OPC-12759 increases proliferation of cultured rat conjunctival goblet cells

PURPOSE

To determine if the gastroprotective drug OPC-12759 increased proliferation of rat conjunctival goblet cells in culture.

METHODS

Cultured goblet cells were incubated with 10(-12) to 10(-8) M OPC-12759 for 1 to 7 days. Fetal bovine serum (FBS) was used as a positive control. Cell proliferation was determined by a MTT [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] colorimetric assay and by immunohistochemical staining with anti-Ki-67, a marker of cell division. Goblet cells were identified by double-labeling with anti-Ki-67, a marker of cell division, and Ulex europaeus agglutinin I lectin, anti-MUC5AC and anticytokeratin 7. Stratified squamous cells were identified by using Griffonia (Bandeiraea) simplicifolia lectin and anticytokeratin 4 antibody.

RESULTS

As determined by MTT conversion to formazan, OPC-12579 at 10(-11) M induced an almost 2-fold increase in goblet cell proliferation on Days 1 and 3 of incubation but not on Days 5 and 7. The FBS at 10% increased cell proliferation by 2- to 3-fold at each time point. Daily replenishment of OPC-12579 for 3 consecutive days induced cell proliferation at all concentrations. Proliferation as determined by the number of Ki-67 positive cells increased by 4- and 3-fold at Days 1 and 3, respectively with addition of 10(-11) M OPC-12579. The FBS at 10% induced a 10-fold increase in goblet cell proliferation on Days 1, 3, and 5. Colocalization of Ulex europaeus agglutinin I, MUC5AC and anticytokeratin 7 with Ki-67 indicated that proliferating cells were goblet cells. Proliferating cells were negative for the nongoblet cell markers Bandeiraea lectin and anticytokeratin 4.

CONCLUSIONS

The OPC-12759 stimulates proliferation of conjunctival goblet cells in primary culture.

Presence and localization of neurotrophins and neurotrophin receptors in rat lacrimal gland

PURPOSE

To determine which of the neurotrophins (NTs)-nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and neurotrophin-4/5 (NT4)-and their receptors (NTrs), TrkA, TrkB, TrkC, and p75, are present in the adult rat lacrimal gland.

METHODS

RT-PCR was performed on RNA isolated from male rat lacrimal gland, using oligonucleotides specific to each NT and NTr. The presence of NT and NTr protein, was determined by Western blot analysis of lacrimal gland homogenate or membranes. The location of NTs and NTrs was determined by immunofluorescence histochemistry. Western blot analyses and immunofluorescence microscopy were performed using primary rabbit polyclonal antibodies raised against NTs and NTrs.

RESULTS

RT-PCR showed positive bands at the appropriate sizes for NGF, BDNF, NT3, and NT4, and for the receptors TrkA, TrkB, TrkC, and p75. Western blot analysis confirmed these results, showing that the lacrimal gland expresses NGF, BDNF, NT3, and NT4 as well as the NTrs TrkA, TrkB, and TrkC and the p75 protein. NGF, BDNF, NT3, and NT4 were localized in the lacrimal gland acini with differing cellular distributions, whereas TrkA, TrkB, and TrkC, were localized in myoepithelial cell and ductal cell membranes. The protein p75 was expressed only on myoepithelial cell membranes.

CONCLUSIONS

Members of the neurotrophin family of growth factors and their receptors are present in rat lacrimal gland, which suggests a role for NTs and their receptors in the lacrimal gland.

Isolation and characterization of cultured human conjunctival goblet cells

PURPOSE

To isolate and characterize goblet cells from normal human conjunctival tissue to determine whether epidermal growth factor (EGF) receptors are present and whether EGF can influence goblet cell proliferation.

METHODS

Goblet cells were isolated from explant cultures established from normal conjunctival tissue harvested from patients during periocular surgery. The cells were grown in RPMI culture medium supplemented with 10% fetal bovine serum and characterized using morphology, histochemistry, indirect immunofluorescence microscopy, molecular biology, and biochemistry. Proliferation was determined with a MTT proliferation assay after exposing goblet cells, which had been serum deprived for 48 hours, to increasing concentrations of epidermal growth factor (EGF; 0-80 ng/mL) for 24 hours.

RESULTS

Goblet cells were isolated from conjunctival explants by scraping nongoblet cells from the culture dish. Human goblet cells exhibited positive reactivity with alcian blue-periodic acid Schiff (PAS) reagent, goblet cell-specific cytokeratin-7, HPA lectin, and MUC5AC, but negative reactivity to the stratified squamous epithelial cell marker, cytokeratin-4. The mRNA for MUC5AC was detected using RT-PCR. The presence of the EGF receptors EGFR, ErbB2, and ErbB3 was confirmed through Western blot analysis of cell lysates. EGF elicited a concentration-dependent increase in goblet cell proliferation of 160% +/- 0.5%, 188% +/- 0.45%, 293% +/- 1.3%, and 220% +/- 0.5% of control values with 10, 20, 40, and 80 ng/mL EGF, respectively.

CONCLUSIONS

Human goblet cells that retain characteristics of goblet cells in vivo can be cultured. EGF receptors are present in human goblet cells, and EGF stimulates their proliferation.

Presence of nerves and their receptors in mouse and human conjunctival goblet cells

PURPOSE

To determine whether neural pathways for controlling goblet cell secretion are present in mouse and human conjunctiva.

METHODS

Mouse conjunctiva was homogenized and subjected to electrophoresis and Western blotting to detect PGP 9.5 (indicates nerves), muscarinic receptor subtypes (indicates parasympathetic pathway), and adrenergic receptors (indicates sympathetic pathway). Mouse eyes and human conjunctival tissue were analyzed by immunofluorescence microscopy. Antibodies to vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and muscarinic and alpha(1)- and beta-adrenergic receptor subtypes were used.

RESULTS

Western blot demonstrated PGP 9.5, M(1), M(2), and M(3) muscarinic receptors and alpha(1A)-, beta(1)-, beta(2)-, and beta(3)-adrenergic receptors in mouse conjunctiva. Immunoreactivity for VIP, TH, and DBH was found adjacent to mouse and human goblet cells. M(1) and M(2) muscarinic receptors were identified throughout mouse conjunctiva, but M(3) receptor was predominantly on goblet cells. All three muscarinic receptor subtypes were detected on goblet cells in human conjunctiva. alpha(1A)-Adrenergic receptors were found on epithelial cells and on goblet cells in mouse and human conjunctiva. beta(1)- and beta(2)-Adrenergic receptors were found on both epithelial and goblet cells in mouse conjunctiva, but not on human conjunctival cells. beta(3)-Adrenergic receptors were found on both epithelial and goblet cells in human conjunctiva but not on mouse conjunctival cells.

CONCLUSIONS

The following conclusions were drawn: parasympathetic nerves and M(1), M(2), and M(3) muscarinic receptors, as well as sympathetic nerves are present on mouse and human goblet cells. The adrenergic receptors beta(1) and beta(2,) but not alpha(1A) and beta(3) are present on mouse conjunctival goblet cells, whereas alpha(1A) and beta(3,) but not beta(1) and beta(2) are present on human conjunctival goblet cells, suggesting that these nerves and receptors could activate goblet cell secretion in mouse and humans.

Development of conjunctival goblet cells and their neuroreceptor subtype expression

PURPOSE

To investigate expression of muscarinic, cholinergic, and adrenergic receptors on developing conjunctival goblet cells.

METHODS

Eyes were removed from rats 9 to 60 days old, fixed, and used for microscopy. For glycoconjugate expression, sections were stained with Alcian blue/periodic acid-Schiffs reagent (AB/PAS) and with the lectins Ulex europeus agglutinin I (UEA-I) and Helix pomatia agglutinin (HPA). Goblet cell bodies were identified using anti-cytokeratin 7 (CK7). Nerve fibers were localized using anti-protein gene product 9.5. Location of muscarinic and adrenergic receptors was investigated using anti-muscarinic and beta-adrenergic receptors.

RESULTS

At days 9 and 13, single apical cells in conjunctival epithelium stained with AB/PAS, UEA-I, and CK7. At days 17 and 60, increasing numbers of goblet cells were identified by AB/PAS, UEA-I, HPA, and CK7. Nerve fibers were localized around stratified squamous cells and at the epithelial base at days 9 and 13, and around goblet cells and at the epithelial base at days 17 and 60. At days 9 and 13, M2- and M3-muscarinic and beta2-adrenergic receptors were found in stratified squamous cells, but M1-muscarinic and beta1-adrenergic receptors were not detected. At days 17 and 60, M2- and M3-muscarinic receptors were found in goblet cells, whereas M1-muscarinic receptors were in stratified squamous cells. Beta1- and beta2-adrenergic receptors were found on both cell types. Beta3-adrenergic receptors were not detected.

CONCLUSIONS

In conjunctiva, nerves, M2- and M3-muscarinic, and beta1- and beta2-adrenergic receptors are present on developing goblet cells and could regulate secretion as eyelids open.

Immunolocalization of muscarinic and VIP receptor subtypes and their role in stimulating goblet cell secretion

PURPOSE

To determine the subtypes of cholinergic muscarinic receptors and receptors for vasoactive intestinal peptide (VIP) present in rat conjunctival goblet cells and whether cholinergic agonists and VIP stimulate goblet cell secretion.

METHODS

Immunofluorescence studies were performed using antibodies against the m1, m2, and m3 muscarinic receptor subtypes and VIP receptors 1 and 2 (VIPR1 and VIPR2). The lectin Ulex europeus agglutinin I was used to measure glycoconjugate secretion, the index of secretion, from goblet cells in an enzyme-linked lectin assay. In this assay, pieces of conjunctiva were placed on filter paper and incubated for 15 to 120 minutes, with or without increasing concentrations of the cholinergic agonist carbachol or VIP. The muscarinic antagonist atropine and the muscarinic receptor-subtype-selective antagonists pirenzepine (M1), gallamine (M2), and 4-4-diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride (4-DAMP mustard; M3) were incubated with carbachol to determine specificity of receptor activation.

RESULTS

Immunoreactivity to M2 and M3 receptors was found on goblet cell membranes subjacent to the secretory granules. Immunoreactivity to M1 receptor was not on goblet cells but was on the stratitfied squamous cells. Immunoreactivity to VIPR2 was found on goblet cells with a localization similar to that of the M2 and M3 receptors. VIPR1 was not found on goblet cells or on the stratified squamous cells. Carbachol and VIP induced a time- and concentration-dependent stimulation of glycoconjugate secretion. Carbachol, at 10(-4) M, induced a threefold increase in glycoconjugate secretion, which was completely inhibited by atropine (10(-5) M). Carbachol-induced secretion was inhibited 54% +/- 8% by pirenzepine (10(-5) M), 69% +/- 14% by gallamine (10(-5) M), and 72% +/- 11% by 4-DAMP mustard (10(-5) M). A twofold increase in glycoconjugate secretion was obtained with VIP at 10(-8) M.

CONCLUSIONS

Cholinergic agonists, through M2 and/or M3 muscarinic receptors, and VIP, through VIPR2, regulate conjunctival goblet cell secretion, suggesting that goblet cell secretion in vivo is under the control of parasympathetic nerves.