-mediated cleavage of P75.

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PURPOSE: Colorectal cancer (CRC) is one most cancer type of high incidence and high mortality rate. Metastasis play an important role in survival rate and life quality of colorectal cancer patients. Nerve growth factor (NGF) has been shown to be involved in the metastasis and deterioration in many cancers, but the detail mechanisms in promoting the metastasis of colorectal cancer remain unknown. In this study, we aimed to explore the mechanism of NGF promoting colorectal cancer metastasis to provide new insights for developing NGF anti-colorectal cancer drugs. METHODS: We examined the expression of NGF in human colorectal cancer by immunohistochemical staining, and Western blot to evaluate the relationship between NGF and colorectal cancer metastasis. Using biochemical experiments including wound healing assay, transwell migration and invasion assay, RT-PCR, Western blot and ELISA to explore the relative mechanism of NGF promoting colorectal cancer cells metastasis in vivo. RESULTS: Our results found that the high expression of NGF was related with high incidence of metastasis. The binding of NGF to TrkA phosphorylated TrkA, which activated MAPK/Erk signaling pathway increasing the expression NGAL to enhance the activity of MMP2 and MMP9, promoted colorectal cancer metastasis. CONCLUSION: Our finding demonstrated that NGF increased NGAL expression to enhance MMPs activity to promoted colorectal cancer cell metastasis by TrkA-MAPK/Erk axis.

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Ovarian cancer is the most lethal gynecological neoplasm, and epithelial ovarian cancer (EOC) accounts for 90% of ovarian malignancies. The 5-year survival is less than 45%, and, unlike other types of cancer, the proportion of women who die from this disease has not improved in recent decades. Nerve growth factor (NGF) and tropomyosin kinase A (TRKA), its high-affinity receptor, play a crucial role in pathogenesis through cell proliferation, angiogenesis, invasion, and migration. NGF/TRKA increase their expression during the progression of EOC by upregulation of oncogenic proteins as vascular endothelial growth factor (VEGF) and c-Myc. Otherwise, the expression of most oncoproteins is regulated by microRNAs (miRs). Our laboratory group reported that the tumoral effect of NGF/TRKA depends on the regulation of miR-145 levels in EOC. Currently, mitochondria have been proposed as new therapeutic targets to activate the apoptotic pathway in the cancer cell. The mitochondria are involved in a myriad of functions as energy production, redox control, homeostasis of Ca+2, and cell death. We demonstrated that NGF stimulation produces an augment in the Bcl-2/BAX ratio, which supports the anti-apoptotic effects of NGF in EOC cells. The review aimed to discuss the role of mitochondria in the interplay between NGF/TRKA and miR-145 and possible therapeutic strategies that may decrease mortality due to EOC.

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In many ways, cancer cells are different from healthy cells. A lot of tactical nano-based drug delivery systems are based on the difference between cancer and healthy cells. Currently, nanotechnology-based delivery systems are the most promising tool to deliver DNA-based products to cancer cells. This review aims to highlight the latest development in the lipids and polymeric nanocarrier for siRNA delivery to the cancer cells. It also provides the necessary information about siRNA development and its mechanism of action. Overall, this review gives us a clear picture of lipid and polymer-based drug delivery systems, which in the future could form the base to translate the basic siRNA biology into siRNA-based cancer therapies.

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Copulation produces different stimuli in the female reproductive tract in camelids, which lead to ovulation. Expression of ß-nerve growth factor (ß-NGF) and its specific receptor, tropomyosin receptor kinase A (TrKA), was studied comparing the oviductal microenvironment of mated and nonmated llamas. ß-NGF and TrKA were expressed in the llama ampulla, isthmus, and utero-tubal-junction (UTJ), and they were mainly colocalized in the apical region of the oviductal mucosa. A TrKA immunosignal was also found in muscle cells and blood vessels, with the highest mark in UTJ muscle cells of copulated females. Both ß-NGF and TrKA transcripts were expressed in the three oviductal segments. Relative TrKA abundance did not differ between mated and nonmated females, but relative ß-NGF abundance was higher in the UTJ of copulated females (p < .05). ß-NGF might not be secreted into the oviductal fluid (OF) since the protein was not found in the OF of mated or nonmated females. Therefore, it can be concluded that the llama oviduct expresses the ß-NGF/TrKA system and that an increase in ß-NGF gene expression in the UTJ 24 h after copulation along with an increase in TrKA protein expression may indicate an important role in the gamete transport and fertilization process in llamas.

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Nerve Growth Factor (NGF) and its high-affinity receptor tropomyosin receptor kinase A (TRKA) increase their expression during the progression of epithelial ovarian cancer (EOC), promoting cell proliferation and angiogenesis through several oncogenic proteins, such as c-MYC and vascular endothelial growth factor (VEGF). The expression of these proteins is controlled by microRNAs (miRs), such as miR-145, whose dysregulation has been related to cancer. The aims of this work were to evaluate in EOC cells whether NGF/TRKA decreases miR-145 levels, and the effect of miR-145 upregulation. The levels of miR-145-5p were assessed by qPCR in ovarian biopsies and ovarian cell lines (human ovarian surface epithelial cells (HOSE), A2780 and SKOV3) stimulated with NGF. Overexpression of miR-145 in ovarian cells was used to evaluate cell proliferation, migration, invasion, c-MYC and VEGF protein levels, as well as tumor formation and metastasis in vivo. In EOC samples, miR-145-5p levels were lower than in epithelial ovarian tumors. Overexpression of miR-145 decreased cell proliferation, migration and invasion of EOC cells, changes that were concomitant with the decrease in c-MYC and VEGF protein levels. We observed decreased tumor formation and suppressed metastasis behavior in mice injected with EOC cells that overexpressed miR-145. As expected, ovarian cell lines stimulated with NGF diminished miR-145-5p transcription and abundance. These results suggest that the tumoral effects of NGF/TRKA depend on the regulation of miR-145-5p levels in EOC cells, and that its upregulation could be used as a possible therapeutic strategy for EOC.

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The molecular mechanisms that control the biosynthetic trafficking, surface delivery, and degradation of TrkA receptor are essential for proper nerve growth factor (NGF) function, and remain poorly understood. Here, we identify Tetraspanin1 (Tspan1) as a critical regulator of TrkA signaling and neuronal differentiation induced by NGF. Tspan1 is expressed by developing TrkA-positive dorsal root ganglion (DRG) neurons and its downregulation in sensory neurons inhibits NGF-mediated axonal growth. In addition, our data demonstrate that Tspan1 forms a molecular complex with the immature form of TrkA localized in the endoplasmic reticulum (ER). Finally, knockdown of Tspan1 reduces the surface levels of TrkA by promoting its preferential sorting towards the autophagy/lysosomal degradation pathway. Together, these data establish a novel homeostatic role of Tspan1, coordinating the biosynthetic trafficking and degradation of TrkA, regardless the presence of NGF.

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Saliva plays an important role in swallowing, chewing and speaking, and is essential for maintaining proper oral health. The aging process leaves to decrease of saliva production causing a condition called xerostomia, which is a big problem for the elderly. Literature shows that during aging the parenchyma of the salivary glands is replaced by fat and connective tissue. Neural growth factor NGF and NGF receptor TrkA are synthesized and secreted by salivary glands SG; however, the physiological role of these proteins in saliva and maintenance of SG has not been fully elucidated. The aim of this study was evaluate alterations in NGF and TrkA expression in sublingual SG SL during the aging process. The cases were divided into two groups for comparison: adult group, individuals between 30 and 60 years old; and elderly group, individuals over 60 years. NGF and TrkA expression were evaluated by immunohistochemistry. Quantitative analysis was measured by Image J software, Mann Whitney”s Test and Pearson’s Correlation Test. Qualitative data were analyzed by Fisher's Exact Test. Analyzing the SL samples, we observed that NGF expression occurred in serous, mucous and ducts cells. The NGF expression in serous acini was diffuse, granular and cytoplasmatic. In both striated and excretory ducts, NGF was quite expressed in the cytoplasm and had a more diffuse than granular pattern. The NGF expression in mucosal cells was smaller and was predominantly in the cytoplasm, the staining pattern was both diffuse and granular. Fisher's Exact Test showed that there was higher labeling in striatal and excretory duct cell cytoplasm in the adult group compared to the elderly one p 0,037. In addition, the granular expression was higher in the striatal duct cells of adults compared to the elderly p 0,043. Mann Whitney's test demonstrated that there was no difference in NGF expression in the adult group compared to the elderly one p≥0.05. Pearson’s correlation test did not show linear correlation between age and expression of NGF. The TrkA expression was more expressive in mucosal acini and ducts. In mucous cells, TrkA was expressed in the cytoplasm and in peribasal portion diffusely and granularly. In ductal cells, TrkA was expressed in almost all cases and the pattern was citoplasmatic and granular. In serous acini, the labeling was predominant cytoplasmatic and diffuse. Fisher's Exact Test showed that the granular labeling of striated duct cells was higher in the elderly group than in the adult one p 0,03. In contrast, the diffuse pattern was higher in striated duct cell of the adults if compared with the elderly p 0,008. Mann Whitney's test demonstrated that there was no difference in TrkA expression in the adult group compared to the elderly one p0.05. Pearson’s correlation test did not show linear correlation between age and expression of TrkA.

A saliva desempenha um papel importante na deglutição, mastigação e fala, e é essencial para manter a saúde bucal adequada. O processo de envelhecimento diminui a produção de saliva, causando uma condição chamada xerostomia, que é um grande problema para os idosos. A literatura mostra que durante o envelhecimento, o parênquima das glândulas salivares é substituído por gordura e tecido conjuntivo. O fator de crescimento neural (NGF) e o receptor para NGF (TrkA) são sintetizados e secretados pelas glândulas salivares (GS); no entanto, o papel fisiológico dessas proteínas na saliva e na manutenção das GS não foi totalmente elucidado. O objetivo deste estudo foi avaliar alterações na expressão de NGF e TrkA na GS sublingual (SL) durante o processo de envelhecimento. Os casos foram divididos em dois grupos para comparação: grupo de adultos, indivíduos entre 30 e 60 anos; e grupo de idosos, indivíduos acima de 60 anos. A expressão de NGF e TrkA foi avaliada por imunoistoquímica. A análise quantitativa foi mensurada pelo software Image J, pelo teste de Mann Whitney e pelo teste de correlação de Pearson. Os dados qualitativos foram analisados pelo teste exato de Fisher. Analisando as amostras de SL, observamos que a expressão de NGF ocorreu principalmente nas células serosas, nas células mucosas e nos ductos. A expressão de NGF nos ácinos serosos foi difusa, granular e citoplasmática. Nos ductos estriado e excretor, o NGF foi bastante expresso no citoplasma e apresentava um padrão mais difuso do que granular. A expressão de NGF nas células da mucosa foi menor quando comparada com as células serosas e ductais e predominantemente no citoplasma, o padrão de coloração foi difuso e granular. O teste exato de Fisher mostrou que houve maior número de casos marcados, no citoplasma dos ductos excretor e estriado, no grupo adulto em comparação com o idoso (p=0,037). Além disso, a expressão granular foi maior nas células do ducto estriado de adultos em comparação com os idosos (p=0,043). O teste de Mann Whitney demonstrou que não houve diferença na expressão de NGF no grupo adulto comparado ao grupo idoso (p≥0,05) e o teste de Correlação de Pearson, mostrou que não houve correlação linear entre a idade dos indivíduos e a expressão do NGF. A expressão de TrkA foi mais expressiva nos ácinos mucosos e nos ductos. Nas células mucosas, o TrkA foi expresso no citoplasma e na porção peribasal de forma difusa e granular. Nas células ductais, oTrkA foi expresso em quase todos os casos e o padrão foi citoplasmático e granular. Nos ácinos serosos, a marcação foi predominantemente citoplasmática e difusa. O teste exato de Fisher mostrou que a marcação granular das células do ducto estriado era maior no grupo de idosos do que no grupo de adultos (p=0,033). Por outro lado, o padrão difuso foi maior nas células do ducto estriado dos adultos se comparado aos idosos (p= 0,008). O teste de Mann Whitney demonstrou que não houve diferença na expressão de TrkA no grupo adulto comparado ao grupo idoso (p≥0,05) e o teste de Correlação de Pearson, mostrou que não houve correlação linear entre a idade dos indivíduos e a expressão do TrkA.

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RESUMO Objetivo: determinar a expressão de neurotrofinas e seus receptores tirosina quinases em pacientes com osteossarcoma (OS) e sua correlação com desfechos clínicos. Métodos: biópsias de tumores primários de pacientes com OS tratados em uma única instituição, consecutivamente, entre 2002 e 2015, foram analisados através de imuno-histoquímica para expressão de receptores de tirosina quinase A e B (TrKA e TrKB), fator de crescimento neural (NGF) e fator neurotrófico derivado do cérebro (BDNF). De forma independente, dois patologistas classificaram os marcadores de imuno-histoquímica como negativos (negativos e focais fracos) ou positivos (moderado focal/difuso ou forte focal/difuso). Resultados: foram analisados dados de 19 pacientes (10 do sexo feminino e 9 do masculino) com mediana de idade de 12 anos (5 a 17,3 anos). Dos tumores, 83,3% estavam localizados em membros inferiores e 63,2% dos pacientes eram metastáticos ao diagnóstico. A sobrevida global em cinco anos foi de 55,3%. BDNF foi positivo em 16 pacientes (84%) e NGF em 14 pacientes (73%). TrKA e TrKB apresentaram coloração positiva em quatro (21,1%) e oito (42,1%) pacientes, respectivamente. A análise de sobrevida não demonstrou diferença significativa entre receptores TrK e neurotrofinas. Conclusão: amostras de OS primário expressam neurotrofinas e receptores TrK através de imuno-histoquímica. Estudos futuros podem auxiliar na identificação do papel das mesmas na patogênese do OS e determinar se há possível correlação prognóstica.

ABSTRACT Objective: to determine the expression of neurotrophins and their tyrosine-kinase receptors in patients with osteosarcoma (OS) and their correlation with clinical outcomes. Methods: we applied immunohistochemistry to biopsy specimens of patients consecutively treated for primary OS at a single institution between 2002 and 2015, analyzing them for expression receptors of tyrosine kinase A and B (TrKA and TrKB), neural growth factor (NGF) and brain derived neurotrophic factor (BDNF). Independently, two pathologists classified the immunohistochemical markers as negative (negative or weak focal) or positive (moderate focal/diffuse or strong focal/diffuse). Results: we analyzed data from 19 patients (10 females and 9 males), with median age of 12 years (5 to 17.3). Tumors' location were 83.3% in the lower limbs, and 63.2% of patients had metastases at diagnosis. Five-year overall survival was 55.3%. BDNF was positive in 16 patients (84%) and NGF in 14 (73%). TrKA and TrKB presented positive staining in four (21,1%) and eight (42,1%) patients, respectively. Survival analysis showed no significant difference between TrK receptors and neurotrophins. Conclusion: primary OS samples express neurotrophins and TrK receptors by immunohistochemistry. Future studies should explore their role in OS pathogenesis and determine their prognostic significance in larger cohorts.

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