Lyn prevents aberrant inflammatory responses to Pseudomonas infection in mammalian systems by repressing a SHIP-1-associated signaling cluster

FcRγIIA response duality in leishmaniasis

Leishmania is responsible for a neglected tropical disease affecting millions of people around the world and could potentially spread more due to climate change. This disease not only leads to significant morbidity but also imposes substantial social and economic burdens on affected populations, often exacerbating poverty and health disparities. Despite the complexity and effectiveness of the immune response, the parasite has developed various strategies to evade detection and manipulates host cells in favor of its replication. These evasion strategies start at early stages of the infection by hijacking immune receptors to silence critical cellular response that would otherwise limit the pathogen's propagation. Among these receptors, Fc receptors have emerged as a significant player in the immune evasion strategies employed by microorganisms, as they could promote inhibitory pathways. This review explores the potential role of one of these immune receptors, the FcγRIIA, in leishmaniasis and how this parasite may use it and the signaling pathways downstream to evade the host immune response. By understanding the potential interactions between Leishmania and immune receptors such as FcγRIIA, we may identify novel targets for therapeutic intervention aimed to enhance the host immune response and reduce the burden of this disease.

CircCDC42-encoded CDC42-165aa regulates macrophage pyroptosis in Klebsiella pneumoniae infection through Pyrin inflammasome activation

The circular RNA (circRNA) family is a group of endogenous non-coding RNAs (ncRNAs) that have critical functions in multiple physiological and pathological processes, including inflammation, cancer, and cardiovascular diseases. However, their roles in regulating innate immune responses remain unclear. Here, we define Cell division cycle 42 (CDC42)-165aa, a protein encoded by circRNA circCDC42, which is overexpressed in Klebsiella pneumoniae (KP)-infected alveolar macrophages. High levels of CDC42-165aa induces the hyperactivation of Pyrin inflammasomes and aggravates alveolar macrophage pyroptosis, while the inhibition of CDC42-165aa reduces lung injury in mice after KP infection by inhibiting Pyrin inflammasome-mediated pyroptosis. Overall, these results demonstrate that CDC42-165aa stimulates Pyrin inflammasome by inhibiting CDC42 GTPase activation and provides a potential clinical target for pathogenic bacterial infection in clinical practice.

Regulation of Microglial Signaling by Lyn and SHIP-1 in the Steady-State Adult Mouse Brain

Chronic neuroinflammation and glial activation are associated with the development of many neurodegenerative diseases and neuropsychological disorders. Recent evidence suggests that the protein tyrosine kinase Lyn and the lipid phosphatase SH2 domain-containing inositol 5' phosphatase-1 (SHIP-1) regulate neuroimmunological responses, but their homeostatic roles remain unclear. The current study investigated the roles of Lyn and SHIP-1 in microglial responses in the steady-state adult mouse brain. Young adult Lyn-/- and SHIP-1-/- mice underwent a series of neurobehavior tests and postmortem brain analyses. The microglial phenotype and activation state were examined by immunofluorescence and flow cytometry, and neuroimmune responses were assessed using gene expression analysis. Lyn-/- mice had an unaltered behavioral phenotype, neuroimmune response, and microglial phenotype, while SHIP-1-/- mice demonstrated reduced explorative activity and exhibited microglia with elevated activation markers but reduced granularity. In addition, expression of several neuroinflammatory genes was increased in SHIP-1-/- mice. In response to LPS stimulation ex vivo, the microglia from both Lyn-/- and SHIP-1-/- showed evidence of hyper-activity with augmented TNF-α production. Together, these findings demonstrate that both Lyn and SHIP-1 have the propensity to control microglial responses, but only SHIP-1 regulates neuroinflammation and microglial activation in the steady-state adult brain, while Lyn activity appears dispensable for maintaining brain homeostasis.

Aspartoacylase suppresses prostate cancer progression by blocking LYN activation

BACKGROUND

Globally, despite prostate cancer (PCa) representing second most prevalent malignancy in male, the precise molecular mechanisms implicated in its pathogenesis remain unclear. Consequently, elucidating the key molecular regulators that govern disease progression could substantially contribute to the establishment of novel therapeutic strategies, ultimately advancing the management of PCa.

METHODS

A total of 49 PCa tissues and 43 adjacent normal tissues were collected from January 2017 to December 2021 at Zhongnan Hospital of Wuhan University. The advanced transcriptomic methodologies were employed to identify differentially expressed mRNAs in PCa. The expression of aspartoacylase (ASPA) in PCa was thoroughly evaluated using quantitative real-time PCR and Western blotting techniques. To elucidate the inhibitory role of ASPA in PCa cell proliferation and metastasis, a comprehensive set of in vitro and in vivo assays were conducted, including orthotopic and tumor-bearing mouse models (n = 8 for each group). A combination of experimental approaches, such as Western blotting, luciferase assays, immunoprecipitation assays, mass spectrometry, glutathione S-transferase pull-down experiments, and rescue studies, were employed to investigate the underlying molecular mechanisms of ASPA's action in PCa. The Student's t-test was employed to assess the statistical significance between two distinct groups, while one-way analysis of variance was utilized for comparisons involving more than two groups. A two-sided P value of less than 0.05 was deemed to indicate statistical significance.

RESULTS

ASPA was identified as a novel inhibitor of PCa progression. The expression of ASPA was found to be significantly down-regulated in PCa tissue samples, and its decreased expression was independently associated with patients' prognosis (HR = 0.60, 95% CI 0.40-0.92, P = 0.018). Our experiments demonstrated that modulation of ASPA activity, either through gain- or loss-of-function, led to the suppression or enhancement of PCa cell proliferation, migration, and invasion, respectively. The inhibitory role of ASPA in PCa was further confirmed using orthotopic and tumor-bearing mouse models. Mechanistically, ASPA was shown to directly interact with the LYN and inhibit the phosphorylation of LYN as well as its downstream targets, JNK1/2 and C-Jun, in both PCa cells and mouse models, in an enzyme-independent manner. Importantly, the inhibition of LYN activation by bafetinib abrogated the promoting effect of ASPA knockdown on PCa progression in both in vitro and in vivo models. Moreover, we observed an inverse relationship between ASPA expression and LYN activity in clinical PCa samples, suggesting a potential regulatory role of ASPA in modulating LYN signaling.

CONCLUSION

Our findings provide novel insights into the tumor-suppressive function of ASPA in PCa and highlight its potential as a prognostic biomarker and therapeutic target for the management of this malignancy.

Lyn attenuates sepsis-associated acute kidney injury by inhibition of phospho-STAT3 and apoptosis

Sepsis-associated acute kidney injury (SA-AKI) is a life-threatening condition associated with high mortality and morbidity. However, the underlying pathogenesis of SA-AKI is still unclear. Lyn belongs to Src family kinases (SFKs), which exert numerous biological functions including modulation in receptor-mediated intracellular signaling and intercellular communication. Previous studies demonstrated that Lyn gene deletion obviously aggravates LPS-induced lung inflammation, but the role and possible mechanism of Lyn in SA-AKI have not been reported yet. Here, we found that Lyn protected against renal tubular injury in cecal ligation and puncture (CLP) induced AKI mouse model by inhibition of signal transducer and activator of transcription 3 (STAT3) phosphorylation and cell apoptosis. Moreover, Lyn agonist MLR-1023 pretreatment improved renal function, inhibited STAT3 phosphorylation and decreased cell apoptosis. Thus, Lyn appears to play a crucial role in orchestrating STAT3-mediated inflammation and cell apoptosis in SA-AKI. Hence, Lyn kinase may be a promising therapeutic target for SA-AKI.

Src Family Kinases: A Potential Therapeutic Target for Acute Kidney Injury

Src family kinases (SFKs) are non-receptor tyrosine kinases and play a key role in regulating signal transduction. The mechanism of SFKs in various tumors has been widely studied, and there are more and more studies on its role in the kidney. Acute kidney injury (AKI) is a disease with complex pathogenesis, including oxidative stress (OS), inflammation, endoplasmic reticulum (ER) stress, autophagy, and apoptosis. In addition, fibrosis has a significant impact on the progression of AKI to developing chronic kidney disease (CKD). The mortality rate of this disease is very high, and there is no effective treatment drug at present. In recent years, some studies have found that SFKs, especially Src, Fyn, and Lyn, are involved in the pathogenesis of AKI. In this paper, the structure, function, and role of SFKs in AKI are discussed. SFKs play a crucial role in the occurrence and development of AKI, making them promising molecular targets for the treatment of AKI.

cGAS modulates cytokine secretion and bacterial burdens by altering the release of mitochondrial DNA in Pseudomonas pulmonary infection

Cyclic GMP-AMP synthase (cGAS) is essential for fighting against viruses and bacteria, but how cGAS is involved in host immune response remains largely elusive. Here, we uncover the crucial role of cGAS in host immunity based on a Pseudomonas aeruginosa pulmonary infection model. cGAS^-/- mice showed more heavy bacterial burdens and serious lung injury accompanied with exorbitant proinflammatory cytokines than wild-type mice. cGAS deficiency caused an accumulation of mitochondrial DNA in cytoplasm, which in turn induced excessive secretion of proinflammatory factors by activating inflammasome and TLR9 signaling. Mechanistically, cGAS deficiency inhibited the recruitment of LC3 by reducing the binding capacity of TBK-1 to p62, leading to impaired mitophagy and augmented release of mitochondrial DNA. Importantly, cytoplasmic mitochondrial DNA also acted as a feedback signal that induced the activation of cGAS. Altogether, these findings identify protective and homeostasis functions of cGAS against Pseudomonas aeruginosa infection, adding significant insight into the pathogenesis of bacterial infectious diseases.

Dopamine D3 receptor signaling alleviates mouse rheumatoid arthritis by promoting Toll-like receptor 4 degradation in mast cells

Dopamine receptors are involved in several immunological diseases. We previously found that dopamine D3 receptor (D3R) on mast cells showed a high correlation with disease activity in patients with rheumatoid arthritis, but the mechanism remains largely elusive. In this study, a murine collagen-induced arthritis (CIA) model was employed in both DBA/1 mice and D3R knockout mice. Here, we revealed that D3R-deficient mice developed more severe arthritis than wild-type mice. D3R suppressed mast cell activation in vivo and in vitro via a Toll-like receptor 4 (TLR4)-dependent pathway. Importantly, D3R promoted LC3 conversion to accelerate ubiquitin-labeled TLR4 degradation. Mechanistically, D3R inhibited mTOR and AKT phosphorylation while enhancing AMPK phosphorylation in activated mast cells, which was followed by autophagy-dependent protein degradation of TLR4. In total, we found that D3R on mast cells alleviated inflammation in mouse rheumatoid arthritis through the mTOR/AKT/AMPK-LC3-ubiquitin-TLR4 signaling axis. These findings identify a protective function of D3R against excessive inflammation in mast cells, expanding significant insight into the pathogenesis of rheumatoid arthritis and providing a possible target for future treatment.

Bitter receptor TAS2R138 facilitates lipid droplet degradation in neutrophils during Pseudomonas aeruginosa infection

Bitter receptors function primarily in sensing taste, but may also have other functions, such as detecting pathogenic organisms due to their agile response to foreign objects. The mouse taste receptor type-2 member 138 (TAS2R138) is a member of the G-protein-coupled bitter receptor family, which is not only found in the tongue and nasal cavity, but also widely distributed in other organs, such as the respiratory tract, gut, and lungs. Despite its diverse functions, the role of TAS2R138 in host defense against bacterial infection is largely unknown. Here, we show that TAS2R138 facilitates the degradation of lipid droplets (LDs) in neutrophils during Pseudomonas aeruginosa infection through competitive binding with PPARG (peroxisome proliferator-activated receptor gamma) antagonist: N-(3-oxododecanoyl)-L-homoserine lactone (AHL-12), which coincidently is a virulence-bound signal produced by this bacterium (P. aeruginosa). The released PPARG then migrates from nuclei to the cytoplasm to accelerate the degradation of LDs by binding PLIN2 (perilipin-2). Subsequently, the TAS2R138-AHL-12 complex targets LDs to augment their degradation, and thereby facilitating the clearance of AHL-12 in neutrophils to maintain homeostasis in the local environment. These findings reveal a crucial role for TAS2R138 in neutrophil-mediated host immunity against P. aeruginosa infection.

STAT3 Differentially Regulates TLR4-Mediated Inflammatory Responses in Early or Late Phases

Toll-like receptor 4 (TLR4) signaling is an important therapeutic target to manage lipopolysaccharide (LPS)-induced inflammation. The transcription factor signal transducer and activator of transcription 3 (STAT3) has been identified as an important regulator of various immune-related diseases and has generated interest as a therapeutic target. Here, we investigated the time-dependent roles of STAT3 in LPS-stimulated RAW264.7 macrophages. STAT3 inhibition induced expression of the pro-inflammatory genes iNOS and COX-2 at early time points. STAT3 depletion resulted in regulation of nuclear translocation of nuclear factor (NF)-κB subunits p50 and p65 and IκBα/Akt/PI3K signaling. Moreover, we found that one Src family kinase, Lyn kinase, was phosphorylated in STAT3 knockout macrophages. In addition to using pharmacological inhibition of NF-κB, we found out that STAT3KO activation of NF-κB subunit p50 and p65 and expression of iNOS was significantly inhibited; furthermore, Akt tyrosine kinase inhibitors also inhibited iNOS and COX-2 gene expression during early time points of LPS stimulation, demonstrating an NF-κB- Akt-dependent mechanism. On the other hand, iNOS expression was downregulated after prolonged treatment with LPS. Activation of NF-κB signaling was also suppressed, and consequently, nitric oxide (NO) production and cell invasion were repressed. Overall, our data indicate that STAT3 differentially regulates early- and late-phase TLR4-mediated inflammatory responses.

Small-Molecule Inhibitor of 8-Oxoguanine DNA Glycosylase 1 Regulates Inflammatory Responses during Pseudomonas aeruginosa Infection

The DNA repair enzyme 8-oxoguanine DNA glycosylase 1 (OGG1), which excises 8-oxo-7,8-dihydroguanine lesions induced in DNA by reactive oxygen species, has been linked to the pathogenesis of lung diseases associated with bacterial infections. A recently developed small molecule, SU0268, has demonstrated selective inhibition of OGG1 activity; however, its role in attenuating inflammatory responses has not been tested. In this study, we report that SU0268 has a favorable effect on bacterial infection both in mouse alveolar macrophages (MH-S cells) and in C57BL/6 wild-type mice by suppressing inflammatory responses, particularly promoting type I IFN responses. SU0268 inhibited proinflammatory responses during Pseudomonas aeruginosa (PA14) infection, which is mediated by the KRAS-ERK1-NF-κB signaling pathway. Furthermore, SU0268 induces the release of type I IFN by the mitochondrial DNA-cGAS-STING-IRF3-IFN-β axis, which decreases bacterial loads and halts disease progression. Collectively, our results demonstrate that the small-molecule inhibitor of OGG1 (SU0268) can attenuate excessive inflammation and improve mouse survival rates during PA14 infection. This strong anti-inflammatory feature may render the inhibitor as an alternative treatment for controlling severe inflammatory responses to bacterial infection.

A Novel Cochlioquinone Derivative, CoB1, Regulates Autophagy in Pseudomonas aeruginosa Infection through the PAK1/Akt1/mTOR Signaling Pathway

Owing to multiple antibiotic resistance, Pseudomonas aeruginosa causes the most intractable infections to human beings worldwide, thus exploring novel drugs to defend against this bacterium remains of great importance. In this study, we purified a novel cochlioquinone B derivative (CoB1) from Salvia miltiorrhiza endophytic Bipolaris sorokiniana and reveal its role in host defense against P. aeruginosa infection by activating cytoprotective autophagy in alveolar macrophages (AMs) both in vivo and in vitro. Using a P. aeruginosa infection model, we observed that CoB1-treated mice manifest weakened lung injury, reduced bacterial systemic dissemination, decreased mortality, and dampened inflammatory responses, compared with the wild type littermates. We demonstrate that CoB1-induced autophagy in mouse AMs is associated with decreased PAK1 expression via the ubiquitination-mediated degradation pathway. The inhibition of PAK1 decreases the phosphorylation level of Akt, blocks the Akt/mTOR signaling pathway, and promotes the release of ULK1/2-Atg13-FIP200 complex from mTOR to initiate autophagosome formation, resulting in increased bacterial clearance capacity. Together, our results provide a molecular basis for the use of CoB1 to regulate host immune responses against P. aeruginosa infection and indicate that CoB1 is a potential option for the treatment of infection diseases.

oprC Impairs Host Defense by Increasing the Quorum-Sensing-Mediated Virulence of Pseudomonas aeruginosa

Pseudomonas aeruginosa, found widely in the wild, causes infections in the lungs and several other organs in healthy people but more often in immunocompromised individuals. P. aeruginosa infection leads to inflammasome assembly, pyroptosis, and cytokine release in the host. OprC is one of the bacterial porins abundant in the outer membrane vesicles responsible for channel-forming and copper binding. Recent research has revealed that OprC transports copper, an essential trace element involved in various physiological processes, into bacteria during copper deficiency. Here, we found that oprC deletion severely impaired bacterial motility and quorum-sensing systems, as well as lowered levels of lipopolysaccharide and pyocyanin in P. aeruginosa. In addition, oprC deficiency impeded the stimulation of TLR2 and TLR4 and inflammasome activation, resulting in decreases in proinflammatory cytokines and improved disease phenotypes, such as attenuated bacterial loads, lowered lung barrier damage, and longer mouse survival. Moreover, oprC deficiency significantly alleviated pyroptosis in macrophages. Mechanistically, oprC gene may impact quorum-sensing systems in P. aeruginosa to alter pyroptosis and inflammatory responses in cells and mice through the STAT3/NF-κB signaling pathway. Our findings characterize OprC as a critical virulence regulator, providing the groundwork for further dissection of the pathogenic mechanism of OprC as a potential therapeutic target of P. aeruginosa.

SHIP-1 Regulates Phagocytosis and M2 Polarization Through the PI3K/Akt-STAT5-Trib1 Circuit in Pseudomonas aeruginosa Infection

SHIP-1 is an inositol phosphatase that hydrolyzes phosphatidylinositol 3-kinase (PI3K) products and negatively regulates protein kinase B (Akt) activity, thereby modulating a variety of cellular processes in mammals. However, the role of SHIP-1 in bacterial-induced sepsis is largely unknown. Here, we show that SHIP-1 regulates inflammatory responses during Gram-negative bacterium Pseudomonas aeruginosa infection. We found that infected-SHIP-1-/- mice exhibited decreased survival rates, increased inflammatory responses, and susceptibility owing to elevated expression of PI3K than wild-type (WT) mice. Inhibiting SHIP-1 via siRNA silencing resulted in lipid raft aggregates, aggravated oxidative damage, and bacterial burden in macrophages after PAO1 infection. Mechanistically, SHIP-1 deficiency augmented phosphorylation of PI3K and nuclear transcription of signal transducer and activator of transcription 5 (STAT5) to induce the expression of Trib1, which is critical for differentiation of M2 but not M1 macrophages. These findings reveal a previously unrecognized role of SHIP-1 in inflammatory responses and macrophage homeostasis during P. aeruginosa infection through a PI3K/Akt-STAT5-Trib1 axis.

Bacterial Type I CRISPR-Cas systems influence inflammasome activation in mammalian host by promoting autophagy

The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated systems (CRISPR-Cas) systems in prokaryotes function at defending against foreign DNAs, providing adaptive immunity to maintain homeostasis. CRISPR-Cas may also influence immune regulation ability in mammalian cells through alterations of pathogenic extent and nature. Recent research has implied that Type I CRISPR-Cas systems of Pseudomonas aeruginosa strain UCBPP-PA14 impede recognition by Toll-like receptor 4, and decrease pro-inflammatory responses both in vitro and in vivo. However, the molecular mechanism by which CRISPR-Cas systems affect host immunity is largely undemonstrated. Here, we explored whether CRISPR-Cas systems can influence autophagy to alter the activation of inflammasome. Using the wild-type PA14 and total CRISPR-Cas region deletion (∆TCR) mutant strain, we elucidated the role and underlying mechanism of Type I CRISPR-Cas systems in bacterial infection, and showed that CRISPR-Cas systems impacted the release of mitochondrial DNA and induction of autophagy. CRISPR-Cas deficiency led to an increase of mitochondrial DNA release, a decrease in autophagy, an increase of inflammasome activation and, ultimately, an elevation of pro-inflammatory response. Our findings illustrate a new important mechanism by which Type I CRISPR-Cas systems control their virulence potency to evade host defense.

Regulation of hematopoietic cell signaling by SHIP-1 inositol phosphatase: growth factors and beyond

SHIP-1 is a hematopoietic-specific inositol phosphatase activated downstream of a multitude of receptors including those for growth factors, cytokines, antigen, immunoglobulin and toll-like receptor agonists where it exerts inhibitory control. While it is constitutively expressed in all immune cells, SHIP-1 expression is negatively regulated by the inflammatory and oncogenic micro-RNA miR-155. Knockout mouse studies have shown the importance of SHIP-1 in various immune cell subsets and have revealed a range of immune-mediated pathologies that are engendered due to loss of SHIP-1's regulatory activity, impelling investigations into the role of SHIP-1 in human disease. In this review, we provide an overview of the literature relating to the role of SHIP-1 in hematopoietic cell signaling and function, we summarize recent reports that highlight the dysregulation of the SHIP-1 pathway in cancers, autoimmune disorders and inflammatory diseases, and lastly we discuss the importance of SHIP-1 in restraining myeloid growth factor signaling.