Fibrocytes are monocyte-derived fibroblast like cells that participate in wound healing, but little is known about what initiates fibrocyte differentiation. Blood platelets contain 60-100-mer polymers of phosphate groups called polyphosphate, and when activated, platelets induce blood clotting (the first step in wound healing) in part by the release of polyphosphate. We find that activated platelets release a factor that promotes fibrocyte differentiation. The factor is abolished by treating the crude platelet factor with the polyphosphate-degrading enzyme polyphosphatase, and polyphosphate promotes fibrocyte differentiation. Macrophages and recruited neutrophils also potentiate wound healing, and polyphosphate also promotes macrophage differentiation and induces chemoattraction of neutrophils. In support of the hypothesis that polyphosphate is a signal that affects leukocytes, we observe saturable binding of polyphosphate to these cells. Polyphosphate also inhibits leukocyte proliferation and proteasome activity. These results suggest new roles for extracellular polyphosphate as a mediator of wound healing and inflammation and also provide a potential link between platelet activation and the progression of fibrosing diseases.

Compared to neutrophil chemoattractants, relatively little is known about the mechanism neutrophils use to respond to chemorepellents. We previously found that the soluble extracellular protein dipeptidyl peptidase IV (DPPIV) is a neutrophil chemorepellent. In this report, we show that an inhibitor of the protease activated receptor 2 (PAR2) blocks DPPIV-induced human neutrophil chemorepulsion, and that PAR2 agonists such as trypsin, tryptase, 2f-LIGRL, SLIGKV, and AC55541 induce human neutrophil chemorepulsion. Several PAR2 agonists in turn block the ability of the chemoattractant fMLP to attract neutrophils. Compared to neutrophils from male and female C57BL/6 mice, neutrophils from male and female mice lacking PAR2 are insensitive to the chemorepulsive effects of DPPIV or PAR2 agonists. Acute respiratory distress syndrome (ARDS) involves an insult-mediated influx of neutrophils into the lungs. In a mouse model of ARDS, aspiration of PAR2 agonists starting 24 h after an insult reduce neutrophil numbers in the bronchoalveolar lavage (BAL) fluid, as well as the post-BAL lung tissue. Together, these results indicate that the PAR2 receptor mediates DPPIV-induced chemorepulsion, and that PAR2 agonists might be useful to induce neutrophil chemorepulsion.

The movement of neutrophils between blood and tissues appears to be regulated by chemoattractants and chemorepellents. Compared to neutrophil chemoattractants, relatively little is known about neutrophil chemorepellents. Slit proteins are endogenously cleaved into a variety of N and C terminal fragments, and these fragments are neuronal chemorepellents and inhibit chemoattraction of many cell types, including neutrophils. In this report, we show that the 140 kDa N-terminal Slit2 fragment (Slit2-N) is a chemoattractant and the 110 kDa N-terminal Slit2 fragment (Slit2-S) is a chemorepellent for human neutrophils. The effects of both Slit2 fragments were blocked by antibodies to the Slit2 receptor Robo1 or the Slit2 co-receptor syndecan-4. Slit2-N did not appear to activate Ras, but increased PIP3 levels. Slit2-N induced chemoattraction was unaffected by Ras inhibitors, reversed by PI3 kinase inhibitors, and blocked by cdc42 and Rac inhibitors. In contrast, Slit2-S activated Ras but did not increase PIP3 levels. Slit2-S induced chemorepulsion was blocked by Ras and Rac inhibitors, not affected by PI3 kinase inhibitors, and was reversed by cdc42 inhibitors. Slit2-N but not Slit2-S increased neutrophil adhesion, myosin II light chain phosphorylation, and polarized actin formation and single pseudopods at the leading edge of cells. Slit2-S induced multiple pseudopods. These data suggest that Slit-2 isoforms use similar receptors but different intracellular signaling pathways, and have different effects on the cytoskeleton and pseudopods, to induce neutrophil chemoattraction or chemorepulsion.

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PCNSL in immune competent patients is a rare extra-nodal non-Hodgkin lymphoma that accounts for 3–4% of newly diagnosed CNS tumors. Treatment consists of high-dose methotrexate (HD-MTX) based polychemotherapy regimen with or without brain radiation. There are few reported cases supporting the use of HD-MTX as a treatment option in such patients with impaired renal function. The objective of this study was to analyze outcomes and tolerance of HD-MTX based chemotherapy regimen (HD-MTX, rituximab and temozolomide, MRT) in patients with PCNSL and renal impairment. We present five patients with median age 63 (range 40 – 67) at diagnosis, with varying degrees of renal impairments, were all treated with and tolerated well of MRT. They are all alive and have been on observation. Cases 2 & 3 had a one functioning kidney and achieved complete responses (CR) without toxicities. Case 1, with history of grade 3 renal insufficiency during his initial HD-MTX and received carboxypeptidase G2 rescue, tolerated re-treatment with MRT at PCNSL recurrence and achieved a partial response (PR) that has been stable for 44 months. Case 4, who had a cadaver-transplanted kidney, was able to get a CR after 8 treatment with MRT. Case 5, with grade 3 chronic kidney disease from type II diabetes mellitus, achieved CR with MRT with slowing down of his MTX clearance. Literature review for reports with PCNSL and renal impairment treated with HD-MTX through March 31, 2022 identified eight cases and their responses and adverse effects summarized. Due to the low number of published cases and limitation of a retrospective analysis, it is impossible to draw a conclusion on the impact of impaired renal function on the tolerance of HD-MTX treatment of PCNSL. However, our findings indicate that a subset of the patients may still benefit from treatment with HD-MTX based chemotherapy.