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Introduction: Tubular aggregates (TA) are skeletal muscle structures that arise from the progressive accumulation of sarcoplasmic reticulum proteins. Cytoplasmic aggregates in muscle fibers have already been observed in mice and humans, mainly during aging and muscle disease processes. However, the effects of muscle regeneration on TA formation have not yet been reported. This study aimed to investigate the relationship between degeneration/regeneration and TA in aged murine models. We investigated the presence and quantity of TA in old males from two murine models with intense muscle degeneration and regeneration. Methods: One murine lineage was a Dmdmdx model of Duchenne muscular dystrophy (n = 6). In the other model, muscle damage was induced by electroporation in C57BL/6J wild-type mice, and analyzed after 5, 15, and 30 days post-electroporation (dpe; n = 15). Regeneration was evaluated based on the quantity of developmental myosin heavy chain (dMyHC)-positive fibers. Results: The frequency of fibers containing TA was higher in aged C57BL/6J (26 ± 8.3%) than in old dystrophic Dmdmdx mice (2.4 ± 2%). Comparing the data from induced degeneration/regeneration in normal mice revealed a reduced proportion of TA-containing fibers after 5 and 30 dpe. Normal aged muscle was able to regenerate and form dMyHC+ fibers, mainly at 5 dpe (0.1 ± 0.1 vs. 16.5 ± 2.6%). However, there was no difference in force or resistance between normal and 30 dpe animals, except for the measurements by the Actimeter device, which showed the worst parameters in the second group. Discussion: Our results suggest that TA also forms in the Dmdmdx muscle but in smaller amounts. The intense degeneration and regeneration of the old dystrophic model resulted in the generation of new muscle fibers with a lower quantity of TA. Data from electroporated wild-type mice support the idea that muscle regeneration leads to a reduction in the amount of TA. We suggest that TA accumulates in muscle fibers throughout physiological aging and that regeneration leads to the formation of new fibers without these structures. In addition, these new fibers do not confer functional benefits to the muscle.
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Biallelic pathogenic variants in TBCK cause encephaloneuropathy, infantile hypotonia with psychomotor retardation, and characteristic facies 3 (IHPRF3). The molecular mechanisms underlying its neuronal phenotype are largely unexplored. In this study, we reported two sisters, who harbored biallelic variants in TBCK and met diagnostic criteria for IHPRF3. We provided evidence that TBCK may play an important role in the early secretory pathway in neuroprogenitor cells (iNPC) differentiated from induced pluripotent stem cells (iPSC). Lack of functional TBCK protein in iNPC is associated with impaired endoplasmic reticulum-to-Golgi vesicle transport and autophagosome biogenesis, as well as altered cell cycle progression and severe impairment in the capacity of migration. Alteration in these processes, which are crucial for neurogenesis, neuronal migration, and cytoarchitecture organization, may represent an important causative mechanism of both neurodevelopmental and neurodegenerative phenotypes observed in IHPRF3. Whether reduced mechanistic target of rapamycin (mTOR) signaling is secondary to impaired TBCK function over other secretory transport regulators still needs further investigation.
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AIMS: Renal dysfunction has been reported in individuals with Down syndrome (DS); however, the causes and mechanisms involved remain unknown. Here, we present a proposal for how the triplication of the amyloid beta precursor protein (APP) and, mainly the amyloid ß peptide 1-42 (Aß42) can favor the development of renal abnormalities in DS. We evaluated the effects of vitamin D3 (VD3) supplementation on morphofunctional aspects and the repercussions on the presence and localization of Aß42, methylenetetrahydrofolate reductase (MTHFR), caspase-3 p12, and P-glycoprotein (Pgp) in the renal tissue of DS mouse model. MAIN METHODS: Twenty female mice (14-week-old) belonging to the B6EiC3Sn-Rb(12.Ts171665Dn)2Cje/CjeDnJ lineage were divided into four experimental groups (nâ¯=â¯5/group): common diet; trisomy (Ts) and wild-type (Wt); and high doses VD3, Ts(VD3), and Wt(VD3). All the groups were treated for 10â¯weeks. At 24â¯weeks, the protocol experimental was interrupted. The kidney was weighed, collected, and processed for immunochemical analysis for Aß42, Caspase-3 p12, MTHFR, and Pgp proteins. All data were analyzed statistically. KEY FINDINGS: Our results showed that VD3 promoted an increase in caspase-3 p12, MTHFR, and Pgp, and consequently contributed to reduced Aß42 in the renal tissue of a mouse model of DS. Furthermore, VD3 treatment affected the plasma creatinine and urea levels and contributed to the attenuation of the dilation of Bowman's space observed in trisomic mice. SIGNIFICANCE: Finally, the results showed that VD3 may activate specific mechanisms involved in reduced Aß42 and tissue repair in the kidneys of a mouse model for Down syndrome.
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Peptídeos beta-Amiloides/metabolismo , Colecalciferol/farmacologia , Síndrome de Down/tratamento farmacológico , Síndrome de Down/metabolismo , Rim/efeitos dos fármacos , Fragmentos de Peptídeos/metabolismo , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/fisiologia , Animais , Caspase 3/metabolismo , Suplementos Nutricionais , Modelos Animais de Doenças , Síndrome de Down/patologia , Feminino , Rim/metabolismo , Rim/patologia , Metilenotetra-Hidrofolato Redutase (NADPH2)/metabolismo , Camundongos , Camundongos Endogâmicos BALB CRESUMO
The histopathological hallmarks present in Alzheimer's disease (AD) brain are plaques of Aß peptide, neurofibrillary tangles of hyperphosphorylated tau protein, and a reduction in nicotinic acetylcholine receptor (nAChR) levels. The role of nAChRs in AD is particularly controversial. Tau protein function is regulated by phosphorylation, and its hyperphosphorylated forms are significantly more abundant in AD brain. Little is known about the relationship between nAChR and phospho-tau degradation machinery. Activation of nAChRs has been reported to increase and decrease tau phosphorylation levels, and the mechanisms responsible for this discrepancy are not presently understood. The co-chaperone BAG2 is capable of regulating phospho-tau levels via protein degradation. In SH-SY5Y cell line and rat primary hippocampal cell culture low endogenous BAG2 levels constitute an intracellular environment conducive to nicotine-induced accumulation of phosphorylated tau protein. Further, nicotine treatment inhibited endogenous expression of BAG2, resulting in increased levels of phosphorylated tau indistinguishable from those induced by BAG2 knockdown. Conversely, overexpression of BAG2 is conducive to a nicotine-induced reduction in cellular levels of phosphorylated tau protein. In both cases the effect of nicotine was p38MAPK-dependent, while the α7 antagonist MLA was synthetic to nicotine treatment, either increasing levels of phospho-Tau in the absence of BAG2, or further decreasing the levels of phospho-Tau in the presence of BAG2. Taken together, these findings reconcile the apparently contradictory effects of nicotine on tau phosphorylation by suggesting a role for BAG2 as an important regulator of p38-dependent tau kinase activity and phospho-tau degradation in response to nicotinic receptor stimulation. Thus, we report that BAG2 expression dictates a functional intracellular switch between the p38-dependent functions of nicotine on tau phosphorylation levels via the α7 nicotinic receptor.
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Chaperonas Moleculares/metabolismo , Nicotina/farmacologia , Receptor Nicotínico de Acetilcolina alfa7/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Proteínas tau/metabolismo , Linhagem Celular Tumoral , Células Cultivadas , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Humanos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação/efeitos dos fármacosRESUMO
AIM: Experimental autoimmune encephalomyelitis (EAE) is a CD4(+)-mediated autoimmune pathology of the central nervous system (CNS) that is used as a model for the study of the human neuroinflammatory disease, multiple sclerosis. During the development of EAE, auto-reactive Th1 and Th17 CD4(+) T cells infiltrate the CNS promoting inflammatory cells recruitment, focal inflammation and tissue destruction. In this sense, statins, agents used to lower lipid levels, have recently shown to exert interesting immunomodulatory function. In fact, statins promote a bias towards a Th2 response, which ameliorates the clinical outcome of EAE. Additionally, simvastatin can inhibit Th17 differentiation. However, many other effects exerted on the immune system by statins have yet to be clarified, in particular during neuroinflammation. Thus, the aim of this study was to investigate the effects of simvastatin on the development of experimental autoimmune encephalomyelitis. METHODS: Mice were immunized with MOG(35-55) and EAE severity was assessed daily and scored using a clinical scale. Cytokine secretion by mononuclear cells infiltrating the CNS was evaluated by flow cytometry. RESULTS: Simvastatin (5 mg/kg/day) improved clinical outcome, induced an increase in TGF-ß mRNA expression and inhibited IL-6, IL-12p40, IL-12p70, RANTES and MIP-1ß secretion (p < 0.05). This was accompanied by a significant decrease in CNS inflammatory mononuclear cell infiltration, with reduced frequencies of both Th1 and Th17 cells. Simvastatin inhibited the proliferation of T lymphocytes co-cultured with primary microglial cells. CONCLUSIONS: Simvastatin treatment promotes EAE clinical amelioration by inhibiting T cell proliferation and CNS infiltration by pathogenic Th1 and Th17 cells.