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.

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.