Monocyte subsets predict mortality after cardiac arrest

Association between inflammation and post-intensive care syndrome: a systematic review

Post-intensive care syndrome describes the physical, cognitive and emotional symptoms which persist following critical illness. At present there is limited understanding of the pathological mechanisms contributing to the development of post-intensive care syndrome. The aim of this systematic review was to synthesise current evidence exploring the association between inflammation and features of post-intensive care syndrome in survivors of critical illness. Relevant databases were systematically searched for studies of human participants exposed to critical illness. We sought studies that reported results for biomarkers with an identified role in the pathophysiology of inflammation obtained at any time-point in the patient journey and an outcome measure of any feature of post-intensive care syndrome at any point following hospital discharge. We included 32 studies, with 23 in the primary analysis and nine in a brain injury subgroup analysis. In the primary analysis, 47 different biomarkers were sampled and 44 different outcome measures were employed. Of the biomarkers which were sampled in five or more studies, interleukin-8, C-reactive protein and interleukin-10 most frequently showed associations with post-intensive care syndrome outcomes in 71%, 62% and 60% of studies, respectively. There was variability in terms of which biomarkers were sampled, time-points of sampling and outcome measures reported. Overall, there was mixed evidence of a potential association between an inflammatory process and long-term patient outcomes following critical illness. Further high-quality research is required to develop a longitudinal inflammatory profile of survivors of critical illness over the recovery period and evaluate the association with outcomes.

Delayed CCL23 response is associated with poor outcomes after cardiac arrest

Chemokines, a family of chemotactic cytokines, mediate leukocyte migration to and entrance into inflamed tissue, contributing to the intensity of local inflammation. We performed an analysis of chemokine and immune cell responses to cardiac arrest (CA). Forty-two patients resuscitated from cardiac arrest were analyzed, and twenty-two patients who underwent coronary artery bypass grafting (CABG) surgery were enrolled. Quantitative antibody array, chemokines, and endotoxin quantification were performed using the patients blood. Analysis of CCL23 production in neutrophils obtained from CA patients and injected into immunodeficient mice after CA and cardiopulmonary resuscitation (CPR) were done using flow cytometry. The levels of CCL2, CCL4, and CCL23 are increased in CA patients. Temporal dynamics were different for each chemokine, with early increases in CCL2 and CCL4, followed by a delayed elevation in CCL23 at forty-eight hours after CA. A high level of CCL23 was associated with an increased number of neutrophils, neuron-specific enolase (NSE), worse cerebral performance category (CPC) score, and higher mortality. To investigate the role of neutrophil activation locally in injured brain tissue, we used a mouse model of CA/CPR. CCL23 production was increased in human neutrophils that infiltrated mouse brains compared to those in the peripheral circulation. It is known that an early intense inflammatory response (within hours) is associated with poor outcomes after CA. Our data indicate that late activation of neutrophils in brain tissue may also promote ongoing injury via the production of CCL23 and impair recovery after cardiac arrest.

Therapeutic potential of mitochondrial transplantation in modulating immune responses post-cardiac arrest: a narrative review

BACKGROUND

Mitochondrial transplantation (MTx) has emerged as a novel therapeutic strategy, particularly effective in diseases characterized by mitochondrial dysfunction. This review synthesizes current knowledge on MTx, focusing on its role in modulating immune responses and explores its potential in treating post-cardiac arrest syndrome (PCAS).

METHODS

We conducted a comprehensive narrative review of animal and human studies that have investigated the effects of MTx in the context of immunomodulation. This included a review of the immune responses following critical condition such as ischemia reperfusion injury, the impact of MTx on these responses, and the therapeutic potential of MTx in various conditions.

RESULTS

Recent studies indicate that MTx can modulate complex immune responses and reduce ischemia-reperfusion injury post-CA, suggesting MTx as a novel, potentially more effective approach. The review highlights the role of MTx in immune modulation, its potential synergistic effects with existing treatments such as therapeutic hypothermia, and the need for further research to optimize its application in PCAS. The safety and efficacy of autologous versus allogeneic MTx, particularly in the context of immune reactions, are critical areas for future investigation.

CONCLUSION

MTx represents a promising frontier in the treatment of PCAS, offering a novel approach to modulate immune responses and restore cellular energetics. Future research should focus on long-term effects, combination therapies, and personalized medicine approaches to fully harness the potential of MTx in improving patient outcomes in PCAS.

Circulating Monocytes Are Predictive and Responsive in Moderate-to-Severe Plaque Psoriasis Subjects Treated with Apremilast

Monocytes play a critical role in the inflammation associated with psoriasis, and their abnormalities have been reported as biomarkers of cardiovascular event risk, a psoriasis comorbidity. Monocytic cells in chronic inflammatory disorders express elevated levels of cAMP phosphodiesterase. Restoring cAMP levels using the oral cAMP phosphodiesterase-4 inhibitor, apremilast, improves clinical outcomes for a subset of patients with psoriasis. We asked whether aberrant monocyte subsets or transcriptomic pathways can function as biomarkers of psoriasis endotypes that can predict enhanced clinical responses to cAMP phosphodiesterase inhibition. A 16-week open-label study of 22 patients with monocyte flow cytometric and transcriptomic analysis was performed. Subjects with elevated hyperadhesive monocyte doublets at baseline were more likely to be responders to apremilast (P < .0001); 82% of subjects with elevated hyperadhesive monocyte doublets achieved 50% reduction in PASI compared with 46% in those without elevated doublets. We observed a significant reduction in hyperadhesive monocyte-containing doublets and monocyte-platelet aggregates, suggesting an effect of apremilast on the adhesiveness of blood monocytes during chronic inflammation. Monocyte differentially expressed gene transcripts predictive of clinical response uncovered pharmacoendotypes with distinct patterns of nucleotide metabolism, energetics, and differentiation. Further study to understand the basis of drug responsiveness and to develop an apremilast psoriasis treatment algorithm using monocyte-refined gene expression is required to validate and become practical in clinical use, offering patients a test that personalizes their likelihood of clinical response.

The relationship between the level of NMLR on admission and the prognosis of patients after cardiopulmonary resuscitation: a retrospective observational study

BACKGROUND

The inflammatory immune response is involved in the pathophysiology of the post-cardiac arrest syndrome and leads to high mortality. The admission (neutrophil + monocyte) to lymphocyte ratio (NMLR) can help us to assess the immune inflammatory status of patients. We aimed to identify factors that affect the prognosis and explore the association between NMLR and the prognosis of patients after cardiopulmonary resuscitation (CPR).

METHODS

This is a retrospective study based on the MIMIC-IV database. We assessed patients admitted to the ICU after cardiopulmonary resuscitation, included demographic characteristics, peripheral blood cell count and blood gas indicators for the first time after admission to the ICU, developed a multivariate COX proportional-hazards model to explore prognostic factors, and divided patients into High NMLR and Low NMLR groups by cutoff values of NMLR. Propensity score matching (PSM) was used to adjust confounding factors.

RESULTS

A total of 955 patients were included in the analysis, with 497 surviving and 458 dying during the follow-up period. In a multivariate Cox proportional-hazards model, age (RR 1.007, p = 0.0411), NMLR levels (RR 1.003, p = 0.0381), lactate (RR 1.097, p < 0.001) and hematocrit (RR 1.101, p < 0.001) were independent risk factors for patient death following CPR. Patients were divided into a high NMLR group (> 14.2) and a low NMLR group (≤ 14.2) based on the optimal threshold for NMLR. Compared to low NMLR group, high NMLR group had higher total vasoactive drugs and lower 28-day survival. After PSM, there were no differences in baseline characteristics. The high NMLR group still had a higher mortality rate (p = 0.001), lower 28-day survival (p = 0.001) and shorter length of stay (p = 0.005) compared to the low NMLR group.

CONCLUSIONS

Age, NMLR levels, lactate levels and hematocrit were independent risk factors for death in patients after CPR. NMLR > 14.2 was associated with higher mortality and was a potential predictor of clinical outcome in patients after CPR.

Neuroinflammation and the immune system in hypoxic ischaemic brain injury pathophysiology after cardiac arrest

Hypoxic ischaemic brain injury after resuscitation from cardiac arrest is associated with dismal clinical outcomes. To date, most clinical interventions have been geared towards the restoration of cerebral oxygen delivery after resuscitation; however, outcomes in clinical trials are disappointing. Therefore, alternative disease mechanism(s) are likely to be at play, of which the response of the innate immune system to sterile injured tissue in vivo after reperfusion has garnered significant interest. The innate immune system is composed of three pillars: (i) cytokines and signalling molecules; (ii) leucocyte migration and activation; and (iii) the complement cascade. In animal models of hypoxic ischaemic brain injury, pro-inflammatory cytokines are central to propagation of the response of the innate immune system to cerebral ischaemia-reperfusion. In particular, interleukin-1 beta and downstream signalling can result in direct neural injury that culminates in cell death, termed pyroptosis. Leucocyte chemotaxis and activation are central to the in vivo response to cerebral ischaemia-reperfusion. Both parenchymal microglial activation and possible infiltration of peripherally circulating monocytes might account for exacerbation of an immunopathological response in humans. Finally, activation of the complement cascade intersects with multiple aspects of the innate immune response by facilitating leucocyte activation, further cytokine release and endothelial activation. To date, large studies of immunomodulatory therapies have not been conducted; however, lessons learned from historical studies using therapeutic hypothermia in humans suggest that quelling an immunopathological response might be efficacious. Future work should delineate the precise pathways involved in vivo in humans to target specific signalling molecules.

Prognostic Significance of Activated Monocytes in Patients with ST-Elevation Myocardial Infarction

Circulating monocytes have different subsets, including classical (CD14++CD16-), intermediate (CD14++CD16+), and nonclassical (CD14+CD16++), which play different roles in cardiovascular physiology and disease progression. The predictive value of each subset for adverse clinical outcomes in patients with coronary artery disease is not fully understood. We sought to evaluate the prognostic efficacy of each monocyte subset in patients with ST-elevation myocardial infarction (STEMI). We recruited 100 patients with STEMI who underwent primary percutaneous coronary intervention (PCI). Blood samples were collected at the time of presentation to the hospital (within 6 h from onset of symptoms, baseline (BL)) and then at 3, 6, 12, and 24 h after presentation. Monocytes were defined as CD45+/HLA-DR+ and then subdivided based on the expression of CD14, CD16, CCR2, CD11b, and CD42. The primary endpoint was a composite of all-cause death, hospitalization for heart failure, stent thrombosis, in-stent restenosis, and recurrent myocardial infarction. Univariate and multivariate Cox proportional hazards models, including baseline comorbidities, were performed. The mean age of our cohort was 58.9 years and 25% of our patients were females. Patients with high levels (above the median) of CD14+CD16++ monocytes showed an increased risk for the primary endpoint in comparison to patients with low levels; adjusted hazard ratio (aHR) for CD14+/CD16++ cells was 4.3 (95% confidence interval (95% CI) 1.2-14.8, p = 0.02), for CD14+/CD16++/CCR2+ cells was 3.82 (95% CI 1.06-13.7, p = 0.04), for CD14+/CD16++/CD42b+ cells was 3.37 (95% CI 1.07-10.6, p = 0.03), for CD14+/CD16++/CD11b+ was 5.17 (95% CI 1.4-18.0, p = 0.009), and for CD14+ HLA-DR+ was 7.5 (95% CI 2.0-28.5, p = 0.002). CD14++CD16-, CD14++CD16+, and their CD11b+, CCR2+, and CD42b+ aggregates were not significantly predictive for our composite endpoint. Our study shows that CD14+ CD16++ monocytes and their subsets expressing CCR2, CD42, and CD11b could be important predictors of clinical outcomes in patients with STEMI. Further studies with a larger sample size and different coronary artery disease phenotypes are needed to verify the findings.

The role of monocytes in thrombotic diseases: a review

Cardiovascular and cerebrovascular diseases are the number one killer threatening people's life and health, among which cardiovascular thrombotic events are the most common. As the cause of particularly serious cardiovascular events, thrombosis can trigger fatal crises such as acute coronary syndrome (myocardial infarction and unstable angina), cerebral infarction and so on. Circulating monocytes are an important part of innate immunity. Their main physiological functions are phagocytosis, removal of injured and senescent cells and their debris, and development into macrophages and dendritic cells. At the same time, they also participate in the pathophysiological processes of pro-coagulation and anticoagulation. According to recent studies, monocytes have been found to play a significant role in thrombosis and thrombotic diseases of the immune system. In this manuscript, we review the relationship between monocyte subsets and cardiovascular thrombotic events and analyze the role of monocytes in arterial thrombosis and their involvement in intravenous thrombolysis. Finally, we summarize the mechanism and therapeutic regimen of monocyte and thrombosis in hypertension, antiphospholipid syndrome, atherosclerosis, rheumatic heart disease, lower extremity deep venous thrombosis, and diabetic nephropathy.

Repeated lipoprotein apheresis and immune response: Effects on different immune cell populations

BACKGROUND

Atherosclerosis is considered a chronic inflammation of arterial vessels with the involvement of several immune cells causing severe cardiovascular diseases. Lipoprotein apheresis (LA) improves cardiovascular conditions of patients with severely disturbed lipid metabolism. In this context, little is known about the impact of LA on various immune cell populations, especially over time.

METHODS

Immune cells of 18 LA-naïve patients starting weekly LA treatment were analyzed before and after four apheresis cycles over the course of 24 weeks by flow cytometry.

RESULTS AND CONCLUSIONS

An acute lowering effect of LA on T cell and natural killer (NK) cell subpopulations expressing CD69 was observed. The non-classical and intermediate monocyte subsets as well as HLA-DR⁺ 6-sulfo LacNAc⁺ monocytes were significantly reduced during the apheresis procedure. We conclude that LA has the capacity to alter various immune cell subsets. However, LA has mainly short-term effects than long-term consequences on proportions of immune cells.

Single-cell immune profiling reveals long-term changes in myeloid cells and identifies a novel subset of CD9+ monocytes associated with COVID-19 hospitalization

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can result in severe immune dysfunction, hospitalization, and death. Many patients also develop long-COVID-19, experiencing symptoms months after infection. Although significant progress has been made in understanding the immune response to acute SARS-CoV-2 infection, gaps remain in our knowledge of how innate immunity influences disease kinetics and severity. We hypothesized that cytometry by time-of-flight analysis of PBMCs from healthy and infected subjects would identify novel cell surface markers and innate immune cell subsets associated with COVID-19 severity. In this pursuit, we identified monocyte and dendritic cell subsets that changed in frequency during acute SARS-CoV-2 infection and correlated with clinical parameters of disease severity. Subsets of nonclassical monocytes decreased in frequency in hospitalized subjects, yet increased in the most severe patients and positively correlated with clinical values associated with worse disease severity. CD9, CD163, PDL1, and PDL2 expression significantly increased in hospitalized subjects, and CD9 and 6-Sulfo LacNac emerged as the markers that best distinguished monocyte subsets amongst all subjects. CD9+ monocytes remained elevated, whereas nonclassical monocytes remained decreased, in the blood of hospitalized subjects at 3-4 months postinfection. Finally, we found that CD9+ monocytes functionally released more IL-8 and MCP-1 after LPS stimulation. This study identifies new monocyte subsets present in the blood of COVID-19 patients that correlate with disease severity, and links CD9+ monocytes to COVID-19 progression.

Quantitative and Functional Assessment of the Influence of Routinely Used Cryopreservation Media on Mononuclear Leukocytes for Medical Research

Quantitative and functional analysis of mononuclear leukocyte populations is an invaluable tool to understand the role of the immune system in the pathogenesis of a disease. Cryopreservation of mononuclear cells (MNCs) is routinely used to guarantee similar experimental conditions. Immune cells react differently to cryopreservation, and populations and functions of immune cells change during the process of freeze–thawing. To allow for a setup that preserves cell number and function optimally, we tested four different cryopreservation media. MNCs from 15 human individuals were analyzed. Before freezing and after thawing, the distribution of leukocytes was quantified by flow cytometry. Cultured cells were stimulated using lipopolysaccharide, and their immune response was quantified by flow cytometry, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). Ultimately, the performance of the cryopreservation media was ranked. Cell recovery and viability were different between the media. Cryopreservation led to changes in the relative number of monocytes, T cells, B cells, and their subsets. The inflammatory response of MNCs was altered by cryopreservation, enhancing the basal production of inflammatory cytokines. Different cryopreservation media induce biases, which needs to be considered when designing a study relying on cryopreservation. Here, we provide an overview of four different cryopreservation media for choosing the optimal medium for a specific task.

Monocyte subset distribution and surface expression of HLA-DR and CD14 in patients after cardiopulmonary resuscitation

Systemic inflammation is a major feature of the post-cardiac arrest syndrome. The three monocyte subpopulations are thought to play an important role in this inflammatory state because they are endowed with numerous pattern recognition receptors, such as CD14, that have been associated with ischemia-reperfusion injury. By contrast, an exaggerated antiinflammatory response has also been described following cardiac arrest, which may be mediated by downregulation of antigen presentation receptor HLA-DR. We report the composition of monocyte subpopulations and the expression of CD14 and HLA-DR following cardiac arrest. Blood specimens were collected from 32 patients at three timepoints in the first 48 h after cardiac arrest. Monocyte subset composition was determined by flow cytometry based on the expression of CD14, CD16, and HLA-DR. Monocyte subset composition and the expression of CD14 and HLA-DR were correlated with patient outcomes. The results were compared to 19 patients with coronary artery disease. Cardiac arrest patients showed a significant decline in the percentage of nonclassical monocytes. Monocyte CD14 expression was upregulated after 24 h and correlated with the time to return of spontaneous circulation. Downregulation of HLA-DR expression was observed mainly among classical monocytes and significantly correlated with the dose of norepinephrine used to treat shock. Downregulation of HLA-DR among nonclassical and intermediate monocytes was significantly associated with disease severity. Our data demonstrate the disturbance of monocyte subset composition with a significant decline in nonclassical monocytes at an early stage following cardiac arrest. Our findings suggest the simultaneous presence of hyperinflammation, as evidenced by upregulation of CD14, and monocyte deactivation, characterized by downregulation of HLA-DR. The extent of monocyte deactivation was significantly correlated with disease severity.

Monocyte subsets predict mortality after cardiac arrest

After successful cardiopulmonary resuscitation (CPR), many patients show signs of an overactive immune activation. Monocytes are a heterogeneous cell population that can be distinguished into 3 subsets by flow cytometry (classical monocytes [CM: CD14⁺⁺CD16^‐], intermediate monocytes [IM: CD14⁺⁺CD16⁺CCR2⁺] and non‐classical monocytes [NCM: CD14⁺CD16⁺⁺CCR2^‐]). Fifty‐three patients admitted to the medical intensive care unit (ICU) after cardiac arrest were included. Blood was taken on admission and after 72 h. The primary endpoint of this study was survival at 6 months and the secondary endpoint was neurological outcome as determined by cerebral performance category (CPC)‐score at 6 months. Median age was 64.5 (49.8‐74.3) years and 75.5% were male. Six‐month mortality was 50.9% and survival with good neurological outcome was 37.7%. Monocyte subset distribution upon admission to the ICU did not differ according to survival. Seventy‐two hours after admission, patients who died within 6 months showed a higher percentage of the pro‐inflammatory subset of IM (8.3% [3.8‐14.6]% vs. 4.1% [1.5–8.2]%; P = 0.025), and a lower percentage of CM (87.5% [79.9–89.0]% vs. 90.8% [85.9–92.7]%; P = 0.036) as compared to survivors. In addition, IM were predictive of outcome independent of time to ROSC and witnessed cardiac arrest, and correlated with CPC‐score at 6 months (R = 0.32; P = 0.043). These findings suggest a possible role of the innate immune system in the pathophysiology of post cardiac arrest syndrome.