Eosinophil ribonucleases and their cutaneous lesion-forming activity.

Eosinophil granule proteins are deposited in cutaneous lesions in many human diseases, but how these proteins contribute to pathophysiology is obscure. We injected eosinophil cationic protein (ECP or RNase 3), eosinophil-derived neurotoxin (EDN or RNase 2), eosinophil peroxidase (EPO), and major basic protein-1 (MBP1) intradermally into guinea pig and rabbit skin. ECP and EDN each induced distinct skin lesions at >or=2.5 microM that began at 2 days, peaking at approximately 7 days and persisting up to 6 wk. These lesions were ulcerated (ECP) or crusted (EDN) with marked cellular infiltration. EPO and MBP1 (10 microM) each produced perceptible induration and erythema with moderate cellular infiltration resolving within 2 wk. ECP and EDN localized to dermal cells within 2 days, whereas EPO and MBP1 remained extracellular. Overall, cellular localization and RNase activity of ECP and EDN were critical for lesion formation; differential glycosylation, net cationic charge, or RNase activity alone did not account for lesion formation. Ulcerated lesions from patients with the hypereosinophilic syndrome showed ECP and EDN deposition comparable to that in guinea pig skin. In conclusion, ECP and EDN disrupt skin integrity and cause inflammation. Their presence in ulcerative skin lesions may explain certain findings in human eosinophil-associated diseases.

Interactions of eosinophil granule proteins with skin: limits of detection, persistence, and vasopermeabilization.

BACKGROUND: Eosinophil granule proteins, including eosinophil cationic protein (ECP), eosinophil-derived neurotoxin (EDN), eosinophil peroxidase (EPO), and major basic protein (MBP), are prominently deposited in skin in several cutaneous disorders and likely contribute to disease pathology. OBJECTIVE: We sought to determine the limit of detection, persistence, and vasopermeabilization activity of the eosinophil granule proteins in skin. METHODS: The eosinophil granule proteins were injected intradermally. Their minimum detectable concentrations in human surgical waste skin and their persistence in guinea pig skin were determined by indirect immunofluorescence. Vasopermeabilization activity in the guinea pig without and with H1 antihistamine (pyrilamine maleate) pretreatment was assessed by extrusion of Evans blue dye-treated plasma. RESULTS: The lowest detectable cutaneous concentrations were 0.05 micromol/L EPO, 0.1 micromol/L MBP, 0.25 micromol/L ECP, and 1 micromol/L EDN. Granule proteins persisted in guinea pig skin in vivo for 1 week (EPO), 2 weeks (ECP), 2.5 weeks (EDN), and 6 weeks (MBP). Each of the eosinophil granule proteins increased cutaneous vasopermeability in a concentration-dependent manner. The potency of vasopermeabilization induced by each granule protein was comparable with that of histamine. Pyrilamine maleate pretreatment of guinea pigs did not alter increased vasopermeability induced by ECP and EDN but significantly inhibited that induced by EPO and MBP. CONCLUSIONS: Micromolar concentrations of eosinophil granule proteins are often deposited in skin in eosinophil-associated cutaneous disorders such as atopic dermatitis. These pathophysiologically relevant concentrations of eosinophil granule proteins cause increased cutaneous vasopermeability (both by means of histamine-independent and histamine-dependent mechanisms) and might alter cutaneous function for days to weeks.