A cell‐penetrating CD40‐TRAF2,3 blocking peptide diminishes inflammation and neuronal loss after ischemia/reperfusion

Abstract

While the administration of anti‐CD154 mAbs in mice validated the CD40‐CD154 pathway as a target against inflammatory disorders, this approach caused thromboembolism in humans (unrelated to CD40 inhibition) and is expected to predispose to opportunistic infections. There is a need for alternative approaches to inhibit CD40 that avoid these complications. CD40 signals through TRAF2,3 and TRAF6‐binding sites. Given that CD40‐TRAF6 is the pathway that stimulates responses key for cell‐mediated immunity against opportunistic pathogens, we examined the effects of pharmacologic inhibition of CD40‐TRAF2,3 signaling. We used a model of ischemia/reperfusion (I/R)‐induced retinopathy, a CD40‐driven inflammatory disorder. Intravitreal administration of a cell‐penetrating CD40‐TRAF2,3 blocking peptide impaired ICAM‐1 upregulation in retinal endothelial cells and CXCL1 upregulation in endothelial and Müller cells. The peptide reduced leukocyte infiltration, upregulation of NOS2/COX‐2/TNF‐α/IL‐1β, and ameliorated neuronal loss, effects that mimic those observed after I/R in Cd40−/− mice. While a cell‐penetrating CD40‐TRAF6 blocking peptide also diminished I/R‐induced inflammation, this peptide (but not the CD40‐TRAF2,3 blocking peptide) impaired control of the opportunistic pathogen Toxoplasma gondii in the retina. Thus, inhibition of the CD40‐TRAF2,3 pathway is a novel and potent approach to reduce CD40‐induced inflammation, while likely diminishing the risk of opportunistic infections that would otherwise accompany CD40 inhibition.

Regulations of Retinal Inflammation: Focusing on Müller Glia

“…In zebrafish, however, TNF-α released by dying retinal neurons induces the resident MG to reprogram and re-enter the cell cycle ( Lahne and Hyde, 2017 ), indicating the possibility of treating retinal inflammation by manipulating the inflammatory responses of MG. CD40 is another member of the TNF family. Intravitreal administration of a cell-penetrating CD40-TRAF2,3 blocking peptide impaired CXCL1 upregulation in endothelial and MG, diminished inflammation and neuronal loss after ischemia/reperfusion, as mentioned above ( Portillo et al, 2021 ). CD40 expression in MG can be increased by diabetes ( Dierschke et al, 2020 ), which amplifies inflammation and induces death of retinal endothelial cells, an event key to the development of capillary degeneration and retinal ischemia ( Subauste, 2019 ).…”

“…Also, the vitamin thiamine confirms once more to be an effective agent in reducing diabetes-induced retinal damage ( Mazzeo et al, 2020 ). CXCL1 upregulation in MG, as well as endothelial, can be impaired by a peptide blocking the CD40-TNF receptor-associated factors (TRAF) 2,3 signaling ( Portillo et al, 2021 ), which can potentially be used for inflammation control. Some interesting studies show novel treatments targeting MG for retinal inflammation control.…”

Disruption of retinal inflammation and the development of diabetic retinopathy in mice by a CD40-derived peptide or mutation of CD40 in Müller cells

“…Cell-penetrating CD40-TRAF2,3-disrupting peptide The peptide consisted of the TRAF2,3 binding site of CD40 that was made cell permeable by linkage to TAT 47-57 cellpenetrating peptide [28]. The peptide was synthesised using D-amino acids following reverse amino acid sequence (retroinverso [ri] format).…”

Proteomic phenotyping of stimulated Müller cells uncovers profound pro-inflammatory signaling and antigen-presenting capacity

“…Here, we provide new insight in CD40 signaling in Müller cells, as IFNγ increased the expression of CD40, whereas TGFβ2, TGFβ3, TNFα and VEGF resulted in lower abundance of CD40 in pRMG. Future studies are needed to further investigate this issue, as the CD40 signaling pathway constitutes a possibility for therapeutical intervention (130). In contrast to the porcine dataset, we could not identify CD40 in the MIO-M1 cells.…”