Eosinophil Chemotaxis and Anterior Uveitis from Topical Dimoprit and Nordimoprit
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Eosinophil Chemotaxis and Anterior Uveitis From Topical Dimoprit and Nordimoprit Joel S. Mindel*tt Alan H. Friedmaat Tali Haimov,f Alex D. Kharlamb,*t and Jonathan M. Freilichj- Topical application of the H2-histamine receptor agonist, dimaprit (S-[4-N,N-dimethylaminopro- pyl]isothiourea), produced eosinophil chemotaxis into the anterior segment of rabbit eyes only when an H2-antagonist was co-administered. Nordimaprit (S-[4-N,N-dimethylaminoethyl]isothiourea), a structural homologue of dimaprit that lacked activity at histamine receptors, produced eosinophil chemotaxis whether or not an H2-antagonist was co-administered. Onset of eosinophil chemotaxis began after 2 or more days of treatment, and was accompanied by corneal edema, opacifkation, and ocular inflammation. There was no concurrent eosinophilia in the peripheral blood or in the conjunctiva. The response occurred in pigmented and albino rabbit eyes, and was facilitated by prior co-administration of proparacaine eye drops. Another dimaprit homologue without activity at histamine receptors, homodimaprit (S-[4-N,N- dimethylaminobutyl]isothiourea), did not produce eosinophil chemotaxis when applied topically, nor did the H2-agonists impromidine, histamine, or 4-methylhistamine, whether co-administered with an H2- antagonist or not. It was concluded that dimaprit and nordimaprit produced a selective eosinophil che- motaxis unrelated to H,- and H2-histamine receptor activity. However, the H2-agonist activity of dimaprit appeared to inhibit this response unless neutralized by an H2-antagonist. Topical application of dimaprit with an H2-antagonist or nordimaprit alone may allow large numbers of non-degranulated eosinophils, free of other cell types, to be harvested from the aqueous humor. Invest Ophthalmol Vis Sci 27:1504- 1511,1986 Histamine is both an Hr and H2-receptor agonist. histamine produced random eosinophil migration Drugs that are more specific for each of these receptors (chemokinesis) and reduced true chemotaxis. Jones and have been synthesized. For example, dimaprit,1 im- Kay13 reported that an initial exposure to histamine 2 3 promidine, and 4-methylhistamine are primarily H2- was chemotactic, but that repeated histamine exposure agonists, while cimetidine4 and tiotidine5 are primarily prevented this effect. This apparent self-deactivation H2-antagonists. In addition, chemical homologues of might have been the result of histaminase release by these drugs have been made that lack significant ago- eosinophils.14 The limited evidence in the literature nist or antagonist activity at histamine receptors,6 e.g., supports the view that eosinophil movement, be it che- nordimaprit and homodimaprit (Fig. 1). Use of these motaxis or chemokinesis, is the result of stimulation I12 15 various agents has allowed identification of Hr and of H2-receptors.' Clark et al found that, with regard H2-receptors at a variety of sites. For example, H2-re- to migration stimuli, eosinophils behaved as a heter- ceptors have been identified in the uterus, heart, and ogeneous population. They speculated that this might on the ocular surface.7'8 be due to variations in the relative frequencies of H,- The chemotactic effect of histamine on eosinophils and H2-receptors, or to the existence of a third type of 9 10 is a subject of controversy. Clark et al and Turnbull histamine receptor, i.e., an H3-receptor. believed that histamine was selectively chemotactic for During preliminary studies on the intraocular pres- eosinophils. However, Litt" reported that histamine- sure effects from the topical application of a combi- induced eosinophil movement was a non-specific effect nation of an H2-antagonist, cimetidine, and an H2-ag- caused by its acidity. Wadee et al12 also found that onist, dimaprit, an acute inflammatory response was noted. The anterior segment of rabbit eyes developed From the ""Ophthalmology Section, Bronx Veterans Hospital, New a selective eosinophil infiltration. It was accompanied York, and the Departments of fOphthalmology and ^Pharmacology by miosis, corneal edema, and a variable amount of of the Mount Sinai School of Medicine, New York, New York. iris depigmentation. The present paper describes the Supported by the Medical Research Service of the Veterans Ad- investigations of this response. ministration, NEI Core Center Grant EY-01867, and the Department of Ophthalmology, Mount Sinai School of Medicine, New York, New York. Materials and Methods Submitted for publication: January 29, 1986. Reprint requests: Joel S. Mindel, MD, PhD, Department of Oph- thalmology, Annenberg 22-14, Mount Sinai School of Medicine, One Dutch Belted rabbits, i.e., pigmented rabbits, were Gustave L. Levy Place, New York, NY 10029. used, except for one experiment with albino rabbits. Downloaded from iovs.arvojournals.org on 09/30/2021 No. 10 EOSINOPHIL CHEMOTAXIS / Mindel er ol. 1505 Animals were maintained in compliance with the DIMAPRIT ARVO Resolution on the Use of Animals in Research. Cimetidine, dimaprit hydrochloride, nordimaprit dihydrochloride, 4-methylhistamine dihydrochloride, NORDIMAPRIT histamine dihydrochloride, homodimaprit, and thio- urea were 0.21 M unless so stated. Their pH's were 5.2, except for thiourea, which was 7.3. Solutions were 2V /3 HOMODIMAPRIT JC-S-CH2-CH2-CH2-CH2—N' made up every 2-3 days. Impromidine was supplied Hfr CH3 as a 3 mM, pH 4.5 solution by the manufacturer; it was used as such and also at dilutions of 0.3, 0.6, 1.2, CH3 CH2—CH2—NH2 and 1.8 mM. Tiotidine solubility was limited, and a 4-METHYLHISTAMINE Np=(? 0.01 M, pH 5.6 solution was used, as it was close to saturation. A proparacaine HC1, 0.5% commercial preparation provided local anesthesia and was used at CH3v IMPROMIDINE times to promote corneal penetration of the other drugs. When proparacaine was administered, it was always the first eye drop given. When both an H2-an- CH3, CIMETIDINE J—CH2—S—CH2—CH2—NH—C—NHCH3 tagonist and an H2-agonist were administered, the for- N NCN mer was given before the latter. Drugs were adminis- tered as 50 n\ eye drops or injected subconjunctivally or intravitreally in 50 /il volumes. Eye drops were given TIOTIDINE ))—£-CH2-S-CH2-CH2-NH-C-NHCH3 by holding the lids away from the globe and opposed NCN for several seconds to prevent overflow. Topical ap- plications of different drugs were separated by at least Fig. 1. Structures of the histamine H2-receptor agonists, dimaprit, impromidine, and 4-methylhistamine; the H -receptor antagonists, 5 min. 2 cimetidine and tiotidine; and the H2-receptor inactive homologues The eosinophil uveitis was evaluated by observing of dimaprit, nordimaprit and homodimaprit. for miosis, iris depigmentation, and corneal clouding. Histologically, the response to all drug treatments was evaluated using light microscopy with hematoxylin- toxicity of impromidine, only one eye of each rabbit eosin stains and Luna eosinophil granule stain.16 Dif- was treated when this drug was used. If uveitis occurred, ferential white cell counts of Giemsa stained peripheral the eye drops were continued for an additional 48 hr blood smears were performed before and at the con- to intensify the reaction, and then the rabbit was killed. clusion of all drug treatments. Rabbits were killed in Each of three albino rabbits received proparacaine a CO gas tank or by intravenous pentobarbital. + cimetidine + dimaprit to the right eye and propar- 2 acaine + dimaprit to the left eye, three times a day until 48 hr after at least one eye developed an inflam- Intraocular Pressure matory response. The rabbit was then killed. Five rabbits had their intraocular pressures measured 4 times a day, while the right eye received: a) days 1- Table 1. Topical drugs producing anterior 7, dimaprit HC1, 0.1 M (2.5%), twice a day; b) days 7- segment eosinophil chemotaxis 14, dimaprit HC1, 0.21 M (5%), twice a day; and c) days 14-25, cimetidine and dimaprit HC1, both 0.21 Number Eyes Response Onset M and both twice a day. The left eyes received NaCl Treated Responding (Days) eye drops of matching pH and tonicity. Intraocular pressures were measured using proparacaine topical H2-antagonist activity Proparacaine + cimetidine anesthesia and a pneumatonometer. + nordimaprit 5 5 2-3 H2-antagonist and H2-agonist Eosinophil Chemotaxis activities Tiotidine + dimaprit 4 1 7 Eye drops were applied three times a day for 12 or Proparacaine + cimetidine + dimaprit 6 6 3-11 more consecutive days in the various combinations Proparacaine + tiotidine shown in Tables 1 and 2. One eye would receive a drug + dimaprit 4 4 3-4 or drug combination without proparacaine, and the No H2 activity contralateral eye would receive the same drug or drug Nordimaprit 5 5 5-10 combination with proparacaine. Due to the systemic Proparacaine + nordimaprit 5 5 2-3 Downloaded from iovs.arvojournals.org on 09/30/2021 1506 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / October 1986 Vol. 27 Table 2. Topical drugs not producing anterior ministered to the right eye. On the fifteenth day, the segment eosinophil chemotaxis animals were killed, and their eyes and blood smears were examined microscopically. Number Days Eyes Treated Comment Intravitreal drugs were injected once in both eyes of eight rabbits anesthetized with pentobarbital. Both eyes H2-agonist activity received the same drugs using 25-gauge needles inserted Dimaprit 4 12 Impromidine, 3 mM 4 1-2 All died through the pars plana: rabbit 1, cimetidine; rabbits 2 4-Methylhistamine 5 14 and 3, dimaprit HC1; rabbit 4, impromidine; rabbit 5, Proparacaine + dimaprit 4 21 tiotidine; rabbit 6, dimaprit + cimetidine in the same Proparacaine + impromidine, 3mM 8 1-2 All died 50 /il injection; and rabbits 7 and 8, dimaprit and ci- Proparacaine + histamine 5 14 metidine in two separate, but simultaneous, 50 /il in- Proparacaine + 4- jections to each eye. methylhistamine 5 14 H2-antagonist activity In Vitro Depigmentation Cimetidine 5 14 Tiotidine 4 14 Iris-ciliary bodies were removed from rabbits im- Proparacaine + cimetidine 5 21 Proparacaine + tiotidine 4 21 mediately after death.