Neutrophil peptide 1 accelerates the clearance of degenerative axons during Wallerian degeneration by activating macrophages after peripheral nerve crush injury

Macrophages play an important role in peripheral nerve regeneration,but the specific mechanism of regeneration is still unclear.Our preliminary findings indicated that neutrophil peptide 1 is an innate immune peptide closely involved in peripheral nerve regeneration.However,the mechanism by which neutrophil peptide 1 enhances nerve regeneration remains unclear.This study was designed to investigate the relationship between neutrophil peptide 1 and macrophages in vivo and in vitro in peripheral nerve crush injury.The functions of RAW 264.7 cells we re elucidated by Cell Counting Kit-8 assay,flow cytometry,migration assays,phagocytosis assays,immunohistochemistry and enzyme-linked immunosorbent assay.Axonal debris phagocytosis was observed using the CUBIC(Clear,Unobstructed Brain/Body Imaging Cocktails and Computational analysis)optical clearing technique during Wallerian degeneration.Macrophage inflammatory factor expression in different polarization states was detected using a protein chip.The results showed that neutrophil peptide 1 promoted the prolife ration,migration and phagocytosis of macrophages,and CD206 expression on the surfa ce of macrophages,indicating M2 polarization.The axonal debris clearance rate during Wallerian degeneration was enhanced after neutrophil peptide 1 intervention.Neutrophil peptide 1 also downregulated inflammatory factors interleukin-1α,-6,-12,and tumor necrosis factor-αin invo and in vitro.Thus,the results suggest that neutrophil peptide 1 activates macrophages and accelerates Wallerian degeneration,which may be one mechanism by which neutrophil peptide 1 enhances peripheral nerve regeneration.

A proteomic approach to better understand the role of human neutrophil peptides in the NSCLC microenvironment

Aim:Although treatment of lung cancer,one of the deadliest diseases worldwide,with immune checkpoint inhibitors(ICIs)has shown promising outcomes,these survival outcomes are only observed in a relatively small subset of lung cancer patients.In a previous study,we elucidated that the presence of human neutrophil peptide(HNP)1,2 and 3 in non-small cell lung cancerous(NSCLC)biopsies is associated with a clinical response towards treatment with PD-1/PD-L1 immune checkpoint inhibitors.Furthermore,HNP1 has shown in vitro an immune-activated function towards lung cancer cells,but the specific role of HNP1 in(lung)cancer is still unknown.The aim of this study was to provide a better understanding of HNP1 in an NSCLC microenvironment.Methods:To gain better insights into the role of HNP1 on cancer growth and to unravel immune responses,in vitro(SILAC-labelled)A549/PBMC(from three healthy donors)cocultures were set up and treated/not treated with HNP1.After 5 days,both secretome and cellular analysis using mass spectrometry were performed on these cocultures.After protein identification in all different tested conditions,pathway analyses(MetaCoreTM)were performed to investigate the biological significance of HNP1 stimulation on the A549/PBMC cocultures.The proteomic outcomes were confirmed by multiplex ELISA for a proinflammatory cytokine panel(TNF-α,IL-1β,IL-2,IL-4,IL-6,IL-12p70 and IL-18).Results:A number of biological pathways and process networks were observed to be upregulated after treatment of the coculture with HNP1.HNP1 stimulation leads to an increase in pathways and proteins stimulating chemotaxis(including plasmin signaling,leucocyte recruitment,CCL2 and CXCL8 expression),proinflammatory cytokine secretion(including IL-1β,IL-6 and TNF-α),dendritic cell(DC)maturation,phagocytosis and antigen presentation,leading to a more efficient adaptive anti-tumoral immunity.Conclusion:These results enhance our understanding of the role of HNP1 in the tumor microenvironment and suggest that HNP1 may be able to induce tumor necrosis by inducing prostimulatory immune responses.

The in vitro inhibitory effect of human neutrophil peptide-1 on human immunodeficiency virus type 1

In order to clarify, the mechanism of inhibition of human neutrophil peptide-1 （ HNP-1 ） on hu- man immunodeficiency vires type 1 （HIV-1 ）, CD4^ ＋ cells were used as the target cells for acute infection with HIV-1, and experiments were peffomed separately with the interaction of different concentrations of HNP-1 with free vires particles, un-infected and infected CD4^＋ cells. The activity of reverse transcriptase （RT） in the supematant of cell cultures of different lots of experiments were then assayed accordingly, and the toxicity effect on human lymphocytic cells MT4 was measured by MTT assay. The experimental results showed that pre-incubation of HNP-1 with the concentrated stock of vires could block the binding of vires to target cells with EC50 of 2.49 μg/ml, while pre-treatment of CD4^＋ cells with HNP- 1 prior to inoculation could reduce the ability of cells to bind vires with EC50 of 20.7 μg/ml. In addition, When culturing the infected CD4^＋ cells in the continuous presence of various concentrations of HNP-1 added immediately after infection, HNP-1 exhibited modest inhibitory effect on viral replication with reduced RT activities in comparison with those of the control group （ P 〈 0.05 at 100 μg/ml of the highest concentration） . No cytotoxieity effect of HNP-1 was observed as demonstrated by MTT assay. These results indicate that HNP-1 exerts anti-HIV activity by at least two levels： direct inactivation of vires particles and effect on the ability of target cells to bind with viruses. The evaluation of two parameters, inhibitoty effect and the cytotoxicity renders HNP-1 an available candidate for anti-HIV therapeutic agent.