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Biomedical subjects

N J van Haeringen

Publications and source records attributed to N J van Haeringen.

At least 19 recordsLinked to original sources
PubMed2000

Flurbiprofen and enantiomers in ophthalmic solution tested as inhibitors of prostanoid synthesis in human blood.

The purpose of this study was to assess the selectivity and potency of the nonsteroidal anti-inflammatory drug (NSAID), flurbiprofen, and its enantiomers in their inhibition of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). An assay was used with freshly drawn, heparinized human whole blood, incubated with 25 microM calcium ionophore A23187 during 60 min to produce thromboxane B2 (TXB2) by activity of COX-1 in platelets. Incubation with E. coli lipopolysaccharide (LPS) during 24 hr produced prostaglandin E2 (PGE2) by induction of COX-2 in monocytes, suppressing any possible contribution of COX-1 activity by the addition of acetylsalicylic acid. Concentration inhibition curves were determined with racemic, S(+), and R(-) flurbiprofen in final concentrations ranging from 10(-3) to 10(-10) M. The stereoselectivity of S(+) flurbiprofen vs. R(-) flurbiprofen, expressed as the reciprocal of the ratio of the concentrations giving 50% inhibition (IC50), is 340 for COX-1 and 56 for COX-2. The selectivity for COX-1 vs. COX-2, expressed as the reciprocal ratio of the IC50, was 32 for racemic, 16 for S(+), and 5.3 for R(-) flurbiprofen. Meloxicam in the same assay showed COX-2 selectivity with a ratio of 0.19.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Constitutive cyclooxygenase-1 and induced cyclooxygenase-2 in isolated human iris inhibited by S(+) flurbiprofen.

The purpose of the present study was to characterize the isoforms of cyclooxygenase (COX) in the human iris before and after stimulation with lipopolysaccharide (LPS) and to determine the selectivity of the nonsteroidal anti-inflammatory drug (NSAID), S(+) flurbiprofen, for inhibition of COX-1 and COX-2 in homogenates of this tissue. Spotblots were made of extracts of human iris in the absence and presence of LPS plus acetylsalicylic acid (aspirin). After reacting with anti-COX-1 and anti-COX-2 immunoglobulin G, the presence of both immunoreactive COX enzymes was substantiated using an indirect immunoperoxidase method. Authentic COX-1 and COX-2 were used as controls. Using an enzyme immune assay (EIA), the production of prostaglandin E2 (PGE2) was quantified in tissue homogenates of human iris under the same conditions as described above. S(+) flurbiprofen was added to tissue homogenates in order to determine the inhibitory effect on PGE2 production. Half maximal inhibitory concentrations (IC50) of S(+) flurbiprofen for the PGE2 production in the tissue homogenates were determined from concentration inhibition curves. The selectivity of S(+) flurbiprofen for inhibition of COX-1 was expressed as the ratio of IC50 for COX-2/COX-1. Spotblots of nonstimulated iris-extracts showed positive staining for COX-1 immunoreactivity (-ir) only. After incubation with LPS plus acetylsalicylic acid, positive staining was observed for both COX-1-ir and COX-2-ir. Concentrations of PGE2 released from homogenates of untreated iris varied from 1.5-4 ng/ml, and of LPS-stimulated tissue from 10-20 ng/ml of assay mixture. S(+) flurbiprofen inhibited PGE2 production of untreated tissue homogenates at an IC50 of 8 x 10(-10) M whereas, in the stimulated tissue, IC50 was found to be 3 x 10(-6) M. The selectivity of S(+) flurbiprofen for inhibition of constitutively present COX-1, relative to the inhibition of induced COX-2, was 3,600. Our results indicate that specific expression of COX isoforms in normal human iris was substantiated at the protein level by immunoreaction on spotblots. COX-1 represents the constitutively present enzyme, and COX-2 appears after stimulation with LPS. At the functional level, S(+) flurbiprofen possesses a specificity for COX-1 in inhibiting PGE2 production.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Incidence of ocular side effects of topical beta blockers in the Netherlands.

BACKGROUND: Several ocular side effects including uveitis, have been reported following topical beta blocker treatment for glaucoma and ocular hypertension. The incidence of these side effects was investigated in the Netherlands. METHODS: A prospective observational design was used whereby monthly questionnaires were sent to all practising ophthalmologists in the Netherlands during 3 consecutive months. Questionnaires were returned at the end of each month. Any patient whose topical beta blocker therapy was altered because of an ocular reaction was noted on this questionnaire. Ophthalmologists who did not return their questionnaires were interviewed by telephone at the end of the study period. The number of patients using topical beta blockers was derived from drug sales figures. RESULTS: 70% (328/467) of the ophthalmologists in the Netherlands participated in the study. During the 3 month study period 34 cases were reported: 15 patients had periorbital dermatitis, in eight patients eyelids and conjunctiva were affected, in seven patients the conjunctiva was affected, and four patients had punctate keratitis. The calculated incidence of ocular side effects during topical beta blocker therapy was 1.51 cases/1000 patient years. CONCLUSION: Topical beta blocker therapy is associated with few clinically important ocular side effects. No cases of uveitis were reported.

Administration, Topical↗
PubMed2000

Topical ophthalmic beta blockers may cause release of histamine through cytotoxic effects on inflammatory cells.

AIM: To evaluate the effects of beta blockers used in ophthalmology on the release of histamine from mixed cell preparations containing human leucocytes and basophils. METHODS: A mixed leucocyte and basophil preparation was obtained from venous blood of healthy non-atopic volunteers. Cell preparations were then incubated with betaxolol, metipranolol, timolol, or carteolol. After incubation for 1 hour the histamine content of the supernatant was analysed by automated fluorometric analysis. Cell viability was tested by measuring lactate dehydrogenase (LDH) concentrations. RESULTS: Betaxolol and metipranolol in concentrations between 10(-2) M and 10(-3) M liberated histamine from human blood cells in a dose dependent manner. Carteolol and timolol had no effect on histamine at these concentrations. At the same concentrations LDH was also detected in the supernatants of cell suspensions incubated with metipranolol or betaxolol. CONCLUSIONS: Betaxolol and metipranolol induce substantial histamine release from human leucocytes, probably as a result of their cytotoxic effect.

Administration, Topical↗
PubMed2000

IgA antibodies to Toxoplasma gondii in human tears.

PURPOSE: To investigate whether mucosal immune responses directed against the ubiquitous parasite Toxoplasma gondii can be detected in tears of healthy humans. METHODS: Nonstimulated tears and blood were obtained from 62 healthy humans (mean age, 35 +/- 10 [SD] years). Serum anti-T. gondii immunoglobulin titers were determined by Sabin-Feldman (SF) dye test. Western blot analysis was used to compare the anti-T. gondii repertoire in tears and serum, and antibody avidity was determined by urea elution. Diluted tear and serum samples were incubated with the intact parasite to determine whether the antibodies found in tears and serum are capable of binding to surface exposed antigens of T. gondii. RESULTS: Eighty-one percent of the individuals tested had an anti-T. gondii IgA response in their tears, whereas only 23% had evidence of systemic immunity against the parasite. There was no apparent relation between chronic infection and presence of anti-T. gondii IgA in tears. Characteristically, the antigens recognized by the IgA antibodies in tears were often limited to at least one of four antigens with molecular weights of 74, 70, 49, and 34 kDa. The avidity of the anti-T. gondii IgA antibodies in tears was similar to the avidity of serum IgG antibodies. IgA antibodies directed against the 49- and 74-kDa antigens recognized epitopes exposed on the surface of the parasite. CONCLUSIONS: A major finding of this study is that tears of many individuals, chronically infected or not, contain IgA antibodies against T. gondii. It is not known whether these frequently observed antibody responses are the result of common mucosal immune responses against T. gondii or represent the natural antibody repertoire.

Adult↗
PubMed1999

Flurbiprofen, S(+), eyedrops: formulation, enantiomeric assay, shelf-life and pharmacology.

Aphakic cystoid macula edema, occurring after cataract extraction is ascribed to trauma-induced production of intra-ocular prostaglandins. Sufficient experimental and clinical evidence supports the use of prostaglandin synthesis inhibitors to countervail this clinical condition. The active S(+)-enantiomer of flurbiprofen, a prostaglandin synthesis inhibitor, has been formulated into a stereoselective, ballast free eyedrop solution in a concentration of 0.015%. Analysis by capillary zone electrophoresis shows shelf-life stability up to four years at room temperature of this enantiomer. The inhibitory effect on the synthesis of prostaglandins as measured on a homogenate bovine iris/ciliary body, remained unaffected during a shelf-life period of three years.

Animals↗
PubMed1998

Cystatins in tears of patients with different corneal conditions.

A presence of cystatins, inhibitors of cysteine protease, was investigated in tears of patients with different corneal pathologies. Tear fluid samples were collected with glass capillaries in 28 patients (28 eyes) and 15 healthy controls (15 eyes). Only after corneal transplantation (8) or in corneal dystrophy (6) but not after cataract extraction (5) or other traumatic conditions of the cornea (9) was a significant difference in inhibitory activity of cystatins measured in comparison with the 15 controls. In this study it could not be decided whether the lower level of cystatins was related to the cause or the effect of the condition of the eye.

Biomarkers↗
PubMed1996

Analysis of human tear fluid components, inhibiting protein adhesion to plastic surfaces.

In a previous paper we reported the presence of components in human tear fluid that block the interaction of proteins with plastic surfaces, interfering with tear protein ELISA and proposed the term coating inhibiting activity. The purpose of the study presented here was to further analyse these components. Coating inhibitory activity in human reflex tears was analysed by lectin affinity chromatography, using the agarose bound lectin Artocarpus integrifolia agglutinin (Jacalin), gel filtration, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), blotting and Jacalin staining. For coating inhibitory activity assay in experimental tear samples, the binding of the protein Avidin-conjugated horseradish peroxidase to the polystyrene surface of ELISA micro-titer plate wells, preincubated with the experimental tear samples was measured. In addition, tears were incubated with scrapings of the ELISA plates used in the assay and with six different types of contact lenses (two rigid gas permeable and four hydrogel soft contact lenses) for analysis of adsorbed components. Lectin affinity chromatography of tears yielded a Jacalin-binding and a non-Jacalin-binding preparation, both exhibiting coating inhibitory activity but representing chemically different preparations as observed by SDS-PAGE. After performing gel filtration, coating inhibitory activity eluted with similar retention in both preparations. In fractions exhibiting activity, tear proteins of low molecular weight (< 40 kDa) were detected. Among these, two Jacalin-binding glycoproteins were detected; a major component of approximately 28 kDa and a somewhat smaller minor component. All low molecular weight components were also detected on the scrapings, incubated with tears. The possibility that coating inhibitory activity in tears might reside in a component of larger molecular size can however not be excluded. The human tear proteins secretory Immunoglobulin A, lactoferrin and lysozyme are not involved in coating inhibition. On one of the two rigid gas permeable contact lenses incubated with the tears, the 28 kDa glycoprotein was detected. From the data obtained in our study we conclude that coating inhibitory activity in tears seems to be associated with multiple components of low molecular weight.

Adsorption↗
PubMed1996

Interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis.

Both nitric oxide and prostaglandins induce vasodilatation which is an important feature of local inflammation. The purpose of the study described here was to investigate a possible interaction between these two types of mediators in an experimental model of allergic conjunctivitis. A conjunctival allergic reaction was induced with antigen in sensitized guinea pigs. Conjunctival vascular permeability changes were evaluated with the prophylactic use of an inhibitor of nitric oxide synthase (L-NAME) and a cycloxygenase inhibitor (indomethacin). To study a possible interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis, the levels of nitrite and PGE2 were determined in lavage fluid. The prophylactic use of L-NAME on the formation of conjunctival edema in response to topical PGD2 administration was studied by measurement of albumin levels in lavage fluid. Both nitric oxide and PGE2 are synthesized in response to antigen provocation and after histamine administration. Nitric oxide and PGE2 are produced simultaneously in the conjunctiva and they showed identical synthesis profiles in response to antigen provocation. Pretreatment with L-NAME inhibited the synthesis of PGE2 whereas exogenous administration of nitric oxide increased the level of PGE2 in lavage fluid. Prophylactic treatment with L-NAME significantly inhibited the PGD2 induced albumin extravasation. Nitric oxide seems to play an important role in the acute phase of allergic conjunctivitis it may stimulate PGE2 production and acts as a secondary mediator in PGD2 and histamine induced conjunctival edema.

Administration, Topical↗
PubMed1995

Spontaneous development of corneal crystalline deposits in MRL/Mp mice.

PURPOSE: The presence of corneal opacities associated with dacryoadenitis and lacrimal gland destruction has led investigators to consider MRL/Mp mice as models for band keratopathy and Sjögren syndrome. In this study, the authors examined the time course of the corneal opacification and investigated whether the opacities were associated with altered serum levels of parathyroid hormone, calcium, and phosphorus, as well as quantitative and qualitative differences in tear production. METHODS: Corneas were analyzed microscopically and tear fluid production was measured by a modified Schirmer test. RESULTS: Corneal lesions were observed as early as the fifth week after birth. The lesions consisted of calcium phosphate and appeared as punctate, crystalline opacities located subeithelially. Lesions were present in 72% (56 of 78) of the MRL/Mp mice, with no significant difference in incidence between MRL/Mp +/+ and MRL/Mp lpr/lpr mice. Corneal calcification was occasionally associated with a self-limiting keratitis and neovascularization. In control mice, corneal opacities were not observed before the animals were 6 months of age. Levels of circulating parathyroid hormone decreased significantly during the first 16 weeks of age in MRL/Mp mice. In addition, MRL/Mp mice of both sexes had a significantly lower tear fluid production as compared to BALB/c mice of the same age. CONCLUSION: Because corneal lesions start to develop in 5-week-old MRL/Mp mice, thereby preceding the clinical signs of systemic autoimmune disease, and may develop in 6-month-old nonautoimmune-prone mice, it is suggested that calcification develops independent of the systemic autoimmune disease and might be restricted to the cornea.

Animals↗
PubMed1994

Analysis of tear fluid proteins in insulin-dependent diabetes mellitus.

Secretory immunoglobulin A, lactoferrin, lysozyme and tear specific pre-albumin were analyzed in stimulated tear fluid of 25 diabetic patients without retinopathy and in 29 diabetic patients with (pre) proliferative retinopathy using high performance liquid chromatography. Results were compared to those obtained in 26 healthy controls to determine the effect of diabetes mellitus on the exocrine function of the main lacrimal gland. Sodium dodecyl sulfate polyacrylamide gel electrophoresis onto minigels was performed on 20 tear samples for verification of high performance liquid chromatography fractions recorded. The mean total protein values in tear fluid (Bradford assay) of diabetics without retinopathy, with retinopathy and healthy controls did not differ significantly (mean in mg/ml +/- SD: 6.4 +/- 2.2, 5.9 +/- 2.0 and 5.7 +/- 1.7, respectively; Mann-Whitney; p > 0.02). High performance liquid chromatography showed an increased secretory immunoglobulin A and decreased peak 5 OD280 (+56% and -38%, respectively; p < 0.02) in patients without retinopathy, whereas in patients with retinopathy lysozyme was increased (+27%; p < 0.01) and tear specific pre-albumin and peak 5 OD280 decreased (-24% and -42%, respectively; p < 0.04), when compared to healthy controls. These inconsistent differences do not uniformly suggest an exocrine dysfunction of the main lacrimal gland in diabetic patients.

Adolescent↗
PubMed1993

Antagonist of platelet-activating factor prevents prostaglandin E2 induced ocular hypertension in rabbits.

Topical application of 250 micrograms of platelet activating factor (PAF) or 5 micrograms of prostaglandin E2 (PGE2) to the rabbit's eye is followed by a rise in intraocular pressure (IOP). The occurrence of PAF in the anterior chamber is held responsible for this effect, as appears from the observed concentrations of PAF in a ng/ml-range in the aqueous humor and from the inhibition in the rise of IOP by systemic pretreatment of rabbits with the PAF-antagonist BN 52021 (10 mg/kg). Corneal and conjunctival edema, occurring after application of PAF, are not influenced by BN 52021. Thus, these effects may be ascribed to the non-specific membrane pertubant action of the high local concentration of PAF, necessary to achieve effective concentrations of PAF in the anterior chamber.

Animals↗
PubMed1993

Antagonists and inhibitors of lipid mediators in experimental inflammation of the cornea.

In experimental immunogenic keratitis, provoked in rabbits by intracorneal injection of 20 microliters of human serum albumin (HSA), various anti-inflammatory agents were studied in their effects on corneal edema, neovascularisation and leukocyte infiltration. Prophylactic treatment with a corticosteroid completely prevented the occurrence of keratitis. Nonsteroidal anti-inflammatory drugs such as a cyclooxygenase inhibitor partly prevented neovascularisation and corneal edema, a lipoxygenase inhibitor, a leukotriene antagonist or platelet-activating factor (PAF)-antagonist BN 52021 partially prevented mainly leukocyte infiltration. Prophylactic topical treatment with the poly-unsaturated fatty acids eicosapentaenoic acid and columbinic acid or a dietary supplement with fish oil showed less symptoms of keratitis in all respects.

Animals↗
PubMed1993

Analysis of corneal aldehyde dehydrogenase patterns in pathologic corneas.

In this study we investigated the properties of corneal aldehyde dehydrogenase (ALDH) in keratoconus corneas using various electrophoretic techniques combined with immunochemical and zymographic identification. Normal corneas and other pathologic corneal buttons obtained during keratoplastic surgery were used as a control. A significant (p < 0.001) lower enzymatic activity was found in keratoconus epithelial extracts (3.1 +/- 2.1 IU/mg protein) compared with normal controls (5.5 +/- 2.6 IU/mg protein), whereas no significant differences were observed in the stromal and endothelial extracts. No significant differences were observed for the corneal ALDH thermolability behavior, nor did any marked changes occur in the position of the 54- and 88-kDa species when comparing the pathologic corneas and normal controls. On the other hand, isoelectric focusing analysis showed a different pattern for the pathologic corneas as compared with controls. Moreover, native-polyacrylamide gel electrophoresis analysis showed that normal corneas exhibit three bands, whereas keratoconus and other pathologic corneas only show two bands. The shift from the three-band pattern to the two-band pattern could be reproduced in vitro using reducing agents, such as glutathione.

Adolescent↗
PubMed1993

Corneal aldehyde dehydrogenase, glutathione reductase, and glutathione S-transferase in pathologic corneas.

Previously we have reported that various pathologic corneas exhibited a "diseased" two-band corneal aldehyde dehydrogenase (ALDH) zymogram after native polyacrylamide gel electrophoresis as compared with the three bands in the normal human cornea. Experimentally, such a "diseased" zymogram pattern could be induced by addition of reduced glutathione (GSH) to the normal corneal epithelial extract. This finding suggests that in vivo the conformation of corneal ALDH may be related to changes in the GSH redox system during the process of corneal diseases. To investigate this hypothesis in keratoconus corneal epithelial extracts and a separate group comprising other corneal disorders, mainly herpes keratitis, we indirectly measured the GSH turnover by assaying the activity of glutathione reductase (GR) which is responsible in producing GSH and glutathione s-transferase (GST), which converts GSH into mercapturic acid. Our results indicate that there is a correlation between the activity of GR and GST in the normal and the separate group of corneal disorders. Because GST is the first enzyme in the mercapturic acid pathway, which detoxifies xenobiotic substrates including aldehydes, as by-products of membrane lipid peroxidation, an elevated GSH turnover might be necessary to counteract oxidative threats. However, no correlation was found between corneal ALDH level with either GR or GST. On the other hand, keratoconus samples demonstrated a distinct enzymatic behavior that was in concordance with our earlier result in the corneal ALDH zymogram after isoelectric focusing. Furthermore, analysis of our several studies tends to support the proposed structural function of ALDH in human cornea.

Aldehyde Dehydrogenase↗
PubMed1993

Separation and characteristics of glycoproteins in tears which inhibit coating and precipitation of protein.

Using a modified turbidimetric assay to determine the protein concentration in human tears by precipitation with trichloroacetic acid (TCA) we found lower protein concentrations if compared with other methods for protein determination. This implies that a factor in human tears is able to inhibit the precipitation of protein by TCA. Earlier a coating inhibitory factor in human tears was described which is able to prevent coating of a polyacrylate surface by proteins using a ELISA methodology. Because of the similarity in its behaviour towards protein we investigated whether the same factor could be responsible for both inhibitory effects. A pool of human tears was separated into various fractions using HPLC whereafter inhibitory activity in the turbidimetric and the coating assay could be found in the same fractions. Characterization of the inhibitory factor was performed by minigel-electrophoresis (SDS-PAGE), after which blotting and staining with a lectin (Jacalin) revealed two subunits of a glycoprotein with a molecular weight of 30 and 70 kD. The inhibitory factor also could be isolated if human tears were incubated for 30 min at 100 degrees C whereafter precipitated protein was removed by centrifugation. Inhibitory activity could be detected in the supernatant and an identical glycoprotein profile could be produced after staining with lectin (Jacalin). The results of this study suggest that a soluble glycoprotein serves as a coating and precipitation inhibitor in tears and may play an important role in the protein to protein interaction on the surface of the eye.

Chemical Precipitation↗
PubMed1993

Production of lipid mediators in experimental keratitis of rabbit eye.

The inhibitors of prostaglandin (PG) or leukotriene (LT) synthesis and antagonists of platelet-activating factor (PAF) or LTs are inhibitory in experimental keratitis and clinical symptoms of keratitis are reproduced by application of these lipid mediators. This suggests that PGE2, LTB4, LTD4, and PAF are involved in experimental immunogenic and toxic keratitis. The objective of the present study is the measurement of the concentrations of lipid mediators in the aqueous humour and their release by the cornea and iris during keratitis. In both inflammatory models the concentrations of PGE2, LTB4, LTD4, and PAF in the aqueous humour were significantly increased as compared to their controls. The release of PGE2, LTB4 and LTD4 from the cornea, and of PGE2, LTB4, and PAF from the iris was significantly increased compared to that from control tissues. The results are consistent with a role for these lipid mediators in the inflammatory models. Combined therapeutic use of synthesis inhibitors or antagonists of these mediators in eye inflammation seems possible and may serve as an alternative to topical corticosteroid therapy.

Animals↗