Immunohistochemical and enzymehistochemical studies of peptidergic, aminergic and cholinergic innervation of the lacrimal gland of the monkey (Macaca fuscata)

Dry eye syndrome: comprehensive etiologies and recent clinical trials

Dry eye syndrome (DES) is multifactorial and likely to be a cause of concern more so than ever given the rapid pace of modernization, which is directly associated with many of the extrinsic causative factors. Additionally, recent studies have also postulated novel etiologies that may provide the basis for alternative treatment methods clinically. Such insights are especially important given that current approaches to tackle DES remains suboptimal. This review will primarily cover a comprehensive list of causes that lead to DES, summarize all the upcoming and ongoing clinical trials that focuses on treating this disease as well as discuss future potential treatments that can improve inclusivity.

Factors that may affect recurrence of trigeminal neuralgia after percutaneous balloon compression

OBJECTIVE

To investigate the efficacy of percutaneous balloon compression of the Gasserian Ganglion (PCGG) in the treatment of trigeminal neuralgia(TN)and the influencing factors of recurrence after PCGG.

METHODS

The clinical data of 221 patients with TN treated by PCGG were retrospectively analyzed and followed-up to explore the postoperative efficacy.

RESULTS

There were 158 cases of immediate disappearance of pain and 59 cases of delayed pain disappearance in patients after one PCGG operation, for an overall efficacy rate of 98.2%. Forty-nine patients experienced recurrence of pain, for a recurrence rate of 22.6%, and average recurrence time of 18 months. The effective rate of medication in patients with recurrent trigeminal neuralgia is 85.7%.Univariate and multivariate logistic regression analyses showed that hypertension disease and delayed pain disappearance were independent factors for recurrence. The incidence of inhibitory reaction of the trigeminal nerve during the operation was 97.3%. The most common postoperative complications were facial numbness, masticatory-muscle weakness, tinnitus, diplopia and keratitis, which occurred at rates of 76.9%, 28.1%, 14.5%, 11.8% and 10.4%, respectively. All of the complications resolved within 3 years after PCGG.

CONCLUSIONS

PCGG is a safe and effective surgical method for the treatment of TN. The pain in most patients disappeared after surgery, leaving sequelae such as facial numbness, masticatory-muscle weakness and tinnitus. The mean time to recurrence of postoperative pain was 18 months, with hypertension disease and delayed pain disappearance as associated factors.

Effects of aerobic exercise on tear secretion and tear film stability in dry eye patients

Background

To study the effects of aerobic exercise (AE) on tear secretion and tear film stability in dry eye patients.

Methods

This study consisted of two parts, each part included 3 groups, namely dry eye without AE group, dry eye with AE group and pre-clinical dry eye with AE group. In part 1, we studied the variations of Schirmer I test and six tear compositions before and after AE (34 eyes in each group). In part 2, we studied the variations of tear meniscus height, first and average non-invasive tear breakup time (F-NITBUT and A-NITBUT), lipid layer thickness, number of incomplete and complete blinks, partial blink rate (PBR) and visual acuity before and after AE (30 eyes in each group).

Results

In dry eye with AE group, Schirmer I test at 0 min after AE increased significantly compared to baseline (P < 0.001), the oxidative stress marker 8-hydroxy-2′-deoxyguanosine after AE decreased significantly compared to baseline (P = 0.035, P = 0.045), F-NITBUT and A-NITBUT after AE prolonged significantly compared to baseline (P < 0.001, P = 0.007, P = 0.036; P < 0.001, P = 0.001, P = 0.044), number of incomplete blinks and PBR at 10 min after AE decreased significantly compared to baseline (P < 0.001; P < 0.001) while number of complete blinks increased significantly (P < 0.001). Besides, significant differences were also found between dry eye with AE group and dry eye without AE group at all above corresponding time point (P < 0.05).

Conclusion

AE promotes tear secretion and improves tear film stability in dry eye patients. AE may be a potential treatment for dry eye.

Trial registration

Chinese Clinical Trial Registry, ChiCTR2000038673. Registered 27 September 2020,

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02230-9.

Calcitonin gene-related peptide levels in tear fluid are elevated in migraine patients compared to healthy controls

BACKGROUND

Calcitonin gene-related peptide (CGRP) released from trigeminal nerve fibres indicates trigeminal activation and has a key role in migraine pathophysiology. The trigeminal nerve directly innervates the eye. Therefore, in this study, we compared Calcitonin gene-related peptide in tear fluid of migraine patients and healthy controls.

METHODS

Calcitonin gene-related peptide concentrations in tear fluid and plasma of 48 episodic and 45 chronic migraine patients and 48 controls were assessed using ELISA.

RESULTS

Calcitonin gene-related peptide levels in tear fluid (0.94 ± 1.11 ng/ml) were ∼140 times higher than plasma concentrations (6.81 ± 4.12 pg/ml). Tear fluid CGRP concentrations were elevated in interictal migraine patients (1.10 ± 1.27 ng/ml, n = 49) compared to controls (0.75 ± 0.80 ng/ml, p = 0.022). There was no difference in tear fluid CGRP levels between interictal episodic and chronic migraine patients (episodic: 1.09 ± 1.47 ng/ml, n = 30 and chronic: 1.10 ± 0.89 ng/ml, n = 19) and no correlation of tear fluid CGRP levels with headache frequency in interictal patients (rho = 0.062, p = 0.674). Unmedicated ictal migraine patients had even more elevated tear fluid CGRP levels than interictal migraine patients (1.92 ± 1.84 ng/ml, n = 13, p = 0.102), while medicated ictal migraine patients had lower levels (0.56 ± 0.47 ng/ml, n = 25, p = 0.011 compared to interictal patients), which were undistinguishable from controls (p = 0.609). In contrast to tear fluid, no significant group differences were found in plasma CGRP levels.

CONCLUSION

To the best of our knowledge, this study shows, for the first time, increased CGRP tear fluid levels in migraine patients compared to healthy subjects. Detection of calcitonin gene-related peptide in tear fluid is non-invasive, and likely allows a more direct access to CGRP released from the trigeminal nerve than plasma sampling.

TFOS DEWS II pain and sensation report

Pain associated with mechanical, chemical, and thermal heat stimulation of the ocular surface is mediated by trigeminal ganglion neurons, while cold thermoreceptors detect wetness and reflexly maintain basal tear production and blinking rate. These neurons project into two regions of the trigeminal brain stem nuclear complex: ViVc, activated by changes in the moisture of the ocular surface and VcC1, mediating sensory-discriminative aspects of ocular pain and reflex blinking. ViVc ocular neurons project to brain regions that control lacrimation and spontaneous blinking and to the sensory thalamus. Secretion of the main lacrimal gland is regulated dominantly by autonomic parasympathetic nerves, reflexly activated by eye surface sensory nerves. These also evoke goblet cell secretion through unidentified efferent fibers. Neural pathways involved in the regulation of meibomian gland secretion or mucin release have not been identified. In dry eye disease, reduced tear secretion leads to inflammation and peripheral nerve damage. Inflammation causes sensitization of polymodal and mechano-nociceptor nerve endings and an abnormal increase in cold thermoreceptor activity, altogether evoking dryness sensations and pain. Long-term inflammation and nerve injury alter gene expression of ion channels and receptors at terminals and cell bodies of trigeminal ganglion and brainstem neurons, changing their excitability, connectivity and impulse firing. Perpetuation of molecular, structural and functional disturbances in ocular sensory pathways ultimately leads to dysestesias and neuropathic pain referred to the eye surface. Pain can be assessed with a variety of questionaires while the status of corneal nerves is evaluated with esthesiometry and with in vivo confocal microscopy.

Human lacrimal gland regeneration: Perspectives and review of literature

The human lacrimal gland is an essential component of the lacrimal functional unit (LFU). Any perturbation of this unit can lead to the debilitating morbid condition called the dry eye syndrome (DES). The current line of therapy available for dry eye remains supportive and palliative with the patient being dependent on life long and frequent administration of lubricating eye drops. Even advanced therapies like punctual plugs, cyclosporine B administration, and salivary gland auto-transplantation have led to a limited success. Under these scenarios, the option of cell based therapy needs to be explored to provide better and long term relief to these patients. This review gives an overview of the efforts in lacrimal gland regeneration and examines the past and ongoing research in cell based therapies in animals as well as human lacrimal gland cultures. The authors discuss their first of its kind functionally viable human lacrimal gland in vitro culture system from fresh exenteration specimens. A brief overview of research in near future and the potential implications of lacrimal gland regenerative therapies have been discussed.

Dry eye management in a Sjögren's syndrome mouse model by inhibition of p38-MAPK pathway

Background

To investigate the therapeutic effect of p38-MAPK inhibitor, SB203580, on dry eye in a mouse model of Sjögren’s syndrome (MRL/lpr mice).

Methods

18 female BALB/c mice and 44 female MRL/lpr mice were included. Mice were randomly assigned to the control or treatment group. The expression of phospho-p38 MAPK in lacrimal glands of BALB/c mice was determined by Western blot analysis following IL-1β treatment at various time points. Different doses of SB203580 were injected into lacrimal glands of MRL/lpr mice and phenol red thread test was performed seven days post-injection. Moreover, the levels of acetylcholine and norepinephrine expression in lacrimal glands of MRL/lpr mice were measured using spectrofluoremetric assay and the histopathology of lacrimal glands was also evaluated.

Results

The expression of p-p38 MAPK in lacrimal glands of BALB/c mice gradually increased following incubation with IL-1β ex vivo. Injection of SB203580 into lacrimal glands significantly improved the results of phenol red thread test in MRL/lpr mice. In addition, the secretions of acetylcholine and norepinephrine increased significantly compared to the control group. Less lymphocytes infiltration was observed in pathological section of lacrimal glands following SB203580 injection.

Conclusions

Our results indicate that the activation of p38-MAPK pathway plays an important role in dry eye of a Sjögren’s syndrome mouse model. Inhibition of p38-MAPK pathway by SB203580 might have potential therapeutic effect on Sjögren’s syndrome associated dry eye.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1256849631103092.

Human orbital sympathetic nerve pathways

PURPOSE

To determine pathways of sympathetic nerves from the orbital apex to the eyelids in human cadaver tissue using immunohistochemistry.

METHODS

Human cadaver orbit tissue was sectioned and immunolabeled with a monoclonal antityrosine hydroxylase antibody.

RESULTS

In the orbital apex, the nasociliary, frontal, lacrimal, and maxillary branches of the trigeminal nerve demonstrated intense staining upon entering the orbit. Immunoreactive axons from the nasociliary and frontal nerves were observed to join the extraocular motor nerves in the posterior orbit. A plexus of immunolabeled nerves was observed to accompany the ophthalmic artery as it entered the orbital apex. The ophthalmic artery and its branches throughout the orbit demonstrated staining of nerve fibers in the peripheral muscularis. The nasociliary nerve contributed sympathetic branches to the ciliary ganglion. Nerves passing through the ciliary ganglion and a few ganglion cell bodies demonstrated mild to moderate tyrosine hydroxylase reactivity. Axons within the short and long ciliary nerves demonstrated strong tyrosine hydroxylase reactivity and were observed to enter the posterior sclera and the suprachoroidal space. The lacrimal gland demonstrated mild pericapillary staining and occasional stromal nerve fibers reactive to the antityrosine hydroxylase antibody. Müller muscle and the inferior tarsal muscle possessed a strong tyrosine hydroxylase-reactive nerve supply that appeared to originate from the anterior terminal branches of the nasociliary and lacrimal nerves.

CONCLUSIONS

Sympathetic nerves enter the orbit via the first and second divisions of the trigeminal nerve and a plexus of nerves surrounding the ophthalmic artery. Extraocular motor nerves receive a sympathetic nerve supply from the sensory nerves in the posterior orbit. Some ciliary ganglion cell bodies demonstrated tyrosine hydroxylase-like reactivity, suggesting a sympathetic modulatory role for the ciliary ganglion. Sympathetics innervate ocular structures via the posterior ciliary nerves. Sympathetic axons travel anteriorly in the orbit via the nasociliary and lacrimal nerves to innervate the sympathetic eyelid muscles. Sympathetic nerves also travel with the frontal branch of the ophthalmic nerve to innervate the forehead skin. The ophthalmic artery and all of its branches contain a perivascular sympathetic nerve supply that may be involved in regulation of blood flow to ocular and orbital structures.

Analysis of contact lens intolerance by exploring neuroanatomic integration of ocular surface defense

This paper reviews the anatomic, neuronal and mechanical factors that affect contact lens wear, and outlines several areas where compromised ocular surface defense arising from dysfunctional neuroanatomic integration might be the source of or a contributor to contact lens intolerance. Suggestions for clinical work-up by analyzing neuroanatomic integration are presented as a logical way to dissect this complex problem.

Regulatory pathways in lacrimal gland epithelium

Tears are a complex fluid that continuously cover the exposed surface of the eye, namely the cornea and conjunctiva. Tears are secreted in response to the multitude of environmental stresses that can harm the ocular surface such as cold, mechanical stimulation, physical injury, noxious chemicals, as well as infections from various organisms. Tears also provide nutrients and remove waste from cells of the ocular surface. Because of the varied function of tears, tears are complex and are secreted by several different tissues. Tear secretion is under tight neural control allowing tears to respond rapidly to changing environmental conditions. The lacrimal gland is the main contributor to the aqueous portion of the tear film and the regulation of secretion from this gland has been well studied. Despite multiple redundencies in pathways to stimulate secretion from the lacrimal gland, defects can occur resulting in dry eye syndromes. These diseases can have deleterious effects on vision. In this review, we summarize the latest information regarding the regulatory pathways, which control secretion from the lacrimal gland, and their roles in the pathogenesis of dry eye syndromes.

Presence of neuronal nitric oxide synthase in autonomic and sensory ganglion neurons innervating the lacrimal glands of the cat: an immunofluorescent and retrograde tracer double-labeling study

It is generally considered that parasympathetic postganglionic nerve fibers innervating the lacrimal gland (LG) arise from the pterygopalatine ganglion (PPG), while sympathetic and sensory innervations arise from the superior cervical ganglion (SCG) and trigeminal ganglion (TG), respectively. Recently, we reported for the first time that the parasympathetic innervation of the cat LG was also provided by the otic ganglion (OG) and ciliary ganglion (CG), and that the sensory innervation was also provided by the superior vagal ganglion (SVG) and superior glossopharyngeal ganglion (SGG). To determine if nitric oxide (NO) is a neurotransmitter of the autonomic and sensory neurons innervating the LG, we injected the cholera toxin B subunit (CTB) as a retrograde tracer into the cat LG, and used double-labeling fluorescent immunohistochemistry for CTB and nitric oxide synthase (NOS). We found that NOS-/CTB-immunofluorescent double-labeled perikarya were localized in the PPG, OG, TG, SVG and SGG, but not in the CG and SCG. The highest numbers of NOS-/CTB-immunofluorescent double-labeled neurons were found in the PPG and TG. In addition, we examined the presence of nitrergic nerve fibers in the LG using NADPH-d histochemistry and found that a large amount of NADPH-d-stained nerve fibers were distributed around the glandular acini and in the walls of glandular ducts and blood vessels. This study provides the first direct evidence showing that NO may act as a neurotransmitter or modulator involved in the parasympathetic and sensory regulation of lacrimal secretion and blood circulation, but may not be implicated in the sympathetic control of LG activities, and that nitrergic nerve fibers in the LG arise mainly from parasympathetic postganglionic neurons in the PPG and sensory neurons in the TG. The present results suggest that NO plays an important role in the regulation of LG activities.

Innervation of the cavernous body of the human efferent tear ducts and function in tear outflow mechanism

The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not previously investigated. Different S-100 protein antisera, neuronal markers (neuron-specific enolase, anti-200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene-related peptide, vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also examined by means of standard transmission electron microscopy. The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins, and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a plexus-like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S-100 protein (S 100), neuron-specific enolase (NSE), anti-200 kDa neurofilament (RT 97), calcitonin gene-related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands. Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural control of the cavernous body of the human efferent tear ducts. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow. Related functions such as a role in the occurrence of epiphora related to emotional responses are relevant. Moreover, malfunction in the innervation of the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passages.

An on-line method for the measurement of total protein output in biological fluids and secretory tissues after stimulation of intrinsic nerves and identification of neurotransmitters using immunohistochemical techniques

Proteins are essential ingredients of life and thus it is essential to measure the level of proteins in biological fluids and tissue homogenates. Several methods have previously been described in the literature for the estimation of proteins using either certain dyes which bind to specific groups of polypeptide side chains producing a protein dye colour complex, methods involving copper binding to peptide bonds or application of an eosin B red dye. In this study, an on-line automated technique based on the Lowry method has been used to estimate total protein output from the isolated lacrimal segments. This method can also be used to estimate total protein from saliva, or any other biological fluid, tissue homogenates or secretory tissues. The on-line automated method for the estimation of total protein from secretory tissues and biological fluid was designed mainly to obtain a rapid, simple and consistent graphical interpretation of result within 40-50 min of starting the experiment. The original chart recording of the time-course response can also be used for publication purposes. With this method, it is possible to investigate the effect of electrical field stimulation on the intrinsic secretomotor nerves employing either wire or platinum electrodes embedded in the perfusing chamber. Moreover, the tissue can also be stimulated with different concentrations of either drugs, hormones or neurotransmitters for different time periods. This method can also be combined with morphology whereby the stimulated tissue can be processed for neuropeptide or neurotransmitter immunohistochemistry to determine which neurotransmitters or neuropeptides are involved in the physiological responses. The automated method is simple and rapid and moreover, it can estimate accurately and directly at physiological pH small amount (ng-microgram) of proteins in effluent samples depending on the sensitivity of the chart recorder. In this study, neuropeptides and neurotransmitters were used as secretagogues in addition to electrical field stimulation.

The Lacrimal Gland and Its Veil of Tears

The secretory cells of the lacrimal gland produce a highly complex product of water, ions and proteins. At least five neurotransmitter receptors and three different second message systems are involved in controlling the different secretory processes of this highly sophisticated secretory epithelium.

Keratoconjunctivitis sicca associated with achalasia of the cardia, adrenocortical insufficiency, and lacrimal gland degeneration: Keratoconjunctivitis sicca secondary to lacrimal gland degeneration may parallel degenerative changes in esophageal and adrenocortical function

OBJECTIVE/DESIGN

This study aimed to examine and describe three siblings with alacrima, the eldest of whom had associated achalasia and adrenocortical insufficiency.

PARTICIPANTS

Three affected siblings and four age-matched control subjects participated. INTERVENTION/MAIN OUTCOME MEASURES: The three children underwent complete ophthalmologic examinations; computed tomographic scanning of brain, orbit, chest, and abdomen; and measurement of serum cortisol. All three were subjected to a short synacthen challenge. Lacrimal gland biopsies were performed on the two younger subjects, and specimens were studied by light and electron microscopy.

RESULTS

All three children showed virtually absent tear secretion as tested by the Schirmer test. The resulting keratopathy was most severe in the oldest child, who developed bilateral corneal melting. The two younger children showed interpalpebral corneal staining with rose bengal. All three children improved after punctal occlusion. Addison's disease was present in the oldest child. Computed tomographic scanning showed absent lacrimal and shrunken adrenal glands in association with achalasia of the cardia in the oldest child. The lacrimal glands were found to be reduced in size in the next eldest child. When evaluated by electron microscopy, the lacrimal gland biopsy specimens from the two younger children showed neuronal degeneration associated with depletion of secretory granules in the acinar cells.

CONCLUSION

In this disease, radiologic evidence of reducing lacrimal gland size with increasing age could represent a degenerative process. This may be paralleled by other signs and the possibility of adrenocortical insufficiency and achalasia of the cardia should be investigated in all children presenting with dry eyes. These children appear to have a progressive neuronal disease.

Selective innervation of different target tissues in guinea-pig cranial exocrine glands by sub-populations of parasympathetic and sympathetic neurons

This study has used multiple-labelling immunohistochemistry and quantitative analysis to examine the projections of subpopulations of parasympathetic and sympathetic neurons to different vascular and secretory structures in five cranial exocrine glands of guinea-pigs. Multiple subpopulations of parasympathetic axons, identified by immunoreactivity (IR) for various combinations of peptides, innervated arteries, arterioles, ducts and acini in sublingual, submandibular, parotid, lacrimal and zygomatic glands, although axons were absent from ducts in the parotid gland. Most parasympathetic axons contained IR for vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), with or without enkephalin (Enk). The proportion of parasympathetic axons that contained Enk-IR varied greatly between target tissues and glands: Enk-IR was more common in axons supplying secretory ducts, acini and arterioles than in axons innervating more proximal arteries; Enk-IR was less common in axons supplying the lacrimal gland than axons supplying the submandibular, lacrimal and zygomatic glands. Sympathetic axons with IR for tyrosine hydroxylase (TH) innervated arterial vessels in all glands, but innervated secretory structures only in the salivary glands. Sympathetic axons supplying proximal arterial segments often contained NPY-IR and sometimes also contained IR for dynorphin. Dynorphin-IR was more common in axons in the parotid, lacrimal and zygomatic glands than in the sublingual and submandibular glands. In contrast, axons supplying arterioles, ducts and acini lacked peptide IR. These results indicate that neuronal pathways regulating proximal arteries in cranial exocrine glands are different from the neuronal pathways regulating arterioles and acini, and may be different from neurons projecting to proximal secretory ducts. Furthermore, the peptides enkephalin, NPY and dynorphin are likely to make variable contributions to autonomic neurotransmission in different arterial segments and in different cranial exocrine glands.

Detection of substance P in human tears by laser desorption mass spectrometry and immunoassay

PURPOSE

To determine whether substance P is present in human tears.

METHODS

Tear samples (1-2 microliters) were collected from one eye of each of 12 subjects. Two of the eyes had dry eye syndrome, two wore contact lenses and had dry eye syndrome, and eight were normal. Five of the eight normal eyes were scheduled to undergo excimer laser refractive surgery, and tears were collected from these eyes before and after surgery. Tear samples were analyzed by laser desorption mass spectrometry. Pooled samples from one individual were subjected to enzyme-linked immunoabsorbent assay.

RESULTS

Laser desorption mass spectra of the 18 tear samples displayed well defined peaks with mass to charge (m/z) ratios ranging from 1343.7 to 1355.9 and/or 1356.9 to 1364.7, corresponding to an average m/z of 1349.8 +/- 1.13 for protonated substance P and 1361.2 +/- 0.54 for oxidized substance P obtained from 14 mass spectra of standards formulated with substance P concentrations ranging from 10(-4) M to 10(-12) M. As confirmation, an enzyme-linked immunoabsorbent assay performed twice on pooled tears from one eye detected substance P in both replicates at a concentration of 125 pg/ml (9.26 x 10(-11) M).

CONCLUSIONS

These findings demonstrate that substance P is a component of tears obtained from normal eyes of men and women ranging in age from 26 to 60 years, from eyes fitted with contact lenses, from eyes with dry eye syndrome, and from eyes 1 and 2 days after excimer laser refractive surgery. Whether the concentration of substance P in tears varies with sex, age, or eye condition, the source of substance P in tears, and its role in tears remains to be discovered.

Control of porcine lacrimal gland secretion by non-cholinergic, non-adrenergic nerves: effects of electrical field stimulation, VIP and NPY

This study employs the technique of electrical field stimulation (EFS) to characterise the effects of endogenous neurotransmitters on protein secretion in the in vitro pig lacrimal gland. The effects of exogenous applications of neurotransmitters on protein output and peroxidase secretion were also investigated for comparative purposes. EFS evoked frequency-dependent (5-20 Hz) increases in protein secretion. The EFS-evoked protein output was abolished with the nerve blocking drug tetrodotoxin (10(-6) M, TTX). Elevated potassium (100 mM KCl) can stimulate protein output in the presence of TTX. Exogenous application of either acetylcholine (ACh, 10(-9)-10(-4) M) or noradrenaline (NA, 10(-8)-10(-4) M) can also result in protein secretion, but they have no detectable effect on peroxidase secretion. In the presence of the cholinergic antagonist, atropine (10(-5) M) the EFS-induced protein output was reduced but not abolished. This atropine-resistant and non-cholinergic nerve-mediated component was further reduced in the combined presence of atropine, phentolamine, and propranolol (all 10(-5) M). When vasoactive intestinal polypeptide (VIP) receptor antagonist (10(-6) M [4-Cl-D-Phe6-Leu17]-VIP) was combined with the cholinergic and adrenergic antagonists, EFS caused a small but detectable increase in protein output. Exogenous application of either 10(-9) M VIP or 10(-9) M neuropeptide-Y (NPY) resulted in protein secretion. Combination of both VIP and NPY only induced an additive effect on protein output. Theophylline (10(-4) M), a phosphodiesterase inhibitor, evoked a small increase in protein output and had no significant effect on the secretory responses elicited by either VIP or NPY. In contrast, theophylline potentiated the non-cholinergic, non-adrenergic EFS-induced protein secretion. The results indicate that protein secretion from the porcine lacrimal gland may be controlled by cholinergic, adrenergic and non-cholinergic, non-adrenergic nerves. The peptidergic neurotransmitters may be VIP and other related neuropeptide(s). In addition to these neurophysiological studies, our results confirm previous findings that the porcine lacrimal nerves contain abundant quantity of NPY and VIP.

Adenovirus infection of the cornea causes histopathologic changes in the lacrimal gland

PURPOSE

To explore the effects on the lacrimal gland of adenovirus infection of the cornea.

METHODS

Rabbit corneas were inoculated with human adenoviruses Ad5, Ad14, or a rabbit adapted form of Ad 5, and in some instances booster inoculations were given. Sections of lacrimal glands removed 21-59 days post-inoculation were immunostained using antibodies against rabbit Class I and Class II MHC molecules, CD4, CD8, CD18, and rabbit thymic lymphocyte antigen (RTLA). Relative numbers of positively stained cells were quantified with a Metamorph image analysis system.

RESULTS

RTLA and CD18 antigens were expressed on many interstitial cells in the normal lacrimal gland, but few expressed CD4 or CD8. The number of RTLA+ cells increased by 60-100% after inoculation of Ad5 and after boosting, and CD18+ cells increased from 33-100% after inoculation of Ad5 and after boosting. Booster inoculations also caused focal lymphocytic infiltration. MHC Class I was expressed on interstitial cells and duct epithelium, but not acinar cells, and there was no detectable difference after viral infection. In controls, MHC Class II was localized to a population of interstitial cells and a few acinar cells. A single inoculation of the Ad5 virus did not result in an increase in the total number of MHC Class II-positive cells at 21 days, but inoculation with the rabbit-adapted Ad 5 and booster inoculations caused a 30% increase.

CONCLUSIONS

Ad5 and rabbit-adapted Ad5 infection of the cornea induce lymphocytic infiltration in the lacrimal gland, and the effect is enhanced by boosting. There is also an increase in expression of MHC Class II after inoculation with rabbit-adapted Ad5 and with booster inoculations.

Distribution pattern of nervous tissue and peptidergic nerve fibers in accessory lacrimal glands

PURPOSE

Demonstration of the distribution pattern of nervous tissue and the occurrence of neuropept human accessory lacrimal glands by means of immunohistochemical methods.

METHODS

Paraffin sections of tissue samples were incubated with antisera against protein gene product (PGP), S-100 protein (S-100), calcitonin gene-related peptide (CGRP) and substance P (SP). The immunoreactions were visualized using both species-specific secondary antibodies and a streptavidin-biotin-peroxidase complex (ABC method).

RESULTS

PGP- and S-100-immunoreactive nerve fibers were distributed in the entire intertubular stroma. In addition, myoepithelial cells, a few clusters of tubulus cells, groups of wandering cells, and scattered cells of the excretory duct system were S-100-immunoreactive. CGRP- and SP-immunoreactivity was found in a few nerve fibers in the intertubular glandular stroma with an association to secretory tubules, blood vessels, intralobular ducts and excretory duct.

CONCLUSIONS

These observations are in agreement with findings in the main lacrimal gland.

Pattern of distribution of neuropeptides in the camel lacrimal gland

The pattern of distribution of neuropeptides, including neuropeptide-Y (NPY), vasoactive intestinal polypeptide (VIP), neurotensin (NT), serotonin (5-HT), galanin (GAL), leucine-enkephalin (LEU-ENK) and calcitoningene-related-peptide (CGRP), in the nerves of the camel lacrimal gland was investigated using immunohistochemical techniques. Fresh lacrimal gland segments, obtained from adult camels slaughtered in the local abattoir, were used for the immunohistochemical techniques. NPY and LEU-ENK immunoreactivity was observed in the nerve cell bodies and nerve fibers of the camel lacrimal gland. VIP, GAL and CGRP were demonstrated predominantly in fine varicose nerve fibers lying on the basolateral surfaces of the lacrimal acinar cells. NT and 5-HT were identified mainly in neurons situated in the periacinar regions, close to the basal surfaces of the acinar cells. It is concluded that the camel lacrimal nerves contain several neuropeptides including NPY, VIP, NT, 5-HT, GAL, LEU-ENK and CGRP which may modulate lacrimal fluid and protein secretion.

Secretion and serotonin release in the isolated rat lacrimal gland: the effects of substance P and calcitonin gene-related peptide

A close anatomical relationship between nerves containing substance P and calcitonin gene-related peptide (CGRP) and mast cells containing serotonin has been demonstrated in the rat lacrimal gland. This study investigates the potential for peptidergic regulation of lacrimal mast cells by examining the actions of substance P, CGRP and serotonin on protein and peroxidase secretion from isolated lacrimal segments and on substance P and CGRP to release serotonin from the lacrimal mast cells. Substance P, CGRP and serotonin evoked marked increases in total protein and peroxidase from the lacrimal. Sodium cromoglycate, a mast cell stabilizer, significantly reduced or blocked the secretory responses elicited by these agonists. Chromatographic analysis using electrochemical detection revealed that substance P, but not CGRP, augmented the release of serotonin from the gland. The substance P evoked peroxidase secretion and serotonin release was blocked by CGRP and by sodium cromoglycate. These results support a role for mast cells in the regulation of lacrimal secretion and suggest a novel regulatory interaction between substance P and CGRP in the control of lacrimal function through a neuro-immune interaction.

Differential distribution of neuronal markers and neuropeptides in the human lacrimal gland

BACKGROUND

The present study was undertaken in an attempt to broaden the spectrum of known neuronal markers and neuropeptides in the main lacrimal gland of the human by light-microscopic immunohistochemistry.

METHODS

Using antisera against the neuronal markers protein gene product (PGP) and S-100 protein (S-100), the distribution of nerve fibers in the human main lacrimal gland was studied. Vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were identified by their specific antisera.

RESULTS

The nerve fibers are distributed throughout the interstice between the glandular tubules. Associations were also found between nerve fibers and both the interlobular ductal system and blood vessels (mainly arterioles). Within the glandular lobules isolated groups of secretory cells stained positive for S-100 protein. Nerve fibers situated in the glandular interstice between the tubules showed predominantly positive immunoreactions for the neuropeptide VIP, while only very few fibers stained positive for CGRP, NPY and the catecholamine marker TH. Nerve fibers associated with interlobular blood vessels were mainly CGRP and NPY positive and stained only very rarely for VIP. The epithelia of interlobular ducts and excretory ducts were associated with CGRP-immunoreactive nerve fibers.

CONCLUSION

The neuropeptides identified in the lacrimal gland indicate the complexity with which a variety of biologic signals regulate and modulate the lacrimal gland.

Immunohistochemical study of leucine-enkephalin and its secretory effects in the isolated pig lacrimal gland

BACKGROUND

In our previous studies immunohistochemical studies have demonstrated the presence of leucine-enkephalin (Leu-Enk) in the intrinsic nerves of the pig lacrimal gland, which are discernible in the interlobular and interacinar areas from where branches that innervate the acinar tissues are sent. Since the intrinsic nerves have been shown to contain Leu-Enk, this study aimed to investigate the secretory effects of this neuropeptide in isolated segments of the pig lacrimal gland and to reconfirm its presence in the neuronal tissue of the lacrimal gland.

METHODS

Leu-Enk was identified using immunohistochemical techniques, while total protein output was measured in the effluent samples by an automated on-line colorimetric method. The Ca2+ and Mg2+ concentrations in the effluent samples were determined using an atomic absorbance spectrophotometer.

RESULTS

Leu-Enk (10(-12)-10(-7) M) evoked marked increases in total protein output from superfused lacrimal gland segments. The secretory effect of Leu-Enk was not blocked by pretreatment of the tissue with atropine but was substantially reduced by a combination of phentolamine and propranolol. The competitive antagonist, naloxone, has no effect on basal protein output, but when combined with Leu-Enk it caused a significant reduction in total protein output. Combining theophylline (10(-3) M) with Leu-Enk resulted in a marked potentiation of total protein output. In superfused lacrimal gland segments Leu-Enk (10(-8) M) evoked a net efflux of magnesium (Mg2+ release) and a net influx of calcium (Ca2+ intake).

CONCLUSION

The results indicated a physiological role for Leu-Enk in the regulation of protein secretion in the pig lacrimal gland.

Localization of nerves adjacent to goblet cells in rat conjunctiva

Neural stimulation of the cornea induces conjunctival goblet cell mucous secretion. Immunofluorescence microscopy was used to determine if nerves are present near conjunctival goblet cells and what types of nerves are present. In euthanized rats, the local anesthetic lidocaine (1%) was placed topically on the ocular surface for 10 min to prevent goblet cell mucous secretion. The ocular surface tissues were removed and either fixed in formaldehyde and then frozen, or frozen first and then post-fixed in formaldehyde. Tissue was sectioned and nerves localized by indirect immunofluorescence microscopy, using antibodies to synaptophysin (indicates nerve, independent of type), vasoactive intestinal peptide (VIP, indicates parasympathetic nerves), tyrosine hydroxylase (TH, indicates sympathetic nerves), dopamine beta-hydroxylase (DBH, indicates sympathetic nerves), phenylethanolamine-N-methyltransferase (PNMT, indicates sympathetic nerves), and calcitonin gene-related peptide (CGRP, indicates sensory nerves). Goblet cells were identified by phase-contrast microscopy. Synpatophysin-containing nerves were present in the basolateral region of conjunctival goblet cells clusters. Nerve fibers immunoreactive to VIP were found in the conjunctiva along the epithelial-stromal junction and around the basolateral aspect of goblet cell clusters. Nerve fibers immunoreactive to TH and DBH were detected surrounding goblet cells and in the conjunctival stroma. Nerve fibers immunoreactive to CGRP were detected in the epithelium and at the epithelial stromal junction, but were not localized near goblet cell clusters. CGRP-containing nerve fibers were also detected in the conjunctival stroma under the epithelium. We conclude that efferent parasympathetic and sympathetic, but not afferent sensory, nerves appear to be located adjacent to conjunctival goblet cell clusters. Activation of efferent parasympathetic and sympathetic nerves could directly stimulate conjunctival goblet cell mucous secretion. Antidromic activation of afferent sensory nerves releasing neurotransmitters could stimulate goblet cell secretion by a paracrine mechanism.

Increased release of immunoreactive calcitonin gene-related peptide (CGRP) in tears after excimer laser keratectomy

The purpose of the study was to quantify the neuropeptide calcitonin gene-related peptide (CGRP) in normal human tear fluid and to determine the effect of photorefractive excimer laser keratectomy (PRK) on its release in tears. CGRP was assayed in tear fluid samples using an enzyme immunoassay (detection limit 0.2 micrograms ml-1). Tear-fluid samples were collected preoperatively, 1, 2 and 7 days after PRK and analysed for CGRP. The changes in tear-fluid secretion were also monitored. The intra-assay variation was 3.0-7.0%. Despite the marked hypersecretion of tears, the concentration of CGRP did not decrease following PRK indicating a concomitant increase in CGRP release by sensory nerves and/or lacrimal gland(s). Consequently, the release of CGRP in tears increased from 197.9 +/- 36.6 ng min-1 (mean +/- S.E.M.) to 1723.0 +/- 402.4 ng min-1 (P < 0.01) on day 1, and to 2304.2 +/- 561.1 ng min-1 (P < 0.01) on day 2. On day 7, only minor elevation (377.02 +/- 83.24 ng min-1) was observed. It is concluded that CGRP is a component of normal human tear fluid. The ocular irritation response related to the photoablation induces an enhanced release of CGRP in tears. As a compound present in corneal sensory nerves CGRP may have a role in wound-healing.

Comparison of immunohistochemical localization of [Met5]enkephalin-Arg6-Gly7-Leu8, [Met5]enkephalin, neuropeptide Y and vasoactive intestinal polypeptide in the superior cervical ganglion of the rat

The localization of [Met5]enkephalin-Arg6-Gly7-Leu8 and [Met5]enkephalin immunoreactivities was studied in the rat superior cervical ganglion. The distribution of these enkephalin-containing peptides in the ganglion was correlated to that of neuropeptide Y and vasoactive intestinal polypeptide. Three different populations of peptide-containing postganglionic neurons were demonstrated. (1) A minor population (10-20%) of principal neurons was immunoreactive for [Met5]enkephalin-Arg6-Gly7-Leu8 but not immunoreactive for neuropeptide Y nor vasoactive intestinal polypeptide. (2) The major population (about 50-70%) was immunoreactive for neuropeptide Y but not for [Met5]enkephalin-Arg6-Gly7-Leu8. (3) Few vasoactive intestinal polypeptide-immunoreactive principal neurons (less than 2% of all principal neurons) were observed in the ganglion. All vasoactive intestinal polypeptide-immunoreactive neurons were also immunoreactive for neuropeptide Y but not for [Met5]enkephalin-Arg6-Gly7-Leu8. [Met5]enkephalin-Arg6-Gly7-Leu8- and [Met5]enkephalin-immunoreactive nerve fibers had a similar distribution. These enkephalin immunoreactive nerve fibers were seen to enclose both neuropeptide Y-containing principal neurons and neurons devoid of neuropeptide Y immunoreactivity. Furthermore, there were enkephalin-immunoreactive fiber baskets around vasoactive intestinal polypeptide-immunoreactive neurons and sometimes also around solitary enkephalin-immunoreactive neurons. Previously reported diverse role of enkephalins in the rat superior cervical ganglion is supported by this study.

Innervation and mast cells of the rat exorbital lacrimal gland: the effects of age

The distribution of nerves and mast cells was studied in the lacrimal glands of 3-5-, 14- and 24-month-old rats, using light microscopic histochemical and immunohistochemical techniques. In 14-month and, to a greater extent, in 24-month-old rats there were signs of chronic inflammation and patchy destruction of acinar, ductal and vascular tissue. The glands of the three different age groups contained acetylcholinesterase (AChE), vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)-, calcitonin gene-related peptide (CGRP)-, tyrosine hydroxylase-, substance P- and the phosphoprotein B-50-immunoreactive nerves. B-50-immunoreactive nerves were distributed around acini, blood vessels and ducts, in a similar manner to VIP and AChE. Substance P- and CGRP-immunoreactive nerves were sparsely distributed in interlobular connective tissue and around ducts and blood vessels. Tyrosine hydroxylase- and NPY-containing nerves were found around blood vessels. The 3-5- and 14-month-old rats had a similar pattern of innervation, however, by 24 months there was a reduction in the number and intensity of immunoreactive nerves. The loss of nerves was particularly associated with damage to the gland. Mast cells were also found in the lacrimal, mostly associated with neurovascular tissue. These could be histochemically labelled with alcian blue/safranin or toluidine blue and were immunohistochemically labelled with histamine and serotonin. Substance P-, CGRP-, VIP- and NPY-immunoreactive nerves were found apposed to mast cells. A large increase in mast cells was observed in 24-month compared to 3-5-month-old rats and these were found throughout the acinar tissue. These results show that a decrease in innervation and also chronic inflammation, with mast cell infiltration, occurs in aged rats. These findings may be contributing factors to reduced tear output in aging.