Programming and memory dynamics of innate leukocytes during tissue homeostasis and inflammation

Immune Homeostasis Maintenance Through Advanced Immune Therapeutics to Target Atherosclerosis

Atherosclerosis remains the leading cause of coronary heart disease (CHD) with enormous health and societal tolls. Traditional drug development approaches have been focused on small molecule-based compounds that aim to lower plasma lipids and reduce systemic inflammation, two primary causes of atherosclerosis. However, despite the widely available lipid-lowering and anti-inflammatory small compounds and biologic agents, CHD prevalence still remains high. Based on recent advances revealing disrupted immune homeostasis during atherosclerosis pathogenesis, novel strategies aimed at rejuvenating immune homeostasis with engineered immune leukocytes are being developed. This chapter aims to assess basic and translational efforts on these emerging strategies for the effective development of atherosclerosis treatment, as well as key challenges in this important translational field.

Tumor Properties Mediate the Relationship Between Peripheral Blood Monocytes and Tumor-Associated Macrophages in Breast Cancer

In cancer patients, circulating monocytes show functional alterations. Since monocytes are precursors of tumor-associated macrophages (TAMs), TAMs ensuring tumor viability are potentially replenished through the recruitment of monocytes with specific properties. We demonstrated that locoregional metastasis and circulating factors, such as CD45-EpCAM + CD44 + CD24-/low circulating tumor cells, and serum MCP-1 and HMGB1 were statistically associated with modulation of the monocyte features in breast cancer patients. The count of circulating CD45-EpCAM + cells correlated with CD68+, CD163 + monocyte in blood, and with density of CD68 + TAM in breast cancer tumors. Overall, the relationship between monocytes and TAMs is mediated by the tumor in breast cancer patients.

Resolving monocytes generated through TRAM deletion attenuate atherosclerosis

Polarization of low-grade inflammatory monocytes facilitates the pathogenesis of atherosclerosis. However, underlying mechanisms as well as approaches for resolving monocyte polarization conducive to the regression of atherosclerosis are not well established. In this report, we demonstrate that TRIF-related adaptor molecule (TRAM) mediated monocyte polarization in vivo and in vitro. TRAM controlled monocyte polarization through activating Src family kinase c-SRC, which not only induces STAT1/STAT5-regulated inflammatory mediators CCR2 and SIRP-α but also suppresses PPARγ-regulated resolving mediator CD200R. Enhanced PPARγ and Pex5 due to TRAM deficiency facilitated peroxisome homeostasis and reduction of cellular reactive oxygen species, further contributing to the establishment of a resolving monocyte phenotype. TRAM-deficient monocytes propagated the resolving phenotype to neighboring monocytes through CD200R-mediated intercellular communication. At the translational level, we show that TRAM-deficient mice were resistant to high-fat diet-induced pathogenesis of atherosclerosis. We further document that intravenous transfusion of TRAM-deficient resolving monocytes into atherosclerotic mice potently reduced the progression of atherosclerosis. Together, our data reveal that targeting TRAM may facilitate the effective generation of resolving monocytes conducive for the treatment of atherosclerosis.

The population characteristics of the main leukocyte subsets and their association with chronic diseases in a community-dwelling population: a cross-sectional study

Aim:

To analyse the characteristics of the main leukocyte subsets and elucidate their distributions amongst the natural population. We wanted to determine whether leukocyte subsets are potential biomarkers to evaluate the risk of common chronic diseases.

Background:

The peripheral blood leukocyte count is a routine exam performed to detect pathogen infections. Recently, subsets of white blood cells and their homeostasis have shown strong associations with some chronic diseases. Therefore, studies aiming to discover whether the distribution of leukocyte counts and its subsets are useful for predicting health conditions are worthwhile.

Methods:

This cross-sectional study analysed 10 564 residents from the basic public health service project of the Health Checkup Program performed by the BaiYun Community Health Service Center. Data on demographic information, physical measurements, medical history, and routine blood examination parameters were collected using questionnaires and health check-ups. Restricted cubic spline incorporated into logistic regression analysis was performed to evaluate the association between subsets of leukocytes and common chronic diseases.

Findings:

The counts of leukocytes and their subsets in males were higher than those in females amongst all age groups, yet the percentages of lymphocytes and neutrophils did not present sex-specific differences. A low lymphocyte count and percentage were associated with old age. The neutrophil-to-lymphocyte ratio (NLR) in patients with hypertension was higher than that in the non-hypertensive population. The risk of NLR in the top quartiles was 1.17-fold higher than that in people in the lowest quartiles.

Conclusions:

The distributions of the white blood cell count and percentage were associated with age, sex, and body mass index (BMI). In addition to the immune barrier for pathogens, the NLR or monocyte-to-lymphocyte ratio (MLR) may be potentially used to indicate the risk of some chronic non-communicable diseases. Homeostasis of subsets of leukocytes may be an important biomarker for body health conditions.

Effects of Smoking on Volume, Conductivity and Scatter Parameters of Leukocytes

Aim: In this study, we aimed to determine changes in leukocytes volume, conductivity and scatter parameters in smokers compared to non-smokers. Methods: A total of 117 individuals (45 smokers and 72 non-smokers) were included in the study. While those who smoked at least 10 pack-years were included in the case group, those who never smoked at all were included in the control group. Results: While there was a statistically significant difference in mean neutrophil volume, mean neutrophil conductivity, mean lymphocyte conductivity, mean lymphocyte scatter, mean monocyte volume, mean monocyte conductivity, mean monocyte scatter, mean eosinophil conductivity values between the two groups, there was no statistically significant difference in mean neutrophil scatter, mean lymphocyte volume, mean eosinophil volume, mean eosinophil scatter values between the two groups. Conclusion: This study showed that smoking affected volume, conductivity and scatter parameters. Clinicians should consider whether the patient smokes if they want to diagnose any diseases using volume, conductivity and scatter parameters. Keywords: smoking, leukocytes, conductivity, scattering, neutrophils

Enhanced Neutrophil Immune Homeostasis Due to Deletion of PHLPP

Neutrophils are known to adopt dynamic and distinct functional phenotypes involved in the modulation of inflammation and immune homeostasis. However, inter-cellular signaling mechanisms that govern neutrophil polarization dynamics are not well understood. Employing a novel model of PHLPP deficient mice, we examined how neutrophils deficient in PHLPP may uniquely modulate immune defense and the host response during acute colitis. We found that PHLPP^-/- mice were protected from dextran sodium sulfate (DSS)-induced septic colitis characterized by minimal body weight-loss, alleviated colon tissue destruction and reduced clinical symptoms. PHLPP^-/- neutrophils have enhanced immune homeostasis as compared to WT neutrophils, reflected in enhanced migratory capacity toward chemoattractants, and reduced expression of inflammatory mediators due to elevated phosphorylation of AKT, STAT1, and ERK. Further, adoptive transfer of PHLPP deficient neutrophils to WT mice is sufficient to potently alleviate the severity of DSS-induced colitis. Our data reveal that PHLPP deficient neutrophils can be uniquely reprogrammed to a state conducive to host inflammation resolution. As a consequence, PHLPP^-/- neutrophils can effectively transfer immune homeostasis in mice subjected to acute colitis. Our findings hold significant and novel insights into the mechanisms by which neutrophils can be effectively reprogrammed into a homeostatic state conducive for treating acute injuries such as septic colitis.

Establishment of reference intervals for complete blood count parameters in venous blood for children in the Xiamen area, China

OBJECTIVES

To observe changes in the complete blood count (CBC) venous blood parameters of healthy children and establish appropriate reference intervals (RIs).

METHODS

Overall, 4066 healthy children were selected and divided into four groups: infants, toddlers, preschool-age children and school-age children. Venous blood was analysed for 17 parameters. Outlier data for each parameter were eliminated and RIs were established based on the Clinical and Laboratory Standards Institute C28-A3c guideline.

RESULTS

The RIs for certain parameters differed among the different age groups. The white blood cell (WBC) count differed among the four age groups. The variation trends for absolute neutrophil count in all age groups were opposite to those for WBC and absolute lymphocyte count. The mean absolute eosinophil count values were significantly higher in the infant group than in the other groups. The RIs for red blood cell were identical across all age groups except in infants. The mean Hb level for infants was significantly lower than that for the other age groups. The mean and RI for platelet count were significantly higher in the infant group than in the other groups.

CONCLUSIONS

There are dynamic variations in the values reported for measurements of most CBC parameters in children. Hence, such results should always be interpreted according to the child's age. Thus establishing appropriate RIs for different age groups in paediatrics is essential.

Suppression of Neutrophil Antimicrobial Functions by Total Particulate Matter From Cigarette Smoke

Chronic cigarette smoking is widely known to alter immune functions and compromise host defense against microbial infection. Neutrophils play an essential role in the immune defense against microbial pathogens and also participate in the development of the inflammatory responses. However, there is limited information about the effects of cigarette smoking on neutrophil response. In this study, cultured bone marrow neutrophils were exposed to total particulate matter (TPM) from cigarette smoke. We found that TPM not only reduced LPS-induced TNFα production, but also suppressed neutrophil bactericidal activity. We also observed that TPM priming reduced the expression of NADPH oxidase component gp91 and iNOS, molecules important for bacterial killing. Mechanistically, we documented that TPM-primed neutrophils have reduced STAT1 activation following subsequent LPS challenge. STAT1 is a key transcription factor responsible for the expression of inflammatory genes as well as gp91 and iNOS. Collectively, reduced STAT1 activation and reduced NADPH oxidase/iNOS may potentially explain the compromised anti-microbial function of TPM-programmed neutrophils. Taken together, our findings reveal that the key innate immune neutrophil is subject to reprogramming by smoking to adopt an immune-suppressed state, potentially responsible for chronic smoking-mediated immunosuppression.

Regulation of immune cell signaling by activated protein C

Innate immune cells are an essential part of the host defense response, promoting inflammation through release of proinflammatory cytokines or formation of neutrophil extracellular traps. While these processes are important for defense against infectious agents or injury, aberrant activation potentiates pathologic inflammatory disease. Thus, understanding regulatory mechanisms that limit neutrophil extracellular traps formation and cytokine release is of therapeutic interest for targeting pathologic diseases. Activated protein C is an endogenous serine protease with anticoagulant activity as well as anti-inflammatory and cytoprotective functions, the latter of which are mediated through binding cell surface receptors and inducing intracellular signaling. In this review, we discuss certain leukocyte functions, namely neutrophil extracellular traps formation and cytokine release, and the inhibition of these processes by activated protein C.