Propranolol Inhibits the Growth of Cervical Cancer Cells by Inhibiting Cyclic Guanosine Monophosphate/Protein Kinase G (cGMP/PKG) Pathway

This study assesses the therapeutic effect of propranolol on cervical cancer and its mechanism. Propranolol’s effect on cervical cancer was evaluated by MTT, Western blotting, flow cytometry and colony formation. By searching Drug Bank and String, cGMP/PKG signaling might be downstream targets of propranolol for subsequent analysis. Our results found that propranolol could significantly inhibit Hela and SiHA cell vitality and clone formation in a dose dependent manner. Further, Annexin V-PE/7-AAD Apoptosis Detection assay showed that propranolol could increase Hela and SiHA cell apoptosis. Finally, propranolol attenuated the phosphorylation level of VASP at Ser239 which is critical for PKG activation. In conclusion, propranolol suppressed cervical cancer cell proliferation via inhibition of cGMP/PKG signaling, which provides an affordable and effective method for cervical cancer remedy.

The cGAS-STING Pathway in Bacterial Infection and Bacterial Immunity

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS), along with the adaptor stimulator of interferon genes (STING), are crucial components of the innate immune system, and their study has become a research hotspot in recent years. Many biochemical and structural studies that have collectively elucidated the mechanism of activation of the cGAS-STING pathway with atomic resolution have provided insights into the roles of the cGAS-STING pathway in innate immunity and clues to the origin and evolution of the modern cGAS-STING signaling pathway. The cGAS-STING pathway has been identified to protect the host against viral infection. After detecting viral dsDNA, cGAS synthesizes a second messenger to activate STING, eliciting antiviral immune responses by promoting the expression of interferons (IFNs) and hundreds of IFN-stimulated genes (ISGs). Recently, the cGAS-STING pathway has also been found to be involved in response to bacterial infections, including bacterial pneumonia, melioidosis, tuberculosis, and sepsis. However, compared with its functions in viral infection, the cGAS-STING signaling pathway in bacterial infection is more complex and diverse since the protective and detrimental effects of type I IFN (IFN-I) on the host depend on the bacterial species and infection mode. Besides, STING activation can also affect infection prognosis through other mechanisms in different bacterial infections, independent of the IFN-I response. Interestingly, the core protein components of the mammalian cGAS-STING signaling pathway have been found in the bacterial defense system, suggesting that this widespread signaling pathway may have originated in bacteria. Here, we review recent findings related to the structures of major molecules involved in the cGAS-STING pathway and the effects of the cGAS-STING pathway in various bacterial infections and bacterial immunity, which may pave the way for the development of new antibacterial drugs that specifically kill bacteria without harmful effects on the host.

Pseudomonas aeruginosa Oligoribonuclease Controls Susceptibility to Polymyxin B by Regulating Pel Exopolysaccharide Production

Polymyxins are considered as the last resort antibiotics to treat infections caused by multidrug-resistant Gram negative pathogens. Pseudomonas aeruginosa is an opportunistic pathogen that causes various infections in humans. Proteins involved in lipopolysaccharide modification and maintaining inner and outer membrane integrities have been found to contribute to the bacterial resistance to polymyxins. Oligoribonuclease (Orn) is an exonuclease that regulates the homeostasis of intracellular (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), thereby regulating the production of extracellular polysaccharide in P. aeruginosa . Previously, we demonstrated that Orn affects the bacterial resistance to fluoroquinolone, β-lactam and aminoglycoside antibiotics. In this study, we found that mutation of orn increased the bacterial survival following polymyxin B treatment in a wild type P. aeruginosa strain PA14. Overexpression of c-di-GMP degradation enzymes in the orn mutant reduced the bacterial survival. By using a fluorescence labeled polymyxin B, we found that mutation of orn increased the bacterial surface bound polymyxin B. Deletion of the Pel synthesis genes or treatment with a Pel hydrolase reduced the surface bound polymyxin B and bacterial survival. We further demonstrated that Pel binds to extracellular DNA (eDNA), which traps polymyxin B and thus protects the bacterial cells. Collectively, our results revealed a novel defense mechanism against polymyxin in P. aeruginosa .

Extracellular matrix-degrading STING nanoagonists for mild NIR-II photothermal-augmented chemodynamic-immunotherapy

Regulation of stimulator of interferon genes (STING) pathway using agonists can boost antitumor immunity for cancer treatment, while the rapid plasma clearance, limited membrane permeability, and inefficient cytosolic transport of STING agonists greatly compromise their therapeutic efficacy. In this study, we describe an extracellular matrix (ECM)-degrading nanoagonist (dNAc) with second near-infrared (NIR-II) light controlled activation of intracellular STING pathway for mild photothermal-augmented chemodynamic-immunotherapy of breast cancer. The dNAc consists of a thermal-responsive liposome inside loading with ferrous sulfide (FeS2) nanoparticles as both NIR-II photothermal converters and Fenton catalysts, 2′3′-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) as the STING agonist, and an ECM-degrading enzyme (bromelain) on the liposome surface. Mild heat generated by dNAc upon NIR-II photoirradiation improves Fenton reaction efficacy to kill tumor cells and cause immunogenic cell death (ICD). Meanwhile, the generated heat triggers a controlled release of cGAMP from thermal-responsive liposomes to active STING pathway. The mild photothermal activation of STING pathway combined with ICD promotes anti-tumor immune responses, which leads to improved infiltration of effector T cells into tumor tissues after bromelain-mediated ECM degradation. As a result, after treatment with dNAc upon NIR-II photoactivation, both primary and distant tumors in a murine mouse model are inhibited and the liver and lung metastasis are effectively suppressed. This work presents a photoactivatable system for STING pathway and combinational immunotherapy with improved therapeutic outcome. Graphical Abstract

Acute Liver Failure in Rats Induced Vasogenic Edema and Nitric Oxide Synthase-Nitric Oxide-cGMP Pathway after Differential Regulation of NMDA Receptors in Cerebral Cortex and Cerebellum

Acute liver failure (ALF) is a complication of severe liver dysfunction resulting from a wide range of factors including alcoholism, drug-abuse, improper medication, viral hepatitis etc., and present with high mortality rate among the human population. ALF led hyperammonemia (HA) induced cerebral dysfunction is considered to be the main cause of death in patients, however, the precise molecular mechanism is not completely understood. The aim of this study was to investigate the status of brain edema and modulation of N-methyl D-aspartate receptors (NMDAR)- Nitric oxide synthase (NOS)- Nitric oxide (NO)- cyclic guanosine monophosphate (cGMP) axis in the cerebral cortex and cerebellum of ALF rats. ALF was induced by intraperitoneal (IP) injection of thioacetamide (TAA). We observed significantly increased brain water content in ALF rats but absence of astrocytes swelling suggested induction of vasogenic edema. Except constant NR2B, down regulation of NR2A, 2C and 2D subunits containing NMDAR genes in cerebral cortex, however, constant NR2A-C but up-regulation of NR2D subunit in cerebellum suggested brain regions specific differential regulation of NMDAR in ALF rats. Significantly increased nNOS gene and protein level were found to be accompanied by the significantly increased level of NO and cGMP in both brain tissues; however, increased eNOS expression in cortex but increased iNOS expression and activity in cerebellum were observed in ALF rats. Together these findings suggested that ALF in rats may trigger differential regulation of NR2A-D subunits containing NMDAR, induction of NOS-NO-cGMP axis and vasogenic edema in cerebral cortex and cerebellum.

Plasma Cyclic Guanosine Monophosphate Is a Promising Biomarker of Clinically Significant Portal Hypertension in Patients With Liver Cirrhosis

Introduction: Despite intensive research, reliable blood-derived parameters to detect clinically significant portal hypertension (CSPH) in patients with cirrhosis are lacking. As altered homeostasis of cyclic guanosine monophosphate (cGMP), the central mediator of vasodilatation, is an essential factor in the pathogenesis of portal hypertension, the aim of our study was to evaluate plasma cGMP as potential biomarker of cirrhotic portal hypertension.Methods: Plasma cGMP was analyzed in cirrhotic patients with CSPH (ascites, n = 39; esophageal varices, n = 31), cirrhotic patients without CSPH (n = 21), patients with chronic liver disease without cirrhosis (n = 11) and healthy controls (n = 8). cGMP was evaluated as predictor of CSPH using logistic regression models. Further, the effect of transjugular intrahepatic portosystemic shunt (TIPS) placement on plasma cGMP was investigated in a subgroup of cirrhotic patients (n = 13).Results: Plasma cGMP was significantly elevated in cirrhotic patients with CSPH compared to cirrhotic patients without CSPH [78.1 (67.6–89.2) pmol/ml vs. 39.1 (35.0–45.3) pmol/l, p < 0.001]. Of note, this effect was consistent in the subgroup of patients with esophageal varices detected at screening endoscopy who had no prior manifestations of portal hypertension (p < 0.001). Cirrhotic patients without CSPH displayed no significant elevation of plasma cGMP compared to patients without cirrhosis (p = 0.347) and healthy controls (p = 0.200). Regression analyses confirmed that cGMP was an independent predictor of CSPH (OR 1.042, 95% CI 1.008–1.078, p = 0.016). Interestingly, portal decompression by TIPS implantation did not lead to normalization of plasma cGMP levels (p = 0.101).Conclusions: Plasma cGMP is a promising biomarker of CSPH in patients with cirrhosis, especially with respect to screening for esophageal varices. The lacking normalization of plasma cGMP after portal decompression suggests that elevated plasma cGMP in cirrhotic portal hypertension is mainly a correlate of systemic and splanchnic vasodilatation, as these alterations have been shown to persist after TIPS implantation.

Volatile anesthetics inhibit presynaptic cGMP signaling to depress presynaptic excitability in rat hippocampal neurons

Volatile anesthetics alter presynaptic function including effects on Ca2+ influx and neurotransmitter release. These actions are proposed to play important roles in their pleiotropic neurophysiological effects including unconsciousness and amnesia. The nitric oxide and cyclic guanosine monophosphate (NO/cGMP) signaling pathway has been implicated in presynaptic mechanisms, and disruption of NO/cGMP signaling has been shown to alter sensitivity to volatile anesthetics in vivo. We investigated NO/cGMP signaling in relation to volatile anesthetic actions in cultured rat hippocampal neurons using pharmacological tools and genetically encoded biosensors of cGMP levels. Using the fluorescent biosensor cGull we found that electrical stmulation-evoked NMDA-type glutamate receptor-independent presynaptic cGMP transients were inhibited -33.2% by isoflurane (0.51 mM) and -23.8% by sevoflurane (0.57 mM) (p<0.0001) compared to a stimulation without anesthetic. Isoflurane and sevoflurane inhibition of stimulation-evoked increases in presynaptic Ca2+ concentration, measured with synaptophysin-GCaMP6f, and synaptic vesicle exocytosis, measured with synaptophysin-pHlourin, were reduced by in neurons expressing the cGMP scavenger sponGee. This reduction in anesthetic effect was recapitulated by inhibiting HCN channels, a cGMP-modulated effector that can facilitate glutamate release. We propose that volatile anesthetics depress presynaptic cGMP signaling and downstream effectors like HCN channels that are essential to presynaptic function and excitability. These findings identify a novel mechanism by which volatile anesthetics depress synaptic transmission via second messenger signaling involving the NO/cGMP pathway.

Novel enhancers of guanylyl cyclase-A activity via allosteric modulation

Natriuretic peptide receptor (NPR)-A (also known as NPR-A, NPR1 or guanylyl cyclase-A, GC-A) is an attractive but challenging target to activate with small molecules. GC-A is activated by endogenous atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), and this activation leads to the production of cyclic guanosine monophosphate (cGMP). This system plays an important role in the regulation of cardiovascular and renal homeostasis. However, utilization of this receptor as a drug target has so far been limited to peptides, even though small molecule modulators allow oral administration and longer half-life. We have identified small molecular allosteric enhancers of GC-A, which strengthened ANP or BNP activation in various in vitro and ex vivo systems. These compounds do not mediate their actions through previously described allosteric binding sites or via known mechanisms of action. In addition, their selectivity and activity are dependent on only one amino acid in GC-A. Our findings show that there is a novel allosteric binding site on GC-A, which can be targeted by small molecules that increase the signaling effects of ANP and BNP.