Relations between the mitogen-activated protein kinase and the cAMP-dependent protein kinase pathways: comradeship and hostility

Melatonin alleviates oxidative stress damage in mouse testes induced by bisphenol A

We investigated the effect of melatonin on bisphenol A (BPA)-induced oxidative stress damage in testicular tissue and Leydig cells. Mice were gavaged with 50 mg/kg BPA for 30 days, and concurrently, were injected with melatonin (10 mg/kg and 20 mg/kg). Leydig cells were treated with 10 μmol/L of BPA and melatonin. The morphology and organ index of the testis and epididymis were observed and calculated. The sperm viability and density were determined. The expressions of melatonin receptor 1A and luteinizing hormone receptor, and the levels of malonaldehyde, antioxidant enzymes, glutathione, steroid hormone synthases, aromatase, luteinizing hormone, testosterone, and estradiol were measured. TUNEL assay was utilized to detect testicular cell apoptosis. The administration of melatonin at 20 mg/kg significantly improved the testicular index and epididymis index in mice treated with BPA. Additionally, melatonin promoted the development of seminiferous tubules in the testes. Furthermore, the treatment with 20 mg/kg melatonin significantly increased sperm viability and sperm density in mice, while also promoting the expressions of melatonin receptor 1A and luteinizing hormone receptor in Leydig cells of BPA-treated mice. Significantly, melatonin reduced the level of malonaldehyde in testicular tissue and increased the expression of antioxidant enzymes (superoxide dismutase 1, superoxide dismutase 2, and catalase) as well as the content of glutathione. Moreover, melatonin also reduced the number of apoptotic Leydig cells and spermatogonia, aromatase expression, and estradiol level, while increasing the expression of steroid hormone synthases (steroidogenic acute regulatory protein, cytochrome P450 family 17a1, cytochrome P450 17α-hydroxylase/20-lyase, and, 17β-hydroxysteroid dehydrogenase) and the level of testosterone. Melatonin exhibited significant potential in alleviating testicular oxidative stress damage caused by BPA. These beneficial effects may be attributed to melatonin's ability to enhance the antioxidant capacity of testicular tissue, promote testosterone synthesis, and reduce testicular cell apoptosis.

An emerging paradigm of CXCL12 involvement in the metastatic cascade

The chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF1), has emerged as a pivotal regulator in the intricate molecular networks driving cancer progression. As an influential factor in the tumor microenvironment, CXCL12 plays a multifaceted role that spans beyond its traditional role as a chemokine inducing invasion and metastasis. Indeed, CXCL12 has been assigned functions related to epithelial-to-mesenchymal transition, cancer cell stemness, angiogenesis, and immunosuppression, all of which are currently viewed as specialized biological programs contributing to the "metastatic cascade" among other cancer hallmarks. Its interaction with its cognate receptor, CXCR4, initiates a cascade of events that not only shapes the metastatic potential of tumor cells but also defines the niches within the secondary organs that support metastatic colonization. Given the profound implications of CXCL12 in the metastatic cascade, understanding its mechanistic underpinnings is of paramount importance for the targeted elimination of rate-limiting steps in the metastatic process. This review aims to provide a comprehensive overview of the current knowledge surrounding the role of CXCL12 in cancer metastasis, especially its molecular interactions rationalizing its potential as a therapeutic target.

The Adenylyl Cyclase Activator Forskolin Increases Influenza Virus Propagation in MDCK Cells by Regulating ERK1/2 Activity

Vaccination is the most effective method for preventing the spread of the influenza virus. Cell-based influenza vaccines have been developed to overcome the disadvantages of egg-based vaccines and their production efficiency has been previously discussed. In this study, we investigated whether treatment with forskolin (FSK), an adenylyl cyclase activator, affected the output of a cell-based influenza vaccine. We found that FSK increased the propagation of three influenza virus subtypes (A/H1N1/California/4/09, A/H3N2/Mississippi/1/85, and B/Shandong/7/97) in Madin-Darby canine kidney (MDCK) cells. Interestingly, FSK suppressed the growth of MDCK cells. This effect could be a result of protein kinase A (PKA)-Src axis activation, which downregulates extracellular signal-regulated kinase (ERK)1/2 activity and delays cell cycle progression from G1 to S. This delay in cell growth might benefit the binding and entry of the influenza virus in the early stages of viral replication. In contrast, FSK dramatically upregulated ERK1/2 activity via the cAMP-PKA-Raf-1 axis at a late stage of viral replication. Thus, increased ERK1/2 activity might contribute to increased viral ribonucleoprotein export and influenza virus propagation. The increase in viral titer induced by FSK could be explained by the action of cAMP in assisting the entry and binding of the influenza virus. Therefore, FSK addition to cell culture systems could help increase the production efficiency of cell-based vaccines against the influenza virus.

Bisphenol-A disturbs hormonal levels and testis mitochondrial activity, reducing male fertility

STUDY QUESTION

How does bisphenol-A (BPA) influence male fertility, and which mechanisms are activated following BPA exposure?

SUMMARY ANSWER

BPA exposure causes hormonal disruption and alters mitochondrial dynamics and activity, ultimately leading to decreased male fertility.

WHAT IS KNOWN ALREADY

As public health concerns following BPA exposure are rising globally, there is a need to understand the exact mechanisms of BPA on various diseases. BPA exposure causes hormonal imbalances and affects male fertility by binding the estrogen receptors (ERs), but the mechanism of how it mediates the hormonal dysregulation is yet to be studied.

STUDY DESIGN SIZE DURATION

This study consisted of a comparative study using mice that were separated into a control group and a group exposed to the lowest observed adverse effect level (LOAEL) (n = 20 mice/group) after a week of acclimatization to the environment. For this study, the LOAEL established by the US Environmental Protection Agency of 50 mg/kg body weight (BW)/day of BPA was used. The control mice were given corn oil orally. Based on the daily variations in BW, both groups were gavaged every day from 6 to 11 weeks (6-week exposure). Before sampling, mice were stabilized for a week. Then, the testes and spermatozoa of each mouse were collected to investigate the effects of BPA on male fertility. IVF was carried out using the cumulus-oocyte complexes from female hybrid B6D2F1/CrljOri mice (n = 3) between the ages of eight and twelve weeks.

PARTICIPANTS/MATERIALS SETTING METHODS

Signaling pathways, apoptosis, and mitochondrial activity/dynamics-related proteins were evaluated by western blotting. ELISA was performed to determine the levels of sex hormones (FSH, LH, and testosterone) in serum. Hematoxylin and eosin staining was used to determine the effects of BPA on histological morphology and stage VII/VIII testicular seminiferous epithelium. Blastocyst formation and cleavage development rate were evaluated using IVF.

MAIN RESULTS AND THE ROLE OF CHANCE

BPA acted by binding to ERs and G protein-coupled receptors and activating the protein kinase A and mitogen-activated protein kinase signaling pathways, leading to aberrant hormone levels and effects on the respiratory chain complex, ATP synthase and protein-related apoptotic pathways in testis mitochondria (P < 0.05). Subsequently, embryo cleavage and blastocyst formation were reduced after the use of affected sperm, and abnormal morphology of seminiferous tubules and stage VII and VIII seminiferous epithelial cells (P < 0.05) was observed. It is noteworthy that histopathological lesions were detected in the testes at the LOAEL dose, even though the mice remained generally healthy and did not exhibit significant changes in BW following BPA exposure. These observations suggest that testicular toxicity is more than a secondary outcome of compromised overall health in the mice due to systemic effects.

LARGE SCALE DATA

Not applicable.

LIMITATIONS REASONS FOR CAUTION

Since the protein expression levels in the testes were validated, in vitro studies in each testicular cell type (Leydig cells, Sertoli cells, and spermatogonial stem cells) would be required to shed further light on the exact mechanism resulting from BPA exposure. Furthermore, the BPA doses employed in this study significantly exceed the typical human exposure levels in real-life scenarios. Consequently, it is imperative to conduct experiments focusing on the effects of BPA concentrations more in line with daily human exposures to comprehensively assess their impact on testicular toxicity and mitochondrial activity.

WIDER IMPLICATIONS OF THE FINDINGS

These findings demonstrate that BPA exposure impacts male fertility by disrupting mitochondrial dynamics and activities in the testes and provides a solid foundation for subsequent investigations into the effects on male reproductive function and fertility following BPA exposure, and the underlying mechanisms responsible for these effects. In addition, these findings suggest that the LOAEL concentration of BPA demonstrates exceptional toxicity, especially when considering its specific impact on the testes and its adverse consequences for male fertility by impairing mitochondrial activity. Therefore, it is plausible to suggest that BPA elicits distinct toxicological responses and mechanistic endpoints based on the particular concentration levels for each target organ.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1A6A1A03025159). No competing interests are declared.

Reproduction strategy of nocturnal marine molluscs: running for love

The cost of reproduction is the core driver of life history evolution in animals. This paper demonstrates that the cumulative distance moved and the duration of movement of sexually immature abalones, Haliotis discus hannai, kept in various male and female groups, were significantly higher than those of sexually mature individuals, except when kept in mixed cultures of mature males and females. After mixed-culture, sexually mature males moved significantly further and for a longer duration than mature female abalones, and even more so than mature male abalones of any other group. Examination of the LC-MS metabolomics of mature males cultured with sexually mature females (AM) and those cultured with sexually immature females (JM) showed that cyclic adenosine monophosphate (cAMP) acted as a differential metabolic biomarker. After 24-h uninterrupted sampling, the concentration of 5-HT and the expression levels of the 5-HT2 and 5-HT6 receptors in AM were significantly higher than those in JM. After further injection of 5-HT2 and 5-HT6 receptor antagonists, the concentrations of cAMP and PKA rose again, but the cumulative movement duration and distance of male abalones decreased significantly, showing that 5-HT was involved in the regulation of movement behavior of male abalones through the 5-HT2 and 5-HT6 receptor-activated cAMP-PKA pathways. The results demonstrated a significant increase in the movement endurance of mature male abalones cultured with mature females, providing a theoretical basis for understanding the adaptive life history strategies of abalones and suggesting ways to protect diverse benthic resources for abalones during the reproductive stage.

Transgenic overexpression of heat shock protein (HSP83) enhances protein kinase A activity, disrupts GP63 surface protease expression and alters promastigote morphology in Leishmania amazonensis

Leishmania parasites undergo morphological changes during their infectious life cycle, including developmental transitions within the sandfly vector, culminating in metacyclic stages that are pre-adapted for infection. Upon entering vertebrate host phagocytes, Leishmania differentiate into intracellular amastigotes, the form that is ultimately transmitted back to the vector to complete the life cycle. Although environmental conditions that induce these cellular transitions are well-established, molecular mechanisms governing Leishmania morphologic differentiation in response to these cues remain largely uncharacterized. Previous studies indicate a key role for HSP83 in both promastigote metacyclogenesis and amastigote differentiation. To further elucidate HSP83 functions in the Leishmania lifecycle, we examined the biological impact of experimentally elevating HSP83 gene expression in Leishmania. Significantly, HSP83 overexpression was associated with altered metacyclic morphology, increased protein kinase A (PKA) activity and decreased expression of the Leishmania major surface protease, GP63. Corroborating these findings, overexpression of the L. amazonensis PKA catalytic subunit resulted in a largely similar phenotype. Our findings demonstrate for the first time in Leishmania, a functional link between HSP83 and PKA in the control of Leishmania gene expression, replication and morphogenesis.

Gene expression profile analysis unravelled the systems level association of renal cell carcinoma with diabetic nephropathy and Matrix-metalloproteinase-9 as a potential therapeutic target

Type 2 diabetes (T2D) and cancer share many common risk factors. However, the potential biological link that connects the two at the molecular level is still unclear. The experimental evidence suggests that several genes and their pathways may be involved in developing cancerous conditions associated with diabetes. In this study, we identified the protein-protein interaction (PPI) networks and the hub protein(s) that interlink T2D and cancer using genome-scale differential gene expression profiles. Further, the PPI network of AMP-activated protein kinase (AMPK) in cancer was analyzed to explore novel insights into the molecular association between the two conditions. The densely connected regions were analyzed by constructing the backbone and subnetworks with key nodes and shortest pathways, respectively. The PPI network studies identified Matrix-metalloproteinase-9 (MMP-9) as a hub protein playing a vital role in glomerulonephritis tubular diseases and some genetic kidney diseases. MMP-9 was also associated with different growth factors, like tumor necrosis factor (TNF-α), transforming growth factor 1 (TGF-1), and pathways like chemokine signaling, NOD-like receptor signaling, etc. Further, the molecular docking and molecular dynamic simulation studies supported the druggability of MMP-9, suggesting it as a potential therapeutic target in treating renal cell carcinoma linked with diabetic kidney disease.Communicated by Ramaswamy H. Sarma.

Glia Cells Control Olfactory Neurogenesis by Fine-Tuning CXCL12

Olfaction depends on lifelong production of sensory neurons from CXCR4 expressing neurogenic stem cells. Signaling by CXCR4 depends on the concentration of CXCL12, CXCR4's principal ligand. Here, we use several genetic models to investigate how regulation of CXCL12 in the olfactory stem cell niche adjusts neurogenesis. We identify subepithelial tissue and sustentacular cells, the olfactory glia, as main CXCL12 sources. Lamina propria-derived CXCL12 accumulates on quiescent gliogenic stem cells via heparan sulfate. Additionally, CXCL12 is secreted within the olfactory epithelium by sustentacular cells. Both sustentacular-cell-derived and lamina propria-derived CXCL12 are required for CXCR4 activation. ACKR3, a high-affinity CXCL12 scavenger, is expressed by mature glial cells and titrates CXCL12. The accurate adjustment of CXCL12 by ACKR3 is critical for CXCR4-dependent proliferation of neuronal stem cells and for proper lineage progression. Overall, these findings establish precise regulation of CXCL12 by glia cells as a prerequisite for CXCR4-dependent neurogenesis and identify ACKR3 as a scavenger influencing tissue homeostasis beyond embryonic development.

3-Hydroxybutyrate ameliorates insulin resistance by inhibiting PPARγ Ser273 phosphorylation in type 2 diabetic mice

3-Hydroxybutyrate (3HB) is a small ketone body molecule produced endogenously by the body in the liver. Previous studies have shown that 3HB can reduce blood glucose level in type 2 diabetic (T2D) patients. However, there is no systematic study and clear mechanism to evaluate and explain the hypoglycemic effect of 3HB. Here we demonstrate that 3HB reduces fasting blood glucose level, improves glucose tolerance, and ameliorates insulin resistance in type 2 diabetic mice through hydroxycarboxylic acid receptor 2 (HCAR2). Mechanistically, 3HB increases intracellular calcium ion (Ca²⁺) levels by activating HCAR2, thereby stimulating adenylate cyclase (AC) to increase cyclic adenosine monophosphate (cAMP) concentration, and then activating protein kinase A (PKA). Activated PKA inhibits Raf1 proto-oncogene serine/threonine-protein kinase (Raf1) activity, resulting in a decrease in extracellular signal-regulated kinases 1/2 (ERK1/2) activity and ultimately inhibiting peroxisome proliferator-activated receptor γ (PPARγ) Ser273 phosphorylation in adipocytes. Inhibition of PPARγ Ser273 phosphorylation by 3HB altered the expression of PPARγ regulated genes and reduced insulin resistance. Collectively, 3HB ameliorates insulin resistance in type 2 diabetic mice through a pathway of HCAR2/Ca²⁺/cAMP/PKA/Raf1/ERK1/2/PPARγ.

Artesunate inhibits PDE4 leading to intracellular cAMP accumulation, reduced ERK/MAPK signaling, and blockade of influenza A virus vRNP nuclear export

Influenza A viruses (IAV) have been a major cause of mortality. Given the potential for future deadly pandemics, effective drugs are needed for the treatment of severe influenzas, such as those caused by H5N1 IAV. The anti-malaria drugs artemisinin and its derivates, including artesunate (AS), have been reported to have broad antiviral activities. Here, we showed AS's antiviral activity against H5N1, H1N1, H3N2 and oseltamivir-resistant influenza A(H1N1)virus in vitro. Moreover, we showed that AS treatment significantly protected mice from lethal challenges with H1N1 and H5N1 IAV. Strikingly, the combination of AS and peramivir treatment significantly improved survival outcomes compared to their monotherapy with either AS or peramivir. Furthermore, we demonstrated mechanistically that AS affected the later stages of IAV replication and limited nuclear export of viral ribonucleoprotein (vRNP) complexes. In A549 cells, we demonstrated for the first time that AS treatment induced cAMP accumulation via inhibiting PDE4, and consequently reduced ERK phosphorylation and blocked IAV vRNP export, and thus suppressed IAV replication. These AS's effects were reversed by the pre-treatment with a cAMP inhibitor SQ22536. Our findings suggest that AS could serve as a novel IAV inhibitor by interfering vRNP nuclear export to prevent and treat IAV infection.

A-Kinase Anchor Protein 95 Is Involved in ERK1/2-Elk-1 Signal Transduction in Colon Cancer

Objectives

To assess A-kinase anchor protein 95 (AKAP95), B-Raf, extracellular regulated protein kinases 1/2 (ERK1/2), and Elk-1 expression in colon cancer tissue, and characterize AKAP95 associations with B-Raf, ERK1/2, Elk-1, and colon cancer clinicopathological indices.

Methods

The immunohistochemistry streptavidin-perosidase (SP) method was used to determine protein expression levels in 64 colon cancer and 32 para-carcinoma tissue specimens.

Results

(1) Positive AKAP95 expression rates in colon cancer tissue were higher when compared with para-carcinoma tissue (92.19% vs. 59.38%, P < 0.05). Similar findings were determined for B-Raf (76.56% vs. 25%, P < 0.05), ERK1/2 (90.63% vs. 31.25%, P < 0.05), and Elk-1 levels (92.19% vs. 40.63%, P < 0.05). (2) No significant associations were identified between AKAP95, B-Raf, ERK1/2, and Elk-1 protein expression and degree of differentiation, histological type, and lymph node metastasis in colon cancer samples (P > 0.05); however, in The Cancer Genome Atlas and Gene Expression Omnibus datasets, AKAP95 was closely related to immune infiltration, and highly expressed AKAP95 was negatively associated with overall survival and relapse free survival rates in colon cancer patients. (3) Correlations were observed between AKAP95 and ERK1/2, AKAP95 and Elk-1, B-Raf and ERK1/2, B-Raf and Elk-1, and ERK1/2 and Elk-1 (all P < 0.05), but no correlation was observed between AKAP95 and B-Raf (P > 0.05).

Conclusions

AKAP95 may affect immune infiltration levels in colon cancer by participating in ERK1/2-Elk-1 signal transduction.

Dopamine, Immunity, and Disease

The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies.

PDE4 inhibitor eliminates breast cancer stem cells via noncanonical activation of mTOR

Ineffective cancer treatment is implicated in metastasis, recurrence, resistance to chemotherapy and radiotherapy, and evasion of immune surveillance. All these failures occur due to the persistence of cancer stem cells (CSCs) even after rigorous therapy, thereby rendering them as essential targets for cancer management. Contrary to the quiescent nature of CSCs, a gene profiler array disclosed that phosphatidylinositol-3-kinase (PI3K), which is known to be crucial for cell proliferation, differentiation, and survival, was significantly upregulated in CSCs. Since PI3K is modulated by cyclic adenosine 3',5' monophosphate (cAMP), analyses of cAMP regulation revealed that breast CSCs expressed increased levels of phosphodiesterase 4 (PDE4) in contrast to normal stem cells. In accordance, the effects of rolipram, a PDE4 inhibitor, were evaluated on PI3K regulators and signaling. The efficacy of rolipram was compared with paclitaxel, an anticancer drug that is ineffective in obliterating breast CSCs. Analyses of downstream signaling components revealed a switch between cell survival and death, in response to rolipram, specifically of the CSCs. Rolipram-mediated downregulation of PDE4A levels in breast CSCs led to an increase in cAMP levels and protein kinase A (PKA) expression. Subsequently, PKA-mediated upregulation of phosphatase and tensin homolog antagonized the PI3K/AKT/mTOR pathway and led to cell cycle arrest. Interestingly, direct yet noncanonical activation of mTOR by PKA, circumventing the influence of PI3K and AKT, temporally shifted the fate of CSCs toward apoptosis. Rolipram in combination with paclitaxel indicated synergistic consequences, which effectively obliterated CSCs within a tumor, thereby suggesting combinatorial therapy as a sustainable and effective strategy to abrogate breast CSCs for better patient prognosis.

Non-canonical β-adrenergic activation of ERK at endosomes

G-protein-coupled receptors (GPCRs), the largest family of signalling receptors, as well as important drug targets, are known to activate extracellular-signal-regulated kinase (ERK)-a master regulator of cell proliferation and survival1. However, the precise mechanisms that underlie GPCR-mediated ERK activation are not clearly understood2-4. Here we investigated how spatially organized β2-adrenergic receptor (β2AR) signalling controls ERK. Using subcellularly targeted ERK activity biosensors5, we show that β2AR signalling induces ERK activity at endosomes, but not at the plasma membrane. This pool of ERK activity depends on active, endosome-localized Gαs and requires ligand-stimulated β2AR endocytosis. We further identify an endosomally localized non-canonical signalling axis comprising Gαs, RAF and mitogen-activated protein kinase kinase, resulting in endosomal ERK activity that propagates into the nucleus. Selective inhibition of endosomal β2AR and Gαs signalling blunted nuclear ERK activity, MYC gene expression and cell proliferation. These results reveal a non-canonical mechanism for the spatial regulation of ERK through GPCR signalling and identify a functionally important endosomal signalling axis.

Hepatic consequences of a mixture of endocrine-disrupting chemicals in male mice

The global epidemic of metabolic syndrome has been partially linked to ubiquitous exposure to endocrine-disrupting chemicals (EDCs). Although the impacts of exposure to single EDCs have been thoroughly studied, the consequences of simultaneous uncontrolled exposure to multiple EDCs require further investigations. Therefore, in this study, we evaluated how exposure to mixtures containing bisphenol A and seven phthalates impacts liver functions and metabolic homeostasis. Male mice were gavaged with either EDCs at four different dose combinations or corn oil (control) for six weeks. The results showed that exposure to EDCs at the human daily exposure limit had a negligible impact on liver function. However, EDC at ≥ 25 orders of magnitude of human-relevant doses had detrimental impacts on overall liver function, leading to metabolic abnormalities, steatohepatitis, and hepatic fibrosis via the activation of both genomic and non-genomic pathways. The metabolic phenotype was linked to alterations in key genes involved in hepatic lipid and glucose metabolism. In contrast, alterations in cytokine expression, oxidative stress, and apoptosis impacted steatohepatitis and fibrosis. Because EDC exposure does not occur independently, the findings of the combined effects of exposure to multiple EDCs have significant relevance for public health.

The Modulation of Melanogenesis in B16 Cells Upon Treatment with Plant Extracts and Isolated Plant Compounds

Plants are a rich source of secondary metabolites that exhibit numerous desired properties. The compounds may influence the biology of melanocytes, pigment cells that produce melanin, by modulating numerous signaling pathways, including cAMP/PKA, MAPKs and PI3K/AKT. Its downstream target is microphthalmia-associated transcription factor, responsible for the expression of the tyrosinase enzyme, which plays a major role in melanogenesis. Therefore, this literature review aims to provide insights related to melanogenesis modulation mechanisms of plant extracts and isolated plant compounds in B16 cells. Database searches were conducted using online-based library search instruments from 2012 to 2022, such as NCBI-PubMed and Google Scholar. Upregulation or downregulation of signaling pathways by phytochemicals can influence skin hypo- and hyperpigmentation by changing the level of melanin production, which may pose a significant cosmetic issue. Therefore, plant extracts or isolated plant compounds may be used in the therapy of pigmentation disorders.

Single-domain near-infrared protein provides a scaffold for antigen-dependent fluorescent nanobodies

Small near-infrared (NIR) fluorescent proteins (FPs) are much needed as protein tags for imaging applications. We developed a 17 kDa NIR FP, called miRFP670nano3, which brightly fluoresces in mammalian cells and enables deep-brain imaging. By exploring miRFP670nano3 as an internal tag, we engineered 32 kDa NIR fluorescent nanobodies, termed NIR-Fbs, whose stability and fluorescence strongly depend on the presence of specific intracellular antigens. NIR-Fbs allowed background-free visualization of endogenous proteins, detection of viral antigens, labeling of cells expressing target molecules and identification of double-positive cell populations with bispecific NIR-Fbs against two antigens. Applying NIR-Fbs as destabilizing fusion partners, we developed molecular tools for directed degradation of targeted proteins, controllable protein expression and modulation of enzymatic activities. Altogether, NIR-Fbs enable the detection and manipulation of a variety of cellular processes based on the intracellular protein profile.

Potential neurotoxicity, immunotoxicity, and carcinogenicity induced by metribuzin and tebuconazole exposure in earthworms (Eisenia fetida) revealed by transcriptome analysis

Metribuzin and tebuconazole have been widely used in agriculture for several decades. Apart from endocrine disruption, little is known about their toxicological effects on organisms without thyroid organs, at the transcriptional level. To explore this toxicity, model earthworm species Eisenia fetida, hatched from the same cocoon and cultured under identical environmental conditions, were independently exposed to the two chemicals at non-lethal concentrations in OECD artificial soil for 48 h after exposure. RNA-seq technology was used to analyze and compare the gene expression profiles of earthworms exposed to metribuzin and tebuconazole. The functions of differentially expressed genes and their standard response patterns of upregulated and downregulated expression for both pesticides were verified. The findings demonstrated that metribuzin and tebuconazole are both potentially toxic to earthworms. Toxicological effects mainly involved the nervous system, immune system, and tumors, at the transcriptional level, as well as the induction of cytochrome P450-dependent detoxification and oxidative stress. In addition, the mitogen-activated protein kinase kinase kinase gene was identified as a biomarker, and the mitogen-activated protein kinase signaling pathway was verified to be a part of the adverse outcome pathway of metribuzin and tebuconazole and their structural analogs.

SUZ12 Loss Amplifies the Ras/ERK Pathway by Activating Adenylate Cyclase 1 in NF1-Associated Neurofibromas

Patients with germline neurofibromatosis type 1 (NF1) microdeletions frequently exhibit hereditary syndromes such as cardiovascular anomalies and have an increased risk of malignant peripheral nerve sheath tumors (MPNSTs). This study aimed to identify the genes codeleted with SUZ12 that are related to MPNST. We used differential gene expression and enrichment analyses to analyze the SUZ12-mutant and SUZ12-wild-type gene expression profiles in the GSE118186 and GSE66743 datasets in Gene Expression Omnibus (GEO). PPI network analysis combined with MPNST patient survival analysis was used to identify ADCY1, which catalyzes the conversion of ATP to cAMP, as a key gene. Moreover, chromatin immunoprecipitation sequencing (ChIP-Seq) showed that the distribution of H3K27me3 in the ADCY1 promoter region and gene body was significantly reduced in SUZ12-mutant cells. To verify the role of ADCY1 in SUZ12 mutation, we used RNA interference and plasmid transfection to interfere with SUZ12 expression in plexiform neurofibroma (pNF) and MPNST cell lines and then treated the cells with forskolin, IBMX and H89. ERK phosphorylation was accelerated and prolonged after siRNA transfection, especially in ipNF05.5 cells, and the intensity and duration of ERK activation were reduced after SUZ12 overexpression. Importantly, the level of p-ERK was consistent with that of Rap1-GTP. Moreover, H89 completely blocked Rap1 activation and the changes in the p-ERK level after SUZ12 siRNA transfection. In conclusion, our findings suggested that SUZ12 loss potentiates the effects of NF1 mutations by amplifying Ras signaling through the ADCY1/cAMP/Rap1/ERK pathway and that SUZ12 may serve as a therapeutic and prognostic biomarker in NF1-associated neurofibromas.

β2-Adrenoceptor Agonists Promote ERK1/2 Dephosphorylation in Human Airway Epithelial Cells by Canonical, cAMP-driven Signaling Independently of β-Arrestin 2

Chronic use of β₂-adrenoceptor agonists as a monotherapy in asthma is associated with a loss of disease control and an increased risk of mortality. Herein, we tested the hypothesis that β₂-adrenoceptor agonists, including formoterol, promote biased, β-arrestin 2 (βArr2)-dependent activation of the mitogen-activated protein (MAP) kinases, ERK1/2, in human airway epithelial cells and, thereby, effect changes in gene expression that could contribute to their adverse clinical outcomes. Three airway epithelial cell models were used: the BEAS-2B cell line, human primary bronchial epithelial cells (HBEC) grown in submersion culture and HBEC that were highly differentiated at an air-liquid interface. Unexpectedly, treatment of all epithelial cell models with formoterol decreased basal ERK1/2 phosphorylation. This was mediated by cAMP-dependent protein kinase and involved the inactivation of C-rapidly-activated fibrosarcoma, which attenuated down-stream ERK1/2 activity, and the induction of dual-specificity phosphatase-1. Formoterol also inhibited the basal expression of early growth response-1, an ERK1/2-regulated gene that controls cell growth and repair in the airways. Neither carvedilol, a β₂-adrenoceptor agonist biased towards βArr2, nor formoterol promoted ERK1/2 phosphorylation in BEAS-2B cells although β₂-adrenoceptor desensitization was compromised in ARRB2-deficient cells. Collectively, these results contest the hypothesis that formoterol activates ERK1/2 in airway epithelia by nucleating a βArr2 signaling complex; instead, they indicate that β₂-adrenoceptor agonists inhibit constitutive ERK1/2 activity in a cAMP-dependent manner. These findings are the antithesis of results obtained using acutely challenged native and engineered HEK293 cells, which have been used extensively to study mechanisms of ERK1/2 activation, and highlight the cell-type-dependence of β₂-adrenoceptor-mediated signaling. Significance Statement It has been proposed that the adverse-effects of β₂-adrenoceptor agonist monotherapy in asthma are mediated by genomic mechanisms that occur principally in airway epithelial cells and are the result of β-arrestin 2-dependent activation of ERK1/2. This study shows that β₂-adrenoceptor agonists, paradoxically, reduced ERK1/2 phosphorylation in airway epithelia by disrupting upstream Ras-C-Raf complex formation and inducing DUSP1. Moreover, these effects were PKA-dependent suggesting that β₂-adrenoceptor agonists were not biased toward β-arrestin 2 and acted via canonical, cAMP-dependent signaling.

Androgen and glucocorticoid receptor phosphorylation following resistance exercise and pre-workout supplementation

PURPOSE

Consumption of caffeine or caffeine containing pre-workout supplements (SUPP) augments steroid hormone responses to resistance exercise (RE). However, the activation of glucocorticoid (GR) and androgen receptors (AR) following RE SUPP has not been investigated. The purpose of this study was to determine the influence of a pre-workout supplement on AR and GR phosphorylation following RE.

METHODS

In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males ((X¯±SD, age = 22 ± 2.4 yrs, hgt = 175 ± 7 cm, body mass = 84.1 ± 11.8 kg) performed four sets of 8 repetitions of barbell back squats at 75% of their 1-repetition maximum (1-RM) with two minutes of rest between sets and a fifth set of barbell back squats at 60% of 1-RM until concentric failure. A SUPP or flavor and color matched placebo (PL) was consumed 60-minutes prior to RE. Vastus lateralis muscle biopsies were obtained prior to supplementation at rest (BL), and ten minutes post-exercise (POST). Biopsies were analyzed for phosphorylated GR (ser134, ser211, and ser226) and phosphorylated AR (ser81, ser213, ser515, ser650) via western blotting.

RESULTS

pGRser134 decreased, and pGRser226 increased following RE (p < 0.05) with no difference between conditions (p > 0.05). pGRser211 was unchanged after RE (p > 0.05). pARser515 increased, and total AR expression decreased after RE (p < 0.05) in SUPP only. Testosterone and cortisol were not different between SUPP and PL at POST (p > 0.05).

CONCLUSION

RE influences AR and GR phosphorylation, and SUPP minimally influences this response in the early recovery period.

Simultaneous readout of multiple FRET pairs using photochromism

Förster resonant energy transfer (FRET) is a powerful mechanism to probe associations in situ. Simultaneously performing more than one FRET measurement can be challenging due to the spectral bandwidth required for the donor and acceptor fluorophores. We present an approach to distinguish overlapping FRET pairs based on the photochromism of the donor fluorophores, even if the involved fluorophores display essentially identical absorption and emission spectra. We develop the theory underlying this method and validate our approach using numerical simulations. To apply our system, we develop rsAKARev, a photochromic biosensor for cAMP-dependent protein kinase (PKA), and combine it with the spectrally-identical biosensor EKARev, a reporter for extracellular signal-regulated kinase (ERK) activity, to deliver simultaneous readout of both activities in the same cell. We further perform multiplexed PKA, ERK, and calcium measurements by including a third, spectrally-shifted biosensor. Our work demonstrates that exploiting donor photochromism in FRET can be a powerful approach to simultaneously read out multiple associations within living cells.

Performing multiple FRET measurements at once can be challenging. Here the authors report a method to discriminate between overlapping FRET pairs, even if the fluorophores display almost identical absorption and emission spectra, based on the photochromism of the donor fluorophores.

The Role of the CXCL12/CXCR4/CXCR7 Chemokine Axis in Cancer

Chemokines are a family of small, secreted cytokines which regulate a variety of cell functions. The C-X-C motif chemokine ligand 12 (CXCL12) binds to C-X-C chemokine receptor type 4 (CXCR4) and C-X-C chemokine receptor type 7 (CXCR7). The interaction of CXCL12 and its receptors subsequently induces downstream signaling pathways with broad effects on chemotaxis, cell proliferation, migration, and gene expression. Accumulating evidence suggests that the CXCL12/CXCR4/CXCR7 axis plays a pivotal role in tumor development, survival, angiogenesis, metastasis, and tumor microenvironment. In addition, this chemokine axis promotes chemoresistance in cancer therapy via complex crosstalk with other pathways. Multiple small molecules targeting CXCR4/CXCR7 have been developed and used for preclinical and clinical cancer treatment. In this review, we describe the roles of the CXCL12/CXCR4/CXCR7 axis in cancer progression and summarize strategies to develop novel targeted cancer therapies.

The RasGEF FgCdc25 regulates fungal development and virulence in Fusarium graminearum via cAMP and MAPK signalling pathways

Ras GTPases act as molecular switches to control various cellular processes by coupling integrated signals in eukaryotes. Activities of Ras GTPases are triggered by Ras GTPase guanine nucleotide exchange factors (RasGEFs) in general, whereas the role of RasGEF in plant pathogenic fungi is largely unknown. In this study, we characterized the only RasGEF protein in Fusarium graminearum, FgCdc25, by combining genetic, cytological and phenotypic strategies. FgCdc25 directly interacted with RasGTPase FgRas2, but not FgRas1, to regulate growth and sexual reproduction. Mutation of the FgCDC25 gene resulted in decreased toxisome formation and deoxynivalenol (DON) production, which was largely depended on cAMP signalling. In addition, FgCdc25 indirectly interacted with FgSte11 in FgSte11-Ste7-Gpmk1 cascade, and the ΔFgcdc25 strain totally abolished the formation of infection structures and was nonpathogenic in planta, which was partially recovered by addition of exogenous cAMP. In contrast, FgCdc25 directly interplayed with FgBck1 in FgBck1-MKK1-Mgv1 cascade to negatively control cell wall integrity. Collectively, these results suggest that FgCdc25 modulates cAMP and MAPK signalling pathways and further regulates fungal development, DON production and plant infection in F. graminearum.

Amlexanox exerts anti-inflammatory actions by targeting phosphodiesterase 4B in lipopolysaccharide-activated macrophages

Amlexanox, an anti-inflammatory agent, is widely used for treating aphthous ulcers. Recently, amlexanox has received considerable attention because of its efficacy in mitigating metabolic inflammation via directly suppressing IKKε/TBK1. However, because the knockdown of IKKε/TBK1 has no anti-inflammatory effect on lipopolysaccharide (LPS)-primed RAW264.7 cells, the mechanism of amlexanox against classical inflammation is independent of IKKε/TBK1. In this study, we aim to examine the effects of amlexanox on LPS-treated macrophages and in a mouse model of endotoxemia. We found that amlexanox significantly inhibited the production of pro-inflammatory mediators, both in vitro and in vivo, while increased interleukin-10 level in LPS-activated macrophages. Mechanistically, amlexanox down-regulated nuclear factor κB and extracellular signal-regulated kinase/activator protein-1 signaling by elevating intracellular 3',5'-cyclic adenosine monophosphate (cAMP) level and subsequently activating protein kinase A. Molecular docking along with fluorescence polarization and enzyme inhibition assays revealed that amlexanox bound directly to phosphodiesterase (PDE) 4B to inhibit its activity. The anti-inflammatory effects of amlexanox could be abolished by the application of cAMP antagonist or PDE4B siRNA. In addition to PDE4B, the activities of PDE1C, 3A, and 3B were directly inhibited by amlexanox. Our results provide mechanistic insight into the clinical utility of amlexanox for the treatment of inflammatory disorders and might contribute to extending the clinical indications of amlexanox.

Pediococcus acidilactici P25 Protected Caenorhabditis elegans against Enterotoxigenic Escherichia coli K88 Infection and Transcriptomic Analysis of Its Potential Mechanisms

Enterotoxigenic Escherichia coli (ETEC) K88 is a zoonotic pathogen. Previous studies have shown that lactic acid bacteria (LAB) have great potential in promoting health and resisting pathogenic infections; however, relatively little research has been done on the Pediococcus genus of LAB. This study is aimed at exploring the mechanisms imparted by Pediococcus acidilactici P25 against ETEC K88 in Caenorhabditis elegans. The probiotic performance of P25 was investigated in vitro. Colonization of K88 in the intestinal tract of C. elegans and abundance of enterotoxin genes were measured. In addition, the transcriptome of C. elegans infected by K88 was analyzed. The result showed that P25 possessed the ability to produce acid, as well as high tolerances to acidic and high bile salt concentrations. Coculture revealed that the growth of ETEC K88 was significantly inhibited by the presence of P25. The median survival of C. elegans fed P25 was 2 days longer than the group infected with K88 alone (P < 0.01). At the same time, the number of colonizing K88 and the abundances of estB and elt were reduced by up to 71.70% and 2.17 times, respectively, by P25. Transcriptome data indicated that P25 affected expression of genes relative to innate immune response and upregulated the abundance of genes in multiple pathways of C. elegans, including peroxisome, longevity, and mitogen-activated protein kinase (MAPK) pathways. These results demonstrated that in the presence of P25, K88 colonization and their expression of enterotoxin genes were reduced. This was accomplished through the alteration of environmental parameters (pH and bile salt) as well as through the promotion of the innate immune response processes, increased longevity, and increased antipathogenic bacteria-related pathways. This work highlights the potential application of P. acidilactici P25 as a probiotic resistant to ETEC K88.

Elucidating cyclic AMP signaling in subcellular domains with optogenetic tools and fluorescent biosensors

The second messenger 3',5'-cyclic nucleoside adenosine monophosphate (cAMP) plays a key role in signal transduction across prokaryotes and eukaryotes. Cyclic AMP signaling is compartmentalized into microdomains to fulfil specific functions. To define the function of cAMP within these microdomains, signaling needs to be analyzed with spatio-temporal precision. To this end, optogenetic approaches and genetically encoded fluorescent biosensors are particularly well suited. Synthesis and hydrolysis of cAMP can be directly manipulated by photoactivated adenylyl cyclases (PACs) and light-regulated phosphodiesterases (PDEs), respectively. In addition, many biosensors have been designed to spatially and temporarily resolve cAMP dynamics in the cell. This review provides an overview about optogenetic tools and biosensors to shed light on the subcellular organization of cAMP signaling.

Role of JNK, MEK and adenylyl cyclase signalling in speed and directionality of enteric neural crest-derived cells

BACKGROUND

Cells derived from the neural crest colonize the developing gut and give rise to the enteric nervous system. The rate at which the ENCC population advances along the bowel will be affected by both the speed and directionality of individual ENCCs. The aim of the study was to use time-lapse imaging and pharmacological activators and inhibitors to examine the role of several intracellular signalling pathways in both the speed and the directionality of individual enteric neural crest-derived cells in intact explants of E12.5 mouse gut. Drugs that activate or inhibit intracellular components proposed to be involved in GDNF-RET and EDN3-ETB signalling in ENCCs were used.

FINDINGS

Pharmacological inhibition of JNK significantly reduced ENCC speed but did not affect ENCC directionality. MEK inhibition did not affect ENCC speed or directionality. Pharmacological activation of adenylyl cyclase or PKA (a downstream cAMP-dependent kinase) resulted in a significant decrease in ENCC speed and an increase in caudal directionality of ENCCs. In addition, adenylyl cyclase activation also resulted in reduced cell-cell contact between ENCCs, however this was not observed following PKA activation, suggesting that the effects of cAMP on adhesion are not mediated by PKA.

CONCLUSIONS

JNK is required for normal ENCC migration speed, but not directionality, while cAMP signalling appears to regulate ENCC migration speed, directionality and adhesion. Collectively, our data demonstrate that intracellular signalling pathways can differentially affect the speed and directionality of migrating ENCCs.

Therapeutic opportunities in colon cancer: Focus on phosphodiesterase inhibitors

Despite novel technologies, colon cancer remains undiagnosed and 25% of patients are diagnosed with metastatic colon cancer. Resistant to chemotherapeutic agents is one of the major problems associated with treating colon cancer which creates the need to develop novel agents targeting towards newer targets. A phosphodiesterase is a group of isoenzyme, which, hydrolyze cyclic nucleotides and thereby lowers intracellular levels of cAMP and cGMP leading to tumorigenic effects. Many in vitro and in vivo studies have confirmed increased PDE expression in different types of cancers including colon cancer. cAMP-specific PDE inhibitors increase intracellular cAMP that leads to activation of effector molecules-cAMP-dependent protein kinase A, exchange protein activated by cAMP and cAMP gated ion channels. These molecules regulate cellular responses and exert its anticancer role through different mechanisms including apoptosis, inhibition of angiogenesis, upregulating tumor suppressor genes and suppressing oncogenes. On the other hand, cGMP specific PDE inhibitors exhibit anticancer effects through cGMP dependent protein kinase and cGMP dependent cation channels. Elevation in cGMP works through activation of caspases, suppression of Wnt/b-catenin pathway and TCF transcription leading to inhibition of CDK and survivin. These studies point out towards the fact that PDE inhibition is associated with anti-proliferative, anti-apoptotic and anti-angiogenic pathways involved in its anticancer effects in colon cancer. Thus, inhibition of PDE enzymes can be used as a novel approach to treat colon cancer. This review will focus on cAMP and cGMP signaling pathways leading to tumorigenesis and the use of PDE inhibitors in colon cancer.

Smallest near-infrared fluorescent protein evolved from cyanobacteriochrome as versatile tag for spectral multiplexing

From a single domain of cyanobacteriochrome (CBCR) we developed a near-infrared (NIR) fluorescent protein (FP), termed miRFP670nano, with excitation at 645 nm and emission at 670 nm. This is the first CBCR-derived NIR FP evolved to efficiently bind endogenous biliverdin chromophore and brightly fluoresce in mammalian cells. miRFP670nano is a monomer with molecular weight of 17 kDa that is 2-fold smaller than bacterial phytochrome (BphP)-based NIR FPs and 1.6-fold smaller than GFP-like FPs. Crystal structure of the CBCR-based NIR FP with biliverdin reveals a molecular basis of its spectral and biochemical properties. Unlike BphP-derived NIR FPs, miRFP670nano is highly stable to denaturation and degradation and can be used as an internal protein tag. miRFP670nano is an effective FRET donor for red-shifted NIR FPs, enabling engineering NIR FRET biosensors spectrally compatible with GFP-like FPs and blue-green optogenetic tools. miRFP670nano unlocks a new source of diverse CBCR templates for NIR FPs.

Multiple roles and diverse regulation of the Ras/cAMP/protein kinase A pathway in Candida albicans

Candida albicans is a major fungal pathogen of humans, causing both superficial and life-threatening systemic infections in immunocompromised people. The conserved Ras/cAMP/PKA pathway plays a key role in regulating multiple traits important for the virulence of C. albicans such as cell growth, yeast-hyphal transition, white-opaque switching, sexual reproduction and biofilm development. Diverse external signals influence cell physiology by activating this signaling pathway. The key components of the Ras/cAMP/PKA pathway include two Ras GTPases (Ras1 and Ras2), an adenylyl cyclase (Cyr1, also known as Cdc35), two cyclic nucleotide phosphodiesterases (Pde1 and Pde2) and the catalytic (Tpk1 and Tpk2) and regulatory (Bcy1) subunits of PKA kinase. Activation of this pathway dramatically alters the gene expression profile via several transcription factors, leading to the activation of specific biological processes. Here, we review the progress made in the past two decades to elucidate the molecular mechanisms by which the Ras/cAMP/PKA pathway senses diverse environmental cues and controls specific cellular responses and its connection with other signaling pathways in C. albicans.

Extracellular calcium increases fibroblast growth factor 2 gene expression via extracellular signal-regulated kinase 1/2 and protein kinase A signaling in mouse dental papilla cells

We previously reported that elevated extracellular calcium (Ca²⁺) levels increase bone morphogenetic protein 2 expression in human dental pulp (hDP) cells. However, it is unknown whether extracellular Ca²⁺ affects the expression of other growth factors such as fibroblast growth factor 2 (FGF2).

Forskolin improves sensitivity to doxorubicin of triple negative breast cancer cells via Protein Kinase A-mediated ERK1/2 inhibition

Triple negative breast cancer (TNBC) is an invasive, metastatic, highly aggressive tumor. Cytotoxic chemotherapy represents the current treatment for TNBC. However, relapse and chemo-resistance are very frequent. Therefore, new therapeutic approaches that are able to increase the sensitivity to cytotoxic drugs are needed. Forskolin, a natural cAMP elevating agent, has been used for several centuries in medicine and its safeness has also been demonstrated in modern studies. Recently, forskolin is emerging as a possible novel molecule for cancer therapy. Here, we investigate the effects of forskolin on the sensitivity of MDA-MB-231 and MDA-MB-468 TNBC cells to doxorubicin through MTT assay, flow cytometry-based assays (cell-cycle progression and cell death), cell number counting and immunoblotting experiments. We demonstrate that forskolin strongly enhances doxorubicin-induced antiproliferative effects by cell death induction. Similar effects are observed with IBMX and isoproterenol cAMP elevating agents and 8-Br-cAMP analog, but not by using 8-pCPT-2'-O-Me-cAMP Epac activator. It is important to note that the forskolin-induced potentiation of sensitivity to doxorubicin is accompanied by a strong inhibition of ERK1/2 phosphorylation, is mimicked by ERK inhibitor PD98059 and is prevented by pre-treatment with Protein Kinase A (PKA) and adenylate cyclase inhibitors. Altogether, our data indicate that forskolin sensitizes TNBC cells to doxorubicin via a mechanism depending on the cAMP/PKA-mediated ERK inhibition. Our findings sustain the evidence of anticancer activity mediated by forskolin and encourage the design of future in-vivo/clinical studies in order to explore forskolin as a doxorubicin sensitizer for possible use in TNBC patients.

Relative importance of phosphatidylinositol-3 kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK3/1) signaling during maturational steroid-induced meiotic G2-M1 transition in zebrafish oocytes

Participation and relative importance of phosphatidylinositol-3 kinase (PI3K) and mitogen-activated protein kinase (MAPK) signalling, either alone or in combination, have been investigated during 17α,20β-dihydroxy-4-pregnen-3-one (DHP)-induced meiotic G2-M1 transition in denuded zebrafish oocyte. Results demonstrate that concomitant with rapid phosphorylation (activation) of Akt (Ser473) and MAPK (ERK1/2) at as early as 15 min of incubation, DHP stimulation promotes enhanced an GVBD response and histone H1 kinase activation between 1 and 5 h in full-grown oocytes in vitro. While p-Akt reaches its peak at 60 to 90 min and undergoes downregulation to the basal level by 240 min, ERK1/2 phosphorylation (activation) increases gradually until 120 min and remains high thereafter. Although, priming with MEK1/2 inhibitor U0126 is without effect, PI3K inhibitors, wortmannin or LY294002, delay the GVBD response significantly (P < 0.001) until 3 h but not at 5 h of incubation. Interestingly, blocking PI3K and MEK function together could abrogate steroid-induced oocyte maturation at all time points tested. While DHP stimulation promotes phospho-PKA catalytic (p-PKAc) dephosphorylation (inactivation) between 30-120 min of incubation, simultaneous inhibition of PI3K and MEK1/2 kinases abrogates DHP action. Conversely, elevated intra-oocyte cAMP, through priming with either adenylyl cyclase (AC) activator forskolin (FK) or dibutyryl cAMP (db-cAMP), abrogates steroid-induced Akt and ERK1/2 phosphorylation. Taken together, these results suggest that DHP-induced Akt and ERK activation precedes the onset of meiosis (GVBD response) in a cAMP-sensitive manner and PI3K/Akt and MEK/MAPK pathways together have a pivotal influence in the downregulation of PKA and resumption of meiotic maturation in zebrafish oocytes in vitro.

Involvement of leptin in the molecular physiology of the placenta

Leptin is a homeostatic regulator in the placenta where it promotes proliferation, protein synthesis and the expression of tolerogenic maternal response molecules such as HLA-G. Leptin also exerts an anti-apoptotic action in placenta controlling the expression of p53 master cell cycle regulator under different stress conditions. On the other hand, leptin is an integrative target of different placental stimuli. The expression of leptin in placenta is regulated by hCG, insulin, steroids, hypoxia and many other growth hormones, suggesting that it might have an important endocrine function in the trophoblastic cells. The leptin expression is induced involving the cAMP/PKA or cAMP/Epac pathways which have profound actions upon human trophoblast function. The activation of PI3K and MAPK pathways also participates in the leptin expression. Estrogens play a central role during pregnancy, particularly 17β-estradiol upregulates the leptin expression in placental cells through genomic and non-genomic actions. The leptin promoter analysis reveals specific elements that are active in placental cells. The transcription factors CREB, AP1, Sp1, NFκB and the coactivator CBP are involved in the placental leptin expression. Moreover, placental leptin promoter is a target of epigenetic marks such as DNA methylation and histone acetylation that regulates not only the leptin expression in placenta during pregnancy but also determines the predisposition of acquiring adult metabolism diseases. Taken together, all these results allow a better understanding of leptin function and regulatory mechanisms of leptin expression in human placental trophoblasts, and support the importance of leptin during pregnancy and in programming adult health.

Personalized analysis of pathway aberrance induced by sevoflurane and propofol

Anesthetic agents are used in surgical operations to reversibly reduce consciousness and pain. Sevoflurane is an inhalational anesthetic. Propofol is a short-acting intravenous general anesthetic. The mechanism of anesthetic agents at pathway level on individual patients has not been reported to date. In the present study, pathway aberrance in the human atrial tissue in response to anesthetics was examined. Microarray data of anesthesia-treated samples were downloaded from the Array Express database. Pathway information was obtained from the Reactome Pathway Database. The individual pathway aberrance score (iPAS) was introduced to identify dysregulated pathways in individual patients. The present data demonstrated 157 dysregulated pathways in the sevoflurane group, and 44 pathways were identified with the least P-values. A subset of 49 differentially expressed genes (DEGs) that were shared between the expression profiling results and the dysregulated pathways results were constructed into a co-expression network. The top 5 ranked DEGs, nuclear receptor subfamily 4 group A member 3 (NR4A3), JUNB proto-oncogene, MYC proto-oncogene, tachykinin precursor 1 and nicotinamide phosphoribosyltransferase, were identified as important in the topology analysis. In the propofol group, 87 dysregulated pathways were identified and 44 pathways had the least P-values. In total 28 DEGs were constructed into a co-expression network, of which 5 DEGs were important in the topology analysis, NR4A3, suppressor of cytokine signaling 3, cyclin dependent kinase inhibitor 1A, C-C motif chemokine ligand 2 and C-X-C motif chemokine ligand 1. A total of 72 dysregulated pathways were identified in common in the two groups. In conclusion, the two types of anesthetics induced partially similar mechanisms. The pathways enriched by DEGs, particularly those that were unique to sevoflurane and propofol, may affect surgical outcomes and aid the prevention of complications from anesthetics.

Cellular and Molecular Mechanisms of REM Sleep Homeostatic Drive: A Plausible Component for Behavioral Plasticity

Homeostatic regulation of REM sleep drive, as measured by an increase in the number of REM sleep transitions, plays a key role in neuronal and behavioral plasticity (i.e., learning and memory). Deficits in REM sleep homeostatic drive (RSHD) are implicated in the development of many neuropsychiatric disorders. Yet, the cellular and molecular mechanisms underlying this RSHD remain to be incomplete. To further our understanding of this mechanism, the current study was performed on freely moving rats to test a hypothesis that a positive interaction between extracellular-signal-regulated kinase 1 and 2 (ERK1/2) activity and brain-derived neurotrophic factor (BDNF) signaling in the pedunculopontine tegmentum (PPT) is a causal factor for the development of RSHD. Behavioral results of this study demonstrated that a short period (<90 min) of selective REM sleep restriction (RSR) exhibited a strong RSHD. Molecular analyses revealed that this increased RSHD increased phosphorylation and activation of ERK1/2 and BDNF expression in the PPT. Additionally, pharmacological results demonstrated that the application of the ERK1/2 activation inhibitor U0126 into the PPT prevented RSHD and suppressed BDNF expression in the PPT. These results, for the first time, suggest that the positive interaction between ERK1/2 and BDNF in the PPT is a casual factor for the development of RSHD. These findings provide a novel direction in understanding how RSHD-associated specific molecular changes can facilitate neuronal plasticity and memory processing.

Bacterial Nucleotidyl Cyclase Inhibits the Host Innate Immune Response by Suppressing TAK1 Activation

Exoenzyme Y (ExoY) is a type III secretion system effector found in 90% of the Pseudomonas aeruginosa isolates. Although it is known that ExoY is a soluble nucleotidyl cyclase that increases the cytoplasmic levels of nucleoside 3',5'-cyclic monophosphates (cNMPs) to mediate endothelial Tau phosphorylation and permeability, its functional role in the innate immune response is still poorly understood. Transforming growth factor β-activated kinase 1 (TAK1) is critical for mediating Toll-like receptor (TLR) signaling and subsequent activation of NF-κB and AP-1, which are transcriptional activators of innate immunity. Here, we report that ExoY inhibits proinflammatory cytokine production through suppressing the activation of TAK1 as well as downstream NF-κB and mitogen-activated protein (MAP) kinases. Mice infected with ExoY-deficient P. aeruginosa had higher levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6), more neutrophil recruitment, and a lower bacterial load in lung tissue than mice infected with wild-type P. aeruginosa Taken together, our findings identify a previously unknown mechanism by which P. aeruginosa ExoY inhibits the host innate immune response.

Targeting the Architecture of Deregulated Protein Complexes in Cancer

The architectures of central signaling hubs are precisely organized by static and dynamic protein-protein interactions (PPIs). Upon deregulation, these PPI platforms are capable to propagate or initiate pathophysiological signaling events. This causes the acquisition of molecular features contributing to the etiology or progression of many diseases, including cancer, where deregulated molecular interactions of signaling proteins have been best studied. The reasons for PPI-dependent reprogramming of cancer-initiating cells are manifold; in many cases, mutations perturb PPIs, enzyme activities, protein abundance, or protein localization. Consequently, the pharmaceutical targeting of PPIs promises to be of remarkable therapeutic value. For this review we have selected three key players of oncogenic signaling which are differently affected by PPI deregulation: two (the small G proteins of the RAS family and the transcription factor MYC) are considered "undruggable" using classical drug discovery approaches and in the case of the third protein discussed here, PKA, standard kinase inhibitors, may be unsuitable in the clinic. These circumstances require alternative strategies, which may lie in pharmaceutical drug interference of critical PPIs accountable for oncogenic signaling.

The many faces of compartmentalized PKA signalosomes

Cellular signal transmission requires the dynamic formation of spatiotemporally controlled molecular interactions. At the cell surface information is received by receptor complexes and relayed through intracellular signaling platforms which organize the actions of functionally interacting signaling enzymes and substrates. The list of hormone or neurotransmitter pathways that utilize the ubiquitous cAMP-sensing protein kinase A (PKA) system is expansive. This requires that the specificity, duration, and intensity of PKA responses are spatially and temporally restricted. Hereby, scaffolding proteins take the center stage for ensuring proper signal transmission. They unite second messenger sensors, activators, effectors, and kinase substrates within cellular micro-domains to precisely control and route signal propagation. A-kinase anchoring proteins (AKAPs) organize such subcellular signalosomes by tethering the PKA holoenzyme to distinct cell compartments. AKAPs differ in their modular organization showing pathway specific arrangements of interaction motifs or domains. This enables the cell- and compartment- guided assembly of signalosomes with unique enzyme composition and function. The AKAP-mediated clustering of cAMP and other second messenger sensing and interacting signaling components along with functional successive enzymes facilitates the rapid and precise dissemination of incoming signals. This review article delineates examples for different means of PKA regulation and for snapshots of compartmentalized PKA signalosomes.

Systematic Quantification of GPCR/cAMP-Controlled Protein Kinase A Interactions

The diffusible second messenger cyclic AMP (cAMP) originates from multiple G protein-coupled receptor (GPCR) cascades activating the intracellular key effector protein kinase A (PKA). Spatially and temporally restricted cAMP-fluxes are directly sensed by macromolecular PKA complexes. The consequences are alterations of molecular interactions, which lead to activation of compartmentalized PKA phosphotransferase activities, regulating a vast array of cellular functions. To decode cell-type and cell-compartment specific PKA functions, the spatio-temporal dynamics of small molecule:protein interactions, protein:protein interactions (PPIs), cAMP-mobilization, and phosphotransferase activities need to be determined directly in the appropriate cellular context. A collection of cell-based reporters has been developed to either visualize or quantitatively measure kinase activities or PKA complex formation/dissociation. In this review, we list a collection of unimolecular and bimolecular PKA biosensors, followed by the specification of the modular design of a Renilla luciferase based protein-fragment complementation assay (PCA) platform for measuring PKA network interactions. We discuss the application spectrum of the PCA reporter to identify, quantify, and dissect dynamic and transient PKA complexes downstream of specific GPCR activities. We specify the implementation of a PCA PKA platform to systematically quantify the concurrent involvement of receptor-cAMP signaling, post-translational modifications, and kinase subunit mutations/perturbations in PKA activation. The systematic quantification of transient PKA network interactions will contribute to a better understanding how GPCR-recognized input signals are streamlined through the compartmentalized and cAMP-interacting PKA signalosome.

High glucose enhances cAMP level and extracellular signal-regulated kinase phosphorylation in Chinese hamster ovary cell: Usage of Br-cAMP in foreign protein β-galactosidase expression

Glucose is a carbon source for Chinese hamster ovary (CHO) cell growth, while low growth rate is considered to enhance the production of recombinant proteins. The present study reveals that glucose concentrations higher than 1 g/L reduce the growth rate and substantially increase in cAMP (∼300%) at a high glucose concentration (10 g/L). High glucose also enhances the phosphorylation of extracellular signal-regulated kinase (ERK) and p27^kip by Western blot analysis. To determine whether the phosphorylation of ERK is involved in the mechanism, a cyclic-AMP dependent protein kinase A (PKA) inhibitor (H-8) or MEK (MAPKK) inhibitor (PD98059) was added to block ERK phosphorylation. We show that both the high glucose-induced ERK phosphorylation and growth rate return to baseline levels. These results suggest that the cAMP/PKA and MAP signaling pathways are involved in the abovementioned mechanism. Interestingly, the direct addition of 8-bromo-cAMP (Br-cAMP), a membrane-permeable cAMP analog, can mimic the similar effects produced by high glucose. Subsequently Br-cAMP could induce β-galactosidase (β-Gal) recombinant protein expression by 1.6-fold. Furthermore, Br-cAMP can additionally enhance the β-Gal production (from 2.8- to 4.5-fold) when CHO cells were stimulated with glycerol, thymidine, dimethyl sulfoxide, pentanoic acid, or sodium butyrate. Thus, Br-cAMP may be used as an alternative agent in promoting foreign protein expression for CHO cells.

Multiplexing PKA and ERK1&2 kinases FRET biosensors in living cells using single excitation wavelength dual colour FLIM

Monitoring of different signalling enzymes in a single assay using multiplex biosensing provides a multidimensional workspace to elucidate biological processes, signalling pathway crosstalk, and determine precise sequence of events at the single living cell level. In this study, we interrogate the complexity in cAMP/PKA-MAPK/ERK1&2 crosstalk by using multi-parameter biosensing experiments to correlate biochemical activities simultaneously in time and space. Using a single excitation wavelength dual colour FLIM method we are able to detect fluorescence lifetime images of two donors to simultaneously measure PKA and ERK1&2 kinase activities in the same cellular localization by using FRET biosensors. To this end, we excite two FRET donors mTFP1 and LSSmOrange with a 440 nm wavelength and we alleviate spectral bleed-through associated limitations with the very dim-fluorescent acceptor ShadowG for mTFP1 and the red-shifted mKate2 for LSSmOrange. The simultaneous recording of PKA and ERK1&2 kinase activities reveals concomitant EGF-mediated activations of both kinases in HeLa cells. Under these conditions the subsequent Forskolin-induced cAMP release reverses the transient increase of EGF-mediated ERK1&2 kinase activity while reinforcing PKA activation. Here we propose a validated methodology for multiparametric kinase biosensing in living cells using FRET-FLIM.

Endocrine and paracrine regulation of meiotic cell cycle progression in teleost oocytes: cAMP at the centre of complex intra-oocyte signalling events

Participation of major endocrine and/or local autocrine/paracrine factors and potential interplay between apparently disparate intra-oocyte signalling events during maintenance and withdrawal of meiotic prophase arrest has been an area of active research in recent years. Studies on oocyte maturation have contributed substantially in the discovery of some of the most important biochemical and cellular events like functional significance of novel membrane-associated steroid receptors, elucidation of maturation promoting factor (MPF), cytostatic factor (CSF) and other signalling cascades that entrain the cell cycle clock to hormonal stimuli. While follicular estrogen has largely been implicated in maintenance of prophase arrest, involvement of maturational steroid and membrane progestin receptor in resumption of meiotic G2-M1 transition in piscine oocytes has been shown earlier. Moreover, detection of ovarian IGF system, maturational gonadotropin stimulation of IGF ligands and potential synergism between maturational steroid and IGF1 in zebrafish oocytes are most recent advancements. Though endocrine/paracrine regulation of cyclic nucleotide-mediated signalling events in meiotic cell cycle progression is well established, involvement of PI3K/Akt signalling cascade has also been reported in fish, amphibian and mammalian oocytes. The major objective of this overview is to describe how fish oocytes maintain high cAMP/PKA activity and how steroid- and/or growth factor-mediated signalling cascade regulate this pathway for the withdrawal of meiotic arrest. Moreover, special emphasis is placed on some recent findings on interaction of PKA with some of the MPF-regulating components (e.g., synthesis of cyclin B or MEK/MAPK signalling cascade) for the maintenance of prophase arrest.

Inhibition of cAMP-Dependent PKA Activates β2-Adrenergic Receptor Stimulation of Cytosolic Phospholipase A2 via Raf-1/MEK/ERK and IP3-Dependent Ca2+ Signaling in Atrial Myocytes

We previously reported in atrial myocytes that inhibition of cAMP-dependent protein kinase (PKA) by laminin (LMN)-integrin signaling activates β2-adrenergic receptor (β2-AR) stimulation of cytosolic phospholipase A2 (cPLA2). The present study sought to determine the signaling mechanisms by which inhibition of PKA activates β2-AR stimulation of cPLA2. We therefore determined the effects of zinterol (0.1 μM; zint-β2-AR) to stimulate ICa,L in atrial myocytes in the absence (+PKA) and presence (-PKA) of the PKA inhibitor (1 μM) KT5720 and compared these results with atrial myocytes attached to laminin (+LMN). Inhibition of Raf-1 (10 μM GW5074), phospholipase C (PLC; 0.5 μM edelfosine), PKC (4 μM chelerythrine) or IP3 receptor (IP3R) signaling (2 μM 2-APB) significantly inhibited zint-β2-AR stimulation of ICa,L in-PKA but not +PKA myocytes. Western blots showed that zint-β2-AR stimulation increased ERK1/2 phosphorylation in-PKA compared to +PKA myocytes. Adenoviral (Adv) expression of dominant negative (dn) -PKCα, dn-Raf-1 or an IP3 affinity trap, each inhibited zint-β2-AR stimulation of ICa,L in + LMN myocytes compared to control +LMN myocytes infected with Adv-βgal. In +LMN myocytes, zint-β2-AR stimulation of ICa,L was enhanced by adenoviral overexpression of wild-type cPLA2 and inhibited by double dn-cPLA2S505A/S515A mutant compared to control +LMN myocytes infected with Adv-βgal. In-PKA myocytes depletion of intracellular Ca2+ stores by 5 μM thapsigargin failed to inhibit zint-β2-AR stimulation of ICa,L via cPLA2. However, disruption of caveolae formation by 10 mM methyl-β-cyclodextrin inhibited zint-β2-AR stimulation of ICa,L in-PKA myocytes significantly more than in +PKA myocytes. We conclude that inhibition of PKA removes inhibition of Raf-1 and thereby allows β2-AR stimulation to act via PKCα/Raf-1/MEK/ERK1/2 and IP3-mediated Ca2+ signaling to stimulate cPLA2 signaling within caveolae. These findings may be relevant to the remodeling of β-AR signaling in failing and/or aging heart, both of which exhibit decreases in adenylate cyclase activity.

A Role for cAMP and Protein Kinase A in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease that has been associated with Cronobacter sakazakii and typically affects premature infants. Although NEC has been actively investigated, little is known about the mechanisms underlying the pathophysiology of epithelial injury and intestinal barrier damage. Cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) are important mediators and regulators of apoptosis. To test the hypothesis that C. sakazakii increases cAMP and PKA activation in experimental NEC resulting in increased epithelial apoptosis, we investigated the effects of C. sakazakii on cAMP and PKA in vitro and in vivo. Specifically, rat intestinal epithelial cells and a human intestinal epithelial cell line were infected with C. sakazakii, and cAMP levels and phosphorylation of PKA were measured. An increase in cAMP was demonstrated after infection, as well as an increase in phosphorylated PKA. Similarly, increased intestinal cAMP and PKA phosphorylation were demonstrated in a rat pup model of NEC. These increases were correlated with increased intestinal epithelial apoptosis. The additional of a PKA inhibitor (KT5720) significantly ameliorated these effects and decreased the severity of experimental NEC. Findings were compared with results from human tissue samples. Collectively, these observations indicate that cAMP and PKA phosphorylation are associated with increased apoptosis in NEC and that inhibition of PKA activation protects against apoptosis and experimental NEC.