Remodeling Articular Immune Homeostasis with an Efferocytosis-inspired Nanoimitator Mitigates Rheumatoid Arthritis

Massive intra-articular infiltration of the pro-inflammatory macrophages is a prominent feature of rheumatoid arthritis (RA) lesions, which are thought to underlie articular immune dysfunction, severe synovitis and ultimate joint erosion. Here we report an efferocytosis-inspired nanoimitator (EINI) for in situ targeted reprogramming of the synovial inflammatory macrophages (SIMs) and thus thwarting their autoimmune attack and reinstating articular immune homeostasis, which mitigates RA. The EINI consisted of a drug-based core with an oxidative stress-responsive phosphatidylserine (PtdSer) corona and a shell of P-selectin-blocking motif, low molecular weight heparin (LMWH). When systemically administrated, the LMWH on the EINI first bound to P-selectin overexpressed on endothelium in subsynovial capillaries, which functioned as an antagonist disrupting neutrophils synovial trafficking. Due to the high dysregulation of the synovial microvasculature, the EINI subsequently enriched in joint synovium where the shell was exfoliated upon the reactive oxygen species stimulation, and PtdSer corona was then exposed. In an efferocytosis-like manner, the PtdSer-coroneted core was in turn phagocytosed by SIMs, which synergistically terminated the SIMs-initiated pathological cascades and serially reconstructed the intra-articular immune homeostasis, conferring a chondroprotection effect. These findings demonstrate that SIMs can be precisely remodeled via the efferocytosis-mimetic strategy, which holds great potential for RA treatment.

Inhibitory Effect of IL-1β on HBV and HDV Replication and HB Antigen-Dependent Modulation of Its Secretion by Macrophages

Co-infection with the hepatitis B virus and hepatitis delta virus (HDV) leads to the most aggressive form of viral hepatitis. Using in vitro infection models, we confirmed that IL-1β, a crucial innate immune molecule for pathogen control, was very potent against HBV from different genotypes. Additionally, we demonstrated for the first time a strong and rapid antiviral effect induced by very low doses of IL-1β against HDV. In parallel, using co-culture assays, we demonstrated that monocytes exposed to HBV, and in particular to HBsAg, during differentiation into pro-inflammatory macrophages secreted less IL-1β. Altogether, our data emphasize the importance of developing combined antiviral strategies that would, for instance, reduce the secretion of HBsAg and stimulate the immune system to produce endogenous IL-1β efficient against both HBV and HDV.

TNFα Mediates Inflammation-Induced Effects on PPARG Splicing in Adipose Tissue and Mesenchymal Precursor Cells

Low-grade chronic inflammation and reduced differentiation capacity are hallmarks of hypertrophic adipose tissue (AT) and key contributors of insulin resistance. We identified PPARGΔ5 as a dominant-negative splicing isoform overexpressed in the AT of obese/diabetic patients able to impair adipocyte differentiation and PPARγ activity in hypertrophic adipocytes. Herein, we investigate the impact of macrophage-secreted pro-inflammatory factors on PPARG splicing, focusing on PPARGΔ5. We report that the epididymal AT of LPS-treated mice displays increased PpargΔ5/cPparg ratio and reduced expression of Pparg-regulated genes. Interestingly, pro-inflammatory factors secreted from murine and human pro-inflammatory macrophages enhance the PPARGΔ5/cPPARG ratio in exposed adipogenic precursors. TNFα is identified herein as factor able to alter PPARG splicing—increasing PPARGΔ5/cPPARG ratio—through PI3K/Akt signaling and SRp40 splicing factor. In line with in vitro data, TNFA expression is higher in the SAT of obese (vs. lean) patients and positively correlates with PPARGΔ5 levels. In conclusion, our results indicate that inflammatory factors secreted by metabolically-activated macrophages are potent stimuli that modulate the expression and splicing of PPARG. The resulting imbalance between canonical and dominant negative isoforms may crucially contribute to impair PPARγ activity in hypertrophic AT, exacerbating the defective adipogenic capacity of precursor cells.

Lipoprotein(a)—The Crossroads of Atherosclerosis, Atherothrombosis and Inflammation

Increased lipoprotein(a) (Lp(a)) levels are an independent predictor of coronary artery disease (CAD), degenerative aortic stenosis (DAS), and heart failure independent of CAD and DAS. Lp(a) levels are genetically determinated in an autosomal dominant mode, with great intra- and inter-ethnic diversity. Most variations in Lp(a) levels arise from genetic variations of the gene that encodes the apolipoprotein(a) component of Lp(a), the LPA gene. LPA is located on the long arm of chromosome 6, within region 6q2.6–2.7. Lp(a) levels increase cardiovascular risk through several unrelated mechanisms. Lp(a) quantitatively carries all of the atherogenic risk of low-density lipoprotein cholesterol, although it is even more prone to oxidation and penetration through endothelia to promote the production of foam cells. The thrombogenic properties of Lp(a) result from the homology between apolipoprotein(a) and plasminogen, which compete for the same binding sites on endothelial cells to inhibit fibrinolysis and promote intravascular thrombosis. LPA has up to 70% homology with the human plasminogen gene. Oxidized phospholipids promote differentiation of pro-inflammatory macrophages that secrete pro-inflammatory cytokines (e. g., interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α). The aim of this review is to define which of these mechanisms of Lp(a) is predominant in different groups of patients.

TNF-α, iNOS Augmentation Due to Macrophages and Neutrophils Activity in Samples from Patients in Intensive Care Unit with COVID-19 Infection

Background and Aims: Cells and secreted molecules by the innate immune system are the essential factors in the pathogenesis and determining the severity of inflammation in COVID-19 patients. Severe inflammation results from increased activity of neutrophils, macrophages, and other cells with their products. Inflammatory cytokines such as tumor necrosis factor-a (TNF-a) increases the severity and pathogenesis of the disease caused by the virus. Phagocytes are armed with inducible nitric oxide synthase (iNOS), that upon stimulation by proinflammatory cytokines augment an immune response against pathogens. Materials and Methods: Two groups of patients were included with COVID-19 infection from the intensive care unit (ICU, n=52) and (non-ICU-care, n=54). Blood samples were collected to measure cells and serum parameters, including lymphocytes, neutrophils, platelet counts, accompanied with C-reactive protein, lactate dehydrogenase, TNF-a and iNOS levels. Results: In the ICU group, increased white blood cells (p=0.048), decreased lymphocytes (p=0.0007), increased neutrophils (p=0.001), decreased platelets, increase serum levels for lactate dehydrogenase (p =0.0001), c-reactive protein (p=0.003), TNF-a (p=0.018), and iNOS (p=0.008) were statistically obtained. Positive correlations were calculated between TNF-a and iNOS (r=0.65, p=0.0002) and with c-reactive protein (r=0.52, p=0.003) and with lactate dehydrogenase (r=0.68, p=0.0001). Conclusion: Inflammation due to macrophages and neutrophils activity in COVID-19 patients and increased mediators correlate with disease progression. It seems that control of the cell activity and their inflammatory cytokines would be considered for therapeutic goals. Changing the polarization of inflammatory macrophages to anti-inflammatory macrophages with therapeutic applications could prevent the severity of the provocative course of the disease.

GPR84 signaling promotes intestinal mucosal inflammation via enhancing NLRP3 inflammasome activation in macrophages

The putative medium-chain free fatty acid receptor GPR84 is a G protein-coupled receptor primarily expressed in myeloid cells that constitute the innate immune system, including neutrophils, monocytes, and macrophages in the periphery and microglia in the brain. The fact that GPR84 expression in leukocytes is remarkably increased under acute inflammatory stimuli such as lipopolysaccharide (LPS) and TNFα suggests that it may play a role in the development of inflammatory and fibrotic diseases. Here we demonstrate that GPR84 is highly upregulated in inflamed colon tissues of active ulcerative colitis (UC) patients and dextran sulfate sodium (DSS)-induced colitis mice. Infiltrating GPR84+ macrophages are significantly increased in the colonic mucosa of both the UC patients and the mice with colitis. Consistently, GPR84−/− mice are resistant to the development of colitis induced by DSS. GPR84 activation imposes pro-inflammatory properties in colonic macrophages through enhancing NLRP3 inflammasome activation, while the loss of GPR84 prevents the M1 polarization and properties of proinflammatory macrophages. CLH536, a novel GPR84 antagonist discovered by us, suppresses colitis by reducing the polarization and function of pro-inflammatory macrophages. These results define a unique role of GPR84 in innate immune cells and intestinal inflammation, and suggest that GPR84 may serve as a potential drug target for the treatment of UC.

Integrated computational and in vivo models reveal Key Insights into Macrophage Be-havior during bone healing

Myeloid-derived monocyte and macrophages are key cells in the bone that contribute to remod-eling and injury repair. However, their temporal polarization status and control of bone-resorbing osteoclasts and bone-forming osteoblasts responses is largely unknown. In this study, we fo-cused on two aspects of monocyte/macrophage dynamics and polarization states over time: 1) the injury-triggered pro- and anti-inflammatory monocytes/macrophages temporal profiles, 2) the contributions of pro- versus anti-inflammatory monocytes/macrophages in coordinating healing response. Bone healing is a complex multicellular dynamic process. While traditional in vitro and in vivo experimentation may capture the behavior of select populations with high resolution, they cannot simultaneously track the behavior of multiple populations. To address this, we have used an integrated a coupled ordinary differential equations (ODEs)-based framework describing mul-tiple cellular species to in vivo bone injury data in order to identify and test various hypotheses regarding bone cell populations dynamics. Our approach allowed us to infer several biological insights including, but not limited to,: 1) anti-inflammatory macrophages are key for early osteo-clast inhibition and pro-inflammatory macrophage suppression, 2) pro-inflammatory macrophag-es are involved in osteoclast bone resorptive activity, whereas osteoblasts promote osteoclast differentiation, 3) Pro-inflammatory monocytes/macrophages rise during two expansion waves, which can be explained by the anti-inflammatory macrophages-mediated inhibition phase be-tween the two waves. In addition, we further tested the robustness of the mathematical model by comparing simulation results to an independent experimental dataset. Taken together, this novel comprehensive mathematical framework allowed us to identify biological mechanisms that best recapitulate bone injury data and that explain the coupled cellular population dynamics involved in the process. Furthermore, our hypothesis testing methodology could be used in other contexts to decipher mechanisms in complex multicellular processes.

An Inhibitor of Grp94 Inhibits OxLDL-Induced Autophagy and Apoptosis in VECs and Stabilized Atherosclerotic Plaques

Background: Oxidized low-density lipoprotein (oxLDL) induces vascular endothelial cell (VEC) injury and atherosclerosis through activating endoplasmic reticulum stress. Expression of glucose-regulated protein 94 (Grp94) is induced by endoplasmic reticulum stress and Grp94 is involved in cardiovascular diseases. This study aimed to determine the role of Grp94 in oxLDL-induced vascular endothelial cell injury and atherosclerosis.Methods and Results: An inhibitor of Grp94, HCP1, was used to investigate the role of Grp94 in oxLDL-induced VEC injury in human umbilical vein endothelial cells and atherosclerosis in apolipoprotein E−/− mice. Results showed that HCP1 inhibited autophagy and apoptosis induced by oxLDL in VECs. And we found that Grp94 might interact with adenosine monophosphate-activated protein kinase (AMPK) and activate its activity. HCP1 inhibited AMPK activity and overexpression of Grp94 blocked the effect of HCP1. Besides, HCP1 activated the activity of mechanistic target of rapamycin complex 1 (mTORC1), co-treatment with AMPK activator acadesine eliminated the effect of HCP1 on mTORC1 activity as well as autophagy. In apolipoprotein E−/− mice, HCP1 suppressed autophagy and apoptosis of atherosclerotic plaque endothelium. In addition, HCP1 increased the content of collagen, smooth muscle cells, and anti-inflammatory macrophages while reducing the activity of MMP-2/9 and pro-inflammatory macrophages in the atherosclerotic lesion.Conclusion: HCP1 inhibited oxLDL-induced VEC injury and promoted the stabilization of atherosclerotic plaque in apoE−/− mice. Grp94 might be a potential therapeutic target in the clinical treatment of atherosclerosis.

Collagen-derived peptide, DGEA, inhibits pro-inflammatory macrophages in biofunctional hydrogels

Macrophages are innate immune cells that play important roles in wound healing. Particularly, M1 macrophages are considered pro‐inflammatory and promote initial phases of inflammation. Long-term exposure to inflammatory stimuli causes an increase in M1 macrophages, which contributes to chronic inflammation. Activated M1 macrophages have been shown to upregulate integrin α2β1 expression. To interfere with α2β1 binding, we designed a biofunctional hydrogel utilizing a collagen I-derived peptide, DGEA (Asp-Gly-Glu-Ala). We hypothesize that M1 macrophage activation can be reduced in the presence of DGEA. Effects of DGEA on M1 macrophages were studied via soluble delivery and immobilization within poly(ethylene glycol) (PEG) hydrogels. We demonstrate that M1 macrophage activation is reduced both via soluble delivery of DGEA in 2D and via immobilized DGEA in a 3D PEG-DGEA hydrogel. This novel biomaterial can manipulate inflammatory macrophage activation and can be applied to prevent chronic inflammatory conditions via macrophage manipulation. Graphical abstract