Infusion of GMSCs relieves autoimmune arthritis by suppressing the externalization of neutrophil extracellular traps via PGE2-PKA-ERK axis.

INTRODUCTION: Rheumatoid arthritis (RA) is a systemic autoimmune disease with limited treatment success, characterized by chronic inflammation and progressive cartilage and bone destruction. Accumulating evidence has shown that neutrophil extracellular traps (NETs) released by activated neutrophils are important for initiating and perpetuating synovial inflammation and thereby could be a promising therapeutic target for RA. K/B × N serum transfer-induced arthritis (STIA) is a rapidly developed joint inflammatory model that somehow mimics the inflammatory response in patients with RA. Human gingival-derived mesenchymal stem cells (GMSCs) have been previously shown to possess immunosuppressive effects in arthritis and humanized animal models. However, it is unknown whether GMSCs can manage neutrophils in autoimmune arthritis. OBJECTIVES: To evaluate whether infusion of GMSCs can alleviate RA by regulating neutrophils and NETs formation. If this is so, we will explore the underlying mechanism(s) in an animal model of inflammatory arthritis. METHODS: The effects of GMSCs on RA were assessed by comparing the symptoms of the K/B × N serum transfer-induced arthritis (STIA) model administered either with GMSCs or with control cells. Phenotypes examined included clinical scores, rear ankle thickness, paw swelling, inflammation, synovial cell proliferation, and immune cell frequency. The regulation of GMSCs on NETs was examined through immunofluorescence and immunoblotting in GMSCs-infused STIA mice and in an in vitro co-culture system of neutrophils with GMSCs. The molecular mechanism(s) by which GMSCs regulate NETs was explored both in vitro and in vivo by silencing experiments. RESULTS: We found in this study that adoptive transfer of GMSCs into STIA mice significantly ameliorated experimental arthritis and reduced neutrophil infiltration and NET formation. In vitro studies also showed that GMSCs inhibited the generation of NETs in neutrophils. Subsequent investigations revealed that GMSCs secreted prostaglandin E2 (PGE2) to activate protein kinase A (PKA), which ultimately inhibited the downstream extracellular signal-regulated kinase (ERK) pathway that is essential for NET formation. CONCLUSION: Our results demonstrate that infusion of GMSCs can ameliorate inflammatory arthritis mainly by suppressing NET formation via the PGE2-PKA-ERK signaling pathway. These findings further support the notion that the manipulation of GMSCs is a promising stem cell-based therapy for patients with RA and other autoimmune and inflammatory diseases.

Network pharmacological prediction and molecular docking analysis of the combination of Atractylodes macrocephala Koidz. and Paeonia lactiflora Pall. in the treatment of functional constipation and its verification.

BACKGROUND: We aimed to reveal the mechanism of functional constipation in the treatment of Atractylodes macrocephala Koidz. (AMK) and Paeonia lactiflora Pall. (PLP). METHODS: The main active ingredients of AMK and PLP were screened by the Traditional Chinese Medicine Systems Pharmacology (TCMSP) platform. A database of functional constipation targets was established by GeneCard and OMIM. An "ingredient-target" network map was constructed with Cytoscape software (version 3.7.1), and molecular docking analysis was performed on the components and genes with the highest scores. The rats in the normal group were given saline, and those in the other groups were given 10 mg/kg diphenoxylate once a day for 14 days. The serum and intestinal tissue levels of adenosine monophosphate (cAMP), protein kinase A (PKA), and adenylyl cyclase (AC) of the rats and aquaporin (AQP)1, AQP3, and AQP8 were measured. RESULTS: AMK and PLP had a significant role in the regulation of targets in the treatment of functional constipation. After treatment with AMK, PLP, or mosapride, the serum and intestinal tissue levels of AC, cAMP, and PKA were significantly downregulated. Groups receiving AMK and PLP or mosapride exhibited a reduction in the level of AQP1, AQP3, and AQP8 to varying degrees. CONCLUSION: Molecular docking analysis revealed that AMK and PLP had a significant role in the regulation of targets in the treatment of functional constipation. Studies have confirmed that AMK and PLP can also affect AC, cAMP, and PKA. AC, cAMP, and PKA in model rats were significantly downregulated. AQP expression is closely related to AC, cAMP, and PKA. AMK and PLP can reduce the expression of AQP1, AQP3, and AQP9 in the colon of constipated rats.

Selective inhibition of phosphodiesterase 4D increases tau phosphorylation at Ser214 residue.

Tau is a protein that normally participates in the assembly and stability of microtubules. However, it can form intraneuronal hyperphosphorylated aggregates that are hallmarks of Alzheimer's disease and other neurodegenerative disorders known as tauopathies. Tau can be phosphorylated by multiple kinases at several sites. Among such kinases, the cAMP-dependent protein kinase A (PKA) phosphorylates tau at Ser214 (pTAU-S214), an event that was shown to reduce the pathological assembly of the protein. Given that the neuronal cAMP/PKA-activated cascade is involved in synaptic plasticity and memory, and that cAMP-enhancing strategies demonstrated promising therapeutic potential for the treatment of cognitive deficits, we investigated the impact of cAMP on pTAU-S214 in N2a cells and rat hippocampal slices. Our results confirm that the activation of adenylyl cyclase increases pTAU-S214 in both model systems and, more interestingly, this effect is mimicked by GEBR-7b, a phosphodiesterase 4D inhibitor with proven pro-cognitive efficacy in rodents.

Rolipram Rescues Memory Consolidation Deficits Caused by Sleep Deprivation: Implication of the cAMP/PKA and cAMP/Epac Pathways.

BACKGROUND: Over the last few years, the number of people suffering from sleeping disorders has increased significantly despite negative effects on cognition and an association with brain inflammation. OBJECTIVES: We assessed memory deficits caused by Sleep Deprivation (SD) to determine the therapeutic effect of phosphodiesterase 4 (PDE4) inhibitors on SD-induced memory deficits and to investigate whether the modulation of memory deficits by PDE4 inhibitors is mediated by a protein kinase A (PKA)-independent pathway in conjunction with a PKA-dependent pathway. METHODS: Adult male mice were divided into four groups. Three SD groups were deprived of Rapid Eye Movement (REM) sleep for 12 h a day for six consecutive days. They were tested daily in the Morris water maze to evaluate learning and memory. One of the SD groups was injected with a PDE4 inhibitor, rolipram (1 mg/kg ip), whereas another had rolipram co-administered with chlorogenic acid (CHA, 20 mg/kg ip), an inhibitor of PKA. After 6 days, the mice were sacrificed, and the hippocampi were evaluated for cyclic AMP (cAMP) and nuclear factor Nrf-2 levels. The hippocampal expression of PKA, phosphorylated cAMP Response Element-Binding Protein (CREB), and phosphorylated glycogen synthase 3ß (Ser389) were also evaluated. RESULTS: SD caused a significant decrease in cAMP levels in the brain and had a detrimental effect on learning and memory. The administration of rolipram or rolipram+CHA resulted in an improvement in cognitive function. CONCLUSION: The present study provides evidence that restoration of memory with PDE4 inhibitors occurs through a dual mechanism involving the PKA and Epac pathways.

Cyclic nucleotide analogs as biochemical tools and prospective drugs.

Cyclic AMP (cAMP) and cyclic GMP (cGMP) are key second messengers involved in a multitude of cellular events. From the wealth of synthetic analogs of cAMP and cGMP, only a few have been explored with regard to their therapeutic potential. Some of the first-generation cyclic nucleotide analogs were promising enough to be tested as drugs, for instance N(6),O(2)'-dibutyryl-cAMP and 8-chloro-cAMP (currently in clinical Phase II trials as an anticancer agent). Moreover, 8-bromo and dibutyryl analogs of cAMP and cGMP have become standard tools for investigations of biochemical and physiological signal transduction pathways. The discovery of the Rp-diastereomers of adenosine 3',5'-cyclic monophosphorothioate and guanosine 3',5'-cyclic monophosphorothioate as competitive inhibitors of cAMP- and cGMP-dependent protein kinases, as well as subsequent development of related analogs, has proven very useful for studying the molecular basis of signal transduction. These analogs exhibit a higher membrane permeability, increased resistance against degradation, and improved target specificity. Furthermore, better understanding of signaling pathways and ligand/protein interactions has led to new therapeutic strategies. For instance, Rp-8-bromo-adenosine 3',5'-cyclic monophosphorothioate is employed against diseases of the immune system. This review will focus mainly on recent developments in cyclic nucleotide-related biochemical and pharmacological research, but also highlights some historical findings in the field.

The regulatory subunit of cAMP-dependent protein kinase as a target for chemotherapy of cancer and other cellular dysfunctional-related diseases.

Three separate experimental approaches, using site-selective cAMP analogs, antisense strategy and retroviral vector-mediated gene transfer, have provided evidence that two isoforms, the RI- and RII-regulatory subunits of cAMP-dependent protein kinase, have opposite roles in cell growth and differentiation; RI being growth stimulatory while RII is a growth-inhibitory and differentiation-inducing protein. As RI expression is enhanced during chemical or viral carcinogenesis, in human cancer cell lines and in primary human tumors, it is a target for cancer diagnosis and therapy. 8-Cl-cAMP and RI antisense oligodeoxynucleotide, those that effectively down-regulate RI alpha and up-regulate RII beta, provide new approaches toward the treatment of cancer. This approach to modulation of RI vs RII cAMP transducers may also be beneficial toward therapy of endocrine or cellular dysfunction-related diseases where abnormal signal transduction of cAMP is critically involved.

Antidiabetic effect of novel modulating peptides of G-protein-coupled kinase in experimental models of diabetes.

AIMS/HYPOTHESIS: G-protein-coupled receptor kinases (GRKs) play a key role in agonist-induced desensitisation of G-protein-coupled receptors (GPCRs) that are involved in metabolic regulation and glucose homeostasis. Our aim was to examine whether small peptides derived from the catalytic domain of GRK2 and -3 would ameliorate Type 2 diabetes in three separate animal models of diabetes. METHODS: Synthetic peptides derived from a kinase-substrate interaction site in GRK2/3 were initially screened for their effect on in vitro melanogenesis, a GRK-mediated process. The most effective peptides were administered intraperitoneally, utilising a variety of dosing regimens, to Psammomys obesus gerbils, Zucker diabetic fatty (ZDF) rats, or db/db mice. The metabolic effects of these peptides were assessed by measuring fasting and fed blood glucose levels and glucose tolerance. RESULTS: Two peptides, KRX-683(107) and KRX-683(124), significantly reduced fed-state blood glucose levels in the diabetic Psammomys obesus. In animals treated with KRX-683(124) at a dose of 12.5 mg/kg weekly for 7 weeks, ten of eleven treated animals responded with mean blood glucose significantly lower than controls (4.7+/-0.4 vs 16.8+/-0.8 mmol/l, p

betaARK1 inhibition improves survival in a mouse model of heart failure induced by myocardial infarction.

Heart failure (HF) is characterized by abnormalities in beta-adrenergic receptor (betaAR) signaling, including an increase in betaAR kinase 1 (betaARK1) levels and activity. Gene therapy using a peptide inhibitor of betaARK1 (betaARKct) in infarcted rabbit hearts has improved compromised cardiac function. To determine whether betaARK1 inhibition improves survival in a mouse model of HF induced by myocardial infarction (MI), we studied wild-type (WT) and transgenic (TG) mice overexpressing betaARKct following MI. There was no difference in infarct size. Survival of WT mice with MI was 25% at 26 weeks. In contrast, 92% of betaARKct TG mice with MI survived (P = 0.01). betaARKct TG mice with MI at 8 weeks showed significantly higher fractional shortening compared with WT mice with MI (25.1 +/- 2.7% versus 14.2 +/- 1.0%; P < 0.05). Moreover, the biochemical betaAR abnormalities in WT mice with MI were prevented in betaARKct TG mice with MI. In conclusion, betaARK1 inhibition results in a marked increase in survival and improved cardiac function in a mouse model of HF induced by MI.