A novel CCR2 antagonist inhibits atherogenesis in apoE deficient mice by achieving high receptor occupancy

Recombinant human proteoglycan 4 lowers inflammation and atherosclerosis susceptibility in female low-density lipoprotein receptor knockout mice

Recombinant human proteoglycan 4 (rhPRG4) is a macromolecular mucin-like glycoprotein that is classically studied as a lubricant within eyes and joints. Given that endogenously produced PRG4 is present within atherosclerotic lesions and genetic PRG4 deficiency increases atherosclerosis susceptibility in mice, in the current study we investigated the anti-atherogenic potential of chronic rhPRG4 treatment. Female low-density lipoprotein receptor knockout mice were fed an atherogenic Western-type diet for 6 weeks and injected three times per week intraperitoneally with 0.5 mg rhPRG4 or PBS as control. Treatment with rhPRG4 was associated with a small decrease in plasma-free cholesterol levels, without a change in cholesteryl ester levels. A marked increase in the number of peritoneal foam cells was detected in response to the peritoneal rhPRG4 administration, which could be attributed to elevated peritoneal leukocyte MSR1 expression levels. However, rhPRG4-treated mice exhibited significantly smaller aortic root lesions of 278 ± 21 × 103 μm2 compared with 339 ± 15 × 103 μm2 in the aortic root of control mice. The overall decreased atherosclerosis susceptibility coincided with a shift in the monocyte and macrophage polarization states towards the patrolling and anti-inflammatory M2-like phenotypes, respectively. Furthermore, rhPRG4 treatment significantly reduced macrophage gene expression levels as well as plasma protein levels of the pro-inflammatory/pro-atherogenic cytokine TNF-alpha. In conclusion, we have shown that peritoneal administration and subsequent systemic exposure to rhPRG4 beneficially impacts the inflammatory state and reduces atherosclerosis susceptibility in mice. Our findings highlight that PRG4 is not only a lubricant but also acts as an anti-inflammatory agent. KEY POINTS: Endogenously produced proteoglycan 4 is found in atherosclerotic lesions and its genetic deficiency in mice is associated with enhanced atherosclerosis susceptibility. In this study we investigated the anti-atherogenic potential of chronic treatment with recombinant human PRG4 in hypercholesterolaemic female low-density lipoprotein receptor knockout mice. We show that recombinant human PRG4 stimulates macrophage foam cell formation, but also dampens the pro-inflammatory state of monocyte/macrophages, eventually leading to a significant reduction in plasma TNF-alpha levels and a lowered atherosclerosis susceptibility. Our findings highlight that peritoneal recombinant human PRG4 treatment can execute effects both locally and systemically and suggest that it will be of interest to study whether rhPRG4 treatment is also able to inhibit the progression and/or induce regression of previously established atherosclerotic lesions.

Colchicine prevents oxidative stress-induced endothelial cell senescence via blocking NF-κB and MAPKs: implications in vascular diseases

BACKGROUND

Smoking, alcohol abuse, and hypertension are - among others, potential risk factors for cardiovascular diseases. These risk factors generate oxidative stress and cause oxidative stress-induced DNA damage, resulting in cellular senescence and senescence-associated secretory phenotype (SASP). The SASP factors in feed-forward response exacerbate inflammation and cause tissue remodeling, resulting in atherosclerotic plaque formation and rupture.

RESULTS

Colchicine inhibited ROS generation and mitigated oxidative stress-induced DNA damage. It dampened oxidative stress-induced endothelial cell senescence and improved the expression of DNA repair protein KU80 and aging marker Lamin B1. The drug attenuated the expression of senescence marker P21 at mRNA and protein levels. The pathway analysis showed that colchicine inhibited NF-κB and MAPKs pathways and subdued mTOR activation. Colchicine also attenuated mRNA expression of interleukin (IL)-1β, IL-6, IL-8, MCP-1, ICAM-1, and E-selectin. Furthermore, colchicine reduced the mRNA and protein expression of matrix metalloproteinase (MMP-2).

CONCLUSION

In summary, colchicine blocked oxidative stress-induced senescence and SASP by inhibiting the activation of NF-κB and MAPKs pathways.

Type I interferon response in astrocytes promotes brain metastasis by enhancing monocytic myeloid cell recruitment

Cancer metastasis to the brain is a significant clinical problem. Metastasis is the consequence of favorable interactions between invaded cancer cells and the microenvironment. Here, we demonstrate that cancer-activated astrocytes create a sustained low-level activated type I interferon (IFN) microenvironment in brain metastatic lesions. We further confirm that the IFN response in astrocytes facilitates brain metastasis. Mechanistically, IFN signaling in astrocytes activates C-C Motif Chemokine Ligand 2 (CCL2) production, which further increases the recruitment of monocytic myeloid cells. The correlation between CCL2 and monocytic myeloid cells is confirmed in clinical brain metastasis samples. Lastly, genetically or pharmacologically inhibiting C-C Motif Chemokine Receptor 2 (CCR2) reduces brain metastases. Our study clarifies a pro-metastatic effect of type I IFN in the brain even though IFN response has been considered to have anti-tumor effects. Moreover, this work expands our understandings on the interactions between cancer-activated astrocytes and immune cells in brain metastasis.

Short-term high-salt consumption does not influence resting or exercising heart rate variability but increases MCP-1 concentration in healthy young adults

High salt consumption increases blood pressure (BP) and cardiovascular disease risk by altering autonomic function and increasing inflammation. However, it is unclear whether salt manipulation alters resting and exercising heart rate variability (HRV), a noninvasive measure of autonomic function, in healthy young adults. The purpose of this investigation was to determine whether short-term high-salt intake 1) alters HRV at rest, during exercise, or exercise recovery and 2) increases the circulating concentration of the inflammatory biomarker monocyte chemoattractant protein 1 (MCP-1). With the use of a randomized, placebo-controlled, crossover study, 20 participants (8 females; 24 ± 4 yr old, 110 ± 10/64 ± 8 mmHg) consumed salt (3,900 mg sodium) or placebo capsules for 10 days each separated by ≥2 wk. We assessed HRV during 10 min of baseline rest, 50 min of cycling (60% V̇o2peak), and recovery. We quantified HRV using the standard deviation of normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), and additional time and frequency domain metrics of HRV. Plasma samples were collected to assess MCP-1 concentration. No main effect of high salt or condition × time interaction was observed for HRV metrics. However, acute exercise reduced HRV (e.g., RMSSD time: P < 0.001, condition: P = 0.877, interaction: P = 0.422). High salt elevated plasma MCP-1 (72.4 ± 12.5 vs. 78.14 ± 14.7 pg/mL; P = 0.010). Irrespective of condition, MCP-1 was moderately associated (P values < 0.05) with systolic (r = 0.32) and mean BP (r = 0.33). Short-term high-salt consumption does not affect HRV; however, it increases circulating MCP-1, which may influence BP in young adults.

Colchicine Protects against Ethanol-Induced Senescence and Senescence-Associated Secretory Phenotype in Endothelial Cells

Inflammaging is a potential risk factor for cardiovascular diseases. It results in the development of thrombosis and atherosclerosis. The accumulation of senescent cells in vessels causes vascular inflammaging and contributes to plaque formation and rupture. In addition to being an acquired risk factor for cardiovascular diseases, ethanol can induce inflammation and senescence, both of which have been implicated in cardiovascular diseases. In the current study, we used colchicine to abate the cellular damaging effects of ethanol on endothelial cells. Colchicine prevented senescence and averted oxidative stress in endothelial cells exposed to ethanol. It lowered the relative protein expression of aging and senescence marker P21 and restored expression of the DNA repair proteins KU70/KU80. Colchicine inhibited the activation of nuclear factor kappa B (NFκ-B) and mitogen activated protein kinases (MAPKs) in ethanol-treated endothelial cells. It reduced ethanol-induced senescence-associated secretory phenotype. In summary, we show that colchicine ameliorated the ethanol-caused molecular events, resulting in attenuated senescence and senescence-associated secretory phenotype in endothelial cells.

The dual-function chemokine receptor CCR2 drives migration and chemokine scavenging through distinct mechanisms

C-C chemokine receptor 2 (CCR2) is a dual-function receptor. Similar to other G protein-coupled chemokine receptors, it promotes monocyte infiltration into tissues in response to the chemokine CCL2, and, like atypical chemokine receptors (ACKRs), it scavenges chemokine from the extracellular environment. CCR2 therefore mediates CCL2-dependent signaling as a G protein-coupled receptor (GPCR) and also limits CCL2 signaling as a scavenger receptor. We investigated the mechanisms underlying CCR2 scavenging, including the involvement of intracellular proteins typically associated with GPCR signaling and internalization. Using CRISPR knockout cell lines, we showed that CCR2 scavenged by constitutively internalizing to remove CCL2 from the extracellular space and recycling back to the cell surface for further rounds of ligand sequestration. This process occurred independently of G proteins, GPCR kinases (GRKs), β-arrestins, and clathrin, which is distinct from other "professional" chemokine scavenger receptors that couple to GRKs, β-arrestins, or both. These findings set the stage for understanding the molecular regulators that determine CCR2 scavenging and may have implications for drug development targeting this therapeutically important receptor.

Vulnerable Atherosclerotic Plaque: Is There a Molecular Signature?

Atherosclerosis and its clinical manifestations, coronary and cerebral artery diseases, are the most common cause of death worldwide. The main pathophysiological mechanism for these complications is the rupture of vulnerable atherosclerotic plaques and subsequent thrombosis. Pathological studies of the vulnerable lesions showed that more frequently, plaques rich in lipids and with a high level of inflammation, responsible for mild or moderate stenosis, are more prone to rupture, leading to acute events. Identifying the vulnerable plaques helps to stratify patients at risk of developing acute vascular events. Traditional imaging methods based on plaque appearance and size are not reliable in prediction the risk of rupture. Intravascular imaging is a novel technique able to identify vulnerable lesions, but it is invasive and an operator-dependent technique. This review aims to summarize the current data from literature regarding the main biomarkers involved in the attempt to diagnose vulnerable atherosclerotic lesions. These biomarkers could be the base for risk stratification and development of the new therapeutic drugs in the treatment of patients with vulnerable atherosclerotic plaques.

Dichotomous Roles of Smooth Muscle Cell-Derived MCP1 (Monocyte Chemoattractant Protein 1) in Development of Atherosclerosis

BACKGROUND

Smooth muscle cells (SMCs) in atherosclerotic plaque take on multiple nonclassical phenotypes that may affect plaque stability and, therefore, the likelihood of myocardial infarction or stroke. However, the mechanisms by which these cells affect stability are only beginning to be explored.

METHODS

In this study, we investigated the contribution of inflammatory MCP1 (monocyte chemoattractant protein 1) produced by both classical Myh11 (myosin heavy chain 11)⁺ SMCs and SMCs that have transitioned through an Lgals3 (galectin 3)⁺ state in atherosclerosis using smooth muscle lineage tracing mice that label all Myh11⁺ cells and a dual lineage tracing system that targets Lgals3-transitioned SMC only.

RESULTS

We show that loss of MCP1 in all Myh11⁺ smooth muscle results in a paradoxical increase in plaque size and macrophage content, driven by a baseline systemic monocytosis early in atherosclerosis pathogenesis. In contrast, knockout of MCP1 in Lgals3-transitioned SMCs using a complex dual lineage tracing system resulted in lesions with an increased Acta2 (actin alpha 2, smooth muscle)⁺ fibrous cap and decreased investment of Lgals3-transitioned SMCs, consistent with increased plaque stability. Finally, using flow cytometry and single-cell RNA sequencing, we show that MCP1 produced by Lgals3-transitioned SMCs influences multiple populations of inflammatory cells in late-stage plaques.

CONCLUSIONS

MCP1 produced by classical SMCs influences monocyte levels beginning early in disease and was atheroprotective, while MCP1 produced by the Lgals3-transitioned subset of SMCs exacerbated plaque pathogenesis in late-stage disease. Results are the first to determine the function of Lgals3-transitioned inflammatory SMCs in atherosclerosis and highlight the need for caution when considering therapeutic interventions involving MCP1.

Myeloid CCR2 Promotes Atherosclerosis after AKI

BACKGROUND

The risk of cardiovascular events rises after AKI. Leukocytes promote atherosclerotic plaque growth and instability. We established a model of enhanced remote atherosclerosis after renal ischemia-reperfusion (IR) injury and investigated the underlying inflammatory mechanisms.

METHODS

Atherosclerotic lesions and inflammation were investigated in native and bone marrow-transplanted LDL receptor-deficient (LDLr^-/- ) mice after unilateral renal IR injury using histology, flow cytometry, and gene expression analysis.

RESULTS

Aortic root atherosclerotic lesions were significantly larger after renal IR injury than in controls. A gene expression screen revealed enrichment for chemokines and their cognate receptors in aortas of IR-injured mice in early atherosclerosis, and of T cell-associated genes in advanced disease. Confocal microscopy revealed increased aortic macrophage proximity to T cells. Differential aortic inflammatory gene regulation in IR-injured mice largely paralleled the pattern in the injured kidney. Single-cell analysis identified renal cell types that produced soluble mediators upregulated in the atherosclerotic aorta. The analysis revealed a marked early increase in Ccl2, which CCR2⁺ myeloid cells mainly expressed. CCR2 mediated myeloid cell homing to the post-ischemic kidney in a cell-individual manner. Reconstitution with Ccr2^-/- bone marrow dampened renal post-ischemic inflammation, reduced aortic Ccl2 and inflammatory macrophage marker CD11c, and abrogated excess aortic atherosclerotic plaque formation after renal IR.

CONCLUSIONS

Our data introduce an experimental model of remote proatherogenic effects of renal IR and delineate myeloid CCR2 signaling as a mechanistic requirement. Monocytes should be considered as mobile mediators when addressing systemic vascular sequelae of kidney injury.

Investigation of the Molecular Mechanisms Underlying the Antiatherogenic Actions of Kaempferol in Human THP-1 Macrophages

Cardiovascular disease (CVD) is causing high mortality worldwide (World Health Organization-WHO, 2015). Atherosclerosis, the hardening and narrowing of arteries caused by the accumulation of fatty acids and lipids (cholesterol plaques), is a main reason of stroke, myocardial infarction, and angina. Present therapies for cardiovascular disease basically use statins such as β-Hydroxy β-methylglutaryl-CoA, with <70% efficacy and multiple side effects. An in vitro investigation was conducted to evaluate the impact of kaempferol, a natural medication, in an atherosclerotic cell model. We used cytotoxicity assays, Boyden chamber invasion assays, and quantitative PCR. Affymetrix microarrays were used to profile the entire transcriptome of kaempferol-treated cell lines, and Partek Genomic Suite was used to interpret the results. Kaempferol was not cytotoxic to THP-1 macrophages. In comparison to the control, kaempferol reduced monocyte migration mediated by monocyte chemotactic protein 1 (MCP-1) by 80%. The qPCR results showed a 73.7-fold reduction in MCP-1 and a 2.5-fold reduction in intercellular adhesion molecule 1 (ICAM-1) expression in kaempferol-treated cells. In interferon gamma (IFN-γ) without kaempferol and IFN-γ with kaempferol treated cells, we found 295 and 168 differentially expressed genes (DEGs), respectively. According to DEG pathway analysis, kaempferol exhibits anti-atherosclerosis and anti-inflammatory characteristics. Kaempferol is an effective and safe therapy for atherosclerosis.

Targeting the CCL2-CCR2 axis for atheroprotection

Decades of research have established atherosclerosis as an inflammatory disease. Only recently though, clinical trials provided proof-of-concept evidence for the efficacy of anti-inflammatory strategies with respect to cardiovascular events, thus offering a new paradigm for lowering residual vascular risk. Efforts to target the inflammasome-interleukin-1β-interleukin-6 pathway have been highly successful, but inter-individual variations in drug response, a lack of reduction in all-cause mortality, and a higher rate of infections also highlight the need for a second generation of anti-inflammatory agents targeting atherosclerosis-specific immune mechanisms while minimizing systemic side effects. CC-motif chemokine ligand 2/monocyte-chemoattractant protein-1 (CCL2/MCP-1) orchestrates inflammatory monocyte trafficking between the bone marrow, circulation, and atherosclerotic plaques by binding to its cognate receptor CCR2. Adding to a strong body of data from experimental atherosclerosis models, a coherent series of recent large-scale genetic and observational epidemiological studies along with data from human atherosclerotic plaques highlight the relevance and therapeutic potential of the CCL2-CCR2 axis in human atherosclerosis. Here, we summarize experimental and human data pinpointing the CCL2-CCR2 pathway as an emerging drug target in cardiovascular disease. Furthermore, we contextualize previous efforts to interfere with this pathway, scrutinize approaches of ligand targeting vs. receptor targeting, and discuss possible pathway-intrinsic opportunities and challenges related to pharmacological targeting of the CCL2-CCR2 axis in human atherosclerotic disease.

Inflammatory Mediators in Atherosclerotic Vascular Remodeling

Atherosclerotic vascular disease remains the most common cause of ischemia, myocardial infarction, and stroke. Vascular function is determined by structural and functional properties of the arterial vessel wall, which consists of three layers, namely the adventitia, media, and intima. Key cells in shaping the vascular wall architecture and warranting proper vessel function are vascular smooth muscle cells in the arterial media and endothelial cells lining the intima. Pathological alterations of this vessel wall architecture called vascular remodeling can lead to insufficient vascular function and subsequent ischemia and organ damage. One major pathomechanism driving this detrimental vascular remodeling is atherosclerosis, which is initiated by endothelial dysfunction allowing the accumulation of intimal lipids and leukocytes. Inflammatory mediators such as cytokines, chemokines, and modified lipids further drive vascular remodeling ultimately leading to thrombus formation and/or vessel occlusion which can cause major cardiovascular events. Although it is clear that vascular wall remodeling is an elementary mechanism of atherosclerotic vascular disease, the diverse underlying pathomechanisms and its consequences are still insufficiently understood.

Pharmacological Targeting of the CCL2/CCR2 Axis for Atheroprotection: A Meta-Analysis of Preclinical Studies

BACKGROUND

The CCL2 (CC-chemokine ligand 2)/CCR2 (CC-chemokine receptor 2) axis governs monocyte recruitment to atherosclerotic lesions. Genetic and epidemiological studies show strong associations of CCL2 levels with atherosclerotic disease. Still, experimental studies testing pharmacological inhibition of CCL2 or CCR2 in atheroprone mice apply widely different approaches and report variable results, thus halting clinical translation.

METHODS

We systematically searched the literature for studies employing pharmacological CCL2/CCR2 blockade in atheroprone mice and meta-analyzed their effects on lesion size and morphology.

RESULTS

In a meta-analysis of 14 studies testing 11 different agents, CCL2/CCR2 blockade attenuated atherosclerotic lesion size in the aortic root or arch (g=-0.75 [-1.17 to -0.32], P=6×10^-4; N=171/171 mice in experimental/control group), the carotid (g=-2.39 [-4.23 to -0.55], P=0.01; N=24/25), and the femoral artery (g=-2.38 [-3.50 to -1.26], P=3×10^-5; N=10/10). Furthermore, CCL2/CCR2 inhibition reduced intralesional macrophage accumulation and increased smooth muscle cell content and collagen deposition. The effects of CCL2/CCR2 inhibition on lesion size correlated with reductions in plaque macrophage accumulation, in accord with a prominent role of CCL2/CCR2 signaling in monocyte recruitment. Subgroup analyses showed comparable efficacy of different CCL2- and CCR2-inhibitors in reducing lesion size and intralesional macrophages. The quality assessment revealed high risk of detection bias due to lack of blinding during outcome assessment, as well as evidence of attrition and reporting bias.

CONCLUSIONS

Preclinical evidence suggests that pharmacological targeting of CCL2 or CCR2 might lower atherosclerotic lesion burden, but the majority of existing studies suffer major quality issues that highlight the need for additional high-quality research.

Particulate Matter-Induced Acute Coronary Syndrome: MicroRNAs as Microregulators for Inflammatory Factors

The most prevalent cause of mortality and morbidity worldwide is acute coronary syndrome (ACS) and its consequences. Exposure to particulate matter (PM) from air pollution has been shown to impair both. Various plausible pathogenic mechanisms have been identified, including microRNAs (miRNAs), an epigenetic regulator for gene expression. Endogenous miRNAs, average 22-nucleotide RNAs (ribonucleic acid), regulate gene expression through mRNA cleavage or translation repression and can influence proinflammatory gene expression posttranscriptionally. However, little is known about miRNA responses to fine PM (PM_2.5, PM₁₀, ultrafine particles, black carbon, and polycyclic aromatic hydrocarbon) from air pollution and their potential contribution to cardiovascular consequences, including systemic inflammation regulation. For the past decades, microRNAs (miRNAs) have emerged as novel, prospective diagnostic and prognostic biomarkers in various illnesses, including ACS. We wanted to outline some of the most important studies in the field and address the possible utility of miRNAs in regulating particulate matter-induced ACS (PMIA) on inflammatory factors in this review.

Effects of a CCR2 antagonist on macrophages and Toll-like receptor 9 expression in a mouse model of diabetic nephropathy

The pathogenesis of diabetic nephropathy (DN) is related to macrophage (Mφ) recruitment to the kidneys, tumor necrosis factor-α (TNF-α) production, and oxidative stress. Toll-like receptor 9 (TLR9) activation is reportedly involved in systemic inflammation, and it exacerbates this condition in metabolic syndrome. Therefore, we hypothesized that TLR9 plays a role in the pathogenesis of DN. Two subsets of kidney Mφs in DN model (db/db) mice were analyzed using flow cytometry to evaluate their distribution and TLR9 expression and function. Mice were administered the CCR2 antagonist INCB3344 for 8 wk; changes in Mφ distribution and function and its therapeutic effects on DN pathology were examined. Bone marrow-derived CD11bhigh (BM-Mφ) and tissue-resident CD11blow Mφs (Res-Mφ) were identified in the mouse kidneys. As DN progressed, the BM-Mφ number, TLR9 expression, and TNF-α production increased significantly. In Res-Mφs, reactive oxygen species (ROS) production and phagocytic activity were enhanced. INCB3344 decreased albuminuria, serum creatinine level, BM-Mφ abundance, TLR9 expression, and TNF-α production by BM-Mφs and ROS production by Res-Mφs. Both increased activation of BM-Mφ via TLR9 and TNF-α production and increased ROS production by Res-Mφs were involved in DN progression. Thus, inactivating Mφs and their TLR9 expression by INCB3344 is a potential therapeutic strategy for DN.NEW & NOTEWORTHY We classified kidney macrophages (Mφs) into bone marrow-derived Mφs (BM-Mφs) expressing high CD11b and tissue-specific resident Mφ (Res-Mφs) expressing low CD11b. In diabetic nephropathy (DN) model mice, Toll-like receptor 9 (TLR9) expression and TNF-α production via TLR9 activation in BM-Mφs and ROS production in Res-Mφs were enhanced. Furthermore, CCR2 antagonist suppressed the kidney infiltration of BM-Mφs and their function and the ROS production by Res-Mφs, with concomitant TLR9 suppression. Our study presents a new therapeutic strategy for DN.

Mendelian Randomization Studies in Stroke: Exploration of Risk Factors and Drug Targets With Human Genetic Data

Elucidating the causes of stroke is key to developing effective preventive strategies. The Mendelian randomization approach leverages genetic variants related to an exposure of interest to investigate the effects of varying that exposure on disease risk. The random allocation of genetic variants at conception reduces confounding from environmental factors and thus strengthens causal inference, analogous to treatment allocation in a randomized controlled trial. With the recent explosion in the availability of human genetic data, Mendelian randomization has proven a valuable tool for studying risk factors for stroke. In this review, we provide an overview of recent developments in the application of Mendelian randomization to unravel the pathophysiology of stroke subtypes and identify therapeutic targets for clinical translation. The approach has offered novel insight into the differential effects of risk factors and antihypertensive, lipid-lowering, and anticoagulant drug classes on risk of stroke subtypes. Analyses have further facilitated the prioritization of novel drug targets, such as for inflammatory pathways underlying large artery atherosclerotic stroke and for the coagulation cascade that contributes to cardioembolic stroke. With continued methodological advances coupled with the rapidly increasing availability of genetic data related to a broad range of stroke phenotypes, the potential for Mendelian randomization in this context is expanding exponentially.

Targeting the chemokine network in atherosclerosis

Chemokines and their receptors represent a potential target for immunotherapy in chronic inflammation. They comprise a large family of cytokines with chemotactic activity, and their cognate receptors are expressed on all cells of the body. This network dictates leukocyte recruitment and activation, angiogenesis, cell proliferation and maturation. Dysregulation of chemokine and chemokine receptor expression as well as function participates in many pathologies including cancer, autoimmune diseases and chronic inflammation. In atherosclerosis, a lipid-driven chronic inflammation of middle-sized and large arteries, chemokines and their receptors participates in almost all stages of the disease from initiation of fatty streaks to mature atherosclerotic plaque formation. Atherosclerosis and its complications are the main driver of mortality and morbidity in cardiovascular diseases (CVD). Hence, exploring new fields of therapeutic targeting of atherosclerosis is of key importance. This review gives an overview of the recent advances on the role of key chemokines and chemokine receptors in atherosclerosis, addresses chemokine-based biomarkers at biochemical, imaging and genetic level in human studies, and highlights the clinial trials targeting atherosclerosis.

Pathogenesis and Management of COVID-19

COVID-19, occurring due to SARS-COV-2 infection, is the most recent pandemic disease that has led to three million deaths at the time of writing. A great deal of effort has been directed towards altering the virus trajectory and/or managing the interactions of the virus with its subsequent targets in the human body; these interactions can lead to a chain reaction-like state manifested by a cytokine storm and progress to multiple organ failure. During cytokine storms the ratio of pro-inflammatory to anti-inflammatory mediators is generally increased, which contributes to the instigation of hyper-inflammation and confers advantages to the virus. Because cytokine expression patterns fluctuate from one person to another and even within the same person from one time to another, we suggest a road map of COVID-19 management using an individual approach instead of focusing on the blockbuster process (one treatment for most people, if not all). Here, we highlight the biology of the virus, study the interaction between the virus and humans, and present potential pharmacological and non-pharmacological modulators that might contribute to the global war against SARS-COV-2. We suggest an algorithmic roadmap to manage COVID-19.

Association of Circulating Monocyte Chemoattractant Protein-1 Levels With Cardiovascular Mortality: A Meta-analysis of Population-Based Studies

Importance

Human genetics and studies in experimental models support a key role of monocyte-chemoattractant protein-1 (MCP-1) in atherosclerosis. Yet, the associations of circulating MCP-1 levels with risk of coronary heart disease and cardiovascular death in the general population remain largely unexplored.

Objective

To explore whether circulating levels of MCP-1 are associated with risk of incident coronary heart disease, myocardial infarction, and cardiovascular mortality in the general population.

Data Sources and Selection

Population-based cohort studies, identified through a systematic review, that have examined associations of circulating MCP-1 levels with cardiovascular end points.

Data Extraction and Synthesis

Using a prespecified harmonized analysis plan, study-specific summary data were obtained from Cox regression models after excluding individuals with overt cardiovascular disease at baseline. Derived hazard ratios (HRs) were synthesized using random-effects meta-analyses.

Main Outcomes and Measures

Incident coronary heart disease (myocardial infarction, coronary revascularization, and unstable angina), nonfatal myocardial infarction, and cardiovascular death (from cardiac or cerebrovascular causes).

Results

The meta-analysis included 7 cohort studies involving 21 401 individuals (mean [SD] age, 53.7 [10.2] years; 10 012 men [46.8%]). Mean (SD) follow-up was 15.3 (4.5) years (326 392 person-years at risk). In models adjusting for age, sex, and race/ethnicity, higher MCP-1 levels at baseline were associated with increased risk of coronary heart disease (HR per 1-SD increment in MCP-1 levels: 1.06 [95% CI, 1.01-1.11]; P = .01), nonfatal myocardial infarction (HR, 1.07 [95% CI, 1.01-1.13]; P = .02), and cardiovascular death (HR, 1.12 [95% CI, 1.05-1.20]; P < .001). In analyses comparing MCP-1 quartiles, these associations followed dose-response patterns. After additionally adjusting for vascular risk factors, the risk estimates were attenuated, but the associations of MCP-1 levels with cardiovascular death remained statistically significant, as did the association of MCP-1 levels in the upper quartile with coronary heart disease. There was no significant heterogeneity; the results did not change in sensitivity analyses excluding events occurring in the first 5 years after MCP-1 measurement, and the risk estimates were stable after additional adjustments for circulating levels of interleukin-6 and high-sensitivity C-reactive protein.

Conclusions and Relevance

Higher circulating MCP-1 levels are associated with higher long-term cardiovascular mortality in community-dwelling individuals free of overt cardiovascular disease. These findings provide further support for a key role of MCP-1-signaling in cardiovascular disease.

Monocyte-Chemoattractant Protein-1 Levels in Human Atherosclerotic Lesions Associate With Plaque Vulnerability

[Figure: see text].

The molecular structure and role of CCL2 (MCP-1) and C-C chemokine receptor CCR2 in skeletal biology and diseases

Monocyte chemoattractant protein-1, also called chemokine (C-C motif) ligand 2 (CCL2) or small inducible cytokine A2, is an inflammatory mediator capable of recruiting monocytes, memory T cells, and dendritic cells. CCL2 is a member of the CC chemokine superfamily, which binds to its receptor, C-C motif chemokine receptor-2 (CCR2), for the induction of chemotactic activity and an increase of calcium influx. It exerts multiple effects on a variety of cells, including monocytes, macrophages, osteoclasts, basophils, and endothelial cells, and is involved in a diverse range of diseases. This review discusses the molecular structure and role of CCL2 and CCR2 in skeletal biology and disease. Molecular structure analyses reveal that CCL2 shares a conserved C-C motif; however, it has only limited sequence homology with other CCL family members. Likewise, CCR2, as a member of the G-protein-coupled seven-transmembrane receptor superfamily, shares conserved cysteine residues, but exhibits very limited sequence homology with other CCR family members. In the skeletal system, the expression of CCL2 is regulated by a variety of factors, such as parathyroid hormone/parathyroid hormone-related peptide, interleukin 1b, tumor necrosis factor-α and transforming growth factor-beta, RANKL, and mechanical forces. The interaction of CCL2 and CCR2 activates several signaling cascades, including PI3K/Akt/ERK/NF-κB, PI3K/MAPKs, and JAK/STAT-1/STAT-3. Understanding the role of CCL2 and CCR2 will facilitate the development of novel therapies for skeletal disorders, including rheumatoid arthritis, osteolysis and other inflammatory diseases related to abnormal chemotaxis.

Design and Characterization of an Intracellular Covalent Ligand for CC Chemokine Receptor 2

Covalently acting inhibitors constitute a large and growing fraction of approved small-molecule therapeutics as well as useful tools for a variety of in vitro and in vivo applications. Here, we aimed to develop a covalent antagonist of CC chemokine receptor 2 (CCR2), a class A GPCR that has been pursued as a therapeutic target in inflammation and immuno-oncology. Based on a known intracellularly binding CCR2 antagonist, several covalent derivatives were synthesized and characterized by radioligand binding and functional assays. These studies revealed compound 14 as an intracellular covalent ligand for CCR2. In silico modeling followed by site-directed mutagenesis confirmed that 14 forms a covalent bond with one of three proximal cysteine residues, which can be engaged interchangeably. To our knowledge, compound 14 represents the first covalent ligand reported for CCR2. Due to its unique properties, it may represent a promising tool for ongoing and future studies of CCR2 pharmacology.

The corepressors GPS2 and SMRT control enhancer and silencer remodeling via eRNA transcription during inflammatory activation of macrophages

While the role of transcription factors and coactivators in controlling enhancer activity and chromatin structure linked to gene expression is well established, the involvement of corepressors is not. Using inflammatory macrophage activation as a model, we investigate here a corepressor complex containing GPS2 and SMRT both genome-wide and at the Ccl2 locus, encoding the chemokine CCL2 (MCP-1). We report that corepressors co-occupy candidate enhancers along with the coactivators CBP (H3K27 acetylase) and MED1 (mediator) but act antagonistically by repressing eRNA transcription-coupled H3K27 acetylation. Genome editing, transcriptional interference, and cistrome analysis reveals that apparently related enhancer and silencer elements control Ccl2 transcription in opposite ways. 4C-seq indicates that corepressor depletion or inflammatory signaling functions mechanistically similarly to trigger enhancer activation. In ob/ob mice, adipose tissue macrophage-selective depletion of the Ccl2 enhancer-transcribed eRNA reduces metaflammation. Thus, the identified corepressor-eRNA-chemokine pathway operates in vivo and suggests therapeutic opportunities by targeting eRNAs in immuno-metabolic diseases.

Biased agonism at chemokine receptors

In the human chemokine system, interactions between the approximately 50 known endogenous chemokine ligands and 20 known chemokine receptors (CKRs) regulate a wide range of cellular functions and biological processes including immune cell activation and homeostasis, development, angiogenesis, and neuromodulation. CKRs are a family of G protein-coupled receptors (GPCR), which represent the most common and versatile class of receptors in the human genome and the targets of approximately one third of all Food and Drug Administration-approved drugs. Chemokines and CKRs bind with significant promiscuity, as most CKRs can be activated by multiple chemokines and most chemokines can activate multiple CKRs. While these ligand-receptor interactions were previously regarded as redundant, it is now appreciated that many chemokine:CKR interactions display biased agonism, the phenomenon in which different ligands binding to the same receptor signal through different pathways with different efficacies, leading to distinct biological effects. Notably, these biased responses can be modulated through changes in ligand, receptor, and or the specific cellular context (system). In this review, we explore the biochemical mechanisms, functional consequences, and therapeutic potential of biased agonism in the chemokine system. An enhanced understanding of biased agonism in the chemokine system may prove transformative in the understanding of the mechanisms and consequences of biased signaling across all GPCR subtypes and aid in the development of biased pharmaceuticals with increased therapeutic efficacy and safer side effect profiles.

EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) nanoparticles as a carrier for the delivery of CCR2- shRNA to atherosclerotic macrophage in vitro

Reducing macrophage recruitment by silencing chemokine (C–C motif) receptor 2 (CCR2) expression is a promising therapeutic approach against atherosclerosis. However the transfection of macrophages with siRNA is often technically challenging. EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) (PLGA) nanoparticles (ENPs) have a specific affinity to tissue factor (TF). In this study, the feasibility of ENPs as a carrier for target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages was investigated. Coumarin-6 loaded ENPs were synthesized using a double-emulsion method. Fluorescence microscopy and flow cytometry assay were taken to examine the uptake of Coumarin-6 loaded ENPs in the cellular model. Then a sequence of shRNA specific to CCR2 mRNA was constructed and encapsulated into ENPs. Target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages in vitro were evaluated. Results showed more uptake of ENPs by the cellular model than common PLGA nanoparticles. CCR2-shRNA loaded ENPs effectively silenced CCR2 gene in the atherosclerotic macrophages and exhibited a favorable cytotoxic profile to cultured cells. With their low cytotoxicity and efficient drug delivery, ENP could be a useful carrier for target delivery of CCR2-shRNA to inflammatory monocytes/macrophages for the therapy against atherosclerosis.

Salt increases monocyte CCR2 expression and inflammatory responses in humans

Inflammation may play a role in the link between high salt intake and its deleterious consequences. However, it is unknown whether salt can induce proinflammatory priming of monocytes and macrophages in humans. We investigated the effects of salt on monocytes and macrophages in vitro and in vivo by performing a randomized crossover trial in which 11 healthy human subjects adhered to a 2-week low-salt and high-salt diet. We demonstrate that salt increases monocyte expression of CCR2, a chemokine receptor that mediates monocyte infiltration in inflammatory diseases. In line with this, we show a salt-induced increase of plasma MCP-1, transendothelial migration of monocytes, and skin macrophage density after high-salt diet. Macrophages demonstrate signs of an increased proinflammatory phenotype after salt exposure, as represented by boosted LPS-induced cytokine secretion of IL-6, TNF, and IL-10 in vitro, and by increased HLA-DR expression and decreased CD206 expression on skin macrophages after high-salt diet. Taken together, our data open up the possibility for inflammatory monocyte and macrophage responses as potential contributors to the deleterious effects of high salt intake.

Genetically Determined Levels of Circulating Cytokines and Risk of Stroke

BACKGROUND

Cytokines and growth factors have been implicated in the initiation and propagation of vascular disease. Observational studies have shown associations of their circulating levels with stroke. Our objective was to explore whether genetically determined circulating levels of cytokines and growth factors are associated with stroke and its etiologic subtypes by conducting a 2-sample Mendelian randomization (MR) study.

METHODS

Genetic instruments for 41 cytokines and growth factors were obtained from a genome-wide association study of 8293 healthy adults. Their associations with stroke and stroke subtypes were evaluated in the MEGASTROKE genome-wide association study data set (67 162 cases; 454 450 controls) applying inverse variance-weighted meta-analysis, weighted-median analysis, Mendelian randomization-Egger regression, and multivariable Mendelian randomization. The UK Biobank cohort was used as an independent validation sample (4985 cases; 364 434 controls). Genetic instruments for monocyte chemoattractant protein-1 (MCP-1/CCL2) were further tested for association with etiologically related vascular traits by using publicly available genome-wide association study data.

RESULTS

Genetic predisposition to higher MCP-1 levels was associated with higher risk of any stroke (odds ratio [OR] per 1 SD increase, 1.06; 95% CI, 1.02-1.09; P=0.0009), any ischemic stroke (OR, 1.06; 95% CI, 1.02-1.10; P=0.002), large-artery stroke (OR, 1.19; 95% CI, 1.09-1.30; P=0.0002), and cardioembolic stroke (OR, 1.14; 95% CI, 1.06-1.23; P=0.0004), but not with small-vessel stroke or intracerebral hemorrhage. The results were stable in sensitivity analyses and remained significant after adjustment for cardiovascular risk factors. Analyses in the UK Biobank showed similar associations for available phenotypes (any stroke: OR, 1.08; 95% CI, 0.99-1.17; P=0.09; any ischemic stroke: OR, 1.07; 95% CI, 0.97-1.18; P=0.17). Genetically determined higher MCP-1 levels were further associated with coronary artery disease (OR, 1.04; 95% CI, 1.00-1.08; P=0.04) and myocardial infarction (OR, 1.05; 95% CI, 1.01-1.09; P=0.02), but not with atrial fibrillation. A meta-analysis of observational studies showed higher circulating MCP-1 levels in patients with stroke in comparison with controls.

CONCLUSIONS

Genetic predisposition to elevated circulating levels of MCP-1 is associated with higher risk of stroke, in particular with large-artery stroke and cardioembolic stroke. Whether targeting MCP-1 or its receptors can lower stroke incidence requires further study.

Antisense Oligonucleotide Inhibition of MicroRNA-494 Halts Atherosclerotic Plaque Progression and Promotes Plaque Stabilization

We have previously shown that third-generation antisense (3GA) inhibition of 14q32 microRNA (miRNA)-494 reduced early development of atherosclerosis. However, patients at risk of atherosclerotic complications generally present with advanced and unstable lesions. Here, we administered 3GAs against 14q32 miRNA-494 (3GA-494), miRNA-329 (3GA-329), or a control (3GA-ctrl) to mice with advanced atherosclerosis. Atherosclerotic plaque formation in LDLr^−/− mice was induced by a 10-week high-fat diet and simultaneous carotid artery collar placement. Parallel to 3GA-treatment, hyperlipidemia was normalized by a diet switch to regular chow for an additional 5 weeks. We show that, even though plasma cholesterol levels were normalized after diet switch, carotid artery plaque progression continued in 3GA-ctrl mice. However, treatment with 3GA-494 and, in part, 3GA-329 halted plaque progression. Furthermore, in the aortic root, intra-plaque collagen content was increased in 3GA-494 mice, accompanied by a reduction in the intra-plaque macrophage content. Pro-atherogenic cells in the circulation, including inflammatory Ly6C^hi monocytes, neutrophils, and blood platelets, were decreased upon miRNA-329 and miRNA-494 inhibition. Taken together, treatment with 3GA-494, and in part with 3GA-329, halts atherosclerotic plaque progression and promotes stabilization of advanced lesions, which is highly relevant for human atherosclerosis.

Circulating Monocyte Chemoattractant Protein-1 and Risk of Stroke: Meta-Analysis of Population-Based Studies Involving 17 180 Individuals

Rationale: Proinflammatory cytokines have been identified as potential targets for lowering vascular risk. Experimental evidence and Mendelian randomization suggest a role of MCP-1 (monocyte chemoattractant protein-1) in atherosclerosis and stroke. However, data from large-scale observational studies are lacking. Objective: To determine whether circulating levels of MCP-1 are associated with risk of incident stroke in the general population. Methods and Results: We used previously unpublished data on 17 180 stroke-free individuals (mean age, 56.7±8.1 years; 48.8% men) from 6 population-based prospective cohort studies and explored associations between baseline circulating MCP-1 levels and risk of any stroke, ischemic stroke, and hemorrhagic stroke during a mean follow-up interval of 16.3 years (280 522 person-years at risk; 1435 incident stroke events). We applied Cox proportional-hazards models and pooled hazard ratios (HRs) using random-effects meta-analyses. After adjustments for age, sex, race, and vascular risk factors, higher MCP-1 levels were associated with increased risk of any stroke (HR per 1-SD increment in ln-transformed MCP-1, 1.07; 95% CI, 1.01-1.14). Focusing on stroke subtypes, we found a significant association between baseline MCP-1 levels and higher risk of ischemic stroke (HR, 1.11 [1.02-1.21]) but not hemorrhagic stroke (HR, 1.02 [0.82-1.29]). The results followed a dose-response pattern with a higher risk of ischemic stroke among individuals in the upper quartiles of MCP-1 levels as compared with the first quartile (HRs, second quartile: 1.19 [1.00-1.42]; third quartile: 1.35 [1.14-1.59]; fourth quartile: 1.38 [1.07-1.77]). There was no indication for heterogeneity across studies, and in a subsample of 4 studies (12 516 individuals), the risk estimates were stable after additional adjustments for circulating levels of IL (interleukin)-6 and high-sensitivity CRP (C-reactive protein). Conclusions: Higher circulating levels of MCP-1 are associated with increased long-term risk of stroke. Our findings along with genetic and experimental evidence suggest that MCP-1 signaling might represent a therapeutic target to lower stroke risk.Visual Overview: An online visual overview is available for this article.

Drug-Target Residence Time Affects in Vivo Target Occupancy through Multiple Pathways

The drug discovery and development process is greatly hampered by difficulties in translating in vitro potency to in vivo efficacy. Recent studies suggest that the long-neglected drug-target residence time parameter complements classical drug affinity parameters (K _I, K _d, IC₅₀, or EC₅₀) and is a better predictor of in vivo efficacy. Compounds with a long drug-target residence time are often more efficacious in vivo. The impact, however, of the drug-target residence time on in vivo efficacy remains controversial due to difficulties in experimentally determining the in vivo target occupancy during drug treatment. To tackle this problem, an in vivo displacement assay was developed using soluble epoxide hydrolase as a biological model. In this report, we experimentally demonstrated that drug-target residence time affects the duration of in vivo drug-target binding. In addition, the drug-target residence time plays an important role in modulating the rate of drug metabolism which also affects the efficacy of the drug.

Macrophage Plasticity and Function in the Eye and Heart

Macrophages are important mediators of inflammation and tissue remodeling. Recent insights into the heterogeneity of macrophage subpopulations have renewed interest in their functional diversity in homeostasis and disease. In addition, their plasticity enables them to perform a variety of functions in response to changing tissue contexts, such as those imposed by aging. These qualities make macrophages particularly intriguing cells given their dichotomous role in protecting against, or accelerating, diseases of the cardiovascular system and the eye, two tissues that are particularly susceptible to the effects of aging. We review novel perspectives on macrophage biology, as informed by recent studies detailing the diversity of macrophage identity and function, as well as mechanisms influencing macrophage behavior that might offer opportunities for new therapeutic strategies.

Colchicine as a Novel Therapy for Suppressing Chemokine Production in Patients With an Acute Coronary Syndrome: A Pilot Study

PURPOSE

Existing literature reports that colchicine inhibits inflammasome activation and downstream inflammatory cytokine production and stabilizes coronary plaque. However, colchicine's effect on chemokines, which orchestrate multiple atheroinflammatory pathways, is unknown.

METHODS

Patients with acute coronary syndrome (ACS) were randomly assigned to colchicine (1.5 mg PO) (n = 12; mean age, 65.2 years) or no treatment (n = 13; mean age, 62.2 years). Blood samples were collected during cardiac catheterization within 24 hours of colchicine administration from the coronary sinus, aortic root, and right atrium. Patients with colchicine-naive stable angina (SAP) (n = 13; mean age, 66.8 years) were additionally sampled. Serum chemokine levels were analyzed with ELISA. In parallel, monocytes from healthy donors were isolated and subjected to colchicine treatment.

FINDINGS

Transcoronary (TC) levels of chemokine ligand 2 (CCL2) and C-X3-C motif chemokine ligand 1 (CX3CL1) were significantly elevated in patients with ACS versus patients with SAP (P < 0.01). TC chemokine ligand 5 (CCL5) levels were not significantly (P = 0.084) elevated in patients with ACS versus patients with SAP. Colchicine treatment markedly reduced TC levels of CCL2, CCL5, and CX3CL1 in patients with ACS (P < 0.05). In vitro colchicine suppressed CCL2 gene expression in stimulated monocytes (P < 0.05). Colchicine treatment reduced the intracellular concentration of all 3 chemokines (P < 0.01) and impaired monocyte chemotaxis (P < 0.05).

IMPLICATIONS

Here, we report for the first time that short-term colchicine therapy significantly reduces the local production of coronary chemokines, in part by attenuating production of these mediators by monocytes. These data provide further evidence of colchicine's beneficial role in patients with ACS.

Significant association between admission serum monocyte chemoattractant protein-1 and early changes in myocardial function in patients with first ST-segment elevation myocardial infarction after primary percutaneous coronary intervention

Background

Recent studies have indicated that monocyte chemoattractant protein-1 (MCP-1) plays an important role in the initiation and progression of ischaemic heart disease. However, no previous research has investigated the correlation between serum MCP-1 levels and early changes in myocardial function in patients with ST-segmental elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (PCI).

Methods

A total of 87 STEMI patients who had undergone a successful primary PCI were consecutively recruited. All the patients included in this study were grouped into two subgroups according to the median value of MCP-1 upon admission. An early change in left ventricular ejection fraction (LVEF) was defined as (LVEF at 3 months post-STEMI)-(LVEF at 2 days post-STEMI).

Results

Serum MCP-1 levels increased gradually over time during the first 72 h after the onset of STEMI. The concentration of hypersensitive cardiac troponin I (hs-cTnI) upon admission as well as at 24 h and 72 h after primary PCI, especially the peak hs-cTnI concentration, declined significantly in the low admission MCP-1 group. As continuous variable, admission MCP-1 also correlated positively with admission hs-cTnI, hs-cTnI at 24 h after primary PCI, and peak hs-cTnI. Additionally, the absolute early change in LVEF improved markedly in the low admission MCP-1 group (3.77% ± 6.05% vs − 0.18% ± 7.69%, p = 0.009) compared to that in the high admission MCP-1 group. Most importantly, the global LVEF in the low admission MCP-1 group also improved significantly at 3 months compared to baseline LVEF (55.79% ± 7.05% vs 59.60% ± 6.51%, p = 0.011), while an improvement in global LVEF was not observed in the high admission MCP-1 group. Furthermore, as a continuous variable, the MCP-1 level up admission also correlated negatively with early changes in LVEF (r = − 0.391, p = 0.001). After assessment by multiple linear regression analysis, the MCP-1 level upon admission remained correlated with early changes in LVEF [beta = − 0.089, 95% CI (− 0.163 to − 0.015), p = 0.020].

Conclusion

MCP-1 upon admission not only correlated positively with hs-cTnI at different time points and peak hs-cTnI, but also associated inversely with early improvements in myocardial function in patients with first STEMI. So we speculated that suppression the expression of MCP-1 via various ways may be a promising therapeutic target in myocardial I/R injury in the future.

Enhancing Drug Residence Time by Shielding of Intra-Protein Hydrogen Bonds: A Case Study on CCR2 Antagonists

The target residence time (RT) for a given ligand is one of the important parameters that have to be optimized during drug design. It is well established that shielding the receptor-ligand hydrogen bond (H-bond) interactions from water has been one of the factors in increasing ligand RT. Building on this foundation, here we report that shielding an intra-protein H-bond, which confers rigidity to the binding pocket and which is not directly involved in drug-receptor interactions, can strongly influence RT for CCR2 antagonists. Based on our recently solved CCR2 structure with MK-0812 and molecular dynamics (MD) simulations, we show that the RT for this and structurally related ligands is directly dependent on the shielding of the Tyr120-Glu291 H-bond from the water. If solvated this H-bond is often broken, making the binding pocket flexible and leading to shorter RT.

The regulation and importance of monocyte chemoattractant protein-1

PURPOSE OF REVIEW

Monocyte chemoattractant protein (MCP)-1, a chemokine regulating monocyte chemotaxis and T-lymphocyte differentiation by binding to the CC chemokine receptor 2 (CCR2), plays a crucial role in the pathogenesis of inflammatory diseases, atherosclerosis and cancer. This review summarizes the current knowledge on the regulation and importance of the MCP-1/CCR2 axis, focusing on the therapeutic potential of its inhibition.

RECENT FINDINGS

Differential modulation of MCP-1 and CCR2 lead to downstream activation pathways, pathogenetic to differing disease conditions characterized by dysregulated monocyte/macrophage tissue recruitment. Pharmacological targeting of the MCP-1/CCR2 axis has led to selective MCP-1/CCR2 antagonists that have now entered phase I/II clinical trials for the treatment of inflammatory diseases, atherosclerosis and cancer. The pleiotropic nonselective MCP-1/CCR2 inhibition by current pharmacological agents is thought to contribute to their anti-inflammatory and antiatherosclerotic effects that is also seen for nutraceutical compounds such as curcumin.

SUMMARY

MCP-1 has a critical role in regulating chemotaxis both in health and disease, with increasing interest in its pharmacological inhibition. However, the therapeutic efficacy and safety of targeting the MCP-1/CCR2 axis is still in evolution.

Cilia-localized LKB1 regulates chemokine signaling, macrophage recruitment, and tissue homeostasis in the kidney

Polycystic kidney disease (PKD) and other renal ciliopathies are characterized by cysts, inflammation, and fibrosis. Cilia function as signaling centers, but a molecular link to inflammation in the kidney has not been established. Here, we show that cilia in renal epithelia activate chemokine signaling to recruit inflammatory cells. We identify a complex of the ciliary kinase LKB1 and several ciliopathy‐related proteins including NPHP1 and PKD1. At homeostasis, this ciliary module suppresses expression of the chemokine CCL2 in tubular epithelial cells. Deletion of LKB1 or PKD1 in mouse renal tubules elevates CCL2 expression in a cell‐autonomous manner and results in peritubular accumulation of CCR2⁺ mononuclear phagocytes, promoting a ciliopathy phenotype. Our findings establish an epithelial organelle, the cilium, as a gatekeeper of tissue immune cell numbers. This represents an unexpected disease mechanism for renal ciliopathies and establishes a new model for how epithelial cells regulate immune cells to affect tissue homeostasis.

Kinetic operational models of agonism for G-protein-coupled receptors

The application of kinetics to research and therapeutic development of G-protein-coupled receptors has become increasingly valuable. Pharmacological models provide the foundation of pharmacology, providing concepts and measurable parameters such as efficacy and potency that have underlain decades of successful drug discovery. Currently there are few pharmacological models that incorporate kinetic activity in such a way as to yield experimentally-accessible drug parameters. In this study, a kinetic model of pharmacological response was developed that provides a kinetic descriptor of efficacy (the transduction rate constant, k_τ) and allows measurement of receptor-ligand binding kinetics from functional data. The model assumes: (1) receptor interacts with a precursor of the response ("Transduction potential") and converts it to the response. (2) The response can decay. Familiar response vs time plots emerge, depending on whether transduction potential is depleted and/or response decays. These are the straight line, the "association" exponential curve, and the rise-and-fall curve. Convenient, familiar methods are described for measuring the model parameters and files are provided for the curve-fitting program Prism (GraphPad Software) that can be used as a guide. The efficacy parameter k_τ is straightforward to measure and accounts for receptor reserve; all that is required is measurement of response over time at a maximally-stimulating concentration of agonist. The modular nature of the model framework allows it to be extended. Here this is done to incorporate antagonist-receptor binding kinetics and slow agonist-receptor equilibration. In principle, the modular framework can incorporate other cellular processes, such as receptor desensitization. The kinetic response model described here can be applied to measure kinetic pharmacological parameters than can be used to advance the understanding of GPCR pharmacology and optimize new and improved therapeutics.

The Interplay of Lipids, Lipoproteins, and Immunity in Atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is an inflammatory disorder of the arterial wall, in which several players contribute to the onset and progression of the disease. Besides the well-established role of lipids, specifically cholesterol, and immune cell activation, new insights on the molecular mechanisms underlying the atherogenic process have emerged.

RECENT FINDINGS

Meta-inflammation, a condition of low-grade immune response caused by metabolic dysregulation, immunological memory of innate immune cells (referred to as "trained immunity"), cholesterol homeostasis in dendritic cells, and immunometabolism, i.e., the interplay between immunological and metabolic processes, have all emerged as new actors during atherogenesis. These observations reinforced the interest in directly targeting inflammation to reduce cardiovascular disease. The novel acquisitions in pathophysiology of atherosclerosis reinforce the tight link between lipids, inflammation, and immune response, and support the benefit of targeting LDL-C as well as inflammation to decrease the CVD burden. How this will translate into the clinic will depend on the balance between costs (monoclonal antibodies either to PCSK9 or to IL-1ß), side effects (increased incidence of death due to infections for anti-IL-1ß antibody), and the benefits for patients at high CVD risk.

Functional diversity of macrophages in vascular biology and disease

Atherosclerosis is a multifactorial chronic inflammatory disease and is largely responsible for cardiovascular disease, the most common cause of global mortality. The hallmark of atherogenesis is immune activation following lipid accumulation in the arterial wall. In particular, macrophages play a non-redundant role in both the progression and regression of inflammation in the atherosclerotic lesion. Macrophages are remarkably heterogeneous phagocytes that perform versatile functions in health and disease. Their functional diversity in vascular biology is only partially mapped. Targeting macrophages is often highlighted as a therapeutic approach for cancer, metabolic and inflammatory diseases. Future strategies for therapeutic intervention in atherosclerosis may benefit from attempts to reduce local proliferation of pro-inflammatory macrophage subsets or enhance resolution of inflammation. Thus, characterisation of macrophage subsets during atherosclerosis would empower clinical interventions. Therefore, it would be of fundamental importance to understand how pathological factors modulate macrophage activity in order to exploit their use in the treatment of atherosclerosis and other diseases.