Sheila Cristina Victório

Defective regulation of adipose tissue autophagy in obesity

Objectives:Autophagy is a highly regulated process that has an important role in the control of a wide range of cellular functions, such as organelle recycling, nutrient availability and tissue differentiation. A recent study has shown an increased autophagic activity in the adipose tissue of obese subjects, and a role for autophagy in obesity-associated insulin resistance was proposed. Body mass reduction is the most efficient approach to tackle insulin resistance in over-weight subjects; however, the impact of weight loss in adipose tissue autophagy is unknown.Subjects:Adipose tissue autophagy was evaluated in mice and humans.Results:First, a mouse model of diet-induced obesity and diabetes was maintained on a 15-day, 40% caloric restriction. At baseline, markers of autophagy were increased in obese mice as compared with lean controls. Upon caloric restriction, autophagy increased in the lean mice, whereas it decreased in the obese mice. The reintroduction of ad libitum feeding was sufficient to rapidly reduce autophagy in the lean mice and increase autophagy in the obese mice. In the second part of the study, autophagy was evaluated in the subcutaneous adipose tissue of nine obese-non-diabetic and six obese-diabetic subjects undergoing bariatric surgery for body mass reduction. Specimens were collected during the surgery and approximately 1 year later. Markers of systemic inflammation, such as tumor necrosis factor-1α, interleukin (IL)-6 and IL-1β were evaluated. As in the mouse model, human obesity was associated with increased autophagy, and body mass reduction led to an attenuation of autophagy in the adipose tissue.Conclusion:Obesity and caloric overfeeding are associated with the defective regulation of autophagy in the adipose tissue. The studies in obese-diabetic subjects undergoing improved metabolic control following calorie restriction suggest that autophagy and inflammation are regulated independently.

n-3 Fatty Acids Induce Neurogenesis of Predominantly POMC-Expressing Cells in the Hypothalamus.

Apoptosis of hypothalamic neurons is believed to play an important role in the development and perpetuation of obesity. Similar to the hippocampus, the hypothalamus presents constitutive and stimulated neurogenesis, suggesting that obesity-associated hypothalamic dysfunction can be repaired. Here, we explored the hypothesis that n-3 polyunsaturated fatty acids (PUFAs) induce hypothalamic neurogenesis. Both in the diet and injected directly into the hypothalamus, PUFAs were capable of increasing hypothalamic neurogenesis to levels similar or superior to the effect of brain-derived neurotrophic factor (BDNF). Most of the neurogenic activity induced by PUFAs resulted in increased numbers of proopiomelanocortin but not NPY neurons and was accompanied by increased expression of BDNF and G-protein–coupled receptor 40 (GPR40). The inhibition of GPR40 was capable of reducing the neurogenic effect of a PUFA, while the inhibition of BDNF resulted in the reduction of global hypothalamic cell. Thus, PUFAs emerge as a potential dietary approach to correct obesity-associated hypothalamic neuronal loss.

Defective Regulation of the Ubiquitin/Proteasome System in the Hypothalamus of Obese Male Mice

In both human and experimental obesity, inflammatory damage to the hypothalamus plays an important role in the loss of the coordinated control of food intake and energy expenditure. Upon prolonged maintenance of increased body mass, the brain changes the defended set point of adiposity, and returning to normal weight becomes extremely difficult. Here we show that in prolonged but not in short-term obesity, the ubiquitin/proteasome system in the hypothalamus fails to maintain an adequate rate of protein recycling, leading to the accumulation of ubiquitinated proteins. This is accompanied by an increased colocalization of ubiquitin and p62 in the arcuate nucleus and reduced expression of autophagy markers in the hypothalamus. Genetic protection from obesity is accompanied by the normal regulation of the ubiquitin/proteasome system in the hypothalamus, whereas the inhibition of proteasome or p62 results in the acceleration of body mass gain in mice exposed for a short period to a high-fat diet. Thus, the defective regulation of the ubiquitin/proteasome system in the hypothalamus may be an important mechanism involved in the progression and autoperpetuation of obesity.

Interferon (IFN) beta treatment induces major histocompatibility complex (MHC) class I expression in the spinal cord and enhances axonal growth and motor function recovery following sciatic nerve crush in mice

R. G. Zanon, L. P. Cartarozzi, S. C. S. Victório, J. C. Moraes, J. Morari, L. A. Velloso and A. L. R. Oliveira (2010) Neuropathology and Applied Neurobiology36, 515–534
Interferon (IFN) beta treatment induces major histocompatibility complex (MHC) class I expression in the spinal cord and enhances axonal growth and motor function recovery following sciatic nerve crush in mice

Absence of IFNγ expression induces neuronal degeneration in the spinal cord of adult mice

BackgroundInterferon gamma (IFNγ) is a pro-inflammatory cytokine, which may be up-regulated after trauma to the peripheral or central nervous system. Such changes include reactive gliosis and synaptic plasticity that are considered important responses to the proper regenerative response after injury. Also, IFNγ is involved in the upregulation of the major histocompatibility complex class I (MHC class I), which has recently been shown to play an important role in the synaptic plasticity process following axotomy. There is also evidence that IFNγ may interfere in the differentiation and survival of neuronal cells. However, little is known about the effects of IFNγ absence on spinal cord neurons after injury.MethodsWe performed a unilateral sciatic nerve transection injury in C57BL/6J (wild type) and IFNγ-KO (mutant) mice and studied motoneuron morphology using light and electron microscopy. One week after the lesion, mice from both strains were sacrificed and had their lumbar spinal cords processed for histochemistry (n = 5 each group) and transmission electron microscopy (TEM, n = 5 each group). Spinal cord sections from non-lesioned animals were also used to investigate neuronal survival and the presence of apoptosis with TUNEL and immunohistochemistry.ResultsWe find that presumed motoneurons in the lower lumbar ventral horn exhibited a smaller soma size in the IFNγ-KO series, regardless of nerve lesion. In plastic embedded sections stained with toluidine blue, the IFNγ-KO mice demonstrated a greater proportion of degenerating neurons in the ventral horn when compared to the control series (p < 0.05). Apoptotic death is suggested based on TUNEL and caspase 3 immunostaining. A sciatic nerve axotomy did not further aggravate the neuronal loss. The cellular changes were supported by electron microscopy, which demonstrated ventral horn neurons exhibiting intracellular vacuoles as well as degenerating nuclei and cytoplasm in the IFNγ-KO mice. Adjacent glial cells showed features suggestive of phagocytosis. Additional ultrastructural studies showed a decreased number of pre-synaptic terminals apposing to motoneurons in mutant mice. Nevertheless, no statistical difference regarding the input covering could be detected among the studied strains.ConclusionAltogether, these results suggest that IFNγ may be neuroprotective and its absence results in neuronal death, which is not further increased by peripheral axotomy.

Decreased MHC I expression in IFN gamma mutant mice alters synaptic elimination in the spinal cord after peripheral injury

BackgroundThe histocompatibility complex (MHC) class I expression in the central nervous system (CNS) regulates synaptic plasticity events during development and adult life. Its upregulation may be associated with events such as axotomy, cytokine exposition and changes in neuron electrical activity. Since IFNγ is a potent inducer of the MHC I expression, the present work investigated the importance of this pro-inflammatory cytokine in the synaptic elimination process in the spinal cord, as well as the motor recovery of IFN−/−, following peripheral injury.MethodsThe lumbar spinal cords of C57BL/6J (wild type) and IFNγ−/− (mutant) mice, subjected to unilateral sciatic nerve transection, were removed and processed for immunohistochemistry and real time RT-PCR, while the sciatic nerves from animals subjected to unilateral crush, were submitted to immunohistochemistry and electron microscopy for counting of the axons. Gait recovery was monitored using the Cat Walk system. Newborn mice astrocyte primary cultures were established in order to study the astrocytic respose in the absence of the IFNγ expression.ResultsIFNγ−/− mutant mice showed a decreased expression of MHC I and β2-microglobulin mRNA coupled with reduced synaptophysin immunolabelling in the lesioned spinal cord segment. Following unilateral nerve transection, the Iba-1 (ionized calcium binding adaptor molecule 1) and glial fibrillary acid protein (GFAP) reactivities increased equally in both strains. In vitro, the astrocytes demonstrated similar GFAP levels, but the proliferation rate was higher in the wild type mice. In the crushed nerves (distal stump), neurofilaments and p75NTR immunolabeling were upregulated in the mutant mice as compared to the wild type and an improvement in locomotor recovery was observed.ConclusionThe present results show that a lack of IFNγ affects the MHC I expression and the synaptic elimination process in the spinal cord. Such changes, however, do not delay peripheral nerve regeneration after nerve injury.

Expressão do complexo de histocompatilidade principal de classe I (MHC I) no sistema nervoso central: plasticidade sináptica e regeneração

It has been recently demonstrated that the major histocompatibility complex of class I (MHC I) expressed in the central nervous system (CNS) does not only function as a molecule of the immune system, but also plays a role in the synaptic plasticity. The expression of MHC I influences the intensity and selectivity of elimination of synapses apposed to neurons that were subjected to lesion, besides influencing the reactivity of neighboring glial cells. MHC I expression and the degree of synaptic rearrangement and glial response after injury correlate with differences in the regenerative potential and functional recovery of isogenic mice strains. In this way, the new aspects regarding MHC I functions in the CNS may guide further studies aiming at searching the involvement of MCH I in neurologic disorders, as well as the development of new therapeutic strategies.Foi demonstrado recentemente que o complexo de histocompatibilidade principal de classe I (MHC I), expresso no sistema nervoso central (SNC), nao funciona somente como molecula com papel imunologico, mas tambem como parte de um mecanismo envolvido na plasticidade sinaptica. A expressao de MHC I interfere na intensidade e seletividade da retracao de sinapses em contato com neuronios que sofreram lesao e tambem influencia a reatividade das celulas gliais proximas a esses neuronios. A intensidade do rearranjo sinaptico e resposta glial apos lesao, ligadas a expressao de MHC I no SNC, repercute em diferencas na capacidade regenerativa e recuperacao funcional em linhagens de camundongos isogenicos. Dessa forma, os novos aspectos sobre a funcao do MHC I no SNC direcionam futuras pesquisas no sentido de buscar o envolvimento do MHC I em doencas neurologicas e tambem o desenvolvimento de novas estrategias terapeuticas.

Expression of class I major histocompatibility complex (MHC I) in the central nervous system: role in synaptic plasticity and regeneration

It has been recently demonstrated that the major histocompatibility complex of class I (MHC I) expressed in the central nervous system (CNS) does not only function as a molecule of the immune system, but also plays a role in the synaptic plasticity. The expression of MHC I influences the intensity and selectivity of elimination of synapses apposed to neurons that were subjected to lesion, besides influencing the reactivity of neighboring glial cells. MHC I expression and the degree of synaptic rearrangement and glial response after injury correlate with differences in the regenerative potential and functional recovery of isogenic mice strains. In this way, the new aspects regarding MHC I functions in the CNS may guide further studies aiming at searching the involvement of MCH I in neurologic disorders, as well as the development of new therapeutic strategies.Foi demonstrado recentemente que o complexo de histocompatibilidade principal de classe I (MHC I), expresso no sistema nervoso central (SNC), nao funciona somente como molecula com papel imunologico, mas tambem como parte de um mecanismo envolvido na plasticidade sinaptica. A expressao de MHC I interfere na intensidade e seletividade da retracao de sinapses em contato com neuronios que sofreram lesao e tambem influencia a reatividade das celulas gliais proximas a esses neuronios. A intensidade do rearranjo sinaptico e resposta glial apos lesao, ligadas a expressao de MHC I no SNC, repercute em diferencas na capacidade regenerativa e recuperacao funcional em linhagens de camundongos isogenicos. Dessa forma, os novos aspectos sobre a funcao do MHC I no SNC direcionam futuras pesquisas no sentido de buscar o envolvimento do MHC I em doencas neurologicas e tambem o desenvolvimento de novas estrategias terapeuticas.

Expresión del complejo principal de histocompatibilidad de clase I (MHC I) en el sistema nervioso central: plasticidad sináptica y regeneración

It has been recently demonstrated that the major histocompatibility complex of class I (MHC I) expressed in the central nervous system (CNS) does not only function as a molecule of the immune system, but also plays a role in the synaptic plasticity. The expression of MHC I influences the intensity and selectivity of elimination of synapses apposed to neurons that were subjected to lesion, besides influencing the reactivity of neighboring glial cells. MHC I expression and the degree of synaptic rearrangement and glial response after injury correlate with differences in the regenerative potential and functional recovery of isogenic mice strains. In this way, the new aspects regarding MHC I functions in the CNS may guide further studies aiming at searching the involvement of MCH I in neurologic disorders, as well as the development of new therapeutic strategies.Foi demonstrado recentemente que o complexo de histocompatibilidade principal de classe I (MHC I), expresso no sistema nervoso central (SNC), nao funciona somente como molecula com papel imunologico, mas tambem como parte de um mecanismo envolvido na plasticidade sinaptica. A expressao de MHC I interfere na intensidade e seletividade da retracao de sinapses em contato com neuronios que sofreram lesao e tambem influencia a reatividade das celulas gliais proximas a esses neuronios. A intensidade do rearranjo sinaptico e resposta glial apos lesao, ligadas a expressao de MHC I no SNC, repercute em diferencas na capacidade regenerativa e recuperacao funcional em linhagens de camundongos isogenicos. Dessa forma, os novos aspectos sobre a funcao do MHC I no SNC direcionam futuras pesquisas no sentido de buscar o envolvimento do MHC I em doencas neurologicas e tambem o desenvolvimento de novas estrategias terapeuticas.