Adenosine Monophosphate-activated Kinase Signaling Pathway Research Articles

Small heterodimer partner interacting leucine zipper protein (SMILE) ameliorates autoimmune arthritis via AMPK signaling pathway and the regulation of B cell activation

Rheumatoid arthritis (RA) is an autoimmune disease that causes joint swelling and inflammation and can involve the entire body. RA is characterized by the increase of pro-inflammatory cytokines such as interleukin (IL) and tumor necrosis factor, and the over-activation of T lymphocytes and B lymphocytes, which may lead to severe chronic inflammation of joints. However, despite numerous studies the pathogenesis and treatment of RA remain unresolved. This study investigated the use of small heterodimer partner-interacting leucine zipper protein (SMILE) overexpression to treat a mouse model of RA. SMILE is an insulin-inducible corepressor through adenosine monophosphate-activated kinase (AMPK) signaling pathway. The injection of a SMILE overexpression vector to mice with collagen induced-arthritis resulted in a milder clinical pathology and a reduced incidence of arthritis, less joint tissue damage, and lower levels of Th17 cells and plasma B cells in the spleen. Immunohistochemistry of the joint tissue showed that SMILE decreased B-cell activating factor (BAFF) receptor (BAFF-R), mTOR, and STAT3 expression but increased AMPK expression. In SMILE-overexpressing transgenic mice with collagen antibody-induced arthritis (CAIA), a decrease in the arthritis score and reductions in tissue damage, the number of B cells, and antibody production were observed. The treatment of immune cells in vitro with curcumin, a known SMILE-inducing agent, led to decreases in plasma B cells, germinal center B cells, IL-17-producing B cells, and BAFF-R-positive B cells. Taken together, our findings demonstrate the therapeutic potential of SMILE in RA, based on its inhibition of B cell activation mediated by the AMPK/mTOR and STAT3 signaling pathway and BAFF-R expression.EtcT49u9cQiSZwStZ5UX76Video abstract

Research Progress on Mechanism of Podocyte Depletion in Diabetic Nephropathy.

Diabetic nephropathy (DN) together with glomerular hyperfiltration has been implicated in the development of diabetic microangiopathy in the initial stage of diabetic diseases. Increased amounts of urinary protein in DN may be associated with functional and morphological alterations of podocyte, mainly including podocyte hypertrophy, epithelial-mesenchymal transdifferentiation (EMT), podocyte detachment, and podocyte apoptosis. Accumulating studies have revealed that disruption in multiple renal signaling pathways had been critical in the progression of these pathological damages, such as adenosine monophosphate-activated kinase signaling pathways (AMPK), wnt/β-catenin signaling pathways, endoplasmic reticulum stress-related signaling pathways, mammalian target of rapamycin (mTOR)/autophagy pathway, and Rho GTPases. In this review, we highlight new molecular insights underlying podocyte injury in the progression of DN, which offer new therapeutic targets to develop important renoprotective treatments for DN over the next decade.

The Role of AMPK Pathway in Neuroprotection.

Adenosine monophosphate-activated kinase (AMPK) is a highly conserved protein kinase found in all eukaryotic genomes. It exists as heterotrimeric protein consisting of α, β, and γ subunits. AMPK is activated by elevated levels of adenosine mono-phosphate (AMP), which is produced during conditions of low ATP production and perhaps mitochondrial dysfunction. Activation of AMPK has been shown to regulate a large number of downstream pathways. These will either increase energy production such as increase oxidation of fatty acids and glucose, or decrease energy utilization such as inhibiting synthesis of glycogen, fatty acid synthesis, and protein synthesis. In addition, being a key regulator of physiological energy dynamics, AMPK has been demonstrated to play roles in regulating various cellular processes such as mitochondrial biogenesis (Jager etal. Proc Natl Acad Sci U S A 104:12017-12022, 2007), autophagy (Hyttinen etal. Rejuven Res 14:651-660, 2011) and inflammation and immune responses (Giri etal. 2004). Retinal neurons have a high energy demand but have a poor energy storage capacity. Because of this, it is likely that the AMPK signaling pathway plays an important role in maintaining energy balance, and therefore may be a therapeutic target to prevent or delay retinal degeneration.

Arsenic Inhibits Neurite Outgrowth by Inhibiting the LKB1–AMPK Signaling Pathway

BackgroundArsenic (As) is an environmental pollutant that induces numerous pathological effects, including neurodevelopmental disorders.Objectives and MethodsWe evaluated the role of the LKB1–AMPK pathway in As-induced developmental neurotoxicity using Neuro-2a (N2a) neuroblastoma cells as a model of developing neurons.ResultsThe addition of low concentrations of As (≤ 5 μM) during differentiation caused an inhibitory effect on the neurite outgrowth in N2a cells in the absence of cell death. Activation of adenosine monophosphate–activated kinase (AMPK) induced by retinoic acid in differentiating cells was blocked by As. Pretreatment with the AMPK-specific activator 5-aminoimidazole-4-carboxamide riboside or overexpression of a constitutively active AMPK-α1 plasmid reversed As-induced inhibition of neurite outgrowth. The activation of LKB1 (serine/threonine kinase 11), a major AMPK kinase, was also suppressed by As by inhibiting both the phosphorylation and the translocation of LKB1 from nucleus to cytoplasm. Antioxidants, such as N-acetyl cysteine and superoxide dismutase, but not catalase, protected against As-induced inactivation of the LKB1–AMPK pathway and reversed the inhibitory effect of As on neurite outgrowth.ConclusionsReduced neurite outgrowth induced by As results from deficient activation of AMPK as a consequence of a lack of activation of LKB1. Oxidative stress induced by As, especially excessive superoxide, plays a critical role in blocking the LKB1–AMPK pathway. Our studies provide insight into the mechanisms underlying As-induced developmental neurotoxicity, which is important for designing a new strategy for protecting children against this neurotoxic substance.