Red ginseng extracts attenuate skin inflammation in atopic dermatitis through p70 ribosomal protein S6 kinase activation

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease with increased immunoglobulin E (IgE) levels. Activation of the mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K) signaling is known to occur in the inflammatory regions of AD skin. We previously demonstrated that red ginseng extract (RGE), as an anti-inflammatory agent, had potential for treating AD. However, it is still unclear whether RGE inhibits mTOR/p70S6K signaling. Thus, we examined the anti-inflammatory effects of RGE on IgE or interferon-γ (IFN-γ) induced signaling pathways. In KU812 human basophils, activation of Fcε receptor type Iα (FCεRI), also known as the high affinity IgE receptor, induced phosphorylation of both mTOR and p70S6K. Moreover, levels of phosphorylated p70S6K (p-p70S6K), but not p-mTOR, were decreased by RGE. RGE also decreased p-p70S6K levels in IFN-γ-stimulated human keratinocytes, suppressing the IFN-γ induced increase in levels of C-C chemokine ligand 2 mRNA. Interestingly, the increased p70S6K phosphorylation in skin lesions of AD model mice was attenuated by RGE treatment. In conclusion, RGE is a potential therapy against inflammatory responses involving the p70S6K signaling pathway.

Boehmenan, a Lignan From the Chinese Medicinal Plant Clematis armandii, Inhibits A431 Cell Growth via Blocking p70S6/S6 Kinase Pathway

Previously, we have shown that boehmenan, a natural product isolated from the dried stem of Caulis clematidis armandii, exhibits various biological activities. The current study investigated the effects of boehmenan on the growth of human epidermoid carcinoma A431 cells. Cell viability and 50% inhibiting concentration (IC₅₀) were assessed by CellTiter-Glo luminescent cell viability assay. Cell cycle arrest was measured by flow cytometry. Intracellular reactive oxygen species production and mitochondrial membrane potential (ΔΨ_m) collapse were analyzed by a fluorescence spectrophotometer. The activation of epidermal growth factor receptor signaling pathway was evaluated by Western blot. The results showed that boehmenan significantly inhibited the growth of A431 cells (IC₅₀ = 1.6 µM) in a concentration- and time-dependent manner. This compound also blocked cell cycle progression at G2/M phase and modulated mitochondrial apoptosis-related proteins, as evidenced by upregulating p21, cleaved caspase-3, and cleaved poly (ADP-ribose) polymerase protein levels and by downregulating Bcl-2, pro-caspase-9 levels. In addition, boehmenan also markedly induced intracellular reactive oxygen species production and ΔΨ_m depolarization in a concentration-dependent manner. Furthermore, boehmenan-attenuated epidermal growth factor mediated the phosphorylation of signal transducer and activator of transcription 3 (STAT3), p70 ribosomal protein S6 kinase (p70S6)/S6 in a concentration-dependent manner. Taken together, our results suggest that boehmenan-mediated antiproliferative property in A431 cells was mediated partially by modulation of mitochondrial function and inhibition of STAT3 and p70S6 signal pathways.

Dysfunctional survival-signaling and stress-intolerance in aged murine and human myocardium

Changes in cytoprotective signaling may influence cardiac aging, and underpin sensitization to ischemic insult and desensitization to 'anti-ischemic' therapies. We tested whether age-dependent shifts in ischemia-reperfusion (I-R) tolerance in murine and human myocardium are associated with reduced efficacies and coupling of membrane, cytoplasmic and mitochondrial survival-signaling. Hormesis (exemplified in ischemic preconditioning; IPC) and expression of proteins influencing signaling/stress-resistance were also assessed in mice. Mouse hearts (18 vs. 2-4 mo) and human atrial tissue (75±2 vs. 55±2 yrs) exhibited profound age-dependent reductions in I-R tolerance. In mice aging negated cardioprotection via IPC, G-protein coupled receptor (GPCR) agonism (opioid, A1 and A3 adenosine receptors) and distal protein kinase c (PKC) activation (4 nM phorbol 12-myristate 13-acetate; PMA). In contrast, p38-mitogen activated protein kinase (p38-MAPK) activation (1 μM anisomycin), mitochondrial ATP-sensitive K(+) channel (mKATP) opening (50 μM diazoxide) and permeability transition pore (mPTP) inhibition (0.2 μM cyclosporin A) retained protective efficacies in older hearts (though failed to eliminate I-R tolerance differences). A similar pattern of change in protective efficacies was observed in human tissue. Murine hearts exhibited molecular changes consistent with altered membrane control (reduced caveolin-3, cholesterol and caveolae), kinase signaling (reduced p70 ribosomal s6 kinase; p70s6K) and stress-resistance (increased G-protein receptor kinase 2, GRK2; glycogen synthase kinase 3β, GSK3β; and cytosolic cytochrome c). In summary, myocardial I-R tolerance declines with age in association with dysfunctional hormesis and transduction of survival signals from GPCRs/PKC to mitochondrial effectors. Differential changes in proteins governing caveolar and mitochondrial function may contribute to signal dysfunction and stress-intolerance.

Dysfunctional survival-signaling and stress-intolerance in aged murine and human myocardium

Changes in cytoprotective signaling may influence cardiac aging, and underpin sensitization to ischemic insult and desensitization to 'anti-ischemic' therapies. We tested whether age-dependent shifts in ischemia-reperfusion (I-R) tolerance in murine and human myocardium are associated with reduced efficacies and coupling of membrane, cytoplasmic and mitochondrial survival-signaling. Hormesis (exemplified in ischemic preconditioning; IPC) and expression of proteins influencing signaling/stress-resistance were also assessed in mice. Mouse hearts (18 vs. 2-4 mo) and human atrial tissue (75±2 vs. 55±2 yrs) exhibited profound age-dependent reductions in I-R tolerance. In mice aging negated cardioprotection via IPC, G-protein coupled receptor (GPCR) agonism (opioid, A1 and A3 adenosine receptors) and distal protein kinase c (PKC) activation (4 nM phorbol 12-myristate 13-acetate; PMA). In contrast, p38-mitogen activated protein kinase (p38-MAPK) activation (1 μM anisomycin), mitochondrial ATP-sensitive K(+) channel (mKATP) opening (50 μM diazoxide) and permeability transition pore (mPTP) inhibition (0.2 μM cyclosporin A) retained protective efficacies in older hearts (though failed to eliminate I-R tolerance differences). A similar pattern of change in protective efficacies was observed in human tissue. Murine hearts exhibited molecular changes consistent with altered membrane control (reduced caveolin-3, cholesterol and caveolae), kinase signaling (reduced p70 ribosomal s6 kinase; p70s6K) and stress-resistance (increased G-protein receptor kinase 2, GRK2; glycogen synthase kinase 3β, GSK3β; and cytosolic cytochrome c). In summary, myocardial I-R tolerance declines with age in association with dysfunctional hormesis and transduction of survival signals from GPCRs/PKC to mitochondrial effectors. Differential changes in proteins governing caveolar and mitochondrial function may contribute to signal dysfunction and stress-intolerance.

AMPK activation regulates neuronal structure in developing hippocampal neurons

AMP-activated protein kinase (AMPK) is a serine/threonine kinase that functions as a cellular and whole organism energy sensor to regulate ATP-consuming (anabolic) and ATP-generating (catabolic) pathways. The heterotrimeric AMPK complex consists of a catalytic α-subunit, regulatory β-subunit, and an AMP/ATP-binding γ-subunit. Several alternate isoforms exist for each subunit (α1, α2, β1, β2, γ1, γ2 and γ3). However, little is known of the expression pattern or function of the individual catalytic complexes in regulating neuronal structure. In this study, we examined the role of AMPK subunits in differentiating hippocampal neurons. We found that during development, the expression of AMPK subunits increase and that activation of AMPK by energetic stress inhibits neuronal development at multiple stages, not only during axon outgrowth, but also during dendrite growth and arborization. The presence of a single functional AMPK catalytic complex was sufficient to mediate these inhibitory effects of energetic stress. Activation of AMPK mediates these effects by suppressing both the mTOR and Akt signaling pathways. These findings demonstrate that the energy-sensing AMPK pathway regulates neuronal structure in distinct regions of developing neurons at multiple stages of development.

7-Ketocholesterol induces P-glycoprotein through PI3K/mTOR signaling in hepatoma cells

7-Ketocholesterol (7-KC) is found at an elevated level in patients with cancer and chronic liver disease. The up-regulation of an efflux pump, P-glycoprotein (P-gp) leads to drug resistance. To elucidate the effect of 7-KC on P-gp, P-gp function and expression were investigated in hepatoma cell lines Huh-7 and HepG2 and in primary hepatocyte-derived HuS-E/2 cells. At a subtoxic concentration, 48-h exposure to 7-KC reduced the intracellular accumulation and cytotoxicity of P-gp substrate doxorubicin in hepatoma cells, but not in HuS-E/2 cells. In Huh-7 cells, 7-KC elevated efflux function through the activation of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. 7-KC activated the downstream protein synthesis initiation factor 4E-BP1 and induced P-gp expression post-transcriptionally. The stimulation of efflux was reversible and could not be prevented by N-acetyl cysteine. Total cellular ATP content remained the same, whereas the lactate production was increased and fluorescence lifetime of protein-bound NADH was shortened. These changes suggested a metabolic shift to glycolysis, but glycolytic inhibitors did not eliminate 7-KC-mediated P-gp induction. These results demonstrate that 7-KC induces P-gp through PI3K/mTOR signaling and decreased the cell-killing efficacy of doxorubicin in hepatoma cells.

Effects of electroacupuncture on the expression of p70 ribosomal protein S6 kinase and ribosomal protein S6 in the hippocampus of rats with vascular dementia

This study investigated the mechanism underlying electroacupuncture therapy for vascular dementia through electroacupuncture at the acupoints of Baihui (DU20), Dazhui (DU14), and bilateral Shenshu (BL23) in a rat model of vascular dementia produced by bilateral middle cerebral artery occlusion. Morris water maze test showed that electroacupuncture improved the learning ability of vascular dementia rats. Western blot assay revealed that the expression of p70 ribosomal protein S6 kinase and ribosomal protein S6 in vascular dementia rats was significantly increased after electroacupuncture, compared with the model group that was not treated with acupuncture. The average escape latency was also shortened after electroacupuncture, and escape strategies in the spatial probe test improved from edge and random searches, to linear and trending swim pathways. The experimental findings indicate that electroacupuncture improves learning and memory ability by up-regulating expression of p70 ribosomal protein S6 kinase and ribosomal protein S6 in the hippocampus of vascular dementia rats.