RESUMEN
With the development of technology and space exploration, studies on long-duration space flights have shown that microgravity induces damage to multiple organs, including the dorsal root ganglia (DRG). However, very little is known about the effects of long-term microgravity on DRG neurons. This study investigated the effects of microgravity on lumbar 5 (L5) DRG neurons in rats using the hindlimb unweighting (HU) model. Male (M) and female (F) Sprague-Dawley rats were randomly divided into M- and F-control (CON) groups and M- and F-HU groups, respectively (n = 10). At the end of HU treatment for 4 weeks, morphological changes were detected. Myelin basic protein (MBP) and degenerated myelin basic protein (dgen-MBP) expressions were analyzed by immunofluorescence and western blot assays. Glial cell line-derived neurotrophic factor (GDNF) protein and mRNA expressions were also analyzed by immunohistochemistry, western blot, and RT-PCR analysis, respectively. Compared with the corresponding CON groups, the HU groups exhibited slightly loose junctions between DRG neurons, some separated ganglion cells and satellite cells, and lightly stained Nissl bodies that were of smaller size and had a scattered distribution. High levels of dgen-MBP and low MBP expressions were appeared and GDNF expressions were significantly decreased in both HU groups. Changes were more pronounced in the F-HU group than in the M-HU group. In conclusion, HU treatment induced damage of L5 DRG neurons, which was correlated with decreased total MBP protein expression, increased dgen-MBP expression, and reduced GDNF protein and mRNA expression. Importantly, these changes were more severe in F-HU rats compared with M-HU rats.
Asunto(s)
Ganglios Espinales/metabolismo , Factor Neurotrófico Derivado de la Línea Celular Glial/metabolismo , Miembro Posterior/fisiopatología , Proteína Básica de Mielina/metabolismo , Animales , Forma de la Célula , Femenino , Masculino , Neuronas/metabolismo , Ratas Sprague-DawleyRESUMEN
Exposure to microgravity results in cardiovascular deconditioning, and cerebrovascular oxidative stress injury has been suggested to occur. To elucidate the mechanism for this condition, we investigated whether simulated microgravity induces mitochondrial dysfunction in rat arteries. Four-week hindlimb unweighting (HU) was used to simulate microgravity in rats. Mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), mitochondrial permeability transition pore (mPTP) opening, mitochondrial respiratory control ratio (RCR), MnSOD/GPx activity and expression, and mitochondrial malondialdehyde (MDA) were examined in rat cerebral and mesenteric VSMCs. Compared with the control rats, mitochondrial ROS levels, mPTP opening, and MDA content increased significantly (P<0.001, P<0.01, and P<0.01, respectively), Δψm, RCR, MnSOD/GPx activity (P<0.001 for Δψm and RCR; P<0.05 for MnSOD; and P<0.001 for GPx activity) and protein abundance of mitochondrial MnSOD/GPx-1 decreased (P<0.001 for MnSOD and GPx-1) in HU rat cerebral but not mesenteric arteries. Chronic treatment with NADPH oxidase inhibitor apocynin and mitochondria-targeted antioxidant mitoTempol promoted recovery of mitochondrial function in HU rat cerebral arteries, but exerted no effects on HU rat mesenteric arteries. Therefore, simulated microgravity resulted in cerebrovascular mitochondrial dysfunction, and crosstalk between NADPH oxidase and mitochondria participated in the process.
Asunto(s)
Arterias Cerebrales/fisiopatología , Mitocondrias/metabolismo , Simulación de Ingravidez/efectos adversos , Acetofenonas/farmacología , Animales , Arterias Cerebrales/ultraestructura , Glutatión Peroxidasa/metabolismo , Suspensión Trasera , Masculino , Potencial de la Membrana Mitocondrial/fisiología , Arterias Mesentéricas/ultraestructura , Mitocondrias/efectos de los fármacos , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Poro de Transición de la Permeabilidad Mitocondrial , NADPH Oxidasas/metabolismo , Compuestos Organofosforados/farmacología , Piperidinas/farmacología , Ratas , Especies Reactivas de Oxígeno/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Losartan, an angiotensin II type 1 receptor blocker, exerts protective effect on soleus muscle atrophy in female rats. Thus, we aimed to examine the effect of losartan treatment on the recovery of atrophied soleus muscles. Female Wistar rats were subjected to hindlimb unloading for 7 d and then reloading for 7 d with either phosphate-buffered saline (PBS; n = 9) or losartan (40 mg/kg/day; n = 9). The soleus muscles were removed at rest (sedentary control [SED]; n = 9), after 7 d of hindlimb unloading (HU; n = 9), and after 7 d of reloading (HUR-PBS or HUR-LOS; n = 9 each). The absolute and relative weights, and fiber cross-sectional area (CSA) of the soleus muscles of rats in the HU group were significantly reduced as compared to those of the rats in the SED group at 7 d post-hindlimb unloading. Seven days of reloading significantly increased the muscle weights of rats in the HUR-PBS and HUR-LOS groups, with the recovery rate of the absolute muscle weight and type I fiber CSA being significantly higher in the HUR-LOS group (6.1% and 10.1%, respectively) than in the HUR-PBS group (4.7% and 5.2%, respectively) (p < 0.05). Moreover, the absolute and relative muscle weight in HUR-PBS were lower than SED; however, no significant difference was observed between the SED and HUR-LOS groups. CSAs of type I and IIa fiber were significantly higher in the HUR-LOS group than in the HU group. Losartan administration during reloading resulted in increased Smad1/5/8 and mTOR signaling and decreased Smad2/3 signaling and protein ubiquitination, facilitating the recovery of atrophied soleus muscle. Therefore, losartan administration-induced muscle recovery may partially be attributed to enhanced Smad1/5/8 and mTOR signaling activation, and reduced activation of canonical TGF-ß signaling (Smad2/3) in the soleus muscle.
Asunto(s)
Suspensión Trasera , Losartán , Animales , Femenino , Miembro Posterior , Losartán/farmacología , Losartán/uso terapéutico , Músculo Esquelético/metabolismo , Atrofia Muscular/metabolismo , Ratas , Ratas Wistar , Proteínas Smad/metabolismo , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
We investigated the protective effect of losartan, an angiotensin II type 1 receptor blocker, on soleus muscle atrophy. Age-matched male and female Wistar rats were subjected to hindlimb unloading, and the soleus muscle was removed on days 1 and 7 for analysis. Females showed greater reductions in relative weight and myofiber cross-sectional area of the soleus muscle than males on day 7 post-hindlimb unloading. Losartan partially protected females against muscle atrophy. Activation of the canonical TGF-ß signaling pathway, assessed via Smad2/3 phosphorylation, was lower in females following losartan treatment and associated with lower levels of protein ubiquitination after 1 (myofibril) and 7 (cytosol) days of unloading. However, no effect was observed in non-canonical TGF-ß signaling (p44/p42 and p38 MAPK phosphorylation) in males or females during unloading. Our results suggest that losartan provides partial protection against hindlimb unloading-induced soleus muscle atrophy in female rats, possibly associated with decreased canonical TGF-ß signaling.
Asunto(s)
Suspensión Trasera , Losartán , Animales , Femenino , Miembro Posterior , Suspensión Trasera/fisiología , Losartán/metabolismo , Losartán/farmacología , Masculino , Músculo Esquelético/metabolismo , Atrofia Muscular/metabolismo , Ratas , Ratas Wistar , Transducción de Señal/fisiología , Factor de Crecimiento Transformador beta/metabolismo , Factor de Crecimiento Transformador beta/farmacologíaRESUMEN
Microgravity exposure results in vascular remodeling and cardiovascular dysfunction. Here, the effects of mitochondrial oxidative stress on vascular smooth muscle cells (VSMCs) in rat cerebral arteries under microgravity simulated by hindlimb unweighting (HU) was studied. Endoplasmic reticulum (ER)-resident transmembrane sensor proteins and phenotypic markers of rat cerebral VSMCs were examined. In HU rats, CHOP expression was increased gradually, and the upregulation of the PERK-eIF2α-ATF4 pathway was the most pronounced in cerebral arteries. Furthermore, PERK/p-PERK signaling, CHOP, GRP78 and reactive oxygen species were augmented by PERK overexpression but attenuated by the mitochondria-targeting antioxidant MitoTEMPO. Meanwhile, p-PI3K, p-Akt and p-mTOR protein levels in VSMCs were increased in HU rat cerebral arteries. Compared with the control, HU rats exhibited lower α-SMA, calponin, SM-MHC and caldesmon protein levels but higher OPN and elastin levels in cerebral VSMCs. The cerebral VSMC phenotype transition from a contractile to synthetic phenotype in HU rats was augmented by PERK overexpression and 740Y-P but reversed by MitoTEMPO and the ER stress inhibitors tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA). In summary, mitochondrial oxidative stress and ER stress induced by simulated microgravity contribute to phenotype transition of cerebral VSMCs through the PERK-eIF2a-ATF4-CHOP pathway in a rat model.
Asunto(s)
Factor de Transcripción Activador 4/genética , Arterias Cerebrales/metabolismo , Factor 2 Eucariótico de Iniciación/genética , Músculo Liso Vascular/metabolismo , Miocitos del Músculo Liso/metabolismo , Factor de Transcripción CHOP/genética , eIF-2 Quinasa/genética , Factor de Transcripción Activador 4/metabolismo , Animales , Antioxidantes/farmacología , Arterias Cerebrales/citología , Arterias Cerebrales/efectos de los fármacos , Retículo Endoplásmico/efectos de los fármacos , Retículo Endoplásmico/genética , Retículo Endoplásmico/metabolismo , Factor 2 Eucariótico de Iniciación/metabolismo , Regulación de la Expresión Génica , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Suspensión Trasera , Masculino , Mitocondrias/efectos de los fármacos , Mitocondrias/genética , Mitocondrias/metabolismo , Músculo Liso Vascular/citología , Músculo Liso Vascular/efectos de los fármacos , Miocitos del Músculo Liso/citología , Miocitos del Músculo Liso/efectos de los fármacos , Compuestos Organofosforados/farmacología , Fenilbutiratos/farmacología , Fosfatidilinositol 3-Quinasas/genética , Fosfatidilinositol 3-Quinasas/metabolismo , Piperidinas/farmacología , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Ratas Sprague-Dawley , Transducción de Señal , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismo , Ácido Tauroquenodesoxicólico/farmacología , Factor de Transcripción CHOP/metabolismo , eIF-2 Quinasa/metabolismoRESUMEN
The purpose of this study was to examine differences in the inhibitory effect of disuse atrophy as a result of intermittent weight bearing in terms of the dynamics of nuclei in rat soleus muscle. Disuse muscle atrophy was induced by hindlimb suspension for two weeks. Forty-nine male Wistar rats (body weight: 190-228 g) were divided into the control group (CON) and the experimental group. The experimental group was subdivided into four groups: hindlimb suspension alone (HS), weight bearing for 10 minutes × 4 times/day (W10), weight bearing for 20 minutes × 2 times/day (W20), and weight bearing for 40 minutes × one time/day (W40). In addition to histochemical examination, this study examined both cell proliferation and apoptosis in terms of the dynamics of myonuclei immuno-histochemically. The mean cross-sectional area of muscle fibers demonstrated the effect of weight bearing. The number of proliferating myonuclei per 100 muscle fibers was decreased in the experimental groups as compared with CON. Proliferating myonuclei in W10 and W40 were more than HS, indicating the effect of weight bearing. Apoptotic myonuclei was increased in the experimental groups as compared with CON. This parameter in W10 and W40 were statistically not significantly different from CON, suggesting that these weight bearing methods can prevent the loss of myonuclei by apoptosis. However, W20 was not significantly different from HS in terms of the dynamics of myonuclei. This suggests that weight bearing for W20 was ineffective. The results in this study indicated the possibility of inducing different effects by the frequency of weight bearing.