Critical role for PI3Kγ-dependent neutrophil reactive oxygen species in WKYMVm-induced microvascular hyperpermeability

Abstract

PI3K has been indicated in regulating microvascular permeability changes during inflammation. However, its role in neutrophil‐driven microvascular leakage in acute inflammation remains unclear. Using intravital microscopy in mice, we examined the role of PI3Kγ and PI3Kδ in formyl peptide WKYMVm‐ and chemokine CXCL2‐induced permeability changes and assessed simultaneously neutrophil adhesion and emigration in post‐capillary venules of murine cremaster muscle. We found a PI3Kγ‐specific mechanism in WKYMVm‐induced but not CXCL2‐induced microvascular hyperpermeability. The increased microvascular permeability triggered by WKYMVm was not entirely due to neutrophil adhesion and emigration in cremasteric microvasculature in different PI3K transgenic mouse strains. The PI3Kγ‐specific hyperpermeability was neutrophil‐mediated as this was reduced after depletion of neutrophils in mouse circulation. Chimeric mice with PI3Kγ‐deficient neutrophils but wild‐type endothelium also showed reduced hyperpermeability. Furthermore, we found that the catalytic function of PI3Kγ was required for reactive oxygen species (ROS) generation in neutrophils stimulated with WKYMVm. Pharmacological scavenging PI3Kγ‐dependent ROS in the tissue eliminated the discrepancy in hyperpermeability between different PI3K transgenic mice and alleviated WKYMVm‐induced microvascular leakage in all mouse strains tested. In conclusion, our study uncovers the critical role for PI3Kγ‐dependent ROS generation by neutrophils in formyl peptide‐induced microvascular hyperpermeability during neutrophil recruitment.

WKYMVm Works by Targeting Immune Cells

“…32 By activating FPR1 and FPR2, WKYMVm is able to activate phospholipase C (PLC) and phosphatidylinositol 3-kinase γ (PI3Kγ) signaling pathways in immune cells. [33][34][35] The activation of PLC can hydrolyze membrane-bound phosphoinositol-4,5-bisphosphate (PIP2) to diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), and then activate protein kinase C (PKC) to induce superoxide production. IP3 mediates the release of stored Ca 2+ in cells to promote immune cell degranulation.…”

“… 34 After PI3Kγ is activated by WKYMVm through FPR1 and FPR2, on the one hand, it can activate PKC to promote the production of superoxide, and on the other hand, it can participate in the superoxide production, chemotaxis, phagocytosis and transcriptional regulation of immune cells by activating protein kinase B (AKT). 34 , 35 Binding to FPR1 and FPR2, WKYMVm can also activate Rho, which is involved in regulating chemotaxis and phagocytosis, and Ras, which activates the mitogen-activated protein kinase (MAPK) signaling pathway, thereby participating in the regulation of superoxide production, chemotaxis, phagocytosis, and transcriptional regulation. 34 Unlike the functional diversity of FPR1 and FPR2, the functions of FPR3 are currently less studied.…”

“… 41 In addition, during the chemotaxis of neutrophils, WKYMVm enhances the leakage of microvessels by promoting the production of PI3Kγ dependent ROS, making it easier for neutrophils to pass through microvessels and reach the inflammatory sites. 35 …”

Combination Therapy of Placenta-Derived Mesenchymal Stem Cells with WKYMVm Promotes Hepatic Function in a Rat Model with Hepatic Disease via Vascular Remodeling

“…Topical application of WKYMVm intensified cutaneous wound healing in streptozotocin (STZ)-induced diabetes via the remodeling of von Willebrand factor (vWF)-positive vessels [ 27 ]. For treatment of bronchopulmonary dysplasia (BPD), a chronic lung disease, WKYMVm was administered through intraperitoneal injection [ 28 ]. Additionally, polylactic-co-glycolic acid (PLGA) could form microspheres encapsulating WKYMVm and consistently released peptides following administration to ischemic hind limbs, extending angiogenic stimulation [ 29 ].…”

Bam32/DAPP1-Dependent Neutrophil Reactive Oxygen Species in WKYMVm-Induced Microvascular Hyperpermeability

“…In addition to its effects on the immune system, WKYMVm functions in large vessels of cardiovascular system by reversing LPS-induced vascular hyporeactivity to phenylephrine in mouse aorta through decreasing the production of nitric oxide (20). One of our previous studies showed that PI3Kγ, an upstream regulator of Bam32 signaling in neutrophils, regulates WKYMVm-induced microvascular hyperpermeability (21). Other than that, the effect of WKYMVm on the crosstalk between the immune system and microvasculature is largely unknown.…”