Liraglutide alleviates high-fat diet-induced kidney injury in mice by regulating the CaMKKß/AMPK pathway.

OBJECTIVE: Liraglutide, a glucagon-like peptide-1 receptor agonist, has been shown to regulate blood sugar and control body weight, but its ability to treat obesity-related nephropathy has been poorly studied. Therefore, this study was designed to observe the characteristics and potential mechanism of liraglutide against obesity-related kidney disease. METHODS: Thirty-six C57BL/6J male mice were randomly divided into six groups (n = 6 per group). Obesity-related nephropathy was induced in mice by continuous feeding of high-fat diet (HFD) for 12 weeks. After 12 weeks, liraglutide (0.6 mg/kg) and AMP-activated protein kinase (AMPK) agonists bortezomib (200 µg/kg) were injected for 12 weeks, respectively. Enzyme-linked immunosorbent assay was employed to detect the levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, blood urea nitrogen, creatinine in serum, as well as urinary protein in urine. Besides, hematoxylin-eosin staining and periodic acid-Schiff staining were used to observe the pathological changes of kidney tissue; immunohistochemistry, western blot, and real-time quantitative PCR to assess the calmodulin-dependent protein kinase kinase beta (CaMKKß)/AMPK signaling pathway activation. RESULTS: Liraglutide significantly reduced serum lipid loading, improved kidney function, and relieved kidney histopathological damage and glycogen deposition in the mouse model of obesity-related kidney disease induced by HFD. In addition, liraglutide also significantly inhibited the CaMKKß/AMPK signaling pathway in kidney tissue of HFD-induced mice. However, bortezomib partially reversed the therapeutic effect of liraglutide on HDF-induced nephropathy in mice. CONCLUSIONS: Liraglutide has a therapeutic effect on obesity-related kidney disease, and such an effect may be achieved by inhibiting the CaMKKß/AMPK signaling pathway in kidney tissue.

Aberrant expression of NEDD4L disrupts mitochondrial homeostasis by downregulating CaMKKß in diabetic kidney disease.

Disturbance in mitochondrial homeostasis within proximal tubules is a critical characteristic associated with diabetic kidney disease (DKD). CaMKKß/AMPK signaling plays an important role in regulating mitochondrial homeostasis. Despite the downregulation of CaMKKß in DKD pathology, the underlying mechanism remains elusive. The expression of NEDD4L, which is primarily localized to renal proximal tubules, is significantly upregulated in the renal tubules of mice with DKD. Coimmunoprecipitation (Co-IP) assays revealed a physical interaction between NEDD4L and CaMKKß. Moreover, deletion of NEDD4L under high glucose conditions prevented rapid CaMKKß protein degradation. In vitro studies revealed that the aberrant expression of NEDD4L negatively influences the protein stability of CaMKKß. This study also explored the role of NEDD4L in DKD by using AAV-shNedd4L in db/db mice. These findings confirmed that NEDD4L inhibition leads to a decrease in urine protein excretion, tubulointerstitial fibrosis, and oxidative stress, and mitochondrial dysfunction. Further in vitro studies demonstrated that si-Nedd4L suppressed mitochondrial fission and reactive oxygen species (ROS) production, effects antagonized by si-CaMKKß. In summary, the findings provided herein provide strong evidence that dysregulated NEDD4L disturbs mitochondrial homeostasis by negatively modulating CaMKKß in the context of DKD. This evidence underscores the potential of therapeutic interventions targeting NEDD4L and CaMKKß to safeguard renal tubular function in the management of DKD.

Transcriptional, biochemical, and immunohistochemical analyses of CaMKKß/2 splice variants that co-localize with CaMKIV in spermatids.

Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) phosphorylates and activates downstream protein kinases, including CaMKI, CaMKIV, PKB/Akt, and AMPK; thus, regulates various Ca2+-dependent physiological and pathophysiological pathways. Further, CaMKKß/2 in mammalian species comprises multiple alternatively spliced variants; however, their functional differences or redundancy remain unclear. In this study, we aimed to characterize mouse CaMKKß/2 splice variants (CaMKKß-3 and ß-3x). RT-PCR analyses revealed that mouse CaMKKß-1, consisting of 17 exons, was predominantly expressed in the brain; whereas, mouse CaMKKß-3 and ß-3x, lacking exon 16 and exons 14/16, respectively, were primarily expressed in peripheral tissues. At the protein level, the CaMKKß-3 or ß-3x variants showed high expression levels in mouse cerebrum and testes. This was consistent with the localization of CaMKKß-3/-3x in spermatids in seminiferous tubules, but not the localization of CaMKKß-1. We also observed the co-localization of CaMKKß-3/-3x with a target kinase, CaMKIV, in elongating spermatids. Biochemical characterization further revealed that CaMKKß-3 exhibited Ca2+/CaM-induced kinase activity similar to CaMKKß-1. Conversely, we noted that CaMKKß-3x impaired Ca2+/CaM-binding ability, but exhibited significantly weak autonomous activity (approximately 500-fold lower than CaMKKß-1 or ß-3) due to the absence of C-terminal of the catalytic domain and a putative residue (Ile478) responsible for the kinase autoinhibition. Nevertheless, CaMKKß-3x showed the ability to phosphorylate downstream kinases, including CaMKIα, CaMKIV, and AMPKα in transfected cells comparable to CaMKKß-1 and ß-3. Collectively, CaMKKß-3/-3x were identified as functionally active and could be bona fide CaMKIV-kinases in testes involved in the activation of the CaMKIV cascade in spermatids, resulting in the regulation of spermiogenesis.

Synthesis and biological evaluation of 2'-hydroxychalcone derivatives as AMPK activators.

A series of 2'-hydroxychalcone derivatives with various substituents on B-ring were synthesized and evaluated for AMP-activated protein kinase (AMPK) activation activity in podocyte cells. The results displayed that hydroxy, methoxy and methylenedioxy groups on B-ring could enhance the activitiy better than O-saturated alkyl, O-unsaturated alkyl or other alkoxy groups. Compounds 27 and 29 possess the highest fold change of 2.48 and 2.73, respectively, which were higher than those of reference compound (8) (1.28) and metformin (1.88). Compounds 27 and 29 were then subjected to a concentration-response study to obtain the EC50 values of 2.0 and 4.8 µM, respectively and MTT assays also showed that cell viability was not influenced by the exposure of podocytes to compounds 27 and 29 at concentrations up to 50 µM. In addition, compound 27 was proved to activate AMPK via calcium/calmodulin-dependent protein kinase kinase ß (CaMKKß)-dependent pathway without affecting intracellular calcium levels. The computational study showed that the potent compounds exhibited stronger ligand-binding strength to CaMKKß, particularly compounds 27 (-8.4 kcal/mol) and 29 (-8.0 kcal/mol), compared to compound 8 (-7.5 kcal/mol). Fragment molecular orbital (FMO) calculation demonstrated that compound 27 was superior to compound 29 due to the presence of methyl group, which amplified the binding by hydrophobic interactions. Therefore, compound 27 would represent a promising AMPK activator for further investigation of the treatment of diabetes and diabetic nephropathy.

A high-concentrate diet induces inflammatory injury via regulating Ca2+/CaMKKß-mediated autophagy in mammary gland tissue of dairy cows.

Introduction: Calmodulin-dependent protein kinase ß (CaMKKß) is closely related to Ca2+ concentration. An increase in Ca2+ concentration in the cytoplasm activates CaMKKß, and activated CaMKKß affects the activities of AMPK and mTOR and induces autophagy. A high-concentrate diet leads to Ca2+ disorder in mammary gland tissue. Objectives: Therefore, this study mainly investigated the induction of mammary gland tissue autophagy by a high-concentrate diet and the specific mechanism of lipopolysaccharide (LPS)-induced autophagy in bovine mammary epithelial cells (BMECs). Material and Methods: Twelve mid-lactation Holstein dairy cows were fed with a 40% concentrate diet (LC) and a 60% concentrate diet (HC) for 3 weeks. At the end of the trial, rumen fluid, lacteal vein blood, and mammary gland tissue were collected. The results showed that the HC diet significantly decreased rumen fluid pH, with a pH lower than 5.6 for more than 3 h, indicating successfully induction of subacute rumen acidosis (SARA). The mechanism of LPS-induced autophagy in BMECs was studied in vitro. First, the cells were divided into a Ctrl group and LPS group to study the effects of LPS on the concentration of Ca2+ and autophagy in BMECs. Then, cells were pretreated with an AMPK inhibitor (compound C) or CaMKKß inhibitor (STO-609) to investigate whether the CaMKKß-AMPK signaling pathway is involved in LPS-induced BMEC autophagy. Results: The HC diet increased the concentration of Ca2+ in mammary gland tissue and pro-inflammatory factors in plasma. The HC diet also significantly increased the expression of CaMKKß, AMPK, and autophagy-related proteins, resulting in mammary gland tissue injury. In vitro cell experiments showed that LPS increased intracellular Ca2+ concentration and upregulated protein expression of CaMKKß, AMPK, and autophagy-related proteins. Compound C pretreatment decreased the expression of proteins related to autophagy and inflammation. In addition, STO-609 pretreatment not only reversed LPS-induced BMECs autophagy but also inhibited the protein expression of AMPK, thereby alleviating the inflammatory response in BMECs. These results suggest that inhibition of the Ca2+/CaMKKß-AMPK signaling pathway reduces LPS-induced autophagy, thereby alleviating inflammatory injury of BMECs. Conclusion: Therefore, SARA may increase the expression of CaMKKß by increasing Ca2+ levels and activate autophagy through the AMPK signaling pathway, thereby inducing inflammatory injury in mammary gland tissue of dairy cows.

Microcystin leucine arginine induces human sperm damage: Involvement of the Ca2+/CaMKKß/AMPK pathway.

As a common pollutant in the water environment, microcystin leucine arginine (MC-LR) can enter semen and damage the sperm in animals. However, the mechanism by which MC-LR damages human sperm is unclear. Therefore, human sperm samples were obtained from the Henan Provincial Sperm Bank and exposed to different concentrations (0, 1, 10, and 100 µg/L) of MC-LR for 1, 2, 4, and 6 h, to invegest the effects and potential mechanism of MC-LR on sperm. The results showed that MC-LR mainly accumulated in the neck and flagellum of human sperm. Compared to the control group, the sperm capacitation rate and motility were significantly decreased in the 100 µg/L group. After exposure of 100 µg/L of MC-LR, the central microtubule and microtubule doublet of sperm flagellum were blurred, asymmetrical, or even lost. Furthermore, the expression levels of flagellin DNAH17, SPEF2, SPAG16, SPAG6, and CFAP44 in human sperm were reduced. Also, the phosphorylation levels of CaMKKß and AMPK can be inhibited by MC-LR. These findings revealed that MC-LR can induce functional and structural damage in human sperm, and the Ca2+/CaMKKß/AMPK pathway may be involved in this process. This study will provide a basis for prevention and treatment of male fertility declines caused by MC-LR.

Reactive oxygen species-mediated oxidative stress accelerates glycolysis via activation of the CaMKKß/AMPK pathway in the yak longissimus dorsi postmortem.

BACKGROUND: Adenosine monophosphate-activated protein kinase (AMPK) is instrumental in the initiation of early postmortem glycolysis and the advent of pale, soft, and exudative (PSE) meat when cellular energy is altered. However, conflicting studies show that AMPK activation without corresponding energy level changes in PSE meat challenges this long-held notion. Here, we examined the effects of reactive oxygen species (ROS)-mediated oxidative stress on AMPK activation in the context of glycolysis, protein solubility, and water-holding capacity (WHC) in the postmortem yak longissimus dorsi (LD) muscle. Further, we explored the mechanisms underlying these effects. RESULTS: Hydrogen peroxide (H2 O2 ) significantly augmented the degree of oxidative stress, increasing the production of ROS and malondialdehyde excessive production and reducing the activity of the anti-oxidants superoxide dismutase and glutathione peroxidase. In turn, oxidative stress dramatically promoted AMPK activation and glycolysis by increasing glycogen depletion and promoting hexokinase and phosphofructokinase activity. Subsequently, lactic acid accumulation increased, leading to a rapid decline in pH, which aggravated protein solubility degree and centrifugal loss in the early postmortem yak LD muscle. Importantly, these changes caused by oxidative stress were eliminated by the AMPK inhibitor. Mechanistically, oxidative stress elevated calcium ion (Ca2+ ) levels, which mobilized calcium/calmodulin-dependent protein kinase ß (CaMKKß) and AMPK. Rescue experiments confirmed that the increases were attenuated using Ca2+ and CaMKKß chelators, respectively. CONCLUSION: These results indicated that oxidative stress caused by ROS hastened early-stage postmortem glycolysis and reduced the WHC of yak meat. These effects were likely mediated by the alternative and energy-independent CaMKKß/AMPK signaling pathway. © 2022 Society of Chemical Industry.

Qian Yang Yu Yin granule improves hypertensive renal damage: A potential role for TRPC6-CaMKKß-AMPK-mTOR-mediated autophagy.

ETHNOPHARMACOLOGICAL RELEVANCE: Qian Yang Yu Yin granules (QYYYG) have a long history in the treatment of hypertensive renal damage (HRD) in China. Clinical studies have found that QYYYG stabilizes blood pressure and prevents early renal damage. However, the exact mechanism is not entirely clear. AIM OF THE STUDY: To evaluate the therapeutic effect and further explore the therapeutic mechanism of QYYYG against HRD. MATERIALS AND METHODS: The efficacy of QYYYG in treating HRD was assessed in spontaneous hypertension rats (SHR). Renal autophagy and the TRPC6-CaMKKß-AMPK pathway in rats were evaluated. The regulatory role of QYYYG in angiotensin II (Ang II) induced abnormal autophagy in rat podocytes was determined by detecting autophagy-related proteins, intracellular Ca2+ content, and the TRPC6-CaMKKß-AMPK-mTOR pathway expressions. Finally, we established a stable rat podocyte cell line overexpressing TRPC6 and used the cells to verify the regulatory effects of QYYYG. RESULTS: QYYYG alleviated HRD and reversed the abnormal expression of autophagy-related genes in the SHR. In vitro, QYYYG protected against Ang II-induced podocyte damage. Furthermore, treatment of podocytes with QYYYG reversed Ang II-induced autophagy and inhibited Ang II-stimulated TRPC6 activation, Ca2+ influx and activation CaMKKß-AMPK pathway. Overexpression of TRPC6 resulted in pronounced activation of CaMKKß, AMPK, and autophagy induction in rat podocytes, which were significantly attenuated by QYYYG. CONCLUSIONS: The present study suggested that QYYYG may exert its HRD protective effects in part by regulating the abnormal autophagy of podocytes through the TRPC6-CaMKKß-AMPK-mTOR pathway.

OR2AT4, an Ectopic Olfactory Receptor, Suppresses Oxidative Stress-Induced Senescence in Human Keratinocytes.

Olfactory receptors (ORs) are the largest protein superfamily in mammals. Certain ORs are ectopically expressed in extranasal tissues and regulate cell type-specific signal transduction pathways. OR2AT4 is ectopically expressed in skin cells and promotes wound healing and hair growth. As the capacities of wound healing and hair growth decline with aging, we investigated the role of OR2AT4 in the aging and senescence of human keratinocytes. OR2AT4 was functionally expressed in human keratinocytes (HaCaT) and exhibited co-expression with G-protein-coupled receptor signaling components, Golfα and adenylate cyclase 3. The OR2AT4 ligand sandalore modulates the intracellular calcium, inositol phosphate, and cyclic adenosine monophosphate (cAMP) levels. The increased calcium level induced by sandalore was attenuated in cells with OR2AT4 knockdown. OR2AT4 activation by sandalore inhibited the senescent cell phenotypes and restored cell proliferation and Ki-67 expression. Sandalore also inhibited the expression of senescence-associated ß-galactosidase and increased p21 expression in senescent HaCaT cells in response to hydrogen peroxide. Additionally, sandalore activated the CaMKKß/AMPK/mTORC1/autophagy signaling axis and promoted autophagy. OR2AT4 knockdown attenuated the increased in the intracellular calcium level, cell proliferation, and AMPK phosphorylation induced by sandalore. These findings demonstrate that the effects of sandalore are mediated by OR2AT4 activation. Our findings suggest that OR2AT4 may be a novel therapeutic target for anti-aging and anti-senescence in human keratinocytes.

CaMK4 overexpression in polycystic kidney disease promotes mTOR-mediated cell proliferation.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive enlargement of fluid-filled cysts, causing nephron loss and a decline in renal function. Mammalian target of rapamycin (mTOR) is overactive in cyst-lining cells and contributes to abnormal cell proliferation and cyst enlargement; however, the mechanism for mTOR stimulation remains unclear. We discovered that calcium/calmodulin (CaM) dependent kinase IV (CaMK4), a multifunctional kinase, is overexpressed in the kidneys of ADPKD patients and PKD mouse models. In human ADPKD cells, CaMK4 knockdown reduced mTOR abundance and the phosphorylation of ribosomal protein S6 kinase (S6K), a downstream target of mTOR. Pharmacologic inhibition of CaMK4 with KN-93 reduced phosphorylated S6K and S6 levels and inhibited cell proliferation and in vitro cyst formation of ADPKD cells. Moreover, inhibition of calcium/CaM-dependent protein kinase kinase-ß and CaM, two key upstream regulators of CaMK4, also decreased mTOR signaling. The effects of KN-93 were independent of the liver kinase B1-adenosine monophosphate-activated protein kinase (AMPK) pathway, and the combination of KN-93 and metformin, an AMPK activator, had additive inhibitory effects on mTOR signaling and in vitro cyst growth. Our data suggest that increased CaMK4 expression and activity contribute to mTOR signaling and the proliferation of cystic cells of ADPKD kidneys.

Jiedutongluotiaogan formula restores pancreatic function by suppressing excessive autophagy and endoplasmic reticulum stress.

CONTEXT: Jiedutongluotiaogan formula (JTTF), a traditional Chinese medicine (TCM), could promote islet function. However, the potential effect of JTTF on endoplasmic reticulum stress (ERS) and autophagy have not been reported. OBJECTIVE: This study explores the potential effect of JTTF on ERS and autophagy in the pancreas. MATERIALS AND METHODS: The Zucker diabetic fatty (ZDF) rats were randomised into five groups, control, model, JTTF (1, 3, 5 g/kg/day for 12 weeks). LPS induced pancreatic ß-cells were treated with JTTF (50, 100, 200 µg/mL). LPS was used to induce pancreatic ß-cell injury, with cell viability and insulin secretion evaluated using MTT, glucose-stimulated insulin secretion (GSIS) assays, and PCR. Intracellular Ca2+ concentration was measured using flow cytometry, while ERS and autophagy levels were monitored via Western blotting and/or immunostaining. RESULTS: Compared with the model group, body weight, FGB, HbA1c, IPGTT, FINs, and HOMA-IR in JTTF treatment groups were significantly reduced. In islets cells treated with JTTF, the pancreatic islet cells in the JTTF group were increased, lipid droplets were reduced, and there was a decrease in Ca2+ (16.67%). After JTTF intervention, PERK, p-PERK, IRE1α, p- IRE1α, ATF6, eIF2α, GRP78, p-ULK1, LC3 and p62 expression decreased, whereas Beclin1and p-mTOR expression increased. In addition, the expression of proteins related to apoptosis in the JTTF groups were lower than those in the control group. DISCUSSION AND CONCLUSIONS: JTTF may alleviate pancreatic ß-cell injury by inhibiting ER stress and excessive autophagy in diabetic rats. This provides a new direction for treating diabetes and restoring pancreatic dysfunction by TCM.

Traumatic-noise-induced hair cell death and hearing loss is mediated by activation of CaMKKß.

BACKGROUND: The Ca2+/calmodulin-dependent protein kinase kinases (CaMKKs) are serine/threonine-directed protein kinases that are activated following increases in intracellular calcium, playing a critical role in neuronal signaling. Inner-ear-trauma-induced calcium overload in sensory hair cells has been well documented in the pathogenesis of traumatic noise-induced hair cell death and hearing loss, but there are no established pharmaceutical therapies available due to a lack of specific therapeutic targets. In this study, we investigated the activation of CaMKKß in the inner ear after traumatic noise exposure and assessed the prevention of noise-induced hearing loss (NIHL) with RNA silencing. RESULTS: Treatment with short hairpin RNA of CaMKKß (shCaMKKß) via adeno-associated virus transduction significantly knocked down CaMKKß expression in the inner ear. Knockdown of CaMKKß significantly attenuated noise-induced hair cell loss and hearing loss (NIHL). Additionally, pretreatment with naked CaMKKß small interfering RNA (siCaMKKß) attenuated noise-induced losses of inner hair cell synapses and OHCs and NIHL. Furthermore, traumatic noise exposure activates CaMKKß in OHCs as demonstrated by immunolabeling for p-CaMKI. CaMKKß mRNA assessed by fluorescence in-situ hybridization and immunolabeling for CaMKKß in OHCs also increased after the exposure. Finally, pretreatment with siCaMKKß diminished noise-induced activation of AMPKα in OHCs. CONCLUSIONS: These findings demonstrate that traumatic-noise-induced OHC loss and hearing loss occur primarily via activation of CaMKKß. Targeting CaMKKß is a key strategy for prevention of noise-induced hearing loss. Furthermore, our data suggest that noise-induced activation of AMPKα in OHCs occurs via the CaMKKß pathway.

L-theanine prevents progression of nonalcoholic hepatic steatosis by regulating hepatocyte lipid metabolic pathways via the CaMKKß-AMPK signaling pathway.

BACKGROUND: L-theanine, a non-protein amino acid was found principally in the green tea, has been previously shown to exhibit potent anti-obesity property and hepatoprotective effect. Herein, we investigated the effects of L-theanine on alleviating nonalcoholic hepatic steatosis in vitro and in vivo, and explored the underlying molecular mechanism. METHODS: In vitro, HepG2 and AML12 cells were treated with 500 µM oleic acid (OA) or treated with OA accompanied by L-theanine. In vivo, C57BL/6J mice were fed with normal control diet (NCD), high-fat diet (HFD), or HFD along with L-theanine for 16 weeks. The levels of triglycerides (TG), accumulation of lipid droplets and the expression of genes related to hepatocyte lipid metabolic pathways were detected in vitro and in vivo. RESULTS: Our data indicated that, in vivo, L-theanine significantly reduced body weight, hepatic steatosis, serum levels of alanine transaminase (ALT), aspartate transaminase (AST), TG and LDL cholesterol (LDL-C) in HFD-induced nonalcoholic fatty liver disease (NAFLD) mice. In vitro, L-theanine also significantly alleviated OA induced hepatocytes steatosis. Mechanic studies showed that L-theanine significantly inhibited the nucleus translocation of sterol regulatory element binding protein 1c (SREBP-1c) through AMPK-mTOR signaling pathway, thereby contributing to the reduction of fatty acid synthesis. We also identified that L-theanine enhanced fatty acid ß-oxidation by increasing the expression of peroxisome proliferator-activated receptor α (PPARα) and carnitine palmitoyltransferase-1 A (CPT1A) through AMP-activated protein kinase (AMPK). Furthermore, our study indicated that L-theanine can active AMPK through its upstream kinase Calmodulin-dependent protein kinase kinase-ß (CaMKKß). CONCLUSIONS: Taken together, our findings suggested that L-theanine alleviates nonalcoholic hepatic steatosis by regulating hepatocyte lipid metabolic pathways via the CaMKKß-AMPK signaling pathway.

Circ_0000518 Promotes Macrophage/Microglia M1 Polarization via the FUS/CaMKKß/AMPK Pathway to Aggravate Multiple Sclerosis.

Evidence has shown that circ_0000518 is upregulated in peripheral of multiple sclerosis (MS) patients, suggesting that it may play an important role in the progression of MS. However, its specific mechanism in MS progression is unclear. In this study, the human microglial clone 3 (HMC3) cells were treated with 100 ng/mL of LPS for 24 h, then the short hairpin RNA against hsa_circ_0000518 (sh-hsa_circ_0000518) was transfected into cells and incubated for 48 h. We found increased circ_0000518 expressions, increased apoptosis and oxidative stress, increased M1 phenotype marker expression, and decreased M2 phenotype marker expression in cells, and that interfering with circ_0000518 expression reversed the effect of LPS on HMC3 cells. Online bioinformatics database analysis indicated that FUS is an RNA binding protein of circ_0000518. Next, we observed increased FUS expression in LPS treated HMC3 cells, and interfering with FUS expression reduced LPS triggered apoptosis and oxidative stress, decreased M1 phenotype marker expression, and promoted M2 phenotype marker expression. Mechanistic studies revealed that interfering with FUS promoted the polarization of HMC3 cells from the M1 phenotype to the M2 phenotype via activation of CaMKKß/AMPK-PGC-1α pathway, whereas this promoting effect was counteracted by STO-609. In an experimental autoimmune encephalomyelitis (EAE) mouse model, we observed that circ_0000518 knockdown reduced circ_0000518 and FUS expression in brain and spinal cord tissues, reduced neurological scores in mice, and alleviated inflammatory cell infiltration in the CNS. Summarily, our study identified that circ_0000518 promotes macrophage/microglial M1 polarization through the FUS/CaMKKß/AMPK pathway and aggravates MS.

Inhibition of autophagy by CRMP2-derived peptide ST2-104 (R9-CBD3) via a CaMKKß/AMPK/mTOR pathway contributes to ischemic postconditioning-induced neuroprotection against cerebral ischemia-reperfusion injury.

Cerebral ischemia, a common cerebrovascular disease, is characterized by functional deficits and apoptotic cell death. Autophagy, a type of programmed cell death, plays critical roles in controlling neuronal damage and metabolic homeostasis, and has been inextricably linked to cerebral ischemia. We previously identified a short peptide aptamer from collapsin response mediator protein 2 (CRMP2), designated the Ca2+ channel-binding domain 3 (CBD3) peptide, that conferred protection against excitotoxicity and traumatic brain injury. ST2-104, a nona-arginine (R9)-fused CBD3 peptide, exerted beneficial effects on neuropathic pain and was neuroprotective in a model of Alzheimer's disease; however, the effect of ST2-104 on cerebral ischemia and its mechanism of action have not been studied. In this study, we modeled cerebral ischemia-reperfusion injury in rats with the middle cerebral artery occlusion (MCAO) as well as challenged SH-SY5Y neuroblastoma cells with glutamate to induce toxicity to interrogate the effects of ST2-104 on autophagy following ischemic/excitotoxic insults. ST2-104 reduced the infarct volume and improved the neurological score of rats subjected to MCAO. ST2-104 protected SH-SY5Y cells from death following glutamate exposure via blunting apoptosis and autophagy as well as limiting excessive calcium entry. 3-Methyladenine (3-MA), an inhibitor of autophagy, promoted the effects of ST2-104 in inhibiting apoptosis triggered by glutamate while rapamycin, an activator of autophagy, failed to do so. ST2-104 peptide reversed glutamate-induced apoptosis via inhibiting Ca2+/CaM-dependent protein kinase kinase ß (CaMKKß)-mediated autophagy, which was partly enhanced by STO-609 (an inhibitor of CaMKKß). ST2-104 attenuated neuronal apoptosis by inhibiting autophagy through CaMKKß/AMPK/mTOR pathway. Our results suggest that the neuroprotective effect of ST2-104 are due to actions on the crosstalk between apoptosis and autophagy via the CaMKKß/AMPK/mTOR signaling pathway. The findings present novel insights into the potential neuroprotection of ST2-104 in cerebral ischemia.

AMPK: a key regulator of energy stress and calcium-induced autophagy.

Autophagy is a well-known cell-survival strategy orchestrated by a conserved set of proteins. It equips the cells with mechanisms to attain homeostasis during unfavorable conditions such as stress by breaking down the cellular components and reusing them for energy as well as for building new components required for survival. A basal level of autophagy is required for achieving homeostasis under normal conditions through regular turnover of macromolecules and organelles. Initiation of autophagy is regulated by two key components of the nutrient/energy sensor pathways; mammalian target of rapamycin 1 (mTORC1) and AMP-activated kinase (AMPK). Under energy-deprived conditions, AMPK is activated triggering autophagy, whereas, in nutrient-rich conditions, the growth-promoting kinase mTORC1 is activated inhibiting autophagy. Thus, the reciprocal regulation of autophagy by AMPK and mTORC1 defines a fundamental mechanism by which cells respond to nutrient availability. Interestingly, cytoplasmic calcium is also found to be an activator of AMPK and autophagy through a calmodulin/CaMKKß pathway. However, the physiological significance of the regulation of autophagy by cytoplasmic calcium is currently unclear. This review focuses on the current understanding of the mechanism of autophagy and its regulation by AMPK.

Sanghuangporus sanghuang Mycelium Prevents Paracetamol-Induced Hepatotoxicity through Regulating the MAPK/NF-κB, Keap1/Nrf2/HO-1, TLR4/PI3K/Akt, and CaMKKß/LKB1/AMPK Pathways and Suppressing Oxidative Stress and Inflammation.

Liver damage induced by paracetamol overdose is the main cause of acute liver failure worldwide. In order to study the hepatoprotective effect of Sanghuangporus sanghuang mycelium (SS) on paracetamol-induced liver injury, SS was administered orally every day for 6 days in mice before paracetamol treatment. SS decreased serum aminotransferase activities and the lipid profiles, protecting against paracetamol hepatotoxicity in mice. Furthermore, SS inhibited the lipid peroxidation marker malondialdehyde (MDA), hepatic cytochrome P450 2E1 (CYP2E1), and the histopathological changes in the liver and decreased inflammatory activity by inhibiting the production of proinflammatory cytokines in paracetamol-induced acute liver failure. Moreover, SS improved the levels of glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase in the liver. Significantly, SS diminished mitogen-activated protein kinase (MAPK), Toll-like receptor 4 (TLR4), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), and the nuclear factor-kappa B (NF-κB) axis, as well as upregulated the Kelch-like ECH-associated protein 1 (Keap1)/erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway, in paracetamol-induced mice. SS mainly inhibited the phosphorylation of the liver kinase B1 (LKB1), Ca2+/calmodulin-dependent kinase kinase ß (CaMKKß), and AMP-activated protein kinase (AMPK) protein expression. Furthermore, the protective effects of SS on paracetamol-induced hepatotoxicity were abolished by compound C, an AMPK inhibitor. In summary, we provide novel molecular evidence that SS protects liver cells from paracetamol-induced hepatotoxicity by inhibiting oxidative stress and inflammation.

PAR2 promotes high-fat diet-induced hepatic steatosis by inhibiting AMPK-mediated autophagy.

Protease-activated receptor 2 (PAR2) is a member of G protein-coupled receptors. There are two types of PAR2 signaling pathways: Canonical G-protein signaling and ß-arrestin signaling. Although PAR2 signaling has been reported to aggravate hepatic steatosis, the exact mechanism is still unclear, and the role of PAR2 in autophagy remains unknown. In this study, we investigated the regulatory role of PAR2 in autophagy during high-fat diet (HFD)-induced hepatic steatosis in mice. Increased protein levels of PAR2 and ß-arrestin-2 and their interactions were detected after four months of HFD. To further investigate the role of PAR2, male and female wild-type (WT) and PAR2-knockout (PAR2 KO) mice were fed HFD. PAR2 deficiency protected HFD-induced hepatic steatosis in male mice, but not in female mice. Interestingly, PAR2-deficient liver showed increased AMP-activated protein kinase (AMPK) activation with decreased interaction between Ca2+/calmodulin-dependent protein kinase kinase ß (CAMKKß) and ß-arrestin-2. In addition, PAR2 deficiency up-regulated autophagy in the liver. To elucidate whether PAR2 plays a role in the regulation of autophagy and lipid accumulation in vitro, PAR2 was overexpressed in HepG2 cells. Overexpression of PAR2 decreased AMPK activation with increased interaction of CAMKKß with ß-arrestin-2 and significantly inhibited autophagic responses in HepG2 cells. Inhibition of autophagy by PAR2 overexpression further exacerbated palmitate-induced lipid accumulation in HepG2 cells. Collectively, these findings suggest that the increase in the PAR2-ß-arrestin-2-CAMKKß complex by HFD inhibits AMPK-mediated autophagy, leading to the alleviation of hepatic steatosis.

Photobiomodulation reduces hepatic lipogenesis and enhances insulin sensitivity through activation of CaMKKß/AMPK signaling pathway.

Photobiomodulation (PBM) could improve systemic blood glucose and insulin resistance in diet-induced diabetic mice. A few possible molecular mechanisms for the beneficial effects of PBM on diabetes have been proposed, but there is still an urgent need to explore the underlying mechanisms that support the application of PBM in the treatment of diabetes. Our study aimed to evaluate the effects of PBM on lipid metabolism in the liver of high-fat diet (HFD)-induced mice and explore the potential mechanisms of PBM on obesity and type 2 diabetes. Here, we administered PBM therapy (wavelength: 635 nm, energy density: 8 J/cm2) daily for eight weeks to HFD-induced mice. We detected that eight-week daily administration of PBM ameliorated HFD-induced gain weight, hyperlipidemia, and hyperglycemia, but also protected against diet-induced hepatic steatosis and insulin resistance. Furthermore, PBM increased AMP-activated protein kinase (AMPK) activation, lowered nuclear translocation of sterol regulatory element binding protein 1 (SREBP1), decreased aberrant lipogenesis, and enhanced insulin sensitive in HFD-induced mice livers. We also observed that Ca2+/calmodulin-dependent protein kinase kinase ß (CaMKKß) activation was responsible for AMPK activation in insulin-resistant HepG2 cells exposed to PBM. In summary, PBM at 635 nm and 8 J/cm2 improved hepatic lipid metabolism and inhibited the development of HFD-induced obesity and type 2 diabetes. Moreover, increased intracellular Ca2+ content and CaMKKß-dependent AMPK activation were possible molecular mechanisms underlying the PBM-induced improvement on obesity and type 2 diabetes.

CaMKKß regulates proliferation, apoptosis, and glycolysis of hepatocellular carcinoma via PI3K/AKT pathway.

BACKGROUND: Hepatocellular carcinoma (HCC) is the most common malignancy of liver cancer. Calcium ions/calmodulins stimulate protein kinase kinases ß (CaMKKß) is a multifunctional protein kinase that is overexpressed in many types of cancer. This study aims to investigate the effect of CaMKKß interference on HCC in HepG2 cells and transplanted tumor mice. METHODS: CaMKKß gene was knocked out in HepG2 cells as an experimental group, empty vector lentivirus as a negative control (NC) group, and untreated HepG2 cells as a control group. Cell proliferation, cell cycle, apoptosis, invasion, and glycolysis potential assays were conducted, respectively. In addition, the expression of PI3K, p-PI3K, AKT, and p-AKT was quantified by Western blot. Finally, the effect of CaMKKß in vivo was investigated using a xenograft model. RESULTS: CaMKKß knockdown significantly suppressed HepG2 cell proliferation, cell cycle, invasion, EMT, and glycolysis, promoted cell apoptosis, and reduced the expression of hexokinase 2 (HK2), pyruvate kinase M (PKM2), and lactate dehydrogenase A (LDHA), p-PI3K, and p-AKT. Post the addition of AKT highly expression plasmid, glucose uptake, lactic acid production, and cell proliferation decreased, accompanied by an increase in apoptosis, which were substantially reversed. Notably, xenograft model experiments in vivo also confirmed that CaMKKß knockdown inhibited HCC growth. CONCLUSIONS: CaMKKß knockdown inhibited cell proliferation, invasion, and glycolysis through the PI3K/AKT pathway, heightened apoptosis, thus promoting the development of HCC. This might be a potential target for the diagnosis and treatment of HCC.