Autonomic nervous system regulates secretion of anti-inflammatory prohormone SMR1 from rat salivary glands.

The autonomic nervous system regulates the secretion of bioactive proteins and peptides from salivary glands that can be important in systemic physiological responses. The prohormone submandibular rat-1, which is highly expressed in rat submandibular glands, can be cleaved to produce polypeptides with analgesic and anti-inflammatory activities. Human genes related to submandibular rat-1 have conserved biological functions and are potentially important in pain suppression, erectile function, and inflammation. In this study we describe the differential expression and posttranslational modification of submandibular rat-1 protein in salivary glands, the urogenital tract, lung, blood, and saliva in male Sprague-Dawley and Brown Norway rats. Submandibular rat-1 protein is secreted into saliva after the administration of beta-adrenergic or cholinergic agonists. Removal of the sympathetic ganglion that innervates the salivary glands results in increased levels of submandibular rat-1 protein in salivary glands. The secretion of submandibular rat-1 in response to physiological stress may provide a large pool of submandibular rat-1-derived peptide products that can promote analgesia and decrease inflammation locally and systemically. This pathway may be conserved among mammals and may constitute an important anti-inflammatory and analgesic response to stress.

The tripeptide phenylalanine-(D) glutamate-(D) glycine modulates leukocyte infiltration and oxidative damage in rat injured spinal cord.

The tripeptide, phenylalanine-glutamate-glycine (FEG) and its d-isomeric form phenylalanine-(D) glutamate-(D) glycine (feG), derived from submandibular gland peptide-T, significantly reduce the allergic inflammatory response and leukocyte trafficking and neutrophil migration into intestine, heart and lungs. Due to these actions, we hypothesized that feG would attenuate the early inflammatory response to spinal cord injury, reduce free radical production and improve neurological outcomes, like other leukocyte-limiting strategies we have used previously. We tested this using a clip compression model of spinal cord injury in rats. Following spinal cord injury at the 4th thoracic cord segment, we quantified leukocyte infiltration, free radical formation and oxidative damage at the lesion site after feG or control peptide phenylalanine-(D) aspartate-(D) glycine treatment. In rats treated with feG at 2 and 12 h, or 6 and 12 h after spinal cord injury, mean myeloperoxidase activity and ED-1 expression were significantly lower ( approximately 40%) than in controls at 24 h. Free radical formation generated in injured spinal cord was detected using 2',7'-dichlorofluorescin-diacetate as a fluorescent probe. Free radical production in the injured cord increased significantly after spinal cord injury and feG treatment significantly reduced this free radical production. Oxidative enzymes, lipid peroxidation and cell death were also significantly ( approximately 40%), gp91 ( approximately 30%), thiobarbituric acid reactive substance levels ( approximately 35%), 4-hydroxynonenal-bound protein ( approximately 35%) and caspase-3 ( approximately 32%). Early administration of feG decreases infiltration of inflammatory cells into the injured spinal cord and intraspinal free radical formation, thereby reducing oxidative damage and secondary cell death after spinal cord injury.

The expression and role of Fas ligand in intestinal inflammation.

Fas ligand (FasL) is involved in the pathogenesis of inflammatory diseases and immune privilege. We examined the expression of FasL in the enteric nervous system (ENS) in murine colitis and guinea-pig ileitis. We studied FasL immunoreactivity, functional integrity of the ENS, severity of colitis, and distribution of neutrophils in wild type and B6/gld mice that lack functional FasL. In ileitis, the distribution of FasL, CD4+ and CD8+ T cells was examined. FasL expression was increased in the ENS of wild type mice with colitis, but decreased labelling of nerve fibres was noted in B6/gld mice. Neutrophils were more abundant and widely distributed in B6/gld mice. Colitis was more severe and persistent in B6/gld mice 7 days after induction. Functional parameters of intestinal secretion and motility in B6/gld mice were the same as controls. In ileitis, FasL expression was increased in the guinea-pig ENS and returned to control levels following the resolution of inflammation. While T cells were not present in the ENS of controls, they were observed during inflammation, but were excluded from ganglia. The number of enteric neurons was unchanged over the course of inflammation. The expression of FasL is altered in intestinal inflammation and contributes to its resolution in experimental colitis.

A novel submandibular gland peptide protects against endotoxic and anaphylactic shock.

Submandibular glands release peptides and proteins that, through exocrine and endocrine actions, facilitate tissue repair in the oral cavity, gastrointestinal tract, and more distal sites such as liver. It has been shown that salivary gland factors also modulate inflammatory responses, because we found that removal of the submandibular glands increases the hypotensive responses to endotoxin. From this observation we proposed that these glands contain a factor that regulates cardiovascular response to shock. With the use of classical peptide isolation procedures, a heptapeptide (TDIFEGG) called submandibular gland peptide T was identified in rat submandibular glands. A synthetic form of this peptide reduced endotoxic shock in sialadenectomized rats by 50% at doses as low as 1 microgram/kg and prevented allergen-induced hypotension by 90% in rats with intact salivary glands at a dose of 100 micrograms/kg. This novel peptide is probably generated from a prohormone, submandibular gland rat 1 protein, a product of the VCSA1 gene. These data indicate that submandibular glands participate in the regulation of systemic homeostasis.

A peptide from the submandibular glands modulates inflammatory responses.

BACKGROUND: The cervical sympathetic trunk-submandibular gland (CST-SMG) axis plays an important role in inflammation. An immunoregulatory heptapeptide, submandibular gland peptide T (SGP-T), was isolated from submandibular glands, and several of its biological activities have been identified. RESULTS: SGP-T reduced shock-induced hypotension and allergen-induced disruption of migrating myoelectric complexes and the magnitude of smooth muscle contraction. The heptapeptide inhibited the influx of neutrophils into carrageenin-soaked sponges. CONCLUSION: SGP-T has several biological activities that collectively help explain the ability of the CST-SMG axis to regulate inflammation.

Submandibular glands: novel structures participating in thermoregulatory responses.

Since submandibular glands participate in the regulation of cardiovascular and immunological responses to bacterial endotoxin, we examined their role as modulators of endotoxin-induced fever. Core body temperatures were measured by telemetry in rats that had either a sham operation or a sialadenectomy 1 week previously and that were maintained at 23-24 degrees C. The sialadenectomized rats showed a circadian variation in body temperature similar to sham-operated rats, although their daytime body temperature was 0.24 +/- 0.01 degree C lower. The fever elicited by intraperitoneal injection of Escherichia coli endotoxin was biphasic, with an initial phase occurring between 2 and 3 h, and a broader second phase peaking between 4 and 8 h after endotoxin injection. The initial fever was similar in the two groups of rats, but the second phase of fever was significantly higher by 0.28 +/- 0.09 and 0.26 +/- 0.07 degree C in sialadenectomized rats receiving 50 or 150 micrograms/kg of endotoxin, respectively. Intravenous treatment with a novel peptide, submandibular gland peptide-T (SGP-T; 100 micrograms/kg), 30 min before endotoxin injection did not affect the early fever response, but significantly suppressed by 0.37 +/- 0.10 degrees C the late-phase fever provoked by 150 micrograms/kg of endotoxin. These results suggest that the submandibular glands modulate thermogenic responses to inflammatory stimuli possibly through the endocrine release of hormones, such as SGP-T.

Salivary glands, their hormones, and thermoregulation.

The effects of the removal of the submandibular glands (sialadenectomy) on the fever induced by bacterial lipopolysaccharide (LPS) were examined. Thermally sensitive radiotransmitters were implanted into the abdomens of adult male Sprague-Dawley rats that experienced at this time either a sham operation or a sialadenectomy, and one week later body temperatures were recorded by telemetry in these rats when conscious. The initial fever (up to 180 min following LPS) response, following the intraperitoneal injection of 150 micrograms/kg E. coli LPS, was similar in the two groups of rats, but the second phase of the fever (240 to 420 min post-LPS) was modestly, but significantly higher (mean = 0.26 degree C) in sialadenectomized rats. A submandibular gland peptide (compound T; 100 micrograms/kg), given one-half hour before the LPS, did not affect the early fever, but suppressed the late-phase fever by 0.37 degree C (mean). The submandibular glands, which form an integral part of the neuroendocrine mechanisms responsible for attenuating the responses of the immune system to inflammatory stimuli, also appear to modulate thermogenic responses to these stimuli.

Neuroimmune mechanisms in health and disease: 2. Disease.

In the second part of their article on the emerging field of neuroimmunology, the authors present an overview of the role of neuroimmune mechanisms in defence against infectious diseases and in immune disorders. During acute febrile illness, immune-derived cytokines initiate an acute phase response, which is characterized by fever, inactivity, fatigue, anorexia and catabolism. Profound neuroendocrine and metabolic changes take place: acute phase proteins are produced in the liver, bone marrow function and the metabolic activity of leukocytes are greatly increased, and specific immune reactivity is suppressed. Defects in regulatory processes, which are fundamental to immune disorders and inflammatory diseases, may lie in the immune system, the neuro endocrine system or both. Defects in the hypothalamus-pituitary-adrenal axis have been observed in autoimmune and rheumatic diseases, chronic inflammatory disease, chronic fatigue syndrome and fibromyalgia. Prolactin levels are often elevated in patients with systemic lupus erythematosus and other autoimmune diseases, whereas the bioactivity of prolactin is decreased in patients with rheumatoid arthritis. Levels of sex hormones and thyroid hormone are decreased during severe inflammatory disease. Defective neural regulation of inflammation likely plays a pathogenic role in allergy and asthma, in the symmetrical form of rheumatoid arthritis and in gastrointestinal inflammatory disease. A better understanding of neuroimmunoregulation holds the promise of new approaches to the treatment of immune and inflammatory diseases with the use of hormones, neurotransmitters, neuropeptides and drugs that modulate these newly recognized immune regulators.

Neuroimmune mechanisms in health and disease: 1. Health.

A novel scientific discipline that examines the complex interdependence of the neural, endocrine and immune systems in health and disease has emerged in recent years. In health, the neuroimmunoregulatory network is fundamental to host defence and to the transfer of immunity to offspring; the network also plays important roles in intestinal physiology and in tissue regeneration, healing and reproduction. The proliferation of lymphocytes in primary lymphoid organs (bone marrow, bursa of Fabricius [in birds] and thymus) and in secondary lymphoid organs (spleen, lymph nodes and mucosal lymphoid tissue) depends on prolactin and growth hormone. These hormones allow immune cells to respond to antigen and to soluble mediators, called cytokines. Immune-derived cytokines are capable of inducing fever and of altering neuro-transmitter activity in the brain and hormone secretion by the pituitary gland. The activation of the hypothalamus-pituitary-adrenal axis by cytokines leads to immunosuppression. Lymphoid organs are innervated, and tissue mast cells respond to neurologic stimuli. In general, acetylcholine and substance P exert immunostimulatory and proinflammatory effects, whereas epinephrine and somatostatin are immunosuppressive and anti-inflammatory. In this article, the authors predict that novel approaches to immunomodulation will be possible by altering the level or efficacy of immunoregulatory hormones and neurotransmitters.

Role for the cervical sympathetic trunk in regulating anaphylactic and endotoxic shock.

This study tests the hypothesis that spinal nerves projecting down the cervical sympathetic trunk contribute to the regulation of systemic immune responses. Decentralization or ablation (ganglionectomy) of the superior cervical ganglia (SCG), which receive innervation from spinal segments C8-T8, were found to reduce the pulmonary inflammatory response consequent to induction of anaphylaxis in rats sensitized to the nematode Nippostrongylus brasiliensis. Furthermore, the hypotensive responses to IV endotoxin were attenuated in sensitized rats by these operations, whereas decentralization without ganglionectomy protected against endotoxic shock in normal (unsensitized) rats. These results suggest that systemic inflammatory events are regulated by the cervical sympathetic nervous system at a level superior to the superior cervical ganglia. Further studies are warranted to investigate the role of the cervical and thoracic sympathetic nerves in the regulation of systemic immunological function.

Physical, chemical, and enzymatic studies on the major sucrase of honey bees (Apis mellifera).

A sucrase from honey bees (Apis mellifera) which precipitates between ammonium sulfate saturations of 50 and 70% (5 mg protein per millilitre) and which makes up the major portion of the sucrases of honey bees was purified to homogeneity as shown by several criteria. A large part of the sucrase was found in the head while most of the rest was in the abdomen (a small amount was in the thorax). The enzyme precipitated between the same values of ammonium sulfate saturation as did the sucrase in honey and honey sucrase exhibited kinetics very similar to those of this enzyme. The enzyme was found to be a relatively nonspecific alpha-glucosidase and was shown to have transglucosidase activity. The production of glucose from sucrose was rectilinear when plotted by the Hofstee method at low substrate concentrations but decreased at high sucrose concentrations. The production of fructose was rectilinear throughout the concentration range used. The production of both glucose and rho-nitrophenol when rho nitrophenyl alpha-D-glucoside was the substrate was linear by the Hofstee plot. These effects were found to be due to transglucolysis and a mechanism of action is proposed. Amino acid and amino sugar analyses indicated that the sucrase was a glycoprotein. The molecular weight was found to be between 51000 and 82000 by three different methods and an so20.w value of 4.0 S was obtained. There was no evidence for subunit structure. Tests of the enzyme under various denaturation conditions did not reveal any unusual stabilities. The sucrase bound very tightly to a hydrophobic column. Iodoacetic acid decreased the activity of the sucrase but a large concentration was needed to bring about a 50% activity loss. Reducing agents caused some activity declines. Diethyl pyrocarbonate activated the enzyme.