Phospholipase D1 regulation of TNF-alpha protects against responses to LPS

Identification and Construction of a R-loop Mediated Diagnostic Model and Associated Immune Microenvironment of COPD through Machine Learning and Single-Cell Transcriptomics

Chronic obstructive pulmonary disease (COPD) is a prevalent chronic inflammatory airway disease with high incidence and significant disease burden. R-loops, functional chromatin structure formed during transcription, are closely associated with inflammation due to its aberrant formation. However, the role of R-loop regulators (RLRs) in COPD remains unclear. Utilizing both bulk transcriptome data and single-cell RNA sequencing data, we assessed the diverse expression patterns of RLRs in the lung tissues of COPD patients. A lower R-loop score was found in patients with COPD and in neutrophils. 12 machine learning algorithms (150 combinations) identified 14 hub RLRs (CBX8, EHD4, HDLBP, KDM6B, NFAT5, NLRP3, NUP214, PAFAH1B3, PINX1, PLD1, POLB, RCC2, RNF213, and VIM) associated with COPD. A RiskScore based on 14 RLRs identified two distinct COPD subtypes. Patient groups at high risk of COPD (low R-loop scores) had a higher immune score and a significant increase in neutrophils in their immune microenvironment compared to low-risk groups. PD-0325901 and QL-X-138 represent prospective COPD treatments for high-risk (low R-loop score) and low-risk (high R-loop score) patients. Finally, RT-PCR experiments confirmed expression differences of 8 RLRs (EHD4, HDLBP, NFAT5, NLRP3, PLD1, PINX1, POLB, and VIM) in COPD mice lung tissue. R-loops significantly contribute to the development of COPD and constructing predictive models based on RLRs may provide crucial insight into personalized treatment strategies for patients with COPD.

Inhibition of phospholipase D promotes neurological function recovery and reduces neuroinflammation after spinal cord injury in mice

Introduction

Spinal cord injury (SCI) is a severely disabling disease. Hyperactivation of neuroinflammation is one of the main pathophysiological features of secondary SCI, with phospholipid metabolism playing an important role in regulating inflammation. Phospholipase D (PLD), a critical lipid-signaling molecule, is known to be involved in various physiological processes, including the regulation of inflammation. Despite this knowledge, the specific role of PLD in SCI remains unclear.

Methods

In this study, we constructed mouse models of SCI and administered PLD inhibitor (FIPI) treatment to investigate the efficacy of PLD. Additionally, transcriptome sequencing and protein microarray analysis of spinal cord tissues were conducted to further elucidate its mechanism of action.

Results

The results showed that PLD expression increased after SCI, and inhibition of PLD significantly improved the locomotor ability, reduced glial scarring, and decreased the damage of spinal cord tissues in mice with SCI. Transcriptome sequencing analysis showed that inhibition of PLD altered gene expression in inflammation regulation. Subsequently, the protein microarray analysis of spinal cord tissues revealed variations in numerous inflammatory factors. Biosignature analysis pointed to an association with immunity, thus confirming the results obtained from transcriptome sequencing.

Discussion

Collectively, these observations furnish compelling evidence supporting the anti-inflammatory effect of FIPI in the context of SCI, while also offering important insights into the PLD function which may be a potential therapeutic target for SCI.

An overview of the mechanisms and potential roles of extracellular vesicles in septic shock

Septic shock, a subset of sepsis, is a fatal condition associated with high morbidity and mortality. However, the pathophysiology of septic shock is not fully understood. Moreover, the diagnostic markers employed for identifying septic shock lack optimal sensitivity and specificity. Current treatment protocols for septic shock have not been effective in lowering the mortality rate of patients. Most cells exhibit the capability to release extracellular vesicles (EVs), nanoscale vesicles that play a vital role in intercellular communication. In recent years, researchers have investigated the potential role of EVs in the pathogenesis, diagnosis, and treatment of different diseases, such as oncological, neurological, and cardiovascular diseases, as well as diabetes and septic shock. In this article, we present an overview of the inhibitory and facilitative roles that EVs play in the process of septic shock, the potential role of EVs in the diagnosis of septic shock, and the potential therapeutic applications of both native and engineered EVs in the management of septic shock.

Flow Chamber Analyses in Cardiovascular Research: Impact of Platelets and the Intercellular Crosstalk with Endothelial Cells, Leukocytes, and Red Blood Cells

Platelets are main drivers of thrombus formation. Besides platelet aggregate formation, platelets interact with different blood cells such as red blood and white blood cells (RBCs, WBCs) and endothelial cells (ECs), to promote thrombus formation and inflammation. In the past, the role of different proteins in platelet adhesion, activation, and aggregate formation has been analyzed using platelets/mice with a genetic loss of a certain protein. These knock-out mouse models have been investigated for changes in experimental arterial thrombosis or hemostasis. In this review, we focused on the Maastricht flow chamber, which is a very elegant tool to analyze thrombus formation under flow using whole blood or different blood cell components of genetically modified mice. Besides, the interaction of platelets with RBCs, WBCs, and ECs under flow conditions has been evaluated with regard to thrombus formation and platelet-mediated inflammation. Importantly, alterations in thrombus formation as emerged in the flow chamber frequently reflect arterial thrombosis in different mouse models. Thus, the results of flow chamber experiments in vitro are excellent indicators for differences in arterial thrombosis in vivo. Taken together, the Maastricht flow chamber can be used to (1) determine the severity of platelet alterations in different knock-out mice; (2) analyze differences in platelet adhesion, aggregation, and activation; (3) investigate collagen and non-collagen-dependent alterations of thrombus formation; and (4) highlight differences in the interaction of platelets with different blood/ECs. Thus, this experimental approach is a useful tool to increase our understanding of signaling mechanisms that drive arterial thrombosis and hemostasis.

Phospholipase D1 Attenuation Therapeutics Promotes Resilience against Synaptotoxicity in 12-Month-Old 3xTg-AD Mouse Model of Progressive Neurodegeneration

Abrogating synaptotoxicity in age-related neurodegenerative disorders is an extremely promising area of research with significant neurotherapeutic implications in tauopathies including Alzheimer's disease (AD). Our studies using human clinical samples and mouse models demonstrated that aberrantly elevated phospholipase D1 (PLD1) is associated with amyloid beta (Aβ) and tau-driven synaptic dysfunction and underlying memory deficits. While knocking out the lipolytic PLD1 gene is not detrimental to survival across species, elevated expression is implicated in cancer, cardiovascular conditions and neuropathologies, leading to the successful development of well-tolerated mammalian PLD isoform-specific small molecule inhibitors. Here, we address the importance of PLD1 attenuation, achieved using repeated 1 mg/kg of VU0155069 (VU01) intraperitoneally every alternate day for a month in 3xTg-AD mice beginning only from ~11 months of age (with greater influence of tau-driven insults) compared to age-matched vehicle (0.9% saline)-injected siblings. A multimodal approach involving behavior, electrophysiology and biochemistry corroborate the impact of this pre-clinical therapeutic intervention. VU01 proved efficacious in preventing in later stage AD-like cognitive decline affecting perirhinal cortex-, hippocampal- and amygdala-dependent behaviors. Glutamate-dependent HFS-LTP and LFS-LTD improved. Dendritic spine morphology showed the preservation of mushroom and filamentous spine characteristics. Differential PLD1 immunofluorescence and co-localization with Aβ were noted.

Cardiac phospholipidome is altered during ischemia and reperfusion in an ex vivo rat model

Acute myocardial infarction (AMI) is the leading cause of death, morbidity, and health costs worldwide. In AMI, a sudden blockage of blood flow causes myocardial ischemia and cell death. Reperfusion after ischemia has paradoxical effects and may exacerbate the myocardial injury, a process known as ischemic reperfusion injury. In this work we evaluated the lipidome of isolated rat hearts, maintained in controlled perfusion (CT), undergoing global ischemia (ISC) or ischemia followed by reperfusion (IR). 153 polar lipid levels were significantly different between conditions. 48 features had q < 0.001 and included 8 phosphatidylcholines and 4 lysophospholipids, which were lower in ISC compared to CT, and even lower in the IR group, suggesting that IR induces more profound changes than ISC. We observed that the levels of 16 alkyl acyl phospholipids were significantly altered during ISC and IR. Overall, these data indicate that myocardial lipid remodelling and possibly damage occurs to a greater extent during reperfusion. The adaptation of cardiac lipidome during ISC and IR described is consistent with the presence of oxidative damage and may reflect the impact of AMI on the lipidome at the cellular level and provide new insights into the role of lipids in the pathophysiology of acute myocardial ischemia/reperfusion injury.

Doxorubicin-Induced Cognitive Impairment: The Mechanistic Insights

Chemotherapy can significantly prolong the survival of patients with breast cancer; Nevertheless, the majority of patients receiving chemotherapy such as doxorubicin may have cognitive deficits that manifest as impairments in learning, reasoning, attention, and memory. The phenomenon of chemotherapy-induced cognitive decline is termed as chemotherapy-related cognitive impairment (CRCI) or chemo-brain. Doxorubicin (DOX), a commonly used drug in adjuvant chemotherapy for patients with breast cancer, has been reported to induce chemo-brain through a variety of mechanisms including DNA damage, oxidative stress, inflammation, dysregulation of apoptosis and autophagy, changes in neurotransmitter levels, mitochondrial dysfunction, glial cell interactions, neurogenesis inhibition, and epigenetic factors. These mechanisms do not operate independently but are inter-related, coordinately contributing to the development of chemo-brain. Here we review the relationships of these mechanisms and pathways in attempt to provide mechanistic insights into the doxorubicin-induced cognitive impairment.

HIPK3 Mediates Inflammatory Cytokines and Oxidative Stress Markers in Monocytes in a Rat Model of Sepsis Through the JNK/c-Jun Signaling Pathway

Sepsis is a fetal immunological disorder and its complication worsens in the patients with hemodialysis which may increase the risk of death. In the present study, we aimed to investigate the effect of homeodomain-interacting protein kinase 3 (HIPK3) on inflammatory factors and oxidative stress markers in monocytes of rats with sepsis by regulating the c-Jun amino-terminal kinase (JNK)/c-Jun signaling pathway. A rat model of sepsis was initially established using cecal ligation and puncture (CLP) and was further identified by enlarged spleen tissues, inflammation, and oxidative stress. Monocytes were isolated from rats with CLP-induced sepsis. HIPK3 was observed to be downregulated while JUN was upregulated in monocytes from rats with CLP-induced sepsis. Furthermore, isolated monocytes were transduced with lentiviral vectors expressing HIPK3 or shRNA against HIPK3 to explore the effect of HIPK3 on viability and apoptosis of monocytes as well as inflammatory factors and oxidative stress markers. The obtained data exhibited that overexpression of HIPK3 or inhibition of the JNK signaling pathway enhanced proliferation, reduced apoptosis of monocytes, alleviated inflammation, and oxidative stress injury. Consistently, our results may provide evidence that HIPK3 could inhibit the JNK/c-Jun signaling pathway, thereby potentially retarding the progression of sepsis.

PLD1 and PLD2 differentially regulate the balance of macrophage polarization in inflammation and tissue injury

Phospholipase D (PLD) isoforms PLD1 and PLD2 serve as the primary nodes where diverse signaling pathways converge. However, their isoform‐specific functions remain unclear. We showed that PLD1 and PLD2 selectively couple to toll‐like receptor 4 (TLR4) and interleukin 4 receptor (IL‐4R) and differentially regulate macrophage polarization of M1 and M2 via the LPS–MyD88 axis and the IL‐4–JAK3 signaling, respectively. Lipopolysaccharide (LPS) enhanced TLR4 or MyD88 interaction with PLD1; IL‐4 induced IL‐4R or JAK3 association with PLD2, indicating isozyme‐specific signaling events. PLD1 and PLD2 are indispensable for M1 polarization and M2 polarization, respectively. Genetic and pharmacological targeting of PLD1 conferred protection against LPS‐induced sepsis, cardiotoxin‐induced muscle injury, and skin injury by promoting the shift toward M2; PLD2 ablation intensified disease severity by promoting the shift toward M1. Enhanced Foxp3⁺ regulatory T cell recruitment also influenced the anti‐inflammatory phenotype of Pld1^LyzCre macrophages. We reveal a previously uncharacterized role of PLD isoforms in macrophage polarization, signifying potential pharmacological interventions for macrophage modulation.

Phospholipase D1 and D2 Synergistically Regulate Thrombus Formation

Previously, we reported that phospholipase D1 (PLD1) and PLD2 inhibition by selective PLD1 and PLD2 inhibitors could prevent platelet aggregation in humans, but not in mice. Moreover, only the PLD1 inhibitor, but not PLD2 inhibitor, could effectively prevent thrombus formation in mice, indicating that PLD might play different roles in platelet function in humans and mice. Although PLD1 and PLD2 were reported to be implicated in thrombotic events, the role of PLD in mice remains not completely clear. Here, we investigated the role of PLD1 and PLD2 in acute pulmonary thrombosis and transient middle cerebral artery occlusion-induced brain injury in mice. The data revealed that inhibition of PLD1, but not of PLD2, could partially prevent pulmonary thrombosis-induced death. Moreover, concurrent PLD1 and PLD2 inhibition could considerably increase survival rate. Likewise, inhibition of PLD1, but not PLD2, partially improved ischemic stroke and concurrent inhibition of PLD1, and PLD2 exhibited a relatively better protection against ischemic stroke, as evidenced by the infarct size, brain edema, modified neurological severity score, rotarod test, and the open field test. In conclusion, PLD1 might play a more important role than PLD2, and both PLD1 and PLD2 could act synergistically or have partially redundant functions in regulating thrombosis-relevant events.

Toona sinensis modulates autophagy and cytokines in lipopolysaccharide-induced RAW 264.7 macrophages

Toona sinensis (TS) is a medicinal herb possessing anti-apoptotic, anti-oxidant, and anti-inflammatory properties and is used to treat diabetes, cancer, and inflammatory diseases. In traditional Chinese medicine theory, TS clears dampness and heat, strengthens the stomach function, and regulates vital energy flow. TS is also used as an astringent and a pesticide. In this study, we aimed to evaluate how TS influences autophagy and cytokines during the inflammatory process in RAW 264.7 macrophages. The treatment groups were pre-supplemented with TS leaf extract; rapamycin was used to enhance autophagy and lipopolysaccharide (LPS) was used to induce inflammation. The expression of autophagy-related proteins was analyzed by western blotting. The survival rate of, and chemokine expression and oxidative stress in the cells were also assessed. TS leaf extract inhibited mammalian target of rapamycin (mTOR) phosphorylation at site S2448 in the macrophages. At relatively higher concentrations (50 and 75 μg/mL), TS elevated the expression of light chain 3 II (LC3-II), which further modulated autophagy. Pre-supplementation with TS leaf extract elevated the total glutathione (GSH) level and GSH/oxidized GSH (GSSG) ratio, but it decreased the GSSG, total nitric oxide, nitrate, nitrite, malondialdehyde, and superoxide anion levels. TS reversed the effects of LPS-induced cytokines, including interleukin (IL)-6 and IL-10. TS did not induce significant toxicity at the studied concentrations. In conclusion, TS leaf extract may modulate autophagy during inflammation. Furthermore, it may prevent cell damage via anti-inflammation and anti-oxidation. Thus, this study supports the ethnomedical use of TS in the prevention of inflammation-related diseases.

The in vitro effects of phospholipase D1-mTOR axis in liver fibrogenesis

AIMS

The activation of hepatic stellate cells (HSCs) plays a central role in liver fibrosis progression. Phospholipase D (PLD) enzymes participate in multiple cellular activities. However, whether and how PLD regulates HSCs activation remain elusive.

MAIN METHODS

The expression of intrahepatic PLD1 and PLD2 was determined in CCl₄-induced mouse liver fibrosis models by western blot and immunohistochemistry. Cell model of liver fibrogenesis was constructed using rat HSCs line (HSC-T6) treated with recombinant transforming growth factor β1 (TGFβ1). Fibrogenesis was evaluated on the aspects of proliferation, expression of pro-fibrogenic markers and migration. The effects mediated by PLD1-mTOR axis on TGFβ1-induced fibrogenesis were evaluated using HSC-T6 treated with small-molecular PLD1 inhibitors, PLD1-SiRNA, rapamycin (mTOR inhibitor) and MHY1485 (mTOR activator).

KEY FINDINGS

Significant increase of PLD1, not PLD2 was documented in CCl₄-induced cirrhotic compared to normal liver tissues. Suppression of PLD1 activities by PLD inhibitors or down-regulation of PLD1 expression in HSC-T6 could significantly restrain TGFβ1-induced fibrogenesis, as reflected by decreased cell proliferation and reduced expression of pro-fibrogenic markers. Besides, either PLD1 inhibitor or PLD1-SiRNA significantly inhibited mTOR activity of HSC-T6. Moreover, PLD1 inhibitors not only exhibited similar effects with rapamycin in TGFβ1-induced fibrogenesis, but also blunted MHY1485 enhanced cell proliferation of HSC-T6.

SIGNIFICANCE

The PLD1-mTOR axis of HSCs could be therapeutically targeted in advanced liver fibrosis.

Enhanced Integrin Activation of PLD2-Deficient Platelets Accelerates Inflammation after Myocardial Infarction

Background: Phospholipase (PL)D1 is crucial for integrin α_IIbβ₃ activation of platelets in arterial thrombosis and TNF-α-mediated inflammation and TGF-β-mediated collagen scar formation after myocardial infarction (MI) in mice. Enzymatic activity of PLD is not responsible for PLD-mediated TNF-α signaling and myocardial healing. The impact of PLD2 in ischemia reperfusion injury is unknown. Methods: PLD2-deficient mice underwent myocardial ischemia and reperfusion (I/R). Results: Enhanced integrin α_IIbβ₃ activation of platelets resulted in elevated interleukin (IL)-6 release from endothelial cells in vitro and enhanced IL-6 plasma levels after MI in PLD2-deficient mice. This was accompanied by enhanced migration of inflammatory cells into the infarct border zone and reduced TGF-β plasma levels after 72 h that might account for enhanced inflammation in PLD2-deficient mice. In contrast to PLD1, TNF-α signaling, infarct size and cardiac function 24 h after I/R were not altered when PLD2 was deleted. Furthermore, TGF-β plasma levels, scar formation and heart function were comparable between PLD2-deficient and control mice 21 days post MI. Conclusions: The present study contributes to our understanding about the role of PLD isoforms and altered platelet signaling in the process of myocardial I/R injury.

The triangle of death of neurons: Oxidative damage, mitochondrial dysfunction, and loss of choline-containing biomolecules in brains of mice treated with doxorubicin. Advanced insights into mechanisms of chemotherapy induced cognitive impairment ("chemobrain") involving TNF-α

Cancer treatments are developing fast and the number of cancer survivors could arise to 20 million in United State by 2025. However, a large fraction of cancer survivors demonstrate cognitive dysfunction and associated decreased quality of life both shortly, and often long-term, after chemotherapy treatment. The etiologies of chemotherapy induced cognitive impairment (CICI) are complicated, made more so by the fact that many anti-cancer drugs cannot cross the blood-brain barrier (BBB). Multiple related factors and confounders lead to difficulties in determining the underlying mechanisms. Chemotherapy induced, oxidative stress-mediated tumor necrosis factor-alpha (TNF-α) elevation was considered as one of the main candidate mechanisms underlying CICI. Doxorubicin (Dox) is a prototypical reactive oxygen species (ROS)-generating chemotherapeutic agent used to treat solid tumors and lymphomas as part of multi-drug chemotherapeutic regimens. We previously reported that peripheral Dox-administration leads to plasma protein damage and elevation of TNF-α in plasma and brain of mice. In the present study, we used TNF-α null (TNFKO) mice to investigate the role of TNF-α in Dox-induced, oxidative stress-mediated alterations in brain. We report that Dox-induced oxidative stress in brain is ameliorated and brain mitochondrial function assessed by the Seahorse-determined oxygen consumption rate (OCR) is preserved in brains of TNFKO mice. Further, we show that Dox-decreased the level of hippocampal choline-containing compounds and brain phospholipases activity are partially protected in TNFKO group in MRS study. Our results provide strong evidence that Dox-targeted mitochondrial damage and levels of brain choline-containing metabolites, as well as phospholipases changes decreased in the CNS are associated with oxidative stress mediated by TNF-α. These results are consistent with the notion that oxidative stress and elevated TNF-α in brain underlie the damage to mitochondria and other pathological changes that lead to CICI. The results are discussed with reference to our identifying a potential therapeutic target to protect against cognitive problems after chemotherapy.

Enzymatic Activity Is Not Required for Phospholipase D Mediated TNF-α Regulation and Myocardial Healing

Phospholipase D1 is a regulator of tumor necrosis factor-α expression and release upon LPS-induced sepsis and following myocardial infarction (MI). Lack of PLD1 leads to a reduced TNF-α mediated inflammatory response and to enhanced infarct size with declined cardiac function 21 days after ischemia reperfusion (I/R) injury. Deficiency of both PLD isoforms PLD1 and PLD2 as well as pharmacological inhibition of the enzymatic activity of PLD with the PLD inhibitor FIPI protected mice from arterial thrombosis and ischemic brain infarction. Here we treated mice with the PLD inhibitor FIPI to analyze if pharmacological inhibition of PLD after myocardial ischemia protects mice from cardiac damage. Inhibition of PLD with FIPI leads to reduced migration of inflammatory cells into the infarct border zone 24 h after experimental MI in mice, providing first evidence for immune cell migration to be dependent on the enzymatic activity of PLD. In contrast to PLD1 deficient mice, TNF-α plasma level was not altered after FIPI treatment of mice. Consequently, infarct size and left ventricular (LV) function were comparable between FIPI-treated and control mice 21 days post MI. Moreover, cell survival 24 h post I/R was not altered upon FIPI treatment. Our results indicate that the enzymatic activity of PLD is not responsible for PLD mediated TNF-α signaling and myocardial healing after I/R injury in mice. Furthermore, reduced TNF-α plasma levels in PLD1 deficient mice might be responsible for increased infarct size and impaired cardiac function 21 days post MI.