Diabetic neuropathy is one of the most deleterious complications of diabetes mellitus in humans. High fat diet (HFD)‐fed C57BL/6 J mice are a widely used animal model for type 2 diabetes mellitus and ...metabolic syndrome. We investigated the effects of metformin and simvastatin on the ultrastructural characteristics of sciatic nerve fibers in these mice. Metformin treatment increased the number of structural defects of the myelin sheet surrounding these fibers in already affected nerves of HFD fed mice, and simvastatin treatment reduced these numbers to the levels seen in control mice. These results warrant further research on the effects of metformin and statins in patients developing diabetic neuropathy and advise caution when deciding about optimal treatment modalities in these patients.
Th2-associated factors such as IL-4 are involved in both the development of Th2 responses (via modulating Th2 cell differentiation) and in the effector phase of Th2 responses (via modulating ...macrophage activation). The IL-1 receptor-like protein ST2 (T1, Fit-1, or DER4) is expressed as a membrane-bound (ST2L) or secreted form (sST2), and has been clearly implicated as a regulator of both the development and effector phases of Th2-type responses. Here we analyze the mechanisms and therapeutic implications of the unique ability of ST2 to promote development and function of type 2 helper T cells through a positive feedback loop, as well as to act as a negative feedback modulator of macrophage pro-inflammatory function.
Ghrelin, the endogenous growth hormone secretagogue, has an important role in metabolic homeostasis. It exists in two major molecular forms: acylated (AG) and unacylated (UAG). Many studies suggest ...different roles for these two forms of ghrelin in energy balance regulation. In the present study, we compared the effects of acute intracerebroventricular administration of AG, UAG and their combination (AG+UAG) to young adult Wistar rats on food intake and central melanocortin system modulation. Although UAG did not affect food intake it significantly increased the number of c-Fos positive neurons in the arcuate (ARC), paraventricular (PVN) and solitary tract (NTS) nuclei. In contrast, UAG suppressed AG-induced neuronal activity in PVN and NTS. Central UAG also modulated hypothalamic expression of Mc4r and Bmp8b, which were increased and Mc3r, Pomc, Agrp and Ucp2, which were decreased. Finally, UAG, AG and combination treatments caused activation of c-Fos in POMC expressing neurons in the arcuate, substantiating a physiologic effect of these peptides on the central melanocortin system. Together, these results demonstrate that UAG can act directly to increase neuronal activity in the hypothalamus and is able to counteract AG-induced neuronal activity in the PVN and NTS. UAG also modulates expression of members of the melanocortin signaling system in the hypothalamus. In the absence of an effect on energy intake, these findings indicate that UAG could affect energy homeostasis by modulation of the central melanocortin system.
Using the rat glioma cell line C6 and the human glioma cell line U251, we demonstrate the multiple mechanisms underlying the in vitro anticancer effects of the C
60 fullerene water suspension (nano-C
...60 or
nC
60) produced by solvent exchange method. Nano-C
60 in a dose-dependent manner reduced the tumor cell numbers after 24 h of incubation. The observed antiglioma action of
nC
60 at high concentration (1 μg/ml) was due to a reactive oxygen species-mediated necrotic cell damage that was partly dependent on oxidative stress-induced activation of extracellular signal-regulated kinase (ERK). On the other hand, low-dose
nC
60 (0.25 μg/ml) did not induce either necrotic or apoptotic cell death, but caused oxidative stress/ERK-independent cell cycle block in G
2/M phase and subsequent inhibition of tumor cell proliferation. Treatment with either high-dose or low-dose
nC
60 caused the appearance of acidified intracytoplasmic vesicles indicative of autophagy, but only the antiglioma effect of low-dose
nC
60 was significantly attenuated by inhibiting autophagy with bafilomycin A1. Importantly, primary rat astrocytes were less sensitive than their transformed counterparts to a cytostatic action of low-dose
nC
60. These data provide grounds for further development of
nC
60 as an anticancer agent.
Abstract Because of the ability to induce cell death in certain conditions, the fullerenes (C60 ) are potential anticancer and toxic agents. The colloidal suspension of crystalline C60 (nano-C60 , n ...C60 ) is extremely toxic, but the mechanisms of its cytotoxicity are not completely understood. By combining experimental analysis and mathematical modelling, we investigate the requirements for the reactive oxygen species (ROS)-mediated cytotoxicity of different n C60 suspensions, prepared by solvent exchange method in tetrahydrofuran (THF/ n C60 ) and ethanol (EtOH/ n C60 ), or by extended mixing in water (aqu/ n C60 ). With regard to their capacity to generate ROS and cause mitochondrial depolarization followed by necrotic cell death, the n C60 suspensions are ranked in the following order: THF/ n C60 >EtOH/ n C60 >aqu/ n C60 . Mathematical modelling of singlet oxygen (1 O2 ) generation indicates that the1 O2 -quenching power (THF/ n C60 <EtOH/ n C60 <aqu/ n C60 ) of the solvent intercalated in the fullerene crystals determines their ability to produce ROS and cause cell damage. These data could have important implications for toxicology and biomedical application of colloidal fullerenes.
•Ghrelin’s metabolic effects are mediated by the mTORC1/S6K1 pathway.•Ghrelin control of plasma insulin is mediated through the mTORC1/S6K1 pathway.•These effects occur at the level of the central ...nervous system.
Signaling through the mammalian target of rapamycin complex 1 (mTORC1) and its effectors the S6-kinases (S6K) in the hypothalamus is thought to be involved in nutrient sensing and control of food intake. Given the anatomical proximity of this pathway to circuits for the hormone ghrelin, we investigated the potential role of the mTORC1/S6K pathway in mediating the metabolic effects of ghrelin. We found that ghrelin promoted phosphorylation of S6K1 in the mouse hypothalamic cell line N-41 and in the rat hypothalamus after intracerebroventricular administration. Rapamycin, an inhibitor of mTORC1, suppressed ghrelin-induced phosphorylation of hypothalamic S6K1 and increased food intake and insulin in rats. Chronic peripheral administration of ghrelin induced a significant increase in body weight, fat mass and food efficiency in wild-type and S6K2-knockout but not in S6K1-knockout mice. We therefore propose that ghrelin-induced hyperphagia, adiposity and insulin secretion are controlled by a central nervous system involving the mTORC1/S6K1 pathway.
We investigated the ability of 19 recently synthesized arylpiperazine compounds to protect human SH-SY5Y neuroblastoma cells from the neurotoxin 6-hydroxydopamine (6-OHDA). The compound with the most ...potent neuroprotective action was N-{3-2-(4-phenyl-piperazin-1-yl)-ethyl-phenyl}-picolinamide (6b), which reduced 6-OHDA-induced apoptotic death through stabilization of mitochondrial membrane and subsequent prevention of superoxide production, caspase activation and DNA fragmentation. 6-OHDA-triggered autophagic response was also reduced by 6b, which prevented inactivation of the main autophagy repressor mTOR, upregulation of proautophagic beclin-1, conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to autophagosome-associated LC3-II, as well as intracytoplasmic acidification induced by 6-OHDA. The inhibition of autophagy using LC3β gene silencing or pharmacological autophagy blockers 3-methyladenine or bafilomycin A1, mimicked the cytoprotective effect of 6b. While the treatment with 6b had no effect on the phosphorylation of proapoptotic MAP kinases ERK and JNK, it markedly increased the phosphorylation of the prosurvival kinase Akt in 6-OHDA-treated cells. Akt inhibitor DEBC or RNA interference-mediated Akt silencing reduced the ability of 6b to block 6-OHDA-triggered apoptotic and autophagic responses, thus confirming their dependency on Akt activation. The cytoprotective effect of 6b was also observed in 6-OHDA-treated neuronal PC12 cells, but not in SH–SY5Y or PC12 cells exposed to 1-methyl-4-phenylpyridinium, indicating that the observed neuroprotection was dependent on the cytotoxic stimulus. Because of the ability to prevent 6-OHDA induced apoptotic/autophagic cell death through activation of Akt, the investigated arylpiperazines could be potential candidates for treatment of neurodegenerative diseases.
•The in vitro neuroprotective action of novel arylpiperazine compounds was assessed.•Arylpiperazines protect SH-SY5Y neuroblastoma cells from the neurotoxin 6-OHDA.•Arylpiperazines block 6-OHDA-triggered mitochondrial damage and oxidative stress.•Arylpiperazines reduce 6-OHDA-induced apoptotic and autophagic cell death.•Neuroprotective action of arylpiperazines is mediated by Akt.
AMP-activated protein kinase (AMPK) is an intracellular energy sensor that regulates metabolic and immune functions mainly through the inhibition of the mechanistic target of rapamycin ...(mTOR)-dependent anabolic pathways and the activation of catabolic processes such as autophagy. The AMPK/mTOR signaling pathway and autophagy markers were analyzed by immunoblotting in blood mononuclear cells of 20 healthy control subjects and 23 patients with an acute demyelinating form of Guillain–Barré syndrome (GBS). The activation of the liver kinase B1 (LKB1)/AMPK/Raptor signaling axis was significantly reduced in GBS compared to control subjects. In contrast, the phosphorylated forms of mTOR activator AKT and mTOR substrate 4EBP1, as well as the levels of autophagy markers LC3-II, beclin-1, ATG5, p62/sequestosome 1, and NBR1 were similar between the two groups. The downregulation of LKB1/AMPK signaling, but not the activation status of the AKT/mTOR/4EBP1 pathway or the levels of autophagy markers, correlated with higher clinical activity and worse outcomes of GBS. A retrospective study in a diabetic cohort of GBS patients demonstrated that treatment with AMPK activator metformin was associated with milder GBS compared to insulin/sulphonylurea therapy. In conclusion, the impairment of the LKB1/AMPK pathway might contribute to the development/progression of GBS, thus representing a potential therapeutic target in this immune-mediated peripheral polyneuropathy.
Abstract The influence of fullerene (C60 ) nanoparticles on the cytotoxicity of a highly reactive free radical nitric oxide (NO) was investigated. Fullerene nanoparticles were prepared by ...mechanochemically assisted complexation with anionic surfactant sodium dodecyl sulfate, macrocyclic oligosaccharide γ-cyclodextrin or the copolymer ethylene vinyl acetate–ethylene vinyl versatate. C60 nanoparticles were characterized by UV–vis and atomic force microscopy. While readily internalized by mouse L929 fibroblasts, C60 nanoparticles were not cytotoxic. Moreover, they partially protected L929 cells from the cytotoxic effect of NO-releasing compounds sodium nitroprusside (SNP), S-nitroso- N -acetylpenicillamine (SNAP), S-nitrosoglutathione (GSNO) and 3-morpholino-sydnonimine (SIN-1). C60 nanoparticles reduced SNP-induced apoptotic cell death by preventing mitochondrial depolarization, caspase activation, cell membrane phosphatidylserine exposure and DNA fragmentation. The protective action of C60 nanoparticles was not exerted via direct interaction with NO, but through neutralization of mitochondria-produced superoxide radical in NO-treated cells, as demonstrated by using different redox-sensitive reporter fluorochromes. These data suggest that C60 complexes with appropriate host molecules might be plausible candidates for preventing NO-mediated cell injury in inflammatory/autoimmune disorders.
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