Excessive linoleic acid induces muscle oxidative stress through 5-lipoxygenase-dependent peroxidation

Oxidative stress in muscles is closely related to the occurrence of insulin resistance, muscle weakness and atrophy, age-related sarcopenia, and cancer. Aldehydes, a primary oxidation intermediate of polyunsaturated fatty acids, have been proven to be an important trigger for oxidative stress. However, the potential role of linoleic acid (LA) as a donor for volatile aldehydes to trigger oxidative stress has not been reported. Here, we reported that excessive dietary LA caused muscle redox imbalance and volatile aldehydes containing hexanal, 2-hexenal, and nonanal were the main metabolites leading to oxidative stress. Importantly, we identified 5-lipoxygenase (5-LOX) as a key enzyme mediating LA peroxidation in crustaceans for the first time. The inhibition of 5-LOX significantly suppressed the content of aldehydes produced by excessive LA. Mechanistically, the activation of the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway facilitated the translocation of 5-LOX from the nucleus to the cytoplasm, where 5-LOX oxidized LA, leading to oxidative stress through the generation of aldehydes. This study suggests that 5-LOX is a potential target to prevent the production of harmful aldehydes.

Hypoxia enhances steroidogenic competence of buffalo (Bubalus bubalis) granulosa cells

Granulosa cells (GCs) synthesize estrogens needed for follicular growth. However, the effects of hypoxia on steroidogenesis in buffalo GCs remain unclear. In this study, the impacts of hypoxic conditions (5% oxygen) on estrogen synthesis in buffalo GCs were examined. The results showed that hypoxia improved both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3β-HSD) and the secretion levels of estradiol in buffalo GCs. Hypoxic conditions promoted the sensitivity of buffalo GCs to FSH. Furthermore, inhibition of cAMP/PKA signaling pathway (H89, a cAMP/PKA signaling pathway inhibitor) reduced both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3β-HSD) and the secretion levels of estradiol in hypoxia-cultured buffalo GCs. Besides, inhibition of cAMP/PKA signaling pathway lowered the responsiveness of buffalo GCs to FSH under hypoxic conditions. The present study indicated that hypoxia enhanced the steroidogenic competence of buffalo GCs principal by affecting cAMP/PKA signaling pathway and subsequent sensitivity of GCs to FSH.

Mitochondrial sAC-cAMP-PKA Axis Modulates the ΔΨm-Dependent Control Coefficients of the Respiratory Chain Complexes: Evidence of Respirasome Plasticity

The current view of the mitochondrial respiratory chain complexes I, III and IV foresees the occurrence of their assembly in supercomplexes, providing additional functional properties when compared with randomly colliding isolated complexes. According to the plasticity model, the two structural states of the respiratory chain may interconvert, influenced by the intracellular prevailing conditions. In previous studies, we suggested the mitochondrial membrane potential as a factor for controlling their dynamic balance. Here, we investigated if and how the cAMP/PKA-mediated signalling influences the aggregation state of the respiratory complexes. An analysis of the inhibitory titration profiles of the endogenous oxygen consumption rates in intact HepG2 cells with specific inhibitors of the respiratory complexes was performed to quantify, in the framework of the metabolic flux theory, the corresponding control coefficients. The attained results, pharmacologically inhibiting either PKA or sAC, indicated that the reversible phosphorylation of the respiratory chain complexes/supercomplexes influenced their assembly state in response to the membrane potential. This conclusion was supported by the scrutiny of the available structure of the CI/CIII2/CIV respirasome, enabling us to map several PKA-targeted serine residues exposed to the matrix side of the complexes I, III and IV at the contact interfaces of the three complexes.

TGR5 agonist inhibits intestinal epithelial cell apoptosis via cAMP/PKA/c-FLIP/JNK signaling pathway and ameliorates dextran sulfate sodium-induced ulcerative colitis

Excessive apoptosis of intestinal epithelial cell (IEC) is a crucial cause of disrupted epithelium homeostasis, leading to the pathogenesis of ulcerative colitis (UC). The regulation of Takeda G protein-coupled receptor-5 (TGR5) in IEC apoptosis and the underlying molecular mechanisms remained unclear, and the direct evidence from selective TGR5 agonists for the treatment of UC is also lacking. Here, we synthesized a potent and selective TGR5 agonist OM8 with high distribution in intestinal tract and investigated its effect on IEC apoptosis and UC treatment. We showed that OM8 potently activated hTGR5 and mTGR5 with EC₅₀ values of 202 ± 55 nM and 74 ± 17 nM, respectively. After oral administration, a large amount of OM8 was maintained in intestinal tract with very low absorption into the blood. In DSS-induced colitis mice, oral administration of OM8 alleviated colitis symptoms, pathological changes and impaired tight junction proteins expression. In addition to enhancing intestinal stem cell (ISC) proliferation and differentiation, OM8 administration significantly reduced the rate of apoptotic cells in colonic epithelium in colitis mice. The direct inhibition by OM8 on IEC apoptosis was further demonstrated in HT-29 and Caco-2 cells in vitro. In HT-29 cells, we demonstrated that silencing TGR5, inhibition of adenylate cyclase or protein kinase A (PKA) all blocked the suppression of JNK phosphorylation induced by OM8, thus abolished its antagonizing effect against TNF-α induced apoptosis, suggesting that the inhibition by OM8 on IEC apoptosis was mediated via activation of TGR5 and cAMP/PKA signaling pathway. Further studies showed that OM8 upregulated cellular FLICE-inhibitory protein (c-FLIP) expression in a TGR5-dependent manner in HT-29 cells. Knockdown of c-FLIP blocked the inhibition by OM8 on TNF-α induced JNK phosphorylation and apoptosis, suggesting that c-FLIP was indispensable for the suppression of OM8 on IEC apoptosis induced by OM8. In conclusion, our study demonstrated a new mechanism of TGR5 agonist on inhibiting IEC apoptosis via cAMP/PKA/c-FLIP/JNK signaling pathway in vitro, and highlighted the value of TGR5 agonist as a novel therapeutic strategy for the treatment of UC.

Xihuang pill induces pyroptosis and inhibits progression of breast cancer cells via activating the cAMP/PKA signalling pathway

Xihuang pill (XHP), a traditional Chinese medicine, has been shown to be effective for breast cancer (BC) therapy in clinical trials. However, the molecular mechanism of XHP in BC remains unclear. The molecular mechanism of XHP in BC was investigated in vivo by generating murine mammary carcinoma 4T1 cell xenografts. Enzyme-linked immunosorbent assay (ELISA) and reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) were used to detect pyroptosis-related indicators. Transcriptome sequencing was used to identify potential targets of XHP. Cell counting kit-8 (CCK-8), EdU, cell wound-healing, and transwell assays were performed to investigate the role of XHP in BC cells. Western blotting was performed to identify proteins related to the cAMP/PKA signalling pathway. XHP inhibited the growth of BC and induced pyroptosis. Western blotting confirmed the significant association between XHP and the cAMP/PKA signalling pathway revealed by Kyoto Encyclopedia of Genes and Genomes pathway analysis. XHP inhibited BC cell proliferation, migration, and invasion, and induced pyroptosis. Inhibiting the cAMP/PKA signalling pathway reversed the anti-cancer activity of XHP. XHP inhibits proliferation, migration, and invasion, and induces pyroptosis of BC cells via activating the cAMP/PKA signalling pathway.

3D-printing magnesium-polycaprolactone loaded with melatonin inhibits the development of osteosarcoma by regulating cell-in-cell structures

Melatonin has been proposed as a potent anticarcinogen presents a short half-life for osteosarcoma (OS). Cell-in-cell (CIC) structures play a role in the development of malignant tumors by changing the tumor cell energy metabolism. This study developed a melatonin-loaded 3D printed magnesium-polycaprolactone (Mg-PCL) scaffold and investigated its effect and molecular mechanism on CIC in OS. Mg-PCL scaffold was prepared by 3D-printing and its characteristic was determined. The effect and molecular mechanism of Mg-PCL scaffold as well as melatonin-loaded Mg-PCL on OS growth and progression were investigated in vivo and in vitro. We found that melatonin receptor 1 (MT1) and CIC expressions were increased in OS tissues and cells. Melatonin treatment inhibit the key CIC pathway, Rho/ROCK, through the cAMP/PKA signaling pathway, interfering with the mitochondrial physiology of OS cells, and thus playing an anti-invasion and anti-metastasis role in OS. The Mg-PCL-MT could significantly inhibit distant organ metastasis of OS in the in vivo model. Our results showed that melatonin-loaded Mg-PCL scaffolds inhibited the proliferation, invasion and metastasis of OS cells through the CIC pathway. The Mg-PCL-MT could be a potential therapeutics for OS.

Methylation-mediated down-regulation of microRNA-497-195 cluster confers osteogenic differentiation in ossification of the posterior longitudinal ligament of the spine via ADORA2A

Aberrant expression of microRNAs (miRNAs) has been associated with spinal ossification of the posterior longitudinal ligament (OPLL). Our initial bioinformatic analysis identified differentially expressed ADORA2A in OPLL and its regulatory miRNAs miR-497 and miR-195. Hence, this study was conducted to clarify the functional relevance of miR-497-195 cluster in OPLL, which may implicate in Adenosine A2A (ADORA2A). PLL tissues were collected from OPLL and non-OPLL patients, followed by quantification of miR-497, miR-195 and ADORA2A expression. The expression of miR-497, miR-195 and/or ADORA2A was altered in posterior longitudinal ligament (PLL) cells, which then were stimulated with cyclic mechanical stress (CMS). We validated that ADORA2A was expressed highly, while miR-497 and miR-195 were down-regulated in PLL tissues of OPLL patients. miR-195 and miR-497 expression in CMS-treated PLL cells was restored by a demethylation reagent 5-aza-2'-deoxycytidine (AZA). Moreover, expression of miR-195 and miR-497 was decreased by promoting promoter CpG island methylation. ADORA2A was verified as the target of miR-195 and miR-497. Overexpression of miR-195 and miR-497 diminished expression of osteogenic factors in PLL cells by inactivating the cAMP/PKA signaling pathway via down-regulation of ADORA2A. Collectively, miR-497-195 cluster augments osteogenic differentiation of PLL cells by inhibiting ADORA2A-dependent cAMP/PKA signaling pathway.

Lidocaine improves cerebral ischemia-reperfusion injury in rats through cAMP/PKA signaling pathway

Influence of lidocaine on rats with cerebral ischemia-reperfusion injury (CIRI) was studied to explore its mechanism of action. A total of 30 Sprague-Dawley rats were randomly divided into control group and model group, and the rat model of CIRI was prepared by the suture-occluded method in the model group. Then the rats in the model group were randomly assigned into the model group (n=10) and the lidocaine group (n=10). The neurological function score of rats was evaluated, and the levels of serum B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in rats were determined using ELISA. TUNEL assay was performed to detect the neuronal apoptosis in the brain of rats. The messenger ribonucleic acid (mRNA) and protein expression levels of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) were measured via RT-PCR and western blotting, respectively. Compared with those in the control group, the rats in the model group had an elevated neurological function score, a raised level of Bcl-2, but a reduced level of Bax in the serum, an obviously increased rate of neuronal apoptosis in the brain and decreased mRNA and protein levels of cAMP and PKA in cerebral tissues. The rats in lidocaine group had a lower neurological function score, a lower level of Bcl-2, but a higher level of Bax in the serum, an evidently lower rate of neuronal apoptosis in the brain and higher mRNA and protein levels of cAMP and PKA in cerebral tissues than those in the model group. Lidocaine can improve the neurological function of rats with CIRI and inhibit neuronal apoptosis in the brain, and its mechanism of action may be related to the activation of the cAMP/PKA signaling pathway.

PACAP38 improves airway epithelial barrier destruction induced by house dust mites allergen

PURPOSE

This study aimed to investigate the mechanism of PACAP38 on house dust mite (HDM)-induced asthmatic airway epithelial barrier destruction.

METHODS

The HDM-induced asthma mice model and 16HBE cell model was established respectively. The enzyme linked immunosorbent assay (ELSIA), cell count and immunohistochemical assay were performed on mice in control group, HDM group and PACAP38 + HDM group.The cAMP/PKA activity, p-CREB and total CREB expression, TEER and the FITC-DX were investigated on cells in control-16HBE group, HDM-16HBE group and PACAP38 + HDM-16HBE group.

RESULTS

The levels of IL-4 and IL-5 in the HDM group were significantly higher than those in the control group (P < 0.05), while the above indexes in the PACAP38 + HDM group were lower than those in the HDM group (P < 0.05). E-cadherin, β-catenin, ZO-1 and occludin in the control group were highly immunoreactive in airway epithelial cells, whereas connexin staining was attenuated after HDM induction. The TEER level, cAMP levels and PKA activity were decreased, while FITC-DX transmittance was increased in HDM-16HBE group (P < 0.05) compared with the control-16HBE group.

CONCLUSION

PACAP38 could reduce the airway inflammation, weaken the AJC protein heterotopia and activate cAMP/PKA signaling pathway in HDM-induced asthma, which indicate that PACAP38 may be an important contributor in HDM-induced asthma.

Zinc pyrithione induces immobilization of human spermatozoa and suppresses the response of the cAMP/PKA signaling pathway

Zinc pyrithione (ZPT), a zinc coordination complex, is used as an antimicrobial agent. This study investigated the molecular mechanisms underlying ZPT-induced spermatozoa immobilization by examining plasma membrane integrity, mitochondrial dysfunction, and the cAMP/PKA signaling pathway response. ZPT inhibited spermatozoa motility and movement patterns in a concentration-dependent manner. The 100% effective concentration (EC₁₀₀) and median effective concentration (EC₅₀) at which ZPT-induced spermatozoa immobilization at 20 s were 40 μmol/L and 16.19 μmol/L, respectively. ZPT did not significantly disrupt spermatozoa plasma membranes, but it exerted a strong and significant effect on the depolarization of mitochondria. In addition, ZPT exposure induced intracellular H⁺ accumulation and Ca²⁺ dissipation in spermatozoa, accompanied by suppression of the cAMP/PKA signaling pathway. Thus, ZPT induces spermatozoa immobilization without significant plasma membrane injury and so could be a candidate microbicidal spermicide.