Primed polymorphonuclear leukocytes from hemodialysis patients enhance monocyte transendothelial migration

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Monocyte to high-density lipoprotein ratio and cardiovascular events in patients on peritoneal dialysis

BACKGROUND AND AIMS

The monocyte to high-density lipoprotein cholesterol ratio (MHR) is associated with multiple cardiovascular diseases. However, the role of the MHR in predicting cardiovascular diseases in patients on peritoneal dialysis remains unclear.

METHODS AND RESULTS

Eight hundred and eighty incident peritoneal dialysis patients were enrolled from November 1, 2005, to February 28, 2017, and followed until May 31, 2017. Primary outcomes were cardiovascular events. Using the X-tile program, these patients were divided into three groups according to the MHR. Kaplan-Meier method and Cox regressions were used for survival analysis. During a median follow-up period of 26 months (interquartile range: 12-39 months), 139 cardiovascular events were recorded. After multiple adjustment, the high MHR group was associated with a 1.97-fold increase in the cardiovascular events hazard compared to that of the low group in the overall population (hazard ratio: 1.97; 95% CI, 1.19-3.28; P = 0.009). Subgroup analysis demonstrated that the association between the MHR and a higher risk of cardiovascular events was strongest in the subgroup of patients with diabetes (P for interaction = 0.004). In this subgroup, the high MHR group was found to be associated with a higher risk of cardiovascular events compared to the low group (hazard ratio: 7.69; 95% CI, 2.76-21.47).

CONCLUSION

This study suggests that the MHR is independently associated with the risk of cardiovascular events in patients undergoing peritoneal dialysis, and diabetes status can influence the association between the MHR and the risk of cardiovascular events.

Monocytes in Uremia

Monocytes play an important role in both innate immunity and antigen presentation for specific cellular immune defense. In patients with chronic renal failure, as well as those treated with maintenance hemodialysis, these cells are largely dysregulated. There is a large body of literature on monocyte alterations in such patients. However, most of the publications report on small series, there is a vast spectrum of different methods and the heterogeneity of the data prevents any meta-analytic approach. Thus, a narrative review was performed to describe the current knowledge. Monocytes from patients with chronic renal failure differ from those of healthy individuals in the pattern of surface molecule expression, cytokine and mediator production, and function. If these findings can be summarized at all, they might be subsumed as showing chronic inflammation in resting cells together with limited activation upon immunologic challenge. The picture is complicated by the fact that monocytes fall into morphologically and functionally different populations and population shifts interact heavily with dysregulation of the individual cells. Severe complications of chronic renal failure such as impaired immune defense, inflammation, and atherosclerosis can be related to several aspects of monocyte dysfunction. Therefore, this review aims to provide an overview about the impairment and activation of monocytes by uremia and the resulting clinical consequences for renal failure patients.

The clinical consequences of neutrophil priming

PURPOSE OF REVIEW

Neutrophils priming has been long studied in vitro. Recent studies describe it in vivo. In pathophysiological conditions, complex, heterogeneous characteristics of priming are described in the last few years.

RECENT FINDINGS

Priming can occur systemically when insults such as sepsis or trauma result in an array of circulating mediators and circulating primed neutrophils seem to exert detrimental effects either directly, or indirectly by interacting with other cells, thereby contributing to the development of organ dysfunction. Local priming of neutrophils augments their ability to clear infection, but may also lead to local bystander tissue injury, for example, in the inflamed joint. The complexity, heterogeneity and dynamic nature of inflammatory responses and the accessibility of cells from local sites make neutrophil priming challenging to study in human disease; however, recent advances have made significant progress to this field.

SUMMARY

Herein, we summarize the literature regarding neutrophil priming in selected conditions. In some diseases and in the setting of specific genetic influences, the priming repertoire seems to be restricted, with only some neutrophil functions upregulated. A greater understanding of the nature of neutrophil priming and its role in human disease is required before this process becomes tractable to therapeutic intervention.