Reduction in vesicant-induced cellular inflammation and hyperalgesia by local injection of corticotropin releasing factor in rabbit eyelid.
OBJECTIVE
This study tested the ability of corticotropin releasing factor (CRF) to mitigate inflammatory cell infiltration and hyperalgesia after a direct subcutaneous doxorubicin injection, a vesicant drug that causes localized inflammation at the site of subcutaneous exposure.


METHODS
This study used 62 adult New Zealand white rabbits.


METHODS
Doxorubicin (1-2 mg), followed by either CRF (300, 150, 75, 35, 20 or 10 microg in 1 ml saline) or saline only, was injected into pairs of rabbit eyelids. One set of doxorubicin and CRF treated eyelid pairs also received injection of a CRF antagonist into one eyelid. The eyelid tissue was assayed from 1-7 days later for morphometric changes in CD11b-positive inflammatory cell infiltrate. Hyperalgesia was assessed using the blink response to von Frey hair stimulation. Epidermal and dermal nerve fibers were visualized immunochemically using an antibody to PGP 9.5. The cellular localization of corticotropin releasing factor was determined immunohistochemically in eyelid tissue.


RESULTS
Doses of CRF from 35 to 150 microg significantly reduced inflammatory cell infiltration at all the post-injury time intervals examined, from 2 h post-injection up until 7 days. Doses of 10 and 20 microg CRF had no effect on local tissue inflammation caused by subcutaneous doxorubicin exposure. Doses of 35-150 microg CRF treatment significantly reduced the development of doxorubicin-induced hyperalgesia; this was maintained up to 4 days. Local CRF injections of 35-150 microg markedly reduced the doxorubicin induction of PGP-positive axons within the epidermis and subepidermis. CRF receptors were localized to the basal layer of the epithelium and to the subcutaneous nerve afferents.


CONCLUSIONS
Local injection of CRF, after a subcutaneous exposure to the vesicant drug doxorubicin, significantly reduced the infiltration of CD11b-positive cells and reduced doxorubicin-induced hyperalgesia in the treated eyelids. This reduction in hyperalgesia appears to be a local peripheral effect, reducing nerve fibers within the subepidermal treatment area. This demonstrates the potential clinical usefulness of CRF because it could be used post-injury as a locally injected treatment; this potent local anti-inflammatory agent may have wide applications following drug, chemical, physical or surgical injury.
McLoon
L K
LK
Department of Ophthalmology, University of Minnesota, Minneapolis 55455, USA. mcloo001@tc.umn.edu
Sandnas
A M
AM
Nockleby
K J
KJ
Wirtschafter
J D
JD
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage*; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage*; D004317:Doxorubicin / Q000633:toxicity; D006930:Hyperalgesia / Q000188:drug therapy*; D016177:Macrophage-1 Antigen / Q000032:analysis; D011817:Rabbits
D000893:Anti-Inflammatory Agents; D016177:Macrophage-1 Antigen; D004317:Doxorubicin; D003346:Corticotropin-Releasing Hormone