A MicroRNA93-Interferon Regulatory Factor-9-Immunoresponsive Gene-1-Itaconic Acid Pathway Modulates M2-Like Macrophage Polarization to Revascularize Ischemic Muscle

Synthetic Antiangiogenic Vascular Endothelial Growth Factor-A Splice Variant Revascularizes Ischemic Muscle in Peripheral Artery Disease

BACKGROUND

Alternative splicing in the eighth exon C-terminus of VEGF-A (vascular endothelial growth factor-A) results in the formation of proangiogenic VEGF165a and antiangiogenic VEGF165b isoforms. The only known difference between these 2 isoform families is a 6-amino acid switch from CDKPRR (in VEGF165a) to SLTRKD (in VEGF165b). We have recently shown that VEGF165b can induce VEGFR2-activation but fails to induce VEGFR1 (VEGF receptor 1)-activation. The molecular mechanisms that regulate VEGF165b's ability toward differential VEGFR2 versus VEGFR1 activation/inhibition are not yet clear.

METHODS AND RESULTS

Hypoxia serum starvation was used as an in vitro peripheral artery disease model. Unilateral single ligation of the femoral artery was used as a preclinical peripheral artery disease model. VEGFR1 activating ligands have 2 arginine (RR) residues in their eighth exon C-terminus, that were replaced by lysine-aspartic acid (KD) in VEGF165b. A synthetic anti-angiogenic VEGF165b splice variant in which the KD residues were switched to RR (VEGF165bKD→RR) activated both VEGFR1- and VEGFR2-signaling pathways to induce ischemic-endothelial cell angiogenic capacity in vitro and enhance perfusion recovery in a severe experimental-peripheral artery disease model significantly higher than VEGF165a. Phosphoproteome arrays showed that the therapeutic efficacy of VEGF165bKD→RR over VEGF165a is due to its ability to induce P38-activation in ischemic endothelial cells.

CONCLUSIONS

Our data shows that the KD residues regulate VEGF165b's VEGFR1 inhibitory property but not VEGFR2. Switching these KD residues to RR resulted in the formation of a synthetic/recombinant VEGF165bKD→RR isoform that has the ability to activate both VEGFR1- and VEGFR2-signaling and induce ischemic-endothelial cell angiogenic and proliferative capacity that matched the angiogenic requirement necessary to achieve perfusion recovery in a severe experimental-peripheral artery disease model.

MicroRNAs as commonly expressed biomarkers for sarcopenia and frailty: A systematic review

BACKGROUND

Coexistent sarcopenia and frailty is more strongly associated with adverse health outcomes than each condition alone. As the importance of coexistent sarcopenia and frailty increases, exploring their underlying mechanisms is warranted. Recently, noncoding ribonucleic acids (RNAs) have been suggested as potential biomarkers of sarcopenia and frailty. This systematic review aimed to summarize noncoding RNAs commonly expressed in sarcopenia and frailty, and to search the predicted target genes and biological pathways of them.

METHODS

We systematically searched the literatures on PubMed, Embase, Cochrane Library, Web of Science, and Scopus for literature published till November 15, 2023. A total of 7,202 literatures were initially retrieved. After de-duplication, 34 studies (26 sarcopenia-related and 8 frailty-related) were full-text reviewed, and 15 studies (11 sarcopenia-related and 4 frailty-related) were finally included.

RESULTS

miR-29a-3p, miR-29b-3p, and miR-328 were identified as commonly expressed in same direction in sarcopenia and frailty. These microRNAs (miRNAs), identified in the literature search using PubMed, modulate transforming growth factor-β signaling via extracellular matrix components and calcineurin/nuclear factor of activated T cells 3 signaling via sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a, which are involved in regulating skeletal muscle fibrosis and the growth of slow-twitch muscle fibers, respectively. miR-155-5p, miR-486, and miR-23a-3p were also commonly expressed in two conditions, although in different or conflicting directions.

CONCLUSION

In this systematic review, we highlight the potential of shared miRNAs that exhibit consistent expression patterns as biomarkers for the early diagnosis and progression assessment of both sarcopenia and frailty.

The role and therapeutic potential of itaconate in lung disease

Lung diseases triggered by endogenous or exogenous factors have become a major concern, with high morbidity and mortality rates, especially after the coronavirus disease 2019 (COVID-19) pandemic. Inflammation and an over-activated immune system can lead to a cytokine cascade, resulting in lung dysfunction and injury. Itaconate, a metabolite produced by macrophages, has been reported as an effective anti-inflammatory and anti-oxidative stress agent with significant potential in regulating immunometabolism. As a naturally occurring metabolite in immune cells, itaconate has been identified as a potential therapeutic target in lung diseases through its role in regulating inflammation and immunometabolism. This review focuses on the origin, regulation, and function of itaconate in lung diseases, and briefly discusses its therapeutic potential.

Local administration of regulatory T cells promotes tissue healing

Regulatory T cells (Tregs) are crucial immune cells for tissue repair and regeneration. However, their potential as a cell-based regenerative therapy is not yet fully understood. Here, we show that local delivery of exogenous Tregs into injured mouse bone, muscle, and skin greatly enhances tissue healing. Mechanistically, exogenous Tregs rapidly adopt an injury-specific phenotype in response to the damaged tissue microenvironment, upregulating genes involved in immunomodulation and tissue healing. We demonstrate that exogenous Tregs exert their regenerative effect by directly and indirectly modulating monocytes/macrophages (Mo/MΦ) in injured tissues, promoting their switch to an anti-inflammatory and pro-healing state via factors such as interleukin (IL)-10. Validating the key role of IL-10 in exogenous Treg-mediated repair and regeneration, the pro-healing capacity of these cells is lost when Il10 is knocked out. Additionally, exogenous Tregs reduce neutrophil and cytotoxic T cell accumulation and IFN-γ production in damaged tissues, further dampening the pro-inflammatory Mo/MΦ phenotype. Highlighting the potential of this approach, we demonstrate that allogeneic and human Tregs also promote tissue healing. Together, this study establishes exogenous Tregs as a possible universal cell-based therapy for regenerative medicine and provides key mechanistic insights that could be harnessed to develop immune cell-based therapies to enhance tissue healing.

Tumor-associated macrophage-derived itaconic acid contributes to nasopharyngeal carcinoma progression by promoting immune escape via TET2

Nasopharyngeal carcinoma (NPC) is a malignant tumor of epithelial origin in head and neck with high incidence rate in South China, Southeast Asia and North Africa. The intervention of tumor-associated macrophages (Mφs) (TAMs)-mediated immunosuppression is a potential therapeutic strategy against tumor metastasis, but the exact mechanisms of TAM-mediated immunosuppression in nasopharyngeal carcinoma are unclear. Furthermore, how TAM affects the occurrence and development of nasopharyngeal carcinoma through metabolism is rarely involved. In this work, we revealed that NPC cells promoted M2-type Mφ polarization and elevated itaconic acid (ITA) release. Also, TAMs facilitated NPC cell proliferation, migration, and invasion through immune response gene 1 (IRG1)-catalyzed ITA production. Then, IRG1-mediated ITA production in TAMs repressed the killing of CD8+ T cells, induced M2-type polarization of TAMs, and reduced the phagocytosis of TAMs. Moreover, we demonstrated ITA played a tumor immunosuppressive role by binding and dampening ten-eleven translocation-2 (TET2) expression. Finally, we proved that ITA promotes NPC growth by facilitating immune escape in CD34+ hematopoietic stem cell humanized mice. In Conclusion, TAM-derived ITA facilitated NPC progression by enhancing immune escape through targeting TET2, highlighting that interfering with the metabolic pathway of ITA may be a potential strategy for NPC treatment.

LRG1 promotes atherosclerosis by inducing macrophage M1-like polarization

Atherosclerosis is a chronic inflammatory disease of the arterial wall characterized by the accumulation of cholesterol-rich lipoproteins in macrophages. How macrophages commit to proinflammatory polarization under atherosclerosis conditions is not clear. Report here that the level of a circulating protein, leucine-rich alpha-2 glycoprotein 1 (LRG1), is elevated in the atherosclerotic tissue and serum samples from patients with coronary artery disease (CAD). LRG1 stimulated macrophages to proinflammatory M1-like polarization through the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways. The LRG1 knockout mice showed significantly delayed atherogenesis progression and reduced levels of macrophage-related proinflammatory cytokines in a high-fat diet-induced Apoe-/- mouse atherosclerosis model. An anti-LRG1 neutralizing antibody also effectively blocked LRG1-induced macrophage M1-like polarization in vitro and conferred therapeutic benefits to animals with ApoE deficiency-induced atherosclerosis. LRG1 may therefore serve as an additional biomarker for CAD and targeting LRG1 could offer a potential therapeutic strategy for CAD patients by mitigating the proinflammatory response of macrophages.

Glycolytic PFKFB3 and Glycogenic UGP2 Axis Regulates Perfusion Recovery in Experimental Hind Limb Ischemia

BACKGROUND

Despite being in an oxygen-rich environment, endothelial cells (ECs) use anaerobic glycolysis (Warburg effect) as the primary metabolic pathway for cellular energy needs. PFKFB (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase)-3 regulates a critical enzymatic checkpoint in glycolysis and has been shown to induce angiogenesis. This study builds on our efforts to determine the metabolic regulation of ischemic angiogenesis and perfusion recovery in the ischemic muscle.

METHODS

Hypoxia serum starvation (HSS) was used as an in vitro peripheral artery disease (PAD) model, and hind limb ischemia by femoral artery ligation and resection was used as a preclinical PAD model.

RESULTS

Despite increasing PFKFB3-dependent glycolysis, HSS significantly decreased the angiogenic capacity of ischemic ECs. Interestingly, inhibiting PFKFB3 significantly induced the angiogenic capacity of HSS-ECs. Since ischemia induced a significant in PFKFB3 levels in hind limb ischemia muscle versus nonischemic, we wanted to determine whether glucose bioavailability (rather than PFKFB3 expression) in the ischemic muscle is a limiting factor behind impaired angiogenesis. However, treating the ischemic muscle with intramuscular delivery of D-glucose or L-glucose (osmolar control) showed no significant differences in the perfusion recovery, indicating that glucose bioavailability is not a limiting factor to induce ischemic angiogenesis in experimental PAD. Unexpectedly, we found that shRNA-mediated PFKFB3 inhibition in the ischemic muscle resulted in an increased perfusion recovery and higher vascular density compared with control shRNA (consistent with the increased angiogenic capacity of PFKFB3 silenced HSS-ECs). Based on these data, we hypothesized that inhibiting HSS-induced PFKFB3 expression/levels in ischemic ECs activates alternative metabolic pathways that revascularize the ischemic muscle in experimental PAD. A comprehensive glucose metabolic gene qPCR arrays in PFKFB3 silenced HSS-ECs, and PFKFB3-knock-down ischemic muscle versus respective controls identified UGP2 (uridine diphosphate-glucose pyrophosphorylase 2), a regulator of protein glycosylation and glycogen synthesis, is induced upon PFKFB3 inhibition in vitro and in vivo. Antibody-mediated inhibition of UGP2 in the ischemic muscle significantly impaired perfusion recovery versus IgG control. Mechanistically, supplementing uridine diphosphate-glucose, a metabolite of UGP2 activity, significantly induced HSS-EC angiogenic capacity in vitro and enhanced perfusion recovery in vivo by increasing protein glycosylation (but not glycogen synthesis).

CONCLUSIONS

Our data present that inhibition of maladaptive PFKFB3-driven glycolysis in HSS-ECs is necessary to promote the UGP2-uridine diphosphate-glucose axis that enhances ischemic angiogenesis and perfusion recovery in experimental PAD.

Role of long noncoding RNAs in diabetes-associated peripheral arterial disease

Diabetes mellitus (DM) is a metabolic disease that heightens the risks of many vascular complications, including peripheral arterial disease (PAD). Various types of cells, including but not limited to endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and macrophages (MΦs), play crucial roles in the pathogenesis of DM-PAD. Long non-coding RNAs (lncRNAs) are epigenetic regulators that play important roles in cellular function, and their dysregulation in DM can contribute to PAD. This review focuses on the developing field of lncRNAs and their emerging roles in linking DM and PAD. We review the studies investigating the role of lncRNAs in crucial cellular processes contributing to DM-PAD, including those in ECs, VSMCs, and MΦ. By examining the intricate molecular landscape governed by lncRNAs in these relevant cell types, we hope to shed light on the roles of lncRNAs in EC dysfunction, inflammatory responses, and vascular remodeling contributing to DM-PAD. Additionally, we provide an overview of the research approach and methodologies, from identifying disease-relevant lncRNAs to characterizing their molecular and cellular functions in the context of DM-PAD. We also discuss the potential of leveraging lncRNAs in the diagnosis and therapeutics for DM-PAD. Collectively, this review provides a summary of lncRNA-regulated cell functions contributing to DM-PAD and highlights the translational potential of leveraging lncRNA biology to tackle this increasingly prevalent and complex disease.

Nanomaterial-Based Repurposing of Macrophage Metabolism and Its Applications

Macrophage immunotherapy represents an emerging therapeutic approach aimed at modulating the immune response to alleviate disease symptoms. Nanomaterials (NMs) have been engineered to monitor macrophage metabolism, enabling the evaluation of disease progression and the replication of intricate physiological signal patterns. They achieve this either directly or by delivering regulatory signals, thereby mapping phenotype to effector functions through metabolic repurposing to customize macrophage fate for therapy. However, a comprehensive summary regarding NM-mediated macrophage visualization and coordinated metabolic rewiring to maintain phenotypic equilibrium is currently lacking. This review aims to address this gap by outlining recent advancements in NM-based metabolic immunotherapy. We initially explore the relationship between metabolism, polarization, and disease, before delving into recent NM innovations that visualize macrophage activity to elucidate disease onset and fine-tune its fate through metabolic remodeling for macrophage-centered immunotherapy. Finally, we discuss the prospects and challenges of NM-mediated metabolic immunotherapy, aiming to accelerate clinical translation. We anticipate that this review will serve as a valuable reference for researchers seeking to leverage novel metabolic intervention-matched immunomodulators in macrophages or other fields of immune engineering.

Itaconate as a key player in cardiovascular immunometabolism

Cardiovascular diseases (CVDs) are the leading cause of death globally, resulting in a major health burden. Thus, an urgent need exists for exploring effective therapeutic targets to block progression of CVDs and improve patient prognoses. Immune and inflammatory responses are involved in the development of atherosclerosis, ischemic myocardial damage responses and repair, calcification, and stenosis of the aortic valve. These responses can involve both large and small blood vessels throughout the body, leading to increased blood pressure and end-organ damage. While exploring potential avenues for therapeutic intervention in CVDs, researchers have begun to focus on immune metabolism, where metabolic changes that occur in immune cells in response to exogenous or endogenous stimuli can influence immune cell effector responses and local immune signaling. Itaconate, an intermediate metabolite of the tricarboxylic acid (TCA) cycle, is related to pathophysiological processes, including cellular metabolism, oxidative stress, and inflammatory immune responses. The expression of immune response gene 1 (IRG1) is upregulated in activated macrophages, and this gene encodes an enzyme that catalyzes the production of itaconate from the TCA cycle intermediate, cis-aconitate. Itaconate and its derivatives have exerted cardioprotective effects through immune modulation in various disease models, such as ischemic heart disease, valvular heart disease, vascular disease, heart transplantation, and chemotherapy drug-induced cardiotoxicity, implying their therapeutic potential in CVDs. In this review, we delve into the associated signaling pathways through which itaconate exerts immunomodulatory effects, summarize its specific roles in CVDs, and explore emerging immunological therapeutic strategies for managing CVDs.

Itaconate in host inflammation and defense

Immune cells undergo rapid and extensive metabolic changes during inflammation. In addition to contributing to energetic and biosynthetic demands, metabolites can also function as signaling molecules. Itaconate (ITA) rapidly accumulates to high levels in myeloid cells under infectious and sterile inflammatory conditions. This metabolite binds to and regulates the function of diverse proteins intracellularly to influence metabolism, oxidative response, epigenetic modification, and gene expression and to signal extracellularly through binding the G protein-coupled receptor (GPCR). Administration of ITA protects against inflammatory diseases and blockade of ITA production enhances antitumor immunity in preclinical models. In this article, we review ITA metabolism and its regulation, discuss its target proteins and mechanisms, and conjecture a rationale for developing ITA-based therapeutics to treat inflammatory diseases and cancer.

A comprehensive review of phytochemicals targeting macrophages for the regulation of colorectal cancer progression

BACKGROUND

Phytochemicals are natural compounds derived from plants, and are now at the forefront of anti-cancer research. Macrophage immunotherapy plays a crucial role in the treatment of colorectal cancer (CRC). In the context of colorectal cancer, which remains highly prevalent and difficult to treat, it is of research value to explore the potential mechanisms and efficacy of phytochemicals targeting macrophages for CRC treatment.

PURPOSE

The aim of this study was to gain insight into the role of phytochemical-macrophage interactions in regulating CRC and to provide a theoretical basis for the development of new therapeutic strategies in the future.

STUDY DESIGN

This review discusses the potential immune mechanisms of phytochemicals for the treatment of CRC by summarizing research of phytochemicals targeting macrophages.

METHODS

We reviewed the PubMed, EMBASE, Web of Science and CNKI databases from their initial establishment to July 2023 to classify and summaries phytochemicals according to their mechanism of action in targeting macrophages.

RESULTS

The results of the literature review suggest that phytochemicals interfere with CRC development by affecting macrophages through four main mechanisms. Firstly, they modulate the production of cytotoxic substances, such as NO and ROS, by macrophages to exert anticancer effects. Secondly, phytochemicals polarize macrophages towards the M1 phenotype, inhibit M2 polarisation and enhance the anti-tumour immune responses. Thirdly, they enhance the secretion of macrophage-derived cytokines and alter the tumour microenvironment, thereby inhibiting tumor growth. Finally, they activate the immune response by targeting macrophages, triggering the recruitment of other immune cells, thereby enhancing the immune killing effect and exerting anti-tumor effects. These findings highlight phytochemicals as potential therapeutic strategies to intervene in colorectal cancer development by modulating macrophage activity, providing a strong theoretical basis for future clinical applications.

CONCLUSION

Phytochemicals exhibit potential anti-tumour effects by modulating macrophage activity and intervening in the colorectal cancer microenvironment by multiple mechanisms.

Hypercholesterolemia impairs collateral artery enlargement by ten-eleven translocation 1-dependent hematopoietic stem cell autonomous mechanism in a murine model of limb ischemia

Objective

The extent of collateral artery enlargement determines the risk of limb loss due to peripheral arterial disease. Hypercholesterolemia impairs collateral artery enlargement, but the underlying mechanism remains poorly characterized. This study tests the hypothesis that hypercholesterolemia impairs collateral artery enlargement through a ten-eleven translocation 1 (Tet1)-dependent hematopoietic stem cell (HSC)-autonomous mechanism that increases their differentiation into proinflammatory Ly6Chi monocytes and restricts their conversion into proangiogenic Ly6Clow monocytes.

Methods

To test our hypothesis, we induced limb ischemia and generated chimeric mouse models by transplanting HSCs from either wild-type (WT) mice or hypercholesterolemic mice into lethally irradiated WT recipient mice.

Results

We found that the lethally irradiated WT recipient mice reconstituted with HSCs from hypercholesterolemic mice displayed lower blood flow recovery and collateral artery enlargement that was nearly identical to that observed in hypercholesterolemic mice, despite the absence of hypercholesterolemia and consistent with an HSC-autonomous mechanism. We showed that hypercholesterolemia impairs collateral artery enlargement by a Tet1-dependent mechanism that increases HSC differentiation toward proinflammatory Ly6Chi monocytes and restricts the conversion of Ly6Chi monocytes into proangiogenic Ly6Clow monocytes. Moreover, Tet1 epigenetically reprograms monocyte gene expression within the HSCs. Restoration of Tet1 expression in HSCs of hypercholesterolemic mice restores WT collateral artery enlargement and blood flow recovery after induction of hindlimb ischemia.

Conclusions

These results show that hypercholesterolemia impairs collateral artery enlargement by a novel Tet1-dependent HSC-autonomous mechanism that epigenetically reprograms monocyte gene expression within the HSCs.

Restoration of epigenetic impairment in the skeletal muscle and chronic inflammation resolution as a therapeutic approach in sarcopenia

Sarcopenia is an age-associated loss of skeletal muscle mass, strength, and function, accompanied by severe adverse health outcomes, such as falls and fractures, functional decline, high health costs, and mortality. Hence, its prevention and treatment have become increasingly urgent. However, despite the wide prevalence and extensive research on sarcopenia, no FDA-approved disease-modifying drugs exist. This is probably due to a poor understanding of the mechanisms underlying its pathophysiology. Recent evidence demonstrate that sarcopenia development is characterized by two key elements: (i) epigenetic dysregulation of multiple molecular pathways associated with sarcopenia pathogenesis, such as protein remodeling, insulin resistance, mitochondria impairments, and (ii) the creation of a systemic, chronic, low-grade inflammation (SCLGI). In this review, we focus on the epigenetic regulators that have been implicated in skeletal muscle deterioration, their individual roles, and possible crosstalk. We also discuss epidrugs, which are the pharmaceuticals with the potential to restore the epigenetic mechanisms deregulated in sarcopenia. In addition, we discuss the mechanisms underlying failed SCLGI resolution in sarcopenia and the potential application of pro-resolving molecules, comprising specialized pro-resolving mediators (SPMs) and their stable mimetics and receptor agonists. These compounds, as well as epidrugs, reveal beneficial effects in preclinical studies related to sarcopenia. Based on these encouraging observations, we propose the combination of epidrugs with SCLI-resolving agents as a new therapeutic approach for sarcopenia that can effectively attenuate of its manifestations.

Dysregulated cellular metabolism in atherosclerosis: mediators and therapeutic opportunities

Accumulating evidence over the past decades has revealed an intricate relationship between dysregulation of cellular metabolism and the progression of atherosclerotic cardiovascular disease. However, an integrated understanding of dysregulated cellular metabolism in atherosclerotic cardiovascular disease and its potential value as a therapeutic target is missing. In this Review, we (1) summarize recent advances concerning the role of metabolic dysregulation during atherosclerosis progression in lesional cells, including endothelial cells, vascular smooth muscle cells, macrophages and T cells; (2) explore the complexity of metabolic cross-talk between these lesional cells; (3) highlight emerging technologies that promise to illuminate unknown aspects of metabolism in atherosclerosis; and (4) suggest strategies for targeting these underexplored metabolic alterations to mitigate atherosclerosis progression and stabilize rupture-prone atheromas with a potential new generation of cardiovascular therapeutics.

A 6-minute Limb Function Assessment for Therapeutic Testing in Experimental Peripheral Artery Disease Models

Background

The translation of promising therapies from pre-clinical models of hindlimb ischemia (HLI) to patients with peripheral artery disease (PAD) has been inadequate. While this failure is multifactorial, primary outcome measures in preclinical HLI models and clinical trials involving patients with PAD are not aligned well. For example, laser Doppler perfusion recovery measured under resting conditions is the most used outcome in HLI studies, whereas clinical trials involving patients with PAD primarily assess walking performance. Here, we sought to develop a 6-min limb function test for preclinical HLI models that assess muscular performance and hemodynamics congruently.

Methods

We developed an in situ 6-min limb function test that involves repeated isotonic (shortening) contractions performed against a submaximal load. Continuous measurement of muscle blood flow was performed using laser Doppler flowmetry. Quantification of muscle power, work, and perfusion are obtained across the test. To assess the efficacy of this test, we performed HLI via femoral artery ligation on several mouse strains: C57BL6J, BALBc/J, and MCK-PGC1α (muscle-specific overexpression of PGC1α). Additional experiments were performed using an exercise intervention (voluntary wheel running) following HLI.

Results

The 6-min limb function test was successful at detecting differences in limb function of C57BL6/J and BALBc/J mice subjected to HLI with effect sizes superior to laser Doppler perfusion recovery. C57BL6/J mice randomized to exercise therapy following HLI had smaller decline in muscle power, greater hyperemia, and performed more work across the 6-min limb function test compared to non-exercise controls with HLI. Mice with muscle-specific overexpression of PGC1α had no differences in perfusion recovery in resting conditions, but exhibited greater capillary density, increased muscle mass and absolute force levels, and performed more work across the 6-min limb function test compared to their wildtype littermates without the transgene.

Conclusion

These results demonstrate the efficacy of the 6-min limb function test to detect differences in the response to HLI across several interventions including where traditional perfusion recovery, capillary density, and muscle strength measures were unable to detect therapeutic differences.

Engineering M2-type macrophages with a metal polyphenol network for peripheral artery disease treatment

Functional cell treatment for critical limb ischemia is limited by cell viability loss and dysfunction resulting from a harmful ischemic microenvironment. Metal-polyphenol networks have emerged as novel cell delivery vehicles for protecting cells from the detrimental ischemic microenvironment and prolonging the survival rate of cells in the ischemic microenvironment. M2 macrophages are closely related to tissue repair, and they secrete anti-inflammatory factors that contribute to lesion repair. However, these cells are easily metabolized in the body with low efficiency. Herein, M2 macrophages were decorated with a metal‒polyphenol network that contains copper ions and epigallocatechin gallate (Cu-EGCG@M2) to increase cell survival and therapeutic potential. Cu-EGCG@M2 synergistically promoted angiogenesis through the inherent angiogenesis effect of M2 macrophages and copper ions. We found that Cu-EGCG@M2 increased in vitro viability and strengthened the in vivo therapeutic effect on the ischemic hindlimbs of mice, which promoted the recovery of blood and muscle regeneration, resulting in superior limb salvage. These therapeutic effects were ascribed to the increased survival rate and therapeutic period of M2 macrophages, as well as the ameliorated microenvironment at the ischemic site. Additionally, Cu-EGCG exhibited antioxidant, anti-inflammatory, and proangiogenic effects. Our findings provide a feasible option for cell-based treatment of CLI.

Peripheral inflammation-induced changes in songbird brain gene expression: 3' mRNA transcriptomic approach

Species-specific neural inflammation can be induced by profound immune signalling from periphery to brain. Recent advances in transcriptomics offer cost-effective approaches to study this regulation. In a population of captive zebra finch (Taeniopygia guttata), we compare the differential gene expression patterns in lipopolysaccharide (LPS)-triggered peripheral inflammation revealed by RNA-seq and QuantSeq. The RNA-seq approach identified more differentially expressed genes but failed to detect any inflammatory markers. In contrast, QuantSeq results identified specific expression changes in the genes regulating inflammation. Next, we adopted QuantSeq to relate peripheral and brain transcriptomes. We identified subtle changes in the brain gene expression during the peripheral inflammation (e.g. up-regulation in AVD-like and ACOD1 expression) and detected co-structure between the peripheral and brain inflammation. Our results suggest benefits of the 3'end transcriptomics for association studies between peripheral and neural inflammation in genetically heterogeneous models and identify potential targets for the future brain research in birds.

Inhibiting anti-angiogenic VEGF165b activates a miR-17-20a-Calcipressin-3 pathway that revascularizes ischemic muscle in peripheral artery disease

BACKGROUND

VEGF165a increases the expression of the microRNA-17-92 cluster, promoting developmental, retinal, and tumor angiogenesis. We have previously shown that VEGF165b, an alternatively spliced anti-angiogenic VEGF-A isoform, inhibits the VEGFR-STAT3 pathway in ischemic endothelial cells (ECs) to decrease their angiogenic capacity. In ischemic macrophages (Møs), VEGF165b inhibits VEGFR1 to induce S100A8/A9 expression, which drives M1-like polarization. Our current study aims to determine whether VEGF165b inhibition promotes perfusion recovery by regulating the microRNA(miR)-17-92 cluster in preclinical PAD.

METHODS

Femoral artery ligation and resection was used as a preclinical PAD model. Hypoxia serum starvation (HSS) was used as an in vitro PAD model. VEGF165b was inhibited/neutralized by an isoform-specific VEGF165b antibody.

RESULTS

Here, we show that VEGF165b-inhibition induces the expression of miR-17-20a (within miR-17-92 (miR-17-18a-19a-19b-20a-92) cluster) in HSS-ECs and HSS-Møs vs. respective normal and/or isotype-matched IgG controls to enhance perfusion recovery. Consistent with the bioinformatics analysis that revealed RCAN3 as a common target of miR-17 and miR-20a, Argonaute-2 pull-down assays showed decreased miR-17-20a expression and higher RCAN3 expression in the RNA-induced silencing complex of HSS-ECs and HSS-Møs vs. respective controls. Inhibiting miR-17-20a induced RCAN3 levels to decrease ischemic angiogenesis and promoted M1-like polarization to impair perfusion recovery. Finally, using STAT3 inhibitors, S100A8/A9 silencers, and VEGFR1-deficient ECs and Møs, we show that VEGF165b-inhibition activates the miR-17-20a-RCAN3 pathway independent of VEGFR1-STAT3 or VEGFR1-S100A8/A9 in ischemic-ECs and ischemic-Møs respectively.

CONCLUSIONS

Our data revealed a hereunto unrecognized therapeutic 'miR-17-20a-RCAN3' pathway in the ischemic vasculature that is VEGFR1-STAT3/S100A8/A9 independent and is activated only upon VEGF165b-inhibition in PAD.

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

An H2 S-BMP6 Dual-Loading System with Regulating Yap/Taz and Jun Pathway for Synergistic Critical Limb Ischemia Salvaging Therapy

Critical limb ischemia, the final course of peripheral artery disease, is characterized by an insufficient supply of blood flow and excessive oxidative stress. H2 S molecular therapy possesses huge potential for accelerating revascularization and scavenging intracellular reactive oxygen species (ROS). Moreover, it is found that BMP6 is the most significantly up-expressed secreted protein-related gene in HUVECs treated with GYY4137, a H2 S donor, based on the transcriptome analysis. Herein, a UIO-66-NH2 @GYY4137@BMP6 co-delivery nanoplatform to strengthen the therapeutic effects of limb ischemia is developed. The established UIO-66-NH2 @GYY4137@BMP6 nanoplatform exerts its proangiogenic and anti-oxidation functions by regulating key pathways. The underlying molecular mechanisms of UIO-66-NH2 @GYY4137@BMP6 dual-loading system lie in the upregulation of phosphorylated YAP/TAZ and Jun to promote HUVECs proliferation and downregulation of phosphorylated p53/p21 to scavenge excessive ROS. Meanwhile, laser-doppler perfusion imaging (LDPI), injury severity evaluation, and histological analysis confirm the excellent therapeutic effects of UIO-66-NH2 @GYY4137@BMP6 in vivo. This work may shed light on the treatment of critical limb ischemia by regulating YAP, Jun, and p53 signaling pathways based on gas-protein synergistic therapy.

Dapagliflozin promotes angiogenesis in hindlimb ischemia mice by inducing M2 macrophage polarization

Critical limb ischemia (CLI) is associated with a higher risk of limb amputation and cardiovascular death. Dapagliflozin has shown great potential in the treatment of cardiovascular disease. However, the effects of dapagliflozin on CLI and the underlying mechanisms have not been fully elucidated. We evaluated the effect of dapagliflozin on recovery from limb ischemia using a mouse model of hindlimb ischemia. The flow of perfusion was evaluated using a laser Doppler system. Tissue response was assessed by analyzing capillary density, arterial density, and the degree of fibrosis in the gastrocnemius muscle. Immunofluorescence and Western blot were used to detect the expression of macrophage polarization markers and inflammatory factors. Our findings demonstrate the significant impact of dapagliflozin on the acceleration of blood flow recovery in a hindlimb ischemia mouse model, concomitant with a notable reduction in limb necrosis. Histological analysis revealed that dapagliflozin administration augmented the expression of key angiogenic markers, specifically CD31 and α-SMA, while concurrently mitigating muscle fibrosis. Furthermore, our investigation unveiled dapagliflozin's ability to induce a phenotypic shift of macrophages from M1 to M2, thereby diminishing the expression of inflammatory factors, including IL-1β, IL-6, and TNF-α. These effects were partially mediated through modulation of the NF-κB signaling pathway. Lastly, we observed that endothelial cell proliferation, migration, and tube-forming function are enhanced in vitro by utilizing a macrophage-conditioned medium derived from dapagliflozin treatment. Taken together, our study provides evidence that dapagliflozin holds potential as an efficacious therapeutic intervention in managing CLI by stimulating angiogenesis, thereby offering a novel option for clinical CLI treatment.

The Dual Role of ACOD1 in Inflammation

Immunometabolism is an interdisciplinary field that focuses on the relationship between metabolic pathways and immune responses. Dysregulated immunometabolism contributes to many pathological settings, such as cytokine storm or immune tolerance. Aconitate decarboxylase 1 (ACOD1, also known as immunoresponsive gene 1), the mitochondrial enzyme responsible for catalyzing itaconate production, was originally identified as a bacterial LPS-inducible gene involved in innate immunity in mouse macrophages. We now know that the upregulation of ACOD1 expression in immune or nonimmune cells plays a context-dependent role in metabolic reprogramming, signal transduction, inflammasome regulation, and protein modification. The emerging function of ACOD1 in inflammation and infection is a double-edged sword. In this review, we discuss how ACOD1 regulates anti-inflammatory or proinflammatory responses in an itaconate-dependent or -independent manner. Further understanding of ACOD1 expression and function may pave the way for the development of precision therapies for inflammatory diseases.

Inhibiting Anti-angiogenic VEGF165b Activates a Novel miR-17-20a-Calcipressin-3 Pathway that Revascularizes Ischemic Muscle in Peripheral Artery Disease

Background

VEGF165a increases the expression of microRNA-17-92 cluster, promoting developmental, retinal, and tumor angiogenesis. We have previously shown that VEGF165b, an alternatively spliced VEGF-A isoform, inhibits the VEGFR-STAT3 pathway in ischemic endothelial cells (ECs) to decrease their angiogenic capacity. In ischemic macrophages (Møs), VEGF165b inhibits VEGFR1 to induce S100A8/A9 expression, which drives M1-like polarization. Our current study aims to determine whether VEGF165b inhibition promotes perfusion recovery by regulating the miR-17-92 cluster in preclinical PAD.

Methods

Hind limb ischemia (HLI) induced by femoral artery ligation and resection was used as a preclinical PAD model. Hypoxia serum starvation (HSS) was used as an in vitro PAD model. VEGF165b was inhibited/neutralized by an isoform-specific VEGF165b antibody.

Results

Systematic analysis of miR-17-92 cluster members (miR-17-18a-19a-19b-20a-92) in experimental-PAD models showed that VEGF165b-inhibition induces miRNA-17-20a (within miR-17-92 cluster) in HSS-ECs and HSS-bone marrow derived macrophages (BMDMs) vs. respective normal and/or isotype matched IgG controls to enhance perfusion-recovery. Consistent with the bioinformatics analysis that revealed RCAN3 as a common target of miR-17 and miR-20a, Argonaute-2 pull-down assays showed decreased miR-17-20a expression and higher RCAN3 expression in the RISC complex of HSS-ECs and HSS-BMDMs vs. the respective controls. Inhibiting miR-17-20a induced RCAN3 levels to decrease ischemic angiogenesis and promoted M1-like polarization to impair perfusion recovery. Finally, using STAT3 inhibitors, S100A8/A9 silencers and VEGFR1-deficient ECs and Møs, we show that VEGF165b inhibition activates the miR-17-20a-RCAN3 pathway independent of VEGFR1-STAT3 or VEGFR1-S100A8/A9 in ischemic ECs and ischemic Møs, respectively.

Conclusion

Our data revealed a hereunto unrecognized therapeutic 'miR-17-20a-RCAN3' pathway in the ischemic vasculature that is VEGFR1-STAT3/S100A8/A9 independent and is activated only upon VEGF165b inhibition in PAD.

Targeting reactive oxygen species and fat acid oxidation for the modulation of tumor-associated macrophages: a narrative review

Tumor-associated macrophages (TAMs) are significant immunocytes infiltrating the tumor microenvironment(TME). Recent research has shown that TAMs exhibit diversity in terms of their phenotype, function, time, and spatial distribution, which allows for further classification of TAM subtypes. The metabolic efficiency of fatty acid oxidation (FAO) varies among TAM subtypes. FAO is closely linked to the production of reactive oxygen species (ROS), which play a role in processes such as oxidative stress. Current evidence demonstrates that FAO and ROS can influence TAMs' recruitment, polarization, and phagocytosis ability either individually or in combination, thereby impacting tumor progression. But the specific mechanisms associated with these relationships still require further investigation. We will review the current status of research on the relationship between TAMs and tumor development from three aspects: ROS and TAMs, FAO and TAMs, and the interconnectedness of FAO, ROS, and TAMs.

Mitochondria-related genes and metabolic profiles of innate and adaptive immune cells in primary Sjögren's syndrome

Background

Primary Sjogren's syndrome (pSS) is a prototypical systemic autoimmune disease characterised by lymphocyte infiltration and immune-complex deposition in multiple organs. The specific distribution of immune cell populations and their relationship with mitochondria remain unknown.

Methods

Histological analysis was performed to assess the specific distribution of innate and adaptive immune cell populations in labial salivary gland (LSG) samples from 30 patients with pSS and 13 patients with non-pSS. The ultrastructural morphometric features of mitochondria within immune cells were observed under the transmission electron microscope (TEM). RNA sequencing was performed on LSG samples from 40 patients with pSS and 7 non-pSS patients. The Single-sample Gene Set Enrichment Analysis (ssGSEA), ESTIMATE, and CIBERSORT algorithms and Pearson correlation coefficients were used to examine the relationship between mitochondria-related genes and immune infiltration. Weighted Gene Co-expression Network Analysis (WGCNA) was used to identify the mitochondria-specific genes and the related pathways based on the immune cell types.

Results

HE staining revealed a massive infiltration of plasma cells with abundant immunoglobulin protein distributed around phenotypically normal-appearing acinar and ductal tissues of patients with pSS. Immunohistochemical analyses revealed that innate immune cells (macrophages, eosinophils and NK cells) were distributed throughout the glandular tissue. Dominant adaptive immune cell infiltration composed of B cells, CD4⁺T cells and CD8⁺ T cells or ectopic lymphoid follicle-like structures were observed in the LSGs of patients with pSS. TEM validated the swelling of mitochondria with disorganised cristae in some lymphocytes that had invaded the glandular tissue. Subsequently, bioinformatic analysis revealed that innate and adaptive immune cells were associated with different mitochondrial metabolism pathways. Mitochondrial electron transport and respiratory chain complexes in the glandular microenvironment were positively correlated with innate immune cells, whereas amino acid and nucleic acid metabolism were negatively correlated with adaptive immune cells. In addition, mitochondrial biogenesis and mitochondrial apoptosis in the glandular microenvironment were closely associated with adaptive immune cells.

Conclusion

Innate and adaptive immune cells have distinct distribution profiles in the salivary gland tissues of patients with pSS and are associated with different mitochondrial metabolic pathways, which may contribute to disease progression.

Itaconate: A Potent Macrophage Immunomodulator

With advances in immunometabolic studies, more and more evidence has shown that metabolic changes profoundly affect the immune function of macrophages. The tricarboxylic acid cycle is a central metabolic pathway of cells. Itaconate, a byproduct of the tricarboxylic acid cycle, is an emerging metabolic small molecule that regulates macrophage inflammation and has received much attention for its potent anti-inflammatory effects in recent years. Itaconate regulates macrophage function through multiple mechanisms and has demonstrated promising therapeutic potential in a variety of immune and inflammatory diseases. New progress in the mechanism of itaconate continues to be made, but it also implies complexity in its action and a need for a more comprehensive understanding of its role in macrophages. In this article, we review the primary mechanisms and current research progress of itaconate in regulating macrophage immune metabolism, hoping to provide new insights and directions for future research and disease treatment.

Immune response gene 1 deficiency aggravates high fat diet-induced nonalcoholic fatty liver disease via promotion of redox-sensitive AKT suppression

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder worldwide. Immune response gene 1 (IRG1) catalyzes the production of bio-active itaconate, which is actively involved in the regulation of signal transduction. A recent study has found that the expression of IRG1 was significantly down-regulated in obesity-associated fatty liver, but the potential roles of IRG1 in the development NAFLD remain unclear. The present study found that genetic deletion of IRG1 aggravated high fat diet (HFD)-induced metabolic disturbance, including obesity, dyslipidemia and insulin resistance. In addition, HFD induced more severe liver steatosis and higher serum ALT and AST level in IRG1 KO mice, which were accompanied with altered expression of genes involved in lipid uptake, synthesis and catabolism. RNA-seq and immunoblot analysis indicated that deficiency of IRG1 is associated with suppressed activation of AKT, a master metabolic regulator. Mechanistically, IRG1/itaconate enhanced the antioxidative NRF2 pathway and prevented redox-sensitive suppression of AKT. Interestingly, supplementation with 4-octyl itaconate (4-OI), a cell-permeable derivate of itaconate, alleviated HFD-induced oxidative stress, AKT suppression and liver steatosis. Therefore, IRG1 probably functions as a protective regulator in the development of NAFLD and the cell-permeable 4-OI might have potential value for the pharmacological intervention of NAFLD.

Adipose tissue macrophages: implications for obesity-associated cancer

Obesity is one of the most serious global health problems, with an incidence that increases yearly and coincides with the development of cancer. Adipose tissue macrophages (ATMs) are particularly important in this context and contribute to linking obesity-related inflammation and tumor progression. However, the functions of ATMs on the progression of obesity-associated cancer remain unclear. In this review, we describe the origins, phenotypes, and functions of ATMs. Subsequently, we summarize the potential mechanisms on the reprogramming of ATMs in the obesity-associated microenvironment, including the direct exchange of dysfunctional metabolites, inordinate cytokines and other signaling mediators, transfer of extracellular vesicle cargo, and variations in the gut microbiota and its metabolites. A better understanding of the properties and functions of ATMs under conditions of obesity will lead to the development of new therapeutic interventions for obesity-related cancer.

Diabetes mellitus in peripheral artery disease: Beyond a risk factor

Peripheral artery disease (PAD) is one of the major cardiovascular diseases that afflicts a large population worldwide. PAD results from occlusion of the peripheral arteries of the lower extremities. Although diabetes is a major risk factor for developing PAD, coexistence of PAD and diabetes poses significantly greater risk of developing critical limb threatening ischemia (CLTI) with poor prognosis for limb amputation and high mortality. Despite the prevalence of PAD, there are no effective therapeutic interventions as the molecular mechanism of how diabetes worsens PAD is not understood. With increasing cases of diabetes worldwide, the risk of complications in PAD have greatly increased. PAD and diabetes affect a complex web of multiple cellular, biochemical and molecular pathways. Therefore, it is important to understand the molecular components that can be targeted for therapeutic purposes. In this review, we describe some major developments in enhancing the understanding of the interactions of PAD and diabetes. We also provide results from our laboratory in this context.

MicroRNA: role in macrophage polarization and the pathogenesis of the liver fibrosis

Macrophages, as central components of innate immunity, feature significant heterogeneity. Numerus studies have revealed the pivotal roles of macrophages in the pathogenesis of liver fibrosis induced by various factors. Hepatic macrophages function to trigger inflammation in response to injury. They induce liver fibrosis by activating hepatic stellate cells (HSCs), and then inflammation and fibrosis are alleviated by the degradation of the extracellular matrix and release of anti-inflammatory cytokines. MicroRNAs (miRNAs), a class of small non-coding endogenous RNA molecules that regulate gene expression through translation repression or mRNA degradation, have distinct roles in modulating macrophage activation, polarization, tissue infiltration, and inflammation regression. Considering the complex etiology and pathogenesis of liver diseases, the role and mechanism of miRNAs and macrophages in liver fibrosis need to be further clarified. We first summarized the origin, phenotypes and functions of hepatic macrophages, then clarified the role of miRNAs in the polarization of macrophages. Finally, we comprehensively discussed the role of miRNAs and macrophages in the pathogenesis of liver fibrotic disease. Understanding the mechanism of hepatic macrophage heterogeneity in various types of liver fibrosis and the role of miRNAs on macrophage polarization provides a useful reference for further research on miRNA-mediated macrophage polarization in liver fibrosis, and also contributes to the development of new therapies targeting miRNA and macrophage subsets for liver fibrosis.

Advances in the research of the role of macrophage/microglia polarization-mediated inflammatory response in spinal cord injury

It is often difficult to regain neurological function following spinal cord injury (SCI). Neuroinflammation is thought to be responsible for this failure. Regulating the inflammatory response post-SCI may contribute to the recovery of neurological function. Over the past few decades, studies have found that macrophages/microglia are one of the primary effector cells in the inflammatory response following SCI. Growing evidence has documented that macrophages/microglia are plastic cells that can polarize in response to microenvironmental signals into M1 and M2 macrophages/microglia. M1 produces pro-inflammatory cytokines to induce inflammation and worsen tissue damage, while M2 has anti-inflammatory activities in wound healing and tissue regeneration. Recent studies have indicated that the transition from the M1 to the M2 phenotype of macrophage/microglia supports the regression of inflammation and tissue repair. Here, we will review the role of the inflammatory response and macrophages/microglia in SCI and repair. In addition, we will discuss potential molecular mechanisms that induce macrophage/microglia polarization, with emphasis on neuroprotective therapies that modulate macrophage/microglia polarization, which will provide new insights into therapeutic strategies for SCI.

Inflammatory and Prothrombotic Biomarkers, DNA Polymorphisms, MicroRNAs and Personalized Medicine for Patients with Peripheral Arterial Disease

Classical risk factors play a major role in the initiation and development of atherosclerosis. However, the estimation of risk for cardiovascular events based only on risk factors is often insufficient. Efforts have been made to identify biomarkers that indicate ongoing atherosclerosis. Among important circulating biomarkers associated with peripheral arterial disease (PAD) are inflammatory markers which are determined by the expression of different genes and epigenetic processes. Among these proinflammatory molecules, interleukin-6, C-reactive protein, several adhesion molecules, CD40 ligand, osteoprotegerin and others are associated with the presence and progression of PAD. Additionally, several circulating prothrombotic markers have a predictive value in PAD. Genetic polymorphisms significantly, albeit moderately, affect risk factors for PAD via altered lipoprotein metabolism, diabetes, arterial hypertension, smoking, inflammation and thrombosis. However, most of the risk variants for PAD are located in noncoding regions of the genome and their influence on gene expression remains to be explored. MicroRNAs (miRNAs) are single-stranded, noncoding RNAs that modulate gene expression at the post-transcriptional level. Patterns of miRNA expression, to some extent, vary in different atherosclerotic cardiovascular diseases. miRNAs appear to be useful in the detection of PAD and the prediction of progression and revascularization outcomes. In conclusion, taking into account one’s predisposition to PAD, i.e., DNA polymorphisms and miRNAs, together with circulating inflammatory and coagulation markers, holds promise for more accurate prediction models and personalized therapeutic options.

Targeting Anti-Angiogenic VEGF165b-VEGFR1 Signaling Promotes Nitric Oxide Independent Therapeutic Angiogenesis in Preclinical Peripheral Artery Disease Models

Nitric oxide (NO) is the critical regulator of VEGFR2-induced angiogenesis. Neither VEGF-A over-expression nor L-Arginine (NO-precursor) supplementation has been effective in helping patients with Peripheral Artery Disease (PAD) in clinical trials. One incompletely studied reason may be due to the presence of the less characterized anti-angiogenic VEGF-A (VEGF165b) isoform. We have recently shown that VEGF165b inhibits ischemic angiogenesis by blocking VEGFR1, not VEGFR2 activation. Here we wanted to determine whether VEGF165b inhibition using a monoclonal isoform-specific antibody against VEGF165b vs. control, improved perfusion recovery in preclinical PAD models that have impaired VEGFR2-NO signaling, including (1) type-2 diabetic model, (2) endothelial Nitric oxide synthase-knock out mice, and (3) Myoglobin transgenic mice that have impaired NO bioavailability. In all PAD models, VEGF165b inhibition vs. control enhanced perfusion recovery, increased microvascular density in the ischemic limb, and activated VEGFR1-STAT3 signaling. In vitro, VEGF165b inhibition vs. control enhanced a VEGFR1-dependent endothelial survival/proliferation and angiogenic capacity. These data demonstrate that VEGF165b inhibition induces VEGFR1-STAT3 activation, which does not require increased NO to induce therapeutic angiogenesis in PAD. These results may have implications for advancing therapies for patients with PAD where the VEGFR2-eNOS-NO pathway is impaired.

Micro-Gel Ensembles for Accelerated Healing of Chronic Wound via pH Regulation

The pH value in the wound milieu plays a key role in cellular processes and cell cycle processes involved in the process of wound healing. Here, a microfluidic assembly technique is employed to fabricate micro-gel ensembles that can precisely tune the pH value of wound surface and accelerate wound healing. The micro-gel ensembles consist of poly (hydroxypropyl acrylate-co-acrylic acid)-magnesium ions (poly-(HPA-co-AA)-Mg²⁺ ) gel and carboxymethyl chitosan (CMCS) gel, which can release and absorb hydrogen ion (H⁺ ) separately at different stages of healing in response to the evolution of wound microenvironment. By regulating the wound pH to affect the proliferation and migration of cell on the wound and the activity of various biological factors in the wound, the physiological processes are greatly facilitated which results in much accelerated healing of chronic wound. This work presents an effective strategy in designing wound healing materials with vast potentials for chronic wound management.

AAV-mediated expression of PFKFB3 in myofibers, but not endothelial cells, improves ischemic muscle function in mice with critical limb ischemia

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) is a powerful driver of angiogenesis through its modulation of glycolytic metabolism within endothelial cells. Recent work has demonstrated that PFKFB3 modulates the response to muscle ischemia, however the cell specificity of these effects is not fully understood. In this study, we tested the impact of viral mediated expression of PFKFB3, driven by gene promoters specific for myofibers or endothelial cells, on ischemic hindlimb revascularization and muscle function. We hypothesized that both endothelium- and muscle-specific expression of PFKFB3 would attenuate limb pathology following femoral artery ligation. Male and female BALB/cJ mice were injected with adeno-associated virus encoding the either a green fluorescent protein (GFP) or PFKFB3 driven by either the human skeletal actin (ACTA1) or cadherin-5 (Cdh5) promoters. Four weeks after AAV treatment, mice were subjected to unilateral femoral artery ligation and limb perfusion and muscle function were assessed. Both endothelium- and muscle-specific PFKFB3 expression resulted in significantly more perfused capillaries within the ischemic limb muscle, but neither changed myofiber size/area. Muscle-, but not endothelium-specific, PFKFB3 expression significantly improved maximal force production in ischemic muscle (P=0.0005). Notably, there was a significant effect of sex on maximal force levels in both cohorts of mice (P=0.0075 and P=0.0481), indicating that female mice had higher ischemic muscle strength compared to male mice, regardless of treatment group. Taken together, these data demonstrate that while both muscle- and endothelium-specific expression of PFKFB3 enhanced ischemic revascularization, only muscle-specific PFKFB3 expression improved muscle function.

CXCR4 blockade in macrophage promotes angiogenesis in ischemic hindlimb by modulating autophagy

Chemokine receptor CXCR4 plays a crucial role in leukocyte recruitment and inflammation regulation to influence tissue repair in ischemic diseases. Here we assessed the effect of CXCR4 expression in macrophages on angiogenesis in the ischemic hindlimb of a mouse. Inflammatory cells were increased in the ischemic muscles of hindlimb, and CXCR4 was highly expressed in the infiltrated macrophages but not in neutrophils. Myeloid-specific CXCR4 knockout attenuated macrophage infiltration and subsequent reduced inflammatory response in the ischemic hindlimb, accompanied with better blood reperfusion and higher capillary density as compared with that in LysM Cre^+/- (Cre) mice. Similar outcomes were also observed in CRE mice whose bone marrow cells were replaced with those from CXCR4-deficient mice. Gene ontology cluster analysis reviewed that Decorin, a negative regulator of angiogenesis, was reduced in CXCR4-deficient macrophages. CXCR4-deficient macrophages were less inducible into M1 phase by lipopolysaccharide and more favorable for M2 polarization under oxygen/glucose deprivation condition. Enhanced autophagy was detected in CXCR4-deficient macrophages, which was associated with less expression of both Decorin and the inflammatory cytokines. In summary, myeloid-specific CXCR4 deficiency reduced monocyte infiltration and the secretion of inflammatory cytokines and Decorin from macrophages, thus blunting inflammation response and promoting angiogenesis in the ischemic hindlimb.

Hypoxic/Ischemic Inflammation, MicroRNAs and δ-Opioid Receptors: Hypoxia/Ischemia-Sensitive Versus-Insensitive Organs

Hypoxia and ischemia cause inflammatory injury and critically participate in the pathogenesis of various diseases in various organs. However, the protective strategies against hypoxic and ischemic insults are very limited in clinical settings up to date. It is of utmost importance to improve our understanding of hypoxic/ischemic (H/I) inflammation and find novel therapies for better prevention/treatment of H/I injury. Recent studies provide strong evidence that the expression of microRNAs (miRNAs), which regulate gene expression and affect H/I inflammation through post-transcriptional mechanisms, are differentially altered in response to H/I stress, while δ-opioid receptors (DOR) play a protective role against H/I insults in different organs, including both H/I-sensitive organs (e.g., brain, kidney, and heart) and H/I-insensitive organs (e.g., liver and muscle). Indeed, many studies have demonstrated the crucial role of the DOR-mediated cyto-protection against H/I injury by several molecular pathways, including NLRP3 inflammasome modulated by miRNAs. In this review, we summarize our recent studies along with those of others worldwide, and compare the effects of DOR on H/I expression of miRNAs in H/I-sensitive and -insensitive organs. The alternation in miRNA expression profiles upon DOR activation and the potential impact on inflammatory injury in different organs under normoxic and hypoxic conditions are discussed at molecular and cellular levels. More in-depth investigations into this field may provide novel clues for new protective strategies against H/I inflammation in different types of organs.

Mycobacterium tuberculosis Induces Irg1 in Murine Macrophages by a Pathway Involving Both TLR-2 and STING/IFNAR Signaling and Requiring Bacterial Phagocytosis

Irg1 is an enzyme that generates itaconate, a metabolite that plays a key role in the regulation of inflammatory responses. Previous studies have implicated Irg1 as an important mediator in preventing excessive inflammation and tissue damage in Mycobacterium tuberculosis (Mtb) infection. Here, we investigated the pattern recognition receptors and signaling pathways by which Mtb triggers Irg1 gene expression by comparing the responses of control and genetically deficient BMDMs. Using this approach, we demonstrated partial roles for TLR-2 (but not TLR-4 or -9), MyD88 and NFκB signaling in Irg1 induction by Mtb bacilli. In addition, drug inhibition studies revealed major requirements for phagocytosis and endosomal acidification in Irg1 expression triggered by Mtb but not LPS or PAM3CSK4. Importantly, the Mtb-induced Irg1 response was highly dependent on the presence of the bacterial ESX-1 secretion system, as well as host STING and Type I IFN receptor (IFNAR) signaling with Type II IFN (IFN-γ) signaling playing only a minimal role. Based on these findings we hypothesize that Mtb induces Irg1 expression in macrophages via the combination of two independent triggers both dependent on bacterial phagocytosis: 1) a major signal stimulated by phagocytized Mtb products released by an ESX-1-dependent mechanism into the cytosol where they activate the STING pathway leading to Type I-IFN production, and 2) a secondary TLR-2, MyD88 and NFκB dependent signal that enhances Irg1 production independently of Type I IFN induction.

The IRG1-Itaconate axis: A regulatory hub for immunity and metabolism in macrophages

Metabolism could be served as a guiding force for immunity, and macrophages undergo drastic metabolic reprogramming during inflammatory processes, including enhancing glycolysis and reshaping the tricarboxylic acid cycle (TCA) cycle. The disrupted TCA cycle facilitates itaconate accumulation, consistent with the significant up-regulation of immune response gene 1 (IRG1) in activated macrophages. IRG1 catalyzes the decarboxylation of cis-aconitate to synthesize itaconate, and notably, the IRG1-Itaconate axis has excellent potential to link macrophages' immunity and metabolism. Here, we review vital molecules that affect the activation of the IRG1-Itaconate axis, including interferon regulatory factor 1/9 (IRF1/9), transcription 1 and 3 (STAT1/3), CCAAT enhancer-binding protein β (C/EBPβ), and the protein kinase C (PKC). We then focus on how the IRG1-Itaconate axis regulates the inflammatory pathway in macrophages, proposed to involve kelch-like ECH-associated protein 1 (Keap1), NOD-, LRR- and pyrin domain-containing 3 (NLRP3), gasdermin D (GSDMD), activating transcription factor 3 (ATF3), receptor-interacting protein kinase-3 (RIPK3), et al. In addition, we provide an overview of the way the axis participates in the metabolism of macrophages. Eventually, we summarize current connections between the IRG1-Itaconate axis and inflammatory diseases, bringing light to new therapeutic opportunities in inflammatory diseases.

Itaconate and itaconate derivatives target JAK1 to suppress alternative activation of macrophages

The Krebs cycle-derived metabolite itaconate and its derivatives suppress the inflammatory response in pro-inflammatory "M1" macrophages. However, alternatively activated "M2" macrophages can take up itaconate. We therefore examined the effect of itaconate and 4-octyl itaconate (OI) on M2 macrophage activation. We demonstrate that itaconate and OI inhibit M2 polarization and metabolic remodeling. Examination of IL-4 signaling revealed inhibition of JAK1 and STAT6 phosphorylation by both itaconate and OI. JAK1 activation was also inhibited by OI in response to IL-13, interferon-β, and interferon-γ in macrophages and in T helper 2 (Th2) cells. Importantly, JAK1 was directly modified by itaconate derivatives at multiple residues, including cysteines 715, 816, 943, and 1130. Itaconate and OI also inhibited JAK1 kinase activity. Finally, OI treatment suppressed M2 macrophage polarization and JAK1 phosphorylation in vivo. We therefore identify itaconate and OI as JAK1 inhibitors, suggesting a new strategy to inhibit JAK1 in M2 macrophage-driven diseases.

Mitochondrial ACOD1/IRG1 in infection and sterile inflammation

Immunometabolism is a dynamic process involving the interplay of metabolism and immune response in health and diseases. Increasing evidence suggests that impaired immunometabolism contributes to infectious and inflammatory diseases. In particular, the mitochondrial enzyme aconitate decarboxylase 1 (ACOD1, best known as immunoresponsive gene 1 [IRG1]) is upregulated under various inflammatory conditions and serves as a pivotal regulator of immunometabolism involved in itaconate production, macrophage polarization, inflammasome activation, and oxidative stress. Consequently, the activation of the ACOD1 pathway is implicated in regulating the pathogenic process of sepsis and septic shock, which are part of a clinical syndrome of life-threatening organ failure caused by a dysregulated host response to pathogen infection. In this review, we discuss the latest research advances in ACOD1 expression and function, with particular attention to how the ACOD1-itaconate pathway affects infection and sterile inflammation diseases. These new insights may give us a deeper understanding of the role of immunometabolism in innate immunity.

Loss of Id3 (Inhibitor of Differentiation 3) Increases the Number of IgM-Producing B-1b Cells in Ischemic Skeletal Muscle Impairing Blood Flow Recovery During Hindlimb Ischemia

OBJECTIVE

Neovascularization can maintain and even improve tissue perfusion in the setting of limb ischemia during peripheral artery disease. The molecular and cellular mechanisms mediating this process are incompletely understood. We investigate the potential role(s) for Id3 (inhibitor of differentiation 3) in regulating blood flow in a murine model of hindlimb ischemia (HLI). Approach and Results: HLI was modeled through femoral artery ligation and resection and blood flow recovery was quantified by laser Doppler perfusion imaging. Mice with global Id3 deletion had significantly impaired perfusion recovery at 14 and 21 days of HLI. Endothelial- or myeloid cell-specific deletion of Id3 revealed no effect on perfusion recovery while B-cell-specific knockout of Id3 (Id3BKO) revealed a significant attenuation of perfusion recovery. Flow cytometry revealed no differences in ischemia-induced T cells or myeloid cell numbers at 7 days of HLI, yet there was a significant increase in B-1b cells in Id3BKO. Consistent with these findings, ELISA (enzyme-linked immunoassay) demonstrated increases in skeletal muscle and plasma IgM. In vitro experiments demonstrated reduced proliferation and increased cell death when endothelial cells were treated with conditioned media from IgM-producing B-1b cells and tibialis anterior muscles in Id3BKO mice showed reduced density of total CD31+ and αSMA+CD31+ vessels.

CONCLUSIONS

This study is the first to demonstrate a role for B-cell-specific Id3 in maintaining blood flow recovery during HLI. Results suggest a role for Id3 in promoting blood flow during HLI and limiting IgM-expressing B-1b cell expansion. These findings present new mechanisms to investigate in peripheral artery disease pathogenesis.

MicroRNAs in peripheral artery disease: potential biomarkers and pathophysiological mechanisms

Peripheral artery disease (PAD) is a disease of atherosclerosis in the lower extremities. PAD carries a massive burden worldwide, while diagnosis and treatment options are often lacking. One of the key points of research in recent years is the involvement of microRNAs (miRNAs), which are short 20-25 nucleotide single-stranded RNAs that can act as negative regulators of post-transcriptional gene expression. Many of these miRNAs have been discovered to be misregulated in PAD patients, suggesting a potential utility as biomarkers for PAD diagnosis. miRNAs have also been shown to play an important role in many different pathophysiological aspects involved in the initiation and progression of the disease including angiogenesis, hypoxia, inflammation, as well as other cellular functions like cell proliferation and migration. The research on miRNAs in PAD has the potential to lead to a whole new class of diagnostic tools and treatments.

S100A8 and S100A9 are elevated in chronically threatened ischemic limb muscle and induce ischemic mitochondrial pathology in mice

Objective

The objective of the present study was to determine whether elevated levels of S100A8 and S100A9 (S100A8/A9) alarmins contribute to ischemic limb pathology.

Methods

Gastrocnemius muscle was collected from control patients without peripheral arterial disease (PAD; n = 14) and patients with chronic limb threatening limb ischemia (CLTI; n = 14). Mitochondrial function was assessed in permeabilized muscle fibers, and RNA and protein analyses were used to quantify the S100A8/A9 levels. Additionally, a mouse model of hindlimb ischemia with and without exogenous delivery of S100A8/A9 was used.

Results

Compared with the non-PAD control muscles, CLTI muscles displayed significant increases in the abundance of S100A8 and S100A9 at both mRNA and protein levels (P < .01). The CLTI muscles also displayed significant impairment in mitochondrial oxidative phosphorylation and increased mitochondrial hydrogen peroxide production compared with the non-PAD controls. The S100A8/A9 levels correlated significantly with the degree of muscle mitochondrial dysfunction (P < .05 for all). C57BL6J mice treated with recombinant S100A8/A9 displayed impaired perfusion recovery and muscle mitochondrial impairment compared with the placebo-treated mice after hindlimb ischemia surgery. These mitochondrial deficits observed after S100A8/A9 treatment were confirmed in the muscle cell culture system under normoxic conditions.

Conclusions

The S100A8/A9 levels were increased in CLTI limb muscle specimens compared with the non-PAD control muscle specimens, and the level of accumulation was associated with muscle mitochondrial impairment. Elevated S100A8/A9 levels in mice subjected to hindlimb ischemia impaired perfusion recovery and mitochondrial function. Together, these findings suggest that the inflammatory mediators S100A8/A9 might be directly involved in ischemic limb pathology.

Despite improvements in the surgical management of chronic limb threatening limb ischemia (CLTI), the rates of major adverse limb events have remained high. Skeletal muscle has emerged as a strong predictor of outcomes in peripheral arterial disease (PAD)/CLTI; however, a complete understanding of muscle pathology in CLTI is lacking. This study identified elevated S100A8 and S100A9 alarmin proteins as a characteristic of CLTI muscle specimens and that the S100A8/A9 levels are associated with the degree of mitochondrial impairment in patient limb muscle specimens. Using a mouse model of PAD, treatment with S100A8/A9 exacerbated ischemic limb pathology, including impaired limb perfusion recovery and muscle mitochondrial impairment. Taken together, these findings connect the inflammatory milieu in the CLTI limb to exacerbated limb muscle outcomes via mitochondrial alterations.

Dynamic Multiscale Regulation of Perfusion Recovery in Experimental Peripheral Arterial Disease: A Mechanistic Computational Model

In peripheral arterial disease (PAD), the degree of endogenous capacity to modulate revascularization of limb muscle is central to the management of leg ischemia. To characterize the multiscale and multicellular nature of revascularization in PAD, we have developed the first computational systems biology model that mechanistically incorporates intracellular, cellular, and tissue-level features critical for the dynamic reconstitution of perfusion after occlusion-induced ischemia. The computational model was specifically formulated for a preclinical animal model of PAD (mouse hindlimb ischemia [HLI]), and it has gone through multilevel model calibration and validation against a comprehensive set of experimental data so that it accurately captures the complex cellular signaling, cell-cell communication, and function during post-HLI perfusion recovery. As an example, our model simulations generated a highly detailed description of the time-dependent spectrum-like macrophage phenotypes in HLI, and through model sensitivity analysis we identified key cellular processes with potential therapeutic significance in the pathophysiology of PAD. Furthermore, we computationally evaluated the in vivo effects of different targeted interventions on post-HLI tissue perfusion recovery in a model-based, data-driven, virtual mouse population and experimentally confirmed the therapeutic effect of a novel model-predicted intervention in real HLI mice. This novel multiscale model opens up a new avenue to use integrative systems biology modeling to facilitate translational research in PAD.

MicroRNA-30b Is Both Necessary and Sufficient for Interleukin-21 Receptor-Mediated Angiogenesis in Experimental Peripheral Arterial Disease

The interleukin-21 receptor (IL-21R) can be upregulated in endothelial cells (EC) from ischemic muscles in mice following hind-limb ischemia (HLI), an experimental peripheral arterial disease (PAD) model, blocking this ligand–receptor pathway-impaired STAT3 activation, angiogenesis, and perfusion recovery. We sought to identify mRNA and microRNA transcripts that were differentially regulated following HLI, based on the ischemic muscle having intact, or reduced, IL-21/IL21R signaling. In this comparison, 200 mRNAs were differentially expressed but only six microRNA (miR)/miR clusters (and among these only miR-30b) were upregulated in EC isolated from ischemic muscle. Next, myoglobin-overexpressing transgenic (MgTG) C57BL/6 mice examined following HLI and IL-21 overexpression displayed greater angiogenesis, better perfusion recovery, and less tissue necrosis, with increased miR-30b expression. In EC cultured under hypoxia serum starvation, knock-down of miR-30b reduced, while overexpression of miR-30b increased IL-21-mediated EC survival and angiogenesis. In Il21r^−/− mice following HLI, miR-30b overexpression vs. control improved perfusion recovery, with a reduction of suppressor of cytokine signaling 3, a miR-30b target and negative regulator of STAT3. Together, miR-30b appears both necessary and sufficient for IL21/IL-21R-mediated angiogenesis and may present a new therapeutic option to treat PAD if the IL21R is not available for activation.

Systematic Review of Potential Anticancerous Activities of Erythrina senegalensis DC (Fabaceae)

The objective of this study was to carry out a systematic review of the substances isolated from the African medicinal plant Erythrina senegalensis, focusing on compounds harboring activities against cancer models detailed in depth herein at both in vitro and in vivo preclinical levels. The review was conducted through Pubmed and Google Scholar. Nineteen out of the forty-two secondary metabolites isolated to date from E. senegalensis displayed interesting in vitro and/or in vivo antitumor activities. They belonged to alkaloid (Erysodine), triterpenes (Erythrodiol, maniladiol, oleanolic acid), prenylated isoflavonoids (senegalensin, erysenegalensein E, erysenegalensein M, alpinumisoflavone, derrone, warangalone), flavonoids (erythrisenegalone, senegalensein, lupinifolin, carpachromene) and pterocarpans (erybraedine A, erybraedine C, phaseollin). Among the isoflavonoids called "erysenegalensein", only erysenealenseins E and M have been tested for their anticancerous properties and turned out to be cytotoxic. Although the stem bark is the most frequently used part of the plant, all pterocarpans were isolated from roots and all alkaloids from seeds. The mechanisms of action of its metabolites include apoptosis, pyroptosis, autophagy and mitophagy via the modulation of cytoplasmic proteins, miRNA and enzymes involved in critical pathways deregulated in cancer. Alpinumisoflavone and oleanolic acid were studied in a broad spectrum of cancer models both in vitro and in preclinical models in vivo with promising results. Other metabolites, including carpachromen, phaseollin, erybraedin A, erysenegalensein M and maniladiol need to be further investigated, as they display potent in vitro effects.

Noncoding RNAs link metabolic reprogramming to immune microenvironment in cancers

Altered metabolic patterns in tumor cells not only meet their own growth requirements but also shape an immunosuppressive microenvironment through multiple mechanisms. Noncoding RNAs constitute approximately 60% of the transcriptional output of human cells and have been shown to regulate numerous cellular processes under developmental and pathological conditions. Given their extensive action mechanisms based on motif recognition patterns, noncoding RNAs may serve as hinges bridging metabolic activity and immune responses. Indeed, recent studies have shown that microRNAs, long noncoding RNAs and circRNAs are widely involved in tumor metabolic rewiring, immune cell infiltration and function. Hence, we summarized existing knowledge of the role of noncoding RNAs in the remodeling of tumor metabolism and the immune microenvironment, and notably, we established the TIMELnc manual, which is a free and public manual for researchers to identify pivotal lncRNAs that are simultaneously correlated with tumor metabolism and immune cell infiltration based on a bioinformatic approach.

Itaconate regulates macrophage function through stressful iron-sulfur cluster disrupting and iron metabolism rebalancing

Lipopolysaccharide (LPS)-stimulated macrophages express an aconitate decarboxylase (IRG1, also called ACOD1), leading to accumulation of the endogenous metabolite itaconate. However, the precise mechanisms by which elevated itaconate levels alter macrophage function are not clear. Our hypothesis is itaconate affects macrophage function through some uncertain mechanism. Based on this, we established a transcriptional and proteomic signature of macrophages stimulated by itaconate and identified the pathways of IL-1β secretion and altered iron metabolism. Consistently, the effect of IRG1 deficiency on IL-1β secretion and iron metabolism was confirmed in IRG1 knockout THP-1 cell lines. Several common inhibitors and other compounds were used to examine the molecular mechanisms involved. Only cysteine and antioxidants (catechin hydrate) could inhibit caspase-1 activation and IL-1β secretion in itaconate-stimulated macrophages. We further found that aconitase activity was decreased by itaconate stimulation. Our results demonstrate the counteracting effects of overexpression of mitochondrial aconitase (ACO2, a tricarboxylic acid cycle enzyme) or cytosolic aconitase (ACO1, an iron regulatory protein) on IL-1β secretion and altered iron metabolism. Both enzyme activities were inhibited by itaconate because of iron-sulfur (Fe-S) cluster destruction. Our findings indicate that the immunoregulatory functions of IRG1 and itaconate in macrophages are stressful Fe-S cluster of aconitases disrupting and iron metabolism rebalancing.