Splenic Macrophages Research Articles

Abstract 4138661: Targeting Arginase I Alleviates Cardiomyopathy

Introduction: Emerging data have shown that pathological cardiac fibrosis and heart failure is driven by recruitment of CD4 + T cells to injured heart tissue. Systemic deletion of CD4 + T cells or splenectomy has been shown to attenuate CD4 + T cell heart infiltration and inflammation. We engineered cargo-less nanoparticles using a biocompatible and biodegradable polymer that target splenic macrophages to overexpress arginase I, leading to local depletion of L-arginine, an amino acid crucial for CD4 + T cell activation and expansion. Hypothesis: Cargo-less nanoparticles attenuate CD4 + T cell activation, expansion, and heart infiltration in experimental models of cardiomyopathy by regulating cross talk between macrophages and CD4 + T cells via L-arginine depletion in the spleen. Methods: Spleen-targeting, cargo-less nanoparticles were synthesized from poly(L-lactide-co-glycolide) (PLLGA) and administered to murine and human macrophages in vitro. Arginase I expression and activity were assessed via Western blotting and arginase activity assay. Epigenetic modulation was analyzed using Western blotting and CHIP-seq. Conditioned media was collected to culture CFSE-labeled T cells to assess proliferation. The nanoparticles were administered to mouse heart failure models induced by isoproterenol or angiotensin II and phenylephrine. Immune cell composition in mouse spleens and hearts was investigated by flow cytometry. Cardiac function was assessed by echocardiography and heart fibrosis was examined via immunohistochemistry and Western blotting. Results: Primary murine macrophages treated with our nanoparticles exhibited a dose-dependent T cell suppression in vitro. This effect was abrogated when an arginase inhibitor was administered together with the nanoparticles. The nanoparticles upregulated arginase I protein expression and arginase activity by increasing histone lactylation. In vivo testing with mouse heart injury models showed that the nanoparticles restored levels of effector and regulatory T cells in injured mice to non-injured levels. Additionally, the nanoparticles reduced cardiac fibrosis and restored ejection fraction. Furthermore, Western blotting of heart tissue lysate revealed that the nanoparticles downregulated the TGFb and p-SMAD signaling pathway. Conclusion: Collectively, these findings highlight a novel therapeutic strategy for heart failure, addressing the gap of fibrosis treatment by targeting upstream immunological pathways.

Activation of MEK‐ERK‐c‐MYC signaling pathway promotes splenic M2-like macrophage polarization to inhibit PHcH-liver cirrhosis

IntroductionPortal hypertension combined with hypersplenism (PHcH) is the main cause of hypocytosis and esophagogastric variceal hemorrhage in patients with liver cirrhosis. Activated macrophages that destroy excess blood cells are the main cause of hypersplenism, but the activating pathway is not very clear. This study aims to investigate the activation types of splenic macrophages and their activation mechanisms, to provide experimental evidence for the biological treatment of splenomegaly, and to find a strategy to improve liver fibrosis and inflammation by intervening in splenic immune cells. This study revealed the occurrence of M2-like polarization of macrophages and upregulation of c-Myc gene expression in the PH spleen.MethodsRNAseq, protein chip, western blot, and chip-seq were performed on macrophages and the in vitro MEK inhibitor rafametinib was used. Carbon tetrachloride and thioacetamide induced mouse cirrhosis models were separately constructed.Resultsc-Myc gene knockout in splenic macrophages reduced M2-like polarization and exacerbated liver fibrosis inflammation. c-Myc activated the MAPK signaling pathway and upregulated the expression of IL-4 and M2-like related genes in PH hypersplenism through the MEK-ERK-c-Myc axis. In addition, the c-Myc gene exerted anti-inflammatory effects by upregulating IL-4-mediated signal transduction to promote M2-like differentiation and anti-inflammatory cytokine secretion.ConclusionsActivation of MEK‐ERK‐c‐MYC signaling pathway promotes splenic M2-like macrophage polarization to inhibit PHcH-liver cirrhosis. Therefore, the induction of macrophage depolarization might represent a new therapeutic approach in the cure of PH hypersplenism, making c-Myc a potential candidate for macrophage polarization therapy.

Myeloid Tgfbr1/2-deficiency leads to a pro-atherogenic environment in ApoE-/- mice

Abstract Background Transforming growth factor beta (TGFβ) and its receptors (TGFβRs) are widely expressed by most human and murine cells and are implicated in several physiological and pathological conditions. In the context of atherosclerosis, TGFβ has been identified as a pleiotropic molecule involved in both pro- and anti-atherogenic processes, with its effects varying depending on the cell type it signals through. Purpose Given that myeloid cells play a major role in atherogenesis, we sought out to unravel the involvement of myeloid TGFβ signaling in atherosclerosis. Methods Aortic leukocytes from ApoE-/- mice fed a Western diet (WD) for 20 weeks were subjected to CITE-Seq analysis to assess the expression profile of Tgfβ and Tgfβrs. To investigate the effect of myeloid Tgfβ signaling on atherosclerosis, LysMCre+Tgfβr1flox/floxTgfβr2flox/floxmT/mGflox/floxApoE-/- (M-Tgfβr1/2dkoApoE-/-) mice and their LysMCre- littermates (ApoE-/-) were fed a WD for 6 weeks. Leukocyte phenotyping was assessed by flow cytometry (FC) and qPCR. Atherosclerotic plaque size in the aortic root was assessed by immunohistochemistry. Results CITE-Seq revealed that aortic ApoE-/- leukocytes highly expressed Tgfb1, whereas Tgfb2 and Tgfb3 were very lowly expressed. Tgfbr1 was mainly expressed in myeloid cells with macrophages and neutrophils showing the highest expression. Tgfbr2 was primarily expressed in T and B cells, while still showing a high level of expression in macrophages. Importantly, Tgfbr3 was not expressed in myeloid cells. Thus, to study the effect of myeloid Tgfβ signaling on atherosclerosis and to mitigate the potential for aberrant signaling that might arise from deleting only one receptor, we generated ApoE-/- mice with myeloid lineage tracing mT/mG alleles and combined deletion of Tgfbr1 and Tgfbr2 in myeloid cells using the LysMCre model. FC analysis of eGFP+ cells, i.e., cells where LysMCre is active, revealed a ~60-80% Tgfbr1/2 deletion efficiency in bone marrow-derived macrophages (BMDM) and in blood, splenic and BM CD11b+ cells, which was accompanied by decreased Smad2/3 signaling. M-Tgfβr1/2dkoApoE-/- mice showed a ~35% increase in blood and splenic CD11b+ cells and a ~25% increase in splenic macrophages compared to ApoE-/- controls, while BM CD11b+ cells were not affected. Tgfbr1/2-deficient BMDMs had increased Il-6, Il-1b and CD38 expression compared to controls, suggesting that Tgfbr1/2-deficient macrophages have acquired a pro-inflammatory phenotype. Interestingly, M-Tgfβr1/2dkoApoE-/- mice had ~30% fewer blood and splenic T cells compared to controls, which was explained by decreased naïve CD4+ and CD8+ T cells. M-Tgfβr1/2dkoApoE-/- mice had a ~50% increase in atherosclerotic plaque burden compared to ApoE-/- controls. Conclusion Our data suggest that impaired myeloid Tgfβ signaling leads to a pro-atherogenic environment in ApoE-/- mice. These effects may be mediated by an altered crosstalk between T cells and Tgfβr1/2-deficient macrophages.

Deoxynivalenol-Induced Spleen Toxicity in Mice: Inflammation, Endoplasmic Reticulum Stress, Macrophage Polarization, and the Dysregulation of LncRNA Expression.

The spleen is a primary target of deoxynivalenol (DON) toxicity, but its underlying molecular mechanisms remain unclear. This study investigates the effects of DON on inflammation, splenic macrophage polarization, endoplasmic reticulum (ER) stress, and transcriptome changes (mRNA and lncRNAs) in mouse spleen. We found that DON exposure at doses of 2.5 or 5 mg/kg BW significantly induced inflammation and polarized splenic macrophages towards the M1 phenotype. Additionally, DON activated PERK-eIF2α-ATF4-mediated ER stress and upregulated apoptosis-related proteins (caspase-12, caspase-3). The ER stress inhibitor, 4-Phenylbutyric acid, significantly alleviated DON-induced ER stress, apoptosis, and the M1 polarization of splenic macrophages. Transcriptome analysis identified 1968 differentially expressed (DE) lncRNAs and 2664 DE mRNAs in mouse spleen following DON exposure. Functional enrichment analysis indicated that the upregulated genes were involved in pathways associated with immunity, including Th17 cell differentiation, TNF signaling, and IL-17 signaling, while downregulated mRNAs were linked to cell survival and growth pathways. Furthermore, 370 DE lncRNAs were predicted to target 255 DE target genes associated with immune processes, including the innate immune response, interferon-beta response, cytokine production regulation, leukocyte apoptosis, and NF-κB signaling genes. This study provides new insights into the mechanisms underlying DON toxicity and its effects on the immune system.

Angelica sinensis polysaccharides ameliorate 5-FU-induced stress anemia via promoting extramedullary erythroblastic island central macrophage-mediated erythroid differentiation

BackgroundChronic anemia, especially chemotherapy-induced anemia, is a common and intractable symptom. Puzzlingly, the conventional anemic treatment may lead to various side effects, and the mechanism of stress anemia remains unclear. MethodsHere, peripheral blood, histopathological and transmission electron microscopical examination, colony forming test, flow cytometry, and qRT-PCR assay were used to investigate the effects of Angelia sinensis polysaccharide (ASP), one main active ingredient of Chinese herb medicine Angelica sinensis, on ameliorating 5-fluorouracil (5-FU)-induced stress anemia. ResultsWe found that intraperitoneal injection to a C57BL/6J mouse ASP 100 mg/kg per day for consecutive 10 days or 14 days, remarkably accelerated the recovery of RBC, hemoglobin, and hematocrit in blood. ASP alleviated 5-FU-caused impairment of bone marrow cell and BFU-E enumeration. Meanwhile, ASP antagonized 5-FU promoting extramedullary erythropoiesis in the spleen, inducing splenomegaly due to stress erythroblastic islands, and occurrence of megakaryocytes and hematopoietic precursors in splenic colonies. ASP increased splenic stress BFU-E enumeration, driving BFU-E differentiation towards Pro-E and end-stage erythroblasts. Furthermore, ASP increased the number of F4/80+VCAM-1+ splenic erythroblastic island central macrophages, upregulating genetic expression of EPOR, Emp, VCAM-1, Hmox-1, Trf, TfR1, Fpn1, Spi-C, DNase2a, Tim4, MertK, and Klf1 in splenocytes. ConclusionsOur findings indicate that the possible mechanism of chemotherapy-induced anemia is related to stress erythroid maturation arrest. Whereas, ASP may promote stress erythroid differentiation via elevated EPO sensitivity in extramedullary hematopoietic organs and enhanced macrophage-mediated adhesion, iron homeostasis and transfer, and nuclear engulfment, which may represent a promising therapeutic strategy.

CpG Methylation of Receptor Activator NF-κB (RANK) Gene Promoter Region Delineates Senescence-Related Decrease of RANK Gene Expression.

While the rapid decrease in estrogen is well known as the main cause of postmenopausal osteoporosis in women, the precise pathogenesis of senile osteoporosis in the elderly regardless of gender is largely unknown. The age-related epigenetic regulation of receptor activator NF-κB (RANK) gene expression was investigated with the use of a high-passaged mouse osteoclast progenitor cell line, RAW264.7, as an in vitro model of aging. In the RAW264.7 cells after repeated passages, receptor RANK expression was downregulated, resulting in decreased soluble RANK ligand (sRANKL)-induced osteoclastogenesis, expression of tartrate-resistant acid phosphatase-5b (TRAcP) and cathepsin K (CTSK). Methylation-specific PCR and bisulfite mapping revealed hypermethylation of CpG-loci located in the RANK gene promoter in multiple-passaged cells. ICON probe-mediated in situ assessment of methylated-cytosine at the CpG loci revealed an increase in the percentage of methylated RAW264.7 cells in the RANK gene in a passage-dependent manner. Conversely, upon treatment with demethylating agent 5-aza-2-deoxycytidine (5-aza-dC), high-passaged RAW264.7 cells displayed restored expression of the RANK gene, osteoclastogenesis, TRAcP and CTSK. Ex vivo cultures of splenic macrophages from young (10.5 W) and aged (12 M) mice also showed that CpG methylation was predominant in the aged animals, resulting in reduced RANK expression and osteoclastogenesis. Reduced RANK expression by age-related accumulation of DNA methylation, albeit in a limited population of osteoclast precursor cells, might be, at least in part, indicative of low-turnover bone characteristic of senile osteoporosis.

Effects of injury size on local and systemic immune cell dynamics in volumetric muscle loss.

We took a systems approach to the analysis of macrophage phenotype in regenerative and fibrotic volumetric muscle loss outcomes in mice together with analysis of systemic inflammation and of other leukocytes in the muscle, spleen, and bone marrow. Macrophage dysfunction in the fibrotic group occurred as early as day 1, persisted to at least day 28, and was associated with increased numbers of leukocytes in the muscle and bone marrow, increased pro-inflammatory marker expression in splenic macrophages, and changes in the levels of pro-inflammatory cytokines in the blood. The most prominent differences were in muscle neutrophils, which were much more abundant in fibrotic outcomes compared to regenerative outcomes at day 1 after injury. However, neutrophil depletion had little to no effect on macrophage phenotype or on muscle repair outcomes. Together, these results suggest that the entire system of immune cell interactions must be considered to improve muscle repair outcomes.

Splenic CD169 + Tim4 + Marginal Metallophilic Macrophages Are Essential for Wound Healing After Myocardial Infarction.

What is new?: We establish for the first time that metallophilic marginal macrophages (MMMs) from the spleen, expressing the markers CD169 and Tim4, circulate in blood and traffic to the heart to help maintain the CD169 + Tim4 + CCR2 - LYVE1 low macrophage population in the heart. After acute myocardial infarction, splenic MMMs augment cardiac trafficking in response to chemotactic signals, resulting in expansion of CD169 + Tim4 + macrophages in the heart that play an essential role in post-MI efferocytosis, wound healing and repair while limiting longer term adverse cardiac remodeling. Analogous to mice, humans also exhibit circulating CD169 + Tim4 + macrophages in the blood that expand after acute ST segment elevation MI. What are the clinical implications?: This study highlights the importance of the cardiosplenic axis in acute MI, and the splenic marginal zone, in determining the course and outcome of post-MI LV remodeling.Pharmacological expansion of splenic marginal zone macrophages alleviated post-MI adverse LV remodeling and inflammation, suggesting that splenic modulation is a potential translational therapeutic approach for limiting post-MI inflammation and improving heart repair.

Apolipoprotein E deficiency leads to the polarization of splenic macrophages towards M1 phenotype by increasing iron content.

Apolipoprotein E (ApoE) plays a crucial role in iron homeostasis in the body, while macrophages are the principal cells responsible for handling iron in mammals. However, it is unknown whether ApoE can affect the functional subtypes and the iron handling capacity of splenic macrophages (SM). Here, we investigated the effects of ApoE deficiency (ApoE-/-) on the polarization and iron content of SM and its potential mechanisms. ApoE-/- was found to induce a significant increase in the expressions of M1 marker genes CD86, IL-1β, IL-6, IL-12, TNF-α and iNOS and a reduction in M2 marker genes CD206, Arg-1, IL-10 and Ym-1 in SM of mice aged 28 weeks, Meanwhile, ApoE-/- caused a significant increase in iron content and expression of ferritin, transferrin receptor 1 (TfR1), iron regulatory protein 1 (IRP1) and heme oxygenase-1 (HO-1) and a reduction in ferroportin1 (Fpn1) in spleen and/or SM of mice aged 28 weeks. It was concluded that ApoE-/- can increase iron content through increased iron uptake mediated by TfR/ IRPs and decreased iron release mediated by Fpn1, leading to polarization of the SM to M1 phenotype.

Th1 cells reduce the osteoblast-like phenotype in valvular interstitial cells by inhibiting NLRP3 inflammasome activation in macrophages

Background and aimsInflammation is initiates the propagation phase of aortic valve calcification. The activation of NLRP3 signaling in macrophages plays a crucial role in the progression of calcific aortic valve stenosis (CAVS). IFN-γ regulates NLRP3 activity in macrophages. This study aimed to explore the mechanism of IFN-γ regulation and its impact on CAVS progression and valve interstitial cell transdifferentiation.Methods and resultsThe number of Th1 cells and the expression of IFN-γ and STAT1 in the aortic valve, spleen and peripheral blood increased significantly as CAVS progressed. To explore the mechanisms underlying the roles of Th1 cells and IFN-γ, we treated CAVS mice with IFN-γ-AAV9 or an anti-IFN-γ neutralizing antibody. While IFN-γ promoted aortic valve calcification and dysfunction, it significantly decreased NLRP3 signaling in splenic macrophages and Ly6C+ monocytes. In vitro coculture showed that Th1 cells inhibited NLPR3 activation in ox-LDL-treated macrophages through the IFN-γR1/IFN-γR2-STAT1 pathway. Compared with untreated medium, conditioned medium from Th1-treated bone marrow–derived macrophages reduced the osteogenic calcification of valvular interstitial cells.ConclusionInhibition of the NLRP3 inflammasome by Th1 cells protects against valvular interstitial cell calcification as a negative feedback mechanism of adaptive immunity toward innate immunity. This study provides a precision medicine strategy for CAVS based on the targeting of anti-inflammatory mechanisms.Graphical

Inhibition of the p62-Nrf2-GPX4 Pathway Confers Sensitivity to Butachlor-Induced Splenic Macrophage Ferroptosis.

Butachlor is widely used in agriculture around the world and therefore poses environmental and public health hazards due to persistent and poor biodegradability. Ferroptosis is a type of iron-mediated cell death controlled by glutathione (GSH) and GPX4 inhibition. P62 is an essential autophagy adaptor that regulates Keap1 to activate nuclear factor erythroid 2-related factor 2 (Nrf2), which effectively suppresses lipid peroxidation, thereby relieving ferroptosis. Here, we found that butachlor caused changes in splenic macrophage structure, especially impaired mitochondrial morphology with disordered structure, which is suggestive of the occurrence of ferroptosis. This was further confirmed by the detection of iron metabolism, the GSH system, and lipid peroxidation. Mechanistically, butachlor suppressed the protein level of p62 and promoted Keap1-mediated degradation of Nrf2, which results in decreased GPX4 expression and accelerated splenic macrophage ferroptosis. These findings suggest that targeting the p62-Nrf2-GPX4 signaling axis may be a promising strategy for treating inflammatory diseases.

Cordycepin Augments the Efficacy of Anti-PD1 against Colon Cancer.

Colon cancer has a poor clinical response to anti-PD1 therapy. This study aimed to evaluate the effect of cordycepin on the efficacy of anti-PD1 treatment in colon cancer. The viability of CT26 mouse colon carcinoma cells, cell-cycle progression, morphology, and the expression of mRNA and protein were assessed. A syngeneic animal model was established by implanting CT26 cells into BALB/c mice for in vivo experiments. Multi-parameter flow cytometry was used to analyze the splenic cell lineages and tumor microenvironment (TME). The in vitro data revealed that cordycepin, but not adenosine, inhibited CT26 cell viability. The protein, but not mRNA, expression levels of A2AR and A2BR were suppressed by cordycepin but not by adenosine in CT26 cells. The combination of cordycepin, but not adenosine, with anti-PD1 exhibited a greater tumor-inhibitory effect than anti-PD1 alone as well as inhibited the expression of A2AR and A2BR in splenic macrophages. In the TME, the combination of cordycepin and anti-PD1 increased the number of CD3+ T cells and neutrophils and decreased the number of natural killer (NK) cells. Overall, cordycepin augmented the antitumor effects of anti-PD1 against mouse colon carcinoma cells and inhibited the expression of the adenosine receptors A2AR and A2BR in splenic macrophages and intratumoral NK cells.

15-epi-lipoxin A5 promotes neutrophil exit from exudates for clearance by splenic macrophages.

Specialized proresolving mediators (SPMs) promote local macrophage efferocytosis but excess leukocytes early in inflammation require additional leukocyte clearance mechanism for resolution. Here, neutrophil clearance mechanisms from localized acute inflammation were investigated in mouse dorsal air pouches. 15-HEPE (15-hydroxy-5Z,8Z,11Z,13E,17Z-eicosapentaenoic acid) levels were increased in the exudates. Activated human neutrophils converted 15-HEPE to lipoxin A5 (5S,6R,15S-trihydroxy-7E,9E,11Z,13E,17Z-eicosapentaenoic acid), 15-epi-lipoxin A5 (5S,6R,15R-trihydroxy-7E,9E,11Z,13E,17Z-eicosapentaenoic acid), and resolvin E4 (RvE4; 5S,15S-dihydroxy-6E,8Z,11Z,13E,17Z-eicosapentaenoic acid). Exogenous 15-epi-lipoxin A5, 15-epi-lipoxin A4 and a structural lipoxin mimetic significantly decreased exudate neutrophils and increased local tissue macrophage efferocytosis, with comparison to naproxen. 15-epi-lipoxin A5 also cleared exudate neutrophils faster than the apparent local capacity for stimulated macrophage efferocytosis, so the fate of exudate neutrophils was tracked with CD45.1 variant neutrophils. 15-epi-lipoxin A5 augmented the exit of adoptively transferred neutrophils from the pouch exudate to the spleen, and significantly increased splenic SIRPa+ and MARCO+ macrophage efferocytosis. Together, these findings demonstrate new systemic resolution mechanisms for 15-epi-lipoxin A5 and RvE4 in localized tissue inflammation, which distally engage the spleen to activate macrophage efferocytosis for the clearance of tissue exudate neutrophils.

Angelica sinensis polysaccharides promote extramedullary stress erythropoiesis via ameliorating splenic glycolysis and EPO/STAT5 signaling-regulated macrophages.

Conventional treatments exhibit various side effects on chronic stress anemia. Extramedullary stress erythropoiesis is a compensatory mechanism, which may effectively counteract anemia. Angelica sinensis polysaccharides (ASP) are the main active ingredient found in Angelica sinensis and exhibit antioxidant and hematopoietic effects. However, the effects of ASP on extramedullary stress erythropoiesis remain to be unclear. Here, we demonstrated the protective effects of ASP on chemotherapeutic drug 5-fluorouracil (5-FU)-induced decline in peripheral blood parameters such as RBC counts, HGB, HCT, and MCH, and the decline of BFU-E colony enumeration in the bone marrow. Meanwhile, ASP promoted extramedullary erythropoiesis, increasing cellular proliferation in the splenic red pulp and cyclin D1 protein expression, abrogating phase G0/G1 arrest of c-kit+ cells in mouse spleen. RT-qPCR and immunohistochemistry further revealed that ASP increased macrophage chemokine Ccl2 genetic expression and the number of F4/80+ macrophages in the spleen. The colony-forming assay showed that ASP significantly increased splenic BFU-E. Furthermore, we found that ASP facilitated glycolytic genes including Hk2, Pgk1, Pkm, Pdk1, and Ldha via PI3K/Akt/HIF2α signaling in the spleen. Subsequently, ASP declined pro-proinflammatory factor IL-1β, whereas upregulating erythroid proliferation-associated genes Gdf15, Bmp4, Wnt2b, and Wnt8a. Moreover, ASP facilitated EPO/STAT5 signaling in splenic macrophages, thus enhancing erythroid lineage Gata2 genetic expression. Our study indicated that ASP may improve glycolysis, promoting the activity of splenic macrophages, subsequently promoting erythroid progenitor cell expansion. Additionally, ASP facilitates erythroid differentiation via macrophage-mediated EpoR/STAT5 signaling; suggesting it might be a promising strategy for stress anemia treatment.

Enhanced autophagy and phagocytosis of apoptotic lymphocytes in splenic macrophages of acute ethanol-treated rats: Light and electron microscopic studies.

Autophagy is a prosurvival mechanism for the clearance of damaged cellular components, specifically upon exposure to various stressors. In lymphoid organs, excessive ethanol consumption increases lymphocyte apoptosis, resulting in immunosuppression. However, ethanol-induced autophagy and related phagocytosis of apoptotic lymphocytes in the spleen have not been studied yet. Adult male Wistar rats were injected intraperitoneally either with 5 g/kg ethanol or phosphate-buffered saline (as a control group) and then sacrificed 0, 3, 6, and 24 hours after injection. Light and transmission electron microscopy (TEM) findings indicated enhanced T cell apoptosis in the white pulps of ethanol-treated rats (ETRs) compared with the control group, which peaked at 6 h and was associated with the accumulation of tingible body macrophages (TBMs). These macrophages exhibited an upregulated autophagic response, as evidenced by enhanced LC3-II (a specific marker of autophagosomes) expression, which peaked at 24h. In addition, double labeling immunofluorescence of LC3-II with lysosomal markers revealed the enhanced formation of autolysosomes in TBMs of ETRs, which was associated with suppression of p62 immunostaining, indicating the enhanced autophagic flux. Interestingly, this elevated autophagic response in ETR TBMs was accompanied by evidence of LC3-associated phagocytosis (LAP) of apoptotic splenocytes. This is based on TUNEL/LC3-II double labeling and TEM observations of phagosomes containing apoptotic bodies, enclosed within phagosomal membranes adjacent to the autophagic vacuoles. It can be concluded that enhanced prosurvival autophagy in splenic TBMs of ETRs and clearing of apoptotic lymphocytes via LAP may contribute to preventing secondary necrosis and autoimmune diseases.

NOD2 activation enhances macrophage Fcγ receptor function and may increase the efficacy of antibody therapy.

Therapeutic antibodies have become a major strategy to treat oncologic diseases. For chronic lymphocytic leukemia, antibodies against CD20 are used to target and elicit cytotoxic responses against malignant B cells. However, efficacy is often compromised due to a suppressive microenvironment that interferes with cellular immune responses. To overcome this suppression, agonists of pattern recognition receptors have been studied which promote direct cytotoxicity or elicit anti-tumoral immune responses. NOD2 is an intracellular pattern recognition receptor that participates in the detection of peptidoglycan, a key component of bacterial cell walls. This detection then mediates the activation of multiple signaling pathways in myeloid cells. Although several NOD2 agonists are being used worldwide, the potential benefit of these agents in the context of antibody therapy has not been explored. Primary cells from healthy-donor volunteers (PBMCs, monocytes) or CLL patients (monocytes) were treated with versus without the NOD2 agonist L18-MDP, then antibody-mediated responses were assessed. In vivo, the Eµ-TCL1 mouse model of CLL was used to test the effects of L18-MDP treatment alone and in combination with anti-CD20 antibody. Treatment of peripheral blood mononuclear cells with L18-MDP led to activation of monocytes from both healthy donors and CLL patients. In addition, there was an upregulation of activating FcγR in monocytes and a subsequent increase in antibody-mediated phagocytosis. This effect required the NF-κB and p38 signaling pathways. Treatment with L18-MDP plus anti-CD20 antibody in the Eµ-TCL model of CLL led to a significant reduction of CLL load, as well as to phenotypic changes in splenic monocytes and macrophages. Taken together, these results suggest that NOD2 agonists help overturn the suppression of myeloid cells, and may improve the efficacy of antibody therapy for CLL.

In vivo upstream factors of mouse hepatotoxic mechanism with sustained hepatic glutathione depletion: Acetaminophen metabolite-erythrocyte adducts and splenic macrophage-generated reactive oxygen species

Investigation of acetaminophen (APAP)-induced liver damage recently indicated the significance of phagocytic NADPH oxidase (NOX)-derived reactive oxygen species (ROS) and ferroptosis in the liver. Here, we focused on phagocytosis by iron-containing erythrocyte-devouring splenic macrophages and explored upstream factors of known APAP hepatotoxic mechanisms in vivo. Splenectomy did not alter hepatic cytochrome P450 (CYP) 2E1 activity or hepatic glutathione (GSH) content. APAP injection into splenectomized mice almost completely suppressed increases in plasma alanine aminotransferase levels and centrilobular hepatic necrosis showing the spleen to be a critical tissue in APAP-induced liver damage. Hepatic GSH was recovered to approximately 50 % content at 8 h. In non-splenectomized mice, liver damage was dramatically suppressed by a sensitive redox probe (DCFH-DA), macrophage-depleting clodronate (CL), and a NOX2 inhibitor. APAP treatment resulted in markedly stronger fluorescence intensity from DCFH-DA due to excessive ROS around splenic macrophages, which was lost upon co-treatment with a CYP inhibitor and CL. Deformed erythrocytes disappeared in mice co-treated with DCFH-DA, CL, the NOX2 inhibitor, and the CYP inhibitor. Simultaneously, these four compounds significantly improved APAP-depleted GSH levels. The CYP inhibitor also prevented the formation of APAP-cell adducts in the blood and spleen. In the spleen, CL co-treatment markedly reduced the number of adducts. Splenic ferrous iron levels were significantly elevated by APAP. Therefore, we demonstrated that splenic macrophages devoured APAP metabolite-erythrocyte adducts and subsequently splenic macrophage-related ROS caused sustained hepatic GSH depletion and excessive erythrocyte deformation around 7 h. Our data indicate in vivo upstream factors of known APAP hepatotoxic mechanisms.

The mechanism of Xihuang pills' intervention in the tumour immune microenvironment for the treatment of liver cancer based on the STAT3-PDL1 pathway

Ethnopharmacological relevanceXihuang pills, a time-honored Chinese compound formula with a history spanning thousands of years, have demonstrated remarkable efficacy in treating various cancers, such as breast cancer, colon cancer, and liver cancer. Clinical applications over the years have established their effectiveness. Several scholars conducting experimental studies have elucidated the potent tumor-suppressing effects of Xihuang pills. While the inhibition of tumor vascular development and prevention of tumor cell invasion and metastasis have been well-explored mechanisms, the impact on the tumor immune microenvironment has received less attention. This study focuses on investigating the immune microenvironment adjustments induced by Xihuang pills in hepatocellular carcinoma. Aim of the studyTumour cells will find an escape phenomenon during tumour immunotherapy, which will affect immunotherapy results. We will research the regulation of the tumour immune microenvironment, to provide a more complete and precise basis for the elucidation of the mechanism of Xihuang pills in treating cancers. It provides new research ideas for people to treat liver cancer. Materials and methodsThrough in vivo and in vitro assessments confirming the intervention effects of Xihuang pills, we observed alterations in T cell typing, macrophage polarization, and tumor-associated cytokine levels. The primary active ingredients of Xihuang pills were identified using UPLC-MS/GC-MS, and relevant pathways in the treatment of hepatocellular carcinoma were predicted through network pharmacology. Combining the network pharmacology approach, we predicted the pathways relevant to Xihuang pills in treating hepatocellular carcinoma and experimentally validated the involvement of PD-1/PD-L1, a key immunity-related axis. ResultsXihuang Pill has a regulatory effect on the tumor immune microenvironment. ConclusionsThe results indicated that Xihuang pills could impact splenic lymphocyte phenotyping, macrophage polarization, and IL-6 cytokine expression in liver cancer mice. The mechanism of action was associated with the regulation of the PD-1/PD-L1 signaling pathway by the STAT3 protein.

High-altitude hypoxia exposure inhibits erythrophagocytosis by inducing macrophage ferroptosis in the spleen.

High-altitude polycythemia (HAPC) affects individuals living at high altitudes, characterized by increased red blood cells (RBCs) production in response to hypoxic conditions. The exact mechanisms behind HAPC are not fully understood. We utilized a mouse model exposed to hypobaric hypoxia (HH), replicating the environmental conditions experienced at 6000 m above sea level, coupled with in vitro analysis of primary splenic macrophages under 1% O2 to investigate these mechanisms. Our findings indicate that HH significantly boosts erythropoiesis, leading to erythrocytosis and splenic changes, including initial contraction to splenomegaly over 14 days. A notable decrease in red pulp macrophages (RPMs) in the spleen, essential for RBCs processing, was observed, correlating with increased iron release and signs of ferroptosis. Prolonged exposure to hypoxia further exacerbated these effects, mirrored in human peripheral blood mononuclear cells. Single-cell sequencing showed a marked reduction in macrophage populations, affecting the spleen's ability to clear RBCs and contributing to splenomegaly. Our findings suggest splenic ferroptosis contributes to decreased RPMs, affecting erythrophagocytosis and potentially fostering continuous RBCs production in HAPC. These insights could guide the development of targeted therapies for HAPC, emphasizing the importance of splenic macrophages in disease pathology.

High-altitude hypoxia exposure inhibits erythrophagocytosis by inducing macrophage ferroptosis in the spleen

High-altitude polycythemia (HAPC) affects individuals living at high altitudes, characterized by increased red blood cells (RBCs) production in response to hypoxic conditions. The exact mechanisms behind HAPC are not fully understood. We utilized a mouse model exposed to hypobaric hypoxia (HH), replicating the environmental conditions experienced at 6000 m above sea level, coupled with in vitro analysis of primary splenic macrophages under 1% O2 to investigate these mechanisms. Our findings indicate that HH significantly boosts erythropoiesis, leading to erythrocytosis and splenic changes, including initial contraction to splenomegaly over 14 days. A notable decrease in red pulp macrophages (RPMs) in the spleen, essential for RBCs processing, was observed, correlating with increased iron release and signs of ferroptosis. Prolonged exposure to hypoxia further exacerbated these effects, mirrored in human peripheral blood mononuclear cells. Single-cell sequencing showed a marked reduction in macrophage populations, affecting the spleen’s ability to clear RBCs and contributing to splenomegaly. Our findings suggest splenic ferroptosis contributes to decreased RPMs, affecting erythrophagocytosis and potentially fostering continuous RBCs production in HAPC. These insights could guide the development of targeted therapies for HAPC, emphasizing the importance of splenic macrophages in disease pathology.