AIMS:Elevated neutrophils are associated with a poor prognosis after acute myocardial infarction (AMI) but it is not known if ethnicity influences the association between neutrophil count and outcome. We aimed to describe the temporal dynamics of neutrophils after AMI, and assess the interaction between ethnicity, neutrophil count, and outcomes after AMI. METHODS:Consecutive patients presenting with AMI between 2016 and 2023 were divided into two groups according to their median neutrophil count. Ethnicity was dichotomised as white and other ethnic groups combined (referred to as 'ethnic minorities'). The primary outcome was in-hospital mortality, with a secondary outcome of 60-day mortality. RESULTS:In our study of 3062 AMI patients (76 % white, 24 % from ethnic minority groups), we found that neutrophil counts rose early post AMI, which coincided with a nadir of the other cell groups. We identified a relative baseline neutropenia in ethnic minority individuals, compared to white individuals (6.85 vs 8.42 × 109/L). We observed a significant, independent association between elevated neutrophils at baseline and the primary outcome of in-hospital mortality (OR 2.06, p < 0.001) and secondary outcome of 60-day all-cause mortality (HR 1.08, p = 0.002). Sub-group analysis revealed a significant interaction between ethnicity and elevated neutrophils (p = 0.004), indicating that a comparable neutrophil count conferred an increased risk for ethnic minority patients for both outcomes. CONCLUSIONS:We report ethnicity-specific leucocyte dynamics after AMI. Furthermore, neutrophil count is associated with a disproportionate risk in ethnic minority compared with white individuals. Understanding post-AMI inflammation and its interaction with ethnicity is essential in providing personalised prognostication and patient management.

Background and Purpose Endothelial cells play central roles in increasing vascular permeability and leukocyte recruitment. Therapeutic approaches for treating endothelial cell barrier dysfunction to reduce unwanted fluid accumulation in tissues are limited. Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) enzymes are implicated in signalling inflammatory endothelial permeability and leukocyte recruitment. We investigated the ability of PI3K inhibitors to influence cutaneous oedema formation and neutrophil accumulation.Experimental Approach We used cultured endothelial cells to determine the effects of inflammatory mediators on permeability and vascular leakage, and a murine model of vascular inflammation in mouse skin in vivo. The effects of inflammatory mediators that induce vascular leakage and neutrophil accumulation (TNF alpha, IL-1 beta and C5a) were examined, with the neuropeptides substance P and alpha-CGRP used as controls. The ability of PI3K inhibitors to modulate inflammatory responses was studied.Key Results A broad spectrum PI3K inhibitor (PI-103) and a selective inhibitor of the class 1A p110 alpha catalytic subunit (BYL-719/alpelisib) inhibited endothelial morphological changes and permeability induced by TNF alpha and IL-1 beta in vitro. In vivo, oedema and neutrophil accumulation induced by TNF alpha and IL-1 beta, but not by the complement fragment C5a, is inhibited by BYL-719, whereas PI-103 blocks effects of all three mediators. Neither influences the acute oedema formation induced by neuropeptides.Conclusions and Implications Selective p110 alpha inhibition of vascular inflammation may provide a novel therapeutic pathway for limiting adverse tissue swelling. Moreover, the limited effect of BYL-719 on C5a-mediated responses implies that this innate component of the immune response will continue to provide essential defence activity during p110 alpha blockade.

Abstract Introduction Sterile inflammation post myocardial infarction (MI) is essential to activation reparative mechanisms. However, excessive inflammation contributes to detrimental recovery and adverse outcomes(1). Several studies have reported an association between elevated leucocyte subpopulations and neutrophil-lymphocyte ratio (NLR) with poor prognosis after MI(2). In healthy volunteers, it is known that black individuals have a lower diurnal neutrophil, basophil, and monocyte count and the term ‘benign ethnic neutropenia’ has been used(3). However, the effect of ethnicity on leucocyte counts after MI is not known. Purpose We aimed to assess the interaction between ethnicity and leucocyte subpopulations and NLR. Understanding post-MI inflammation and its interaction with ethnicity is essential in providing personalised patient management and prognostication. Methods We conducted a single centre retrospective observational study of consecutive patients presenting with ST-segment elevation MI (STEMI) between 2016 and 2022. Patients were divided into white and other ethnic groups combined (‘ethnic minorities’) based on self-reported ethnicity. Leucocyte subpopulations, neutrophil and monocyte lymphocyte ratios (NLR and MLR, respectively) at baseline and for 4 days post admission were compared. Baseline variables were analysed with Shapiro-Wilk testing and presented as median (IQR). Area under the curve (AUC) was used to analyse magnitude of change in longitudinal analysis with smoothed conditional means (LOESS) to display trends in the data. Univariate and multivariate linear regression analyses were used to investigate for an association between ethnicity and baseline clinical variables. Results We included 1933 STEMI patients, of whom 1477 (76%) were white and 456 (24%) were from ethnic minority groups. Baseline neutrophils (7.73 [5.9-10] vs 9.04 [6.7-11.9] x109/L), monocytes (0.52 [0.38-0.69] vs 0.6 [0.44-0.82] x109/L), basophils (0.03 [0.02-0.04] vs 0.04 [0.02-0.06] x109/L), NLR (4.47 [2.93-7.19] vs 5.61 [3.64-8.89]) and MLR (0.3 [0.21-0.43] vs 0.36 [0.26-0.53]) were significantly lower (all p<0.001) in ethnic minority vs white patients. There were no differences in peak troponin T or CRP. Longitudinal assessment of leucocyte subgroups and NLR showed that white patients had a significantly higher AUC and difference between minimum and maximum values (delta) for neutrophils, monocytes, basophils and NLR (Panel 1). After correction, we observed a negative association between being in the ethnic minority group and baseline NLR (p=0.005) and basophil count (p<0.001). Conclusions Despite baseline differences in leucocyte subgroups and NLR according to ethnicity, there is a distinct interaction among patients with STEMI suggesting an ethnicity-specific inflammatory profile. Blunting of the magnitude and duration of leucocyte response is novel, and future work will focus on the implications for prognosis and tailored therapy.

Type of funding sources: Foundation. Main funding source(s): British Heart foundation Haematopoietic stem cells can acquire mutations and produce mutant blood cells. When this occurs in the absence of overt blood disease, it is clonal haematopoiesis of indeterminate potential (CHIP). CHIP is a novel, independent risk factor for ischaemic heart disease and heart failure (HF)(1). However, the molecular mechanisms are poorly understood. Myocardial infarction (MI) is a leading cause of HF due to ventricular remodelling and scar formation(2). We postulate CHIP mutations result in aberrant inflammation that contributes to maladaptive ventricular remodelling following MI. We investigated clinical outcomes and immune cell biology in CHIP and non-CHIP patients (pts) with acute ST-segment elevation MI (STEMI). Identify and quantify mutations with variant allele frequency (VAF)≥1% in STEMI pts. Assess leukocyte mutational burden. Investigate transcription profiles and leukocyte function in CHIP and non-CHIP STEMI pts. 119 pts diagnosed with STEMI were prospectively recruited (REC19/SC/0362). We collected clinical data, including echocardiogram (echo) parameters and isolated plasma and peripheral blood mononucleated cells (PBMCs) from blood collected 48-96 hours post onset of chest pain. PBMCs were screened for mutations and analysed by flow cytometry. We assessed CHIP VAF with digital droplet PCR in flow-sorted monocytes (Mono), T and B-cells. We performed single-cell RNAseq (10x Genomics) on PBMCs. Luminex or ELISA kits were used to measure plasma proteins. 59/119 recruited pts had CHIP (VAF≥1%). CHIP pts were significantly older than non-CHIP pts. DNMT3A was the most commonly mutated gene (28%), followed by TET2 (17%) and ASXL1 (5.3%). 53 pts had impaired LV ejection fraction (LVEF) at admission and a follow-up Echo at median 4.6 months (2.5-8 IQR) post STEMI. They were classified as responder (R) n=24, Δ LVEF≥5% or non-responder (NR) n=29, ΔLVEF<5%. Pts with DNMT3A CHIP were 12 times more likely to be NR (p=0.02). Baseline LVEF was similar in CHIP and non-CHIP pts, but ΔLVEF was significantly reduced in DNMT3A vs non-CHIP pts (p<0.01). DNMT3A mutations were highest in Mono (mean VAF 6.3%), present in B cells (3%) but rare in T cells (1.7%). Within the Mono population, DNMT3A mutant pts had significantly higher proportions of classical Mono compared to non-CHIP (p=0.02). Using scRNAseq, we computed Mono trajectories and differential gene expression. Compared to non-CHIP, DNMT3A-mutant samples upregulated receptor for advanced glycation end-products (RAGE) and toll-like receptor signaling gene signatures. Despite this, we did not observe raised leukocyte count or detect increased levels of inflammatory cytokines in DNMT3A-mutant pts plasma samples. DNMT3A CHIP is associated with poor LVEF recovery post-STEMI due to a dysregulated inflammatory response to acute myocardial injury. Furthermore, our data suggests that this may occur via different mechanisms than non-CHIP NR.

Inflammatory edema formation and polymorphonuclear leukocyte (neutrophil) accumulation are common components of cutaneous vascular inflammation, and their assessment is a powerful investigative and drug development tool but typically requires independent cohorts of animals to assess each. We have established the use of a mathematical formula to estimate the ellipsoidal-shaped volume of the edematous wheal or bleb after intradermal injections of substances in mice pretreated intravenously with Evans blue dye (which binds to plasma albumin) to act as an edema marker. Whereas previous extraction of Evans blue dye with formamide is suitable for all strains of mice, we report this quicker and more reliable assessment of edema volume in situ. This therefore allows neutrophil accumulation to be assessed from the same mouse using the myeloperoxidase assay. Importantly, we examined the influence of Evans blue dye on the spectrometry readout at the wavelength at which myeloperoxidase activity is measured. The results indicate that it is feasible to quantify edema formation and neutrophil accumulation in the same mouse skin site. Thus, we show techniques that can assess edema formation and neutrophil accumulation at the same site in the same mouse, allowing paired measurements and reducing the total use of mice by 50%.

Oedema formation and polymorphonuclear leukocyte (neutrophil) accumulation are involved in both acute and chronic inflammation. Calcitonin gene-related peptide (CGRP) is a sensory neuropeptide that is released from stimulated sensory nerves. CGRP is a potent vasodilator neuropeptide, especially when administered to the cutaneous microvasculature, with a long duration of action. Here, we have investigated the ability of vasodilator amounts of CGRP to modulate oedema formation and neutrophil accumulation induced in the cutaneous microvasculature of the mouse. To learn more about the mechanism of action of endogenous CGRP, we have investigated the response to the inflammatory stimulants tumour necrosis factor alpha (TNFα) and carrageenan in three different murine models: a model where sensory nerves were depleted by resiniferatoxin (RTX); a pharmacological method to investigate the effect of a selective CGRP receptor antagonist; and a genetic approach using wildtype (WT) and αCGRP knockout (KO) mice. Our results show that exogenous CGRP potentiates oedema formation induced by substance P (SP) and TNFα. This is further supported by our findings from sensory nerve-depleted mice (in the absence of all neuropeptides), which indicated that sensory nerves are involved in mediating the oedema formation and neutrophil accumulation induced by TNFα, and also carrageenan in cutaneous microvasculature. Furthermore, endogenous CGRP was shown to contribute to this inflammatory response as carrageenan-induced oedema formation is attenuated in WT mice treated with the CGRP receptor antagonist, and in αCGRPKO mice. It is therefore concluded that CGRP can contribute to inflammation by promoting oedema formation in skin, but this response is dependent on the pro-inflammatory stimulus and circumstance.

The treatment of hypertension and heart failure remains a major challenge to healthcare providers. Despite therapeutic advances, heart failure affects more than 26 million people worldwide and is increasing in prevalence due to an ageing population. Similarly, despite an improvement in blood pressure management, largely due to pharmacological interventions, hypertension remains a silent killer. This is in part due to its ability to contribute to heart failure. Development of novel therapies will likely be at the forefront of future cardiovascular studies to address these unmet needs. Calcitonin gene-related peptide (CGRP) is a 37 amino acid potent vasodilator with positive-ionotropic and -chronotropic effects. It has been reported to have beneficial effects in hypertensive and heart failure patients. Interestingly, changes in plasma CGRP concentration in patients after myocardial infarction, heart failure, and in some forms of hypertension, also support a role for CGRP on hemodynamic functions. Rodent studies have played an important role thus far in delineating mechanisms involved in CGRP-induced cardioprotection. However, due to the short plasma half-life of CGRP, these well documented beneficial effects have often proven to be acute and transient. Recent development of longer lasting CGRP agonists may therefore offer a practical solution to investigating CGRP further in cardiovascular disease in vivo. Furthermore, pre-clinical murine studies have hinted at the prospect of cardioprotective mechanisms of CGRP which is independent of its hypotensive effect. Here, we discuss past and present evidence of vascular-dependent and -independent processes by which CGRP could protect the vasculature and myocardium against cardiovascular dysfunction.

Ageing is associated with increased vulnerability to environmental cold exposure. Previously, we identified the role of the cold-sensitive transient receptor potential (TRP) A1, M8 receptors as vascular cold sensors in mouse skin. We hypothesised that this dynamic cold-sensor system may become dysfunctional in ageing. We show that behavioural and vascular responses to skin local environmental cooling are impaired with even moderate ageing, with reduced TRPM8 gene/protein expression especially. Pharmacological blockade of the residual TRPA1/TRPM8 component substantially diminished the response in aged, compared with young mice. This implies the reliance of the already reduced cold-induced vascular response in ageing mice on remaining TRP receptor activity. Moreover, sympathetic-induced vasoconstriction was reduced with downregulation of the α2c adrenoceptor expression in ageing. The cold-induced vascular response is important for sensing cold and retaining body heat and health. These findings reveal that cold sensors, essential for this neurovascular pathway, decline as ageing onsets.

The transient receptor potential (TRP) channels, TRPA1 and TRPM8, are thermo-receptors that detect cold and cool temperatures and play pivotal roles in mediating the cold-induced vascular response. In this study, we investigated the role of TRPA1 and TRPM8 in the thermoregulatory behavioural responses to environmental cold exposure by measuring core body temperature and locomotor activity using a telemetry device that was surgically implanted in mice. The core body temperature of mice that were cooled at 4 °C over 3 h was increased and this was accompanied by an increase in UCP-1 and TRPM8 level as detected by Western blot. We then established an effective route, by which the TRP antagonists could be administered orally with palatable food. This avoids the physical restraint of mice, which is crucial as that could influence the behavioural results. Using selective pharmacological antagonists A967079 and AMTB for TRPA1 and TRPM8 receptors, respectively, we show that TRPM8, but not TRPA1, plays a direct role in thermoregulation response to whole body cold exposure in the mouse. Additionally, we provide evidence of increased TRPM8 levels after cold exposure which could be a protective response to increase core body temperature to counter cold.

The neuropeptide CGRP (calcitonin gene-related peptide) is a potent vasodilator, with a cardioprotective role, although the precise mechanisms are unclear. Here we show the ability of endogenous and exogenous CGRP to restore blood pressure, when nitric oxide synthesis is blocked, in a model of cardiovascular disease associated with endothelial dysfunction and impaired nitric oxide production. Male wild-type and αCGRP knockout mice received L-nitro-arginine methyl ester (150 mg/kg in drinking water) to induce a sustained hypertension with evidence of cardiovascular remodeling. The hypertensive response was exacerbated in L-nitro-arginine methyl ester-treated αCGRP knockouts, indicating that endogenous αCGRP acts in a protective manner, when nitric oxide production is diminished. Exogenous CGRP rescued αCGRP knockout mice from both hypertension and cardiovascular remodeling. Further studies using a nonrecovery protocol with a CGRP receptor antagonist (BIBN4096 BS) revealed that CGRP acts via the canonical CGRP receptor (CLR [calcitonin-like receptor]/RAMP1 [receptor activity-modifying protein]); with no effect of an antagonist (AC187) of a second CGRP-responsive receptor (the amylin-1 receptor, CTR [calcitonin receptor]/RAMP1). Blood flow, in resistance vessels of the exteriorised mesentery, was investigated. Noradrenaline–induced vasoconstriction with recovery, in L-nitro-arginine methyl ester-treated wild-type mice. However, αCGRP knockout, or BIBN4096 BS-treated wild-type mice demonstrated a similar constrictor response to noradrenaline, but significantly impaired blood flow recovery. The combined findings highlight that αCGRP protects against cardiovascular dysfunction, signaling via the canonical CGRP receptor and acting when nitric oxide production is lost, such as in endothelial dysfunction associated with vascular disease. These in vivo results support the proposal that CGRP provides a novel treatment for cardiovascular disease.

Recently, we found that the deletion of TRPC5 leads to increased inflammation and pain-related behaviour in two animal models of arthritis. (-)-Englerin A (EA), an extract from the East African plant Phyllanthus engleri has been identified as a TRPC4/5 agonist. Here, we studied whether or not EA has any anti-inflammatory and analgesic properties via TRPC4/5 in the carrageenan model of inflammation. We found that EA treatment in CD1 mice inhibited thermal hyperalgesia and mechanical allodynia in a dose-dependent manner. Furthermore, EA significantly reduced the volume of carrageenan-induced paw oedema and the mass of the treated paws. Additionally, in dorsal root ganglion (DRG) neurons cultured from WT 129S1/SvIm mice, EA induced a dose-dependent cobalt uptake that was surprisingly preserved in cultured DRG neurons from 129S1/SvIm TRPC5 KO mice. Likewise, EA-induced anti-inflammatory and analgesic effects were preserved in the carrageenan model in animals lacking TRPC5 expression or in mice treated with TRPC4/5 antagonist ML204.This study demonstrates that while EA activates a sub-population of DRG neurons, it induces a novel TRPC4/5-independent analgesic and anti-inflammatory effect in vivo. Future studies are needed to elucidate the molecular and cellular mechanisms underlying EA’s anti-inflammatory and analgesic effects.