CXCR2 inhibitors: Friends or Foes?

Abstract

Purpose : Vitreous IL-1β, TNFα, and angiogenic CXCR2 ligands are upregulated in human angiogenic retinopathies and in mouse oxygen-induced retinopathy (OIR). We have reported upregulated expression of CXCR2 ligands in human Müller (HMC) and retinal microvascular endothelial cells (HRMEC) after direct or reciprocal treatment with conditioned media (CM) following stimulation with IL-1β or TNFα, and that CXCR2 KO mice have 30% less pre-retinal neovascularization (PRNV) in OIR.

We aimed to 1) explore CXCR2 ligand and VEGF protein levels in the CM from IL-1β- or TNFα-stimulated HMC; 2) test HMC CM effects on HRMEC proliferation (and if this could be blocked by CXCR2 inhibitors (CXCR2i)); 3) measure systemic CXCR2i effects on PRNV in OIR; and 4) assess the long-term effects of deficient CXCR2 signaling in CXCR2 KO mice.

Methods : 12hr serum-starved HMC were stimulated with 1ng/mL of IL-1β, TNFα, or 0.1%BSA for 2hrs, the media was replaced, and CM collected after 6hr. A membrane-based sandwich immunoassay was used to quantify CXCL1, 5, 8 and VEGF proteins. The HMC CM was added to HRMEC in the presence or absence of CXCR2i (SB225002 (SB) and Reparixin) and proliferation quantified. CXCR2 WT mice in OIR model received daily intraperitoneal injections of SB225002 or DMSO vehicle control from p12-p17. Neovascular and avascular areas were quantified in isolectinB4 stained p17 retinas. Electroretinography, optokinetic reflex, fluorescein angiography and IHC were compared in adult CXCR2 KO and WT mice.

Results : CM from IL-1β or TNFα -stimulated HMC contained higher levels of CXCL8, 1, and/or 5, but not VEGF, and induced HRMEC proliferation. This effect was reduced by co-treatment with CXCR2i. Systemic SB in OIR reduced PRNV by 30% suggesting that CXCR2 inhibitors may help retinopathies. However, CXCR2 adult mice develop neutrophilia, increased PMN in vascular lumina abutting venular walls in several tissues (i.e., lung, liver, retina), delayed blood flow to the retina, alterations in Iba1+ cell distribution and activation, decreased ERG a- and b-wave amplitudes, and reduced visual acuity.

Conclusions : CXCR2 inhibitors are in clinical trials or cancer and other chronic conditions. Although attractive as therapies for retinopathy, we fear that chronic CXCR2 inhibition may compromise perfusion and induce functional damage in the retina (and potentially other organs/tissues) which could threaten vision and human health. Their safety should be explored further.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.