Effect of manganese on luteinizing hormone-releasing hormone secretion in adult male rats.

Recently studies have demonstrated that low doses of (Mn(+2)) in the form of manganese chloride can stimulate specific puberty-related hormones and advance signs of pubertal development in immature female and male rats. In the present study, we used an in vitro system to evaluate the ability of 0, 50, 250, and 500 microM doses of Mn(+2) to stimulate luteinizing hormone-releasing hormone (LHRH) secretion and to assess the hypothalamic mechanism of this action in adult male Sprague-Dawley rats. We demonstrated that Mn(+2) at 500 microM, but not the lower doses, increased LHRH release, nitric oxide (NO) synthase (NOS) activity, and the content of cyclic cGMP in the medial basal hypothalamus. Inhibition of NOS with a competitive inhibitor (Nomega-nitro-L-arginine methyl ester hydrochloride) prevented the Mn-induced increase in LHRH release. Additionally, methylene blue and KT5823, specific inhibitors of guanylyl cyclase and protein kinase G (PKG), respectively, also blocked the stimulatory effect of Mn(+2) on LHRH release. These in vitro studies demonstrated that the hypothalamic mechanism of Mn(+2) action in adult males is by activation of the NOS/NO system, resulting in increases in cGMP and PKG and thus the secretion of LHRH from the nerve terminals. These results indicate Mn(+2) can cause LHRH release in adult males, and this action is discussed in relation to age, gender, as well as mechanistic and functional differences between adult and immature animals.

Chronology of advances in neuroendocrine immunomodulation.

This review documents the remarkable progress over the last 50 years of our knowledge of the control of anterior pituitary hormone release and synthesis by a family of peptidic releasing and inhibiting hormones, synthesized in hypothalamic neurons and released into the hypophysial portal vessels. These vessels transport them to the anterior pituitary, where they stimulate release and synthesis of pituitary hormones or inhibit these processes. In general, there are at least two hypothalamic hormones for each pituitary hormone-vasopressin and corticotrophin-releasing hormone (CRH) for adrenocorticotropin hormone (ACTH) and growth hormone-releasing hormone (GHRH) and growth hormone-inhibiting hormone (GIH) for growth hormone (GH). Some of these hormones have extrapituitary action: for example, luteinizing hormone-releasing hormone (LHRH) stimulates mating behavior. High doses of LHRH have an inhibitory action on the growth of prostate cancer. Proinflammatory and anti-inflammatory cytokines act not only in the brain, but also on the pituitary and peripheral tissues. All of these transmitters are controlled by neuronal transmitters. We anticipate further rapid progress and clinical application of these transmitters and the discovery of new ones.

Participation of the endocannabinoid system in the effect of TNF-alpha on hypothalamic release of gonadotropin-releasing hormone.

It is known that Delta(9)-tetrahydrocannabinol (THC), the major active ingredient of marijuana, can suppress reproductive function. Also, we reported previously that the endocannabinoid, anandamide (AEA), inhibited gonadotropin-releasing hormone (LHRH) release from medial basal hypothalamus (MBH) of male rats incubated in vitro as well as reduced plasma LH levels after i.c.v. AEA injections into the cerebral lateral ventricle. On the other hand, it is known that during endotoxemia the hypothalamic gonadotropin axis is inhibited. Therefore, the aim of the present study was to determine whether the effect of TNF-alpha, a proinflammatory cytokine induced by lipopolysaccharide (LPS) that inhibits LHRH release, is mediated by the activation of the endocannabinoid system. The intraperitoneal injection of LPS (5 mg/kg) as well as the i.c.v. injection of tumor necrosis factor-alpha (TNF-alpha) (100 ng/rat) increased significantly the AEA synthesis measured ex vivo in MBHs removed 3 h after the treatments. To examine the possibility that TNF-alpha also acted by increasing the synthesis of AEA that was released and activated the CB1-r followed by inhibition of LHRH release, we measured the effect of TNF-alpha on the AEA synthase activity in MBHs incubated in vitro. As expected, we found that TNF-alpha (2.9 x 10(-9) M) increased the AEA synthesis. Second, we showed that TNF-alpha reduced significantly the forskolin-stimulated LHRH release and that the CB1-r antagonist AM251 (10(-5) M) blocked that inhibition, supporting the hypothesis that TNF-alpha inhibits LHRH release, acting at least in part by activating the endocannabinoid system. Therefore, our data demonstrate a key role for the endocannabinoid system in the response of the reproductive system to inflammatory signals.

Inhibition of salivary secretion by activation of cannabinoid receptors.

It is known that marijuana use decreases saliva secretion. Therefore, we hypothesized that cannabinoid receptors (CBs) are located in salivary glands to mediate that effect. In these experiments, we used the submandibular gland (SMG) of male rats, which is one of the major salivary glands. Mammalian tissues contain at least two types of CBs, CB1 and CB2, mainly located in the nervous system and peripheral tissues, respectively. Both receptors are coupled to Gi protein and respond by inhibiting the activity of adenylyl cyclase. We demonstrated that both CB1 and CB2 are present in the SMG, each showing specific localizations. The best-known endocannabinoid is anandamide (AEA), which binds with high affinity to CB1 and CB2. We showed that AEA markedly reduced forskolin-induced increase of cAMP content in vitro. This effect was blocked by AM251 and AM630 (CB1 and CB2 antagonists, respectively), indicating that both receptors are implicated in SMG physiology. In addition, we showed that AEA injected intraglandularly to anesthetized rats inhibited norepinephrine (NE)- and methacholine (MC)-stimulated saliva secretion in vivo and that both AM251 or AM630 prevented the inhibitory action of AEA. Also, the intraglandular injection of AM251 increased saliva secretion induced by lower doses of NE or MC. This increase was synergized after coinjection with AM630. Therefore, we concluded that AEA decreases saliva secretion in the SMG acting through CB1 and CB2 receptors.

The role of nitric oxide (NO) in control of LHRH release that mediates gonadotropin release and sexual behavior.

Nitric oxide (NO) plays a crucial role in reproduction at every level in the organism. In the brain, it activates the release of luteinizing hormone-releasing hormone (LHRH). The axons of the LHRH neurons project to the mating centers in the brain stem and by efferent pathways, evoke the lordosis reflex in female rats. In males, there is activation of NOergic terminals that release NO in the corpora cavernosa penis to induce erection by generation of cyclic guanosine monophosphate (cGMP). NO also activates the release of LHRH which reaches the pituitary and activates the release of gonadotropins by activating neural NO synthase (NOS) in the pituitary gland. Follicle stimulating hormone (FSH)RH selectively releases FSH also by activating NOS. Leptin releases LHRH by activating NOS to release FSH and LH with the same potency as LHRH. These actions are mediated by specific receptors on the gonadotropes for LHRH, FSHRH and leptin. The responsiveness of the pituitary is controlled by gonadal steroids. In the gonad, NO plays an important role inducing ovulation and in causing luteolysis; whereas in the reproductive tract, it relaxes uterine muscle via cGMP and constricts it by prostaglandins.

Effect of neurogenic stress and ethanol on nitric oxide synthase and cyclooxygenase activities in rat adrenals.

Repeated restraint stress (RRS) in male rats activated the pituitary adrenal system, as indicated by increases in adrenal weight and plasma corticosterone concentration that were accompanied by a decrease in constitutive nitric oxide synthase (cNOS), but not inducible NOS (iNOS). iNOS activated cyclooxgenase, causing elevated prostaglandin E(2) (PGE(2)) and F(2 alpha) in the adrenals, but had no effect on lipoxygenase. Administration of ethanol (ETOH) was also associated with elevated adrenal weight and a slight increase in corticosterone coupled with a decrease in both cNOS and iNOS and PGs in the adrenal. When ETOH was administered together with RRS, a decrease in iNOS and PGE release was noted consequent to a reduction in iNOS. Thus, ETOH probably reduced RRS-induced adrenocorticotropic hormone release. Adrenals were incubated in vitro to further evaluate the role of NO in these processes. Results indicated that NO released by sodium nitroprusside increased corticosterone release presumably by activating guanylyl cyclase with production of cyclic guanosine monophosphate (cGMP), because although NO also increased PGE release, PGE(2) (10(-5)-10(-9) M) decreased corticosterone release, an effect that was highly significant at a concentration of 10(-7) M PGE(2). ETOH (100 mM) had no effect on corticosterone release and did not block the increase in corticosterone caused by NO; however, ETOH reduced PGE release into the medium and blocked PGE(2) release induced by NO. Consequently, NO activated corticosterone release not by PGs, but by activation of guanylyl cyclase and release of cGMP. PGs have a negative feedback to suppress corticosterone release.

Hypertension induced by nitric oxide synthase inhibition activates the atrial natriuretic peptide (ANP) system.

We assessed the effect of nitric oxide (NO) synthase inhibition on plasma atrial natriuretic peptide (ANP) concentration and content in some brain structures [neurohypophysis (NH), adenohypophysis (AH), medial basal hypothalamus (MHB) and olfactory bulb (OB)] in rats before and after blood volume expansion (BVE). Male Wistar rats were injected i.p. with N(pi)-nitro-L-arginine (L-NNA), 25 mg/kg of body weight, 40 min before the experiment (acute treatment) or L-NNA at a dose of 25 mg/kg body weight, twice a day, for 4 days (chronic treatment). The acute treatment caused an increase in the blood pressure and plasma ANP concentration in rats under basal conditions and after BVE. A decrease in ANP content was observed in the OB and NH, whereas no significant changes were found in the AH or MBH. In chronically treated rats, we also found an increase in blood pressure and in plasma ANP concentration under basal conditions and after BVE. The ANP content increased in the OB, NH and AH. These results indicate that systemic NO synthase inhibition increases ANP concentration in plasma and in areas of the central nervous system. We hypothesize that ANP participates in the hypertension-induced by NO synthesis blockade acting by baroreceptors input to the brain to stimulate ANP release and synthesis that reduces NO prival hypertension.

Inhibition of stimulated ascorbic acid and luteinizing hormone-releasing hormone release by nitric oxide synthase or guanyl cyclase inhibitors.

Ascorbic acid (AA), an antioxidant, is present in high concentrations in the hypothalamus. Previously, we have shown that AA inhibited stimulated release of luteinizing hormone-releasing hormone (LHRH) from medial basal hypothalami in vitro. We have also demonstrated that cell membrane depolarization by high [K(+)] media-induced AA release that is blocked by N(G)-mono-methyl-L-arginine, a competitive inhibitor of nitric oxide synthase (NOS), indicating that the release process is mediated by NO. The release of LHRH is also mediated by NO. We hypothesized that AA is a co-transmitter released with classical transmitters from synaptic vesicles that acts to reduce chemically the NO formed, thereby providing feed-forward inhibitory control over LHRH release. Because NO acts by activating guanylyl cyclase (GC) resulting in production of cGMP, in the present investigation we studied the effects of an NOS inhibitor LY 83583 and GC inhibitor, O.D.Q. to further characterize the role of NO in high [K(+)]-induced AA and LHRH release. Medial basal hypothalami were incubated in 0.5 ml of Krebs-Ringer Bicarbonate buffer or medium containing increased potassium [K(+) = 56 mM] for 1 hr or combinations of high [K(+)] + LY 83583 or O.D.Q. for 1 hr. AA and LHRH released into the incubation medium were measured by high-pressure liquid chromatography and radioimmunoassay, respectively. Cell membrane depolarization with high [K(+)] produced a significant increase in both AA and LHRH release. A combination of high [K(+)] + LY 83583 or high [K(+)] + O.D.Q. decreased basal AA and completely blocked high [K(+)]-induced AA and LHRH release. As in the case of high [K(+)], LHRH release induced by the excitatory amino acid N-methyl-D-aspartic acid (NMDA) was blocked by both the inhibitors. NMDA alone failed to alter AA release, but the combined presence of NMDA and the inhibitors totally blocked AA release. Because LY 83583 and O.D.Q. were shown to inhibit NOS and soluble GC, respectively, the data demonstrate that basal and high [K(+)]-induced AA and high [K(+)] and NMDA-stimulated LHRH release were mediated by NO by its activation of GC and consequent generation of cGMP.

17beta-estradiol stimulates ascorbic acid and LHRH release from the medial basal hypothalamus in adult male rats.

In the present investigation, 17beta-estradiol (E(2)) and tamoxifen, an antiestrogen, were evaluated for their effects on the release of ascorbic acid (AA) and luteinizing hormone-releasing hormone (LHRH). Medial basal hypothalami (MBH) from adult male rats were incubated with graded concentrations of E(2) (10 (-9) to 10(-6) M) or a combination of E(2) (10(-7) M) and tamoxifen (10(-7) and 10(-6) M ) in 0.5 ml of Krebs Ringer bicarbonate buffer for 1 hr. AA and LHRH in the incubation medium were measured by high-performance liquid chromatography and radioimmunoassay, respectively. E(2) significantly elevated both AA and LHRH release and the minimal effective dose was 10(-7) M. A combination of E(2) (10(-7) M) and tamoxifen (10(-6) M) totally blocked E(2)-induced AA and LHRH release. The stimulatory effect of E(2) was also suppressed in the presence of N(G)-monomethyl-L-arginine, a competitive inhibitor of nitric oxide synthase (NOS), illustrating that the release is mediated by nitric oxide (NO). To further characterize the role of NO, the tissues were incubated with E(2) or a combination of E(2) + (6 anilino-5, 8-quinolinedione) LY 83583 (10(-6) and 10(-5) M), an inhibitor of NOS. LY 83583 was effective in suppressing E(2)-induced AA and LHRH release, demonstrating that the effect was mediated by cyclic GMP. Incubation of the tissues with E(2) or a combination of E(2) + 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (O.D.Q.) (10(-5) and 10(-4) M), a specific inhibitor of soluble guanylyl cyclase failed to alter AA release but significantly suppressed LHRH release. The role of a prostaglandin synthesis blocker in E(2)-induced AA and LHRH release was tested by incubating the tissues with E(2) or a combination of E(2) + indomethacin (1.8 x 10 (-7) or 1.8 x 10(-6) M). Indomethacin produced a significant decrease in E(2)-induced AA and LHRH release, suggesting that the release process required prostaglandins as an intracellular mediator. In conclusion, E(2) stimulated both AA and LHRH release and the effect was mediated by NO and prostaglandins.

Inhibition of melatonin-induced ascorbic acid and LHRH release by a nitric oxide synthase and cyclic GMP inhibitor.

Melatonin (MEL), the principle secretory product of the pineal gland, has been shown to function as an antioxidant and free-radical scavenger. We previously showed that the release of ascorbic acid (AA) and luteinizing hormone releasing hormone (LHRH) from medial basal hypothalamus (MBH) was mediated by nitric oxide (NO) that released cyclic guanosine 3'5'-mono-phosphate (cGMP). Therefore, it was of interest to evaluate the effect of MEL on AA and LHRH release and study the effect of a nitric oxide synthase (NOS) inhibitor, 6-anilino-5,8-quinoline-dione (LY 83583), and a guanylyl cyclase (GC) inhibitor, 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (O.D.Q.), on the release process. Because NO has been shown to activate soluble guanylyl cyclase that elicited an elevation of cGMP in target cells, in the current investigation LY 83583, O.D.Q., or N(G)-monomethyl-l-arginine (NMMA), a competitive inhibitor of NOS, were used to evaluate their effects on MEL-induced AA and LHRH release. Medial basal hypothalami were incubated in 0.5 ml of Krebs-Ringer bicarbonate (KRB) buffer for 1 hr. Subsequently, the tissues were incubated with graded concentrations of MEL (10(-8) to 10(-4) M), MEL + NMMA (3 x 10(-4) M), MEL + LY 83583 (10(-6) M), or MEL + O.D.Q. (10(-5) M) for 1 hr. Ascorbic acid and LHRH released into the medium were measured by high-performance liquid chromatography (HPLC) and radio-immunoassay (RIA), respectively. Melatonin (10(-6) and 10(-5) M) significantly stimulated both AA and LHRH release, but the lower and the highest concentrations were ineffective. A combination of MEL + NMMA completely blocked both AA and LHRH release, supporting a role for NO in the releasing action. Both LY 83583 and O.D.Q. significantly suppressed MEL-induced AA and LHRH release, emphasizing the role of NOS, GC, and cGMP in mediating the action of MEL. The data of these in vitro experiments support a role for MEL in the hypothalamic control of AA and LHRH release.

Caspase 1 deficiency reduces inflammation-induced brain transcription.

The systemic inflammatory response syndrome (SIRS) is a life-threatening medical condition characterized by a severe and generalized inflammatory state that can lead to multiple organ failure and shock. The CNS regulates many features of SIRS such as fever, cardiovascular, and neuroendocrine responses. Central and systemic manifestations of SIRS can be induced by LPS or IL-1beta administration. The crucial role of IL-1beta in inflammation has been further highlighted by studies of mice lacking caspase 1 (casp1, also known as IL-1beta convertase), a protease that cleaves pro-IL-1beta into mature IL-1beta. Indeed, casp1 knockout (casp1(-/-)) mice survive lethal doses of LPS. The key role of IL-1beta in sickness behavior and its de novo expression in the CNS during inflammation led us to test the hypothesis that IL-1beta plays a major role modulating the brain transcriptome during SIRS. We show a gene-environment effect caused by LPS administration in casp1(-/-) mice. During SIRS, the expression of several genes, such as chemokines, GTPases, the metalloprotease ADAMTS1, IL-1RA, the inducible nitric oxide synthase, and cyclooxygenase-2, was differentially increased in casp1(-/-) mice. Our findings may contribute to the understanding of the molecular changes that take place within the CNS during sepsis and SIRS and the development of new therapies for these serious conditions. Our results indicate that those genes may also play a role in several neuropsychiatric conditions in which inflammation has been implicated and indicate that casp1 might be a potential therapeutic target for such disorders.

Endocannabinoids in TNF-alpha and ethanol actions.

During marijuana and alcohol consumption as well as during inflammation the reproductive axis is inhibited, mainly through the inhibition of luteinizing hormone-releasing hormone release. In male rats, this inhibitory effect is mediated, at least in part, by the activation of hypothalamic cannabinoid type 1 receptors (CB1). During inflammation, this activation of the endocannabinoid system seems to be mediated by an increase in TNF-alpha production followed by anandamide augmentations, similarly the effect of intragastric administration of ethanol (3 g/kg) seems to be due to an increase in anandamide. On the other hand, a number of different actions mediated by the endocannabinoid system in various organs and tissues have been described. Both cannabinoid receptors, CB1 and CB2, are localized in the submandibular gland where they mediate the inhibitory effect of intrasubmandibular injections of the endocannabinoid anandamide (6 x 10(-5)M) on salivary secretion. Lipopolysaccharide (5 mg/kg/3 h) injected intraperitoneally and ethanol (3 g/kg/1 h) injected intragastrically inhibited the salivary secretion induced by the sialogogue metacholine; this inhibitory effect was blocked by CB1 and/or CB2 receptor antagonists. Similar to the hypothalamus, these effects seem to be mediated by increased anandamide. In summary, similar mechanisms mediate the inhibitory actions of endocannabinoids and cannabinoids in both hypothalamus and submandibular gland during drug consumption and inflammation.

Age-dependent regulation of chromaffin cell proliferation by growth factors, dehydroepiandrosterone (DHEA), and DHEA sulfate.

The adrenal gland comprises two endocrine tissues of distinct origin, the catecholamine-producing medulla and the steroid-producing cortex. The inner adrenocortical zone, which is in direct contact with the adrenomedullary chromaffin cells, produces dehydroepiandrostendione (DHEA) and DHEA sulfate (DHEAS). These two androgens exhibit potential effects on neurogenesis, neuronal survival, and neuronal stem cell proliferation. Unlike the closely related sympathetic neurons, chromaffin cells are able to proliferate throughout life. The aim of this study was to investigate the effect of DHEA and DHEAS on proliferation of bovine chromaffin cells from young and adult animals. We demonstrated that graded concentrations of leukemia inhibitory factor induced proliferation of chromaffin cells from young animals, whereas EGF had no effect. On the contrary, EGF increased the cell proliferation in cells from adult animals, whereas leukemia inhibitory factor was inactive. In both cases, DHEA decreased the proliferative effect induced by the growth factors. Surprisingly, DHEAS enhanced, in a dose-dependent-manner, the effect of growth factors on proliferation in cells from adult animals but not from young animals. Flutamide, ICI 182,780, and RU 486 had no effect on the action of DHEA or DHEAS on chromaffin cell proliferation. These data show that DHEA and its sulfated form, DHEAS, differentially regulate growth-factor-induced proliferation of bovine chromaffin cells. In addition, the sensitivity of chromaffin cells to different growth factors is age-dependent. Furthermore, these two androgens may act through a receptor other than the classical steroid receptors.

Role of ammonia and nitric oxide in the decrease in plasma prolactin levels in prehepatic portal hypertensive male rats.

OBJECTIVES: Since very little is known about neuroendocrine changes that occur in portal-systemic hepatic encephalopathy, we studied plasma prolactin (PRL) levels and the involvement of hyperammonemia, nitric oxide (NO) and dopaminergic and adrenergic systems in the control of this hormone secretion in a male rat model of prehepatic portal hypertension (PH). METHODS: We conducted in vivo studies to determine plasma ammonia and PRL levels. Dopamine (DA), dihydroxyphenylacetic acid (DOPAC), epinephrine and norepinephrine content in medial basal hypothalamus (MBH) and anterior pituitary (AP) were measured. In addition, NO synthase (NOS) activity and protein expression were evaluated in APs. In in vitro studies, the APs from intact rats were incubated with different doses of ammonia and PRL secretion was determined. In ex vivo studies, the APs from normal and PH rats were incubated in the presence of ammonia and/or a NOS inhibitor, NG-nitro-L-arginine-methyl ester (L-NAME) and PRL secretion was determined. RESULTS: PH rats had a significant increase in plasma ammonia levels (p < 0.001) and a decrease in plasma PRL levels (p < 0.05). Neither DA nor DOPAC content or DOPAC/DA ratios were modified in both MBH and APs; however, we observed a significant increase in norepinephrine content in both MBH and AP (p < 0.001 and p < 0.05, respectively) and a significant increase in epinephrine in APs (p < 0.001). Moreover, PH produced an increase in NOS activity (p < 0.01) and NOS protein expression (p < 0.0001) in APs. The ammonia (100 microM) significantly reduced PRL secretion from APs in vitro (p < 0.05). The presence of L-NAME, an inhibitor of NOS, abrogated the inhibitory effect of ammonia on PRL secretion from APs from control and PH rats. CONCLUSIONS: We found that plasma PRL levels were decreased in PH rats probably due to the high ammonia levels. The central noradrenergic system could also mediate this decrease. Also, the increase in NOS activity and/or content in AP induced NO production that directly inhibited PRL secretion from the AP, without the participation of the dopaminergic system.

Phosphodiesterase genes are associated with susceptibility to major depression and antidepressant treatment response.

Cyclic nucleotide phosphodiesterases (PDEs) constitute a family of enzymes that degrade cAMP and cGMP. Intracellular cyclic nucleotide levels increase in response to extracellular stimulation by hormones, neurotransmitters, or growth factors and are down-regulated through hydrolysis catalyzed by PDEs, which are therefore candidate therapeutic targets. cAMP is a second messenger implicated in learning, memory, and mood, and cGMP modulates nervous system processes that are controlled by the nitric oxide (NO)/cGMP pathway. To investigate an association between genes encoding PDEs and susceptibility to major depressive disorder (MDD), we genotyped SNPs in 21 genes of this superfamily in 284 depressed Mexican Americans who participated in a prospective, double-blind, pharmacogenetic study of antidepressant response, and 331 matched controls. Polymorphisms in PDE9A and PDE11A were found to be associated with the diagnosis of MDD. Our data are also suggestive of the association between SNPs in other PDE genes and MDD. Remission on antidepressants was significantly associated with polymorphisms in PDE1A and PDE11A. Thus, we found significant associations with both the diagnosis of MDD and remission in response to antidepressants with SNPs in the PDE11A gene. We show here that PDE11A haplotype GAACC is significantly associated with MDD. We conclude that PDE11A has a role in the pathophysiology of MDD. This study identifies a potential CNS role for the PDE11 family. The hypothesis that drugs affecting PDE function, particularly cGMP-related PDEs, represent a treatment strategy for major depression should therefore be tested.

Decrease in salivary secretion by radiation mediated by nitric oxide and prostaglandins.

OBJECTIVE: In the present work, we evaluated the effect of exposing the submandibular glands (SMG) to radiation, studying different functional parameters such as salivary secretion, nitric oxide (NO) production, reactive oxygen species formation, prostaglandin (PGE) content and apoptosis. METHODS: We irradiated rats in the head and neck region with a single dose of gamma-ray radiation of 15 Gy. Two hours after radiation, we measured norepinephrine-induced salivary secretion. After that, the SMG were dissected, and in this tissue, we measured the activity of NO synthase (NOS), the PGE content, the amount of reactive oxygen species, apoptotic cells and mitochondrial inducible NOS (iNOS) expression. RESULTS: We found that radiation decreased salivary secretion when 10 and 30 microg/kg of norepinephrine was administered via the right femoral vein. We observed that iNOS activity was reduced and PGE content increased after radiation in SMG, indicating that NO and PGEs may participate in salivary secretion. The expression of mitochondrial NOS was increased after radiation leading to the formation of large amounts of NO that acts as a proapoptotic signal. In fact, we observed an augmentation in apoptotic cells. In this study, we also observed an increase in lipid peroxidation induced by radiation that may contribute to tissue damage. CONCLUSIONS: Our results indicate that radiation induced a decrease in salivary secretion and SMG iNOS activity, meanwhile the PGE content, the lipid peroxidation and apoptosis increased in the tissue. These modifications decrease salivary secretion.

Toll-like receptor 4 plays a crucial role in the immune-adrenal response to systemic inflammatory response syndrome.

Sepsis and septic shock are leading killers in the noncoronary intensive care unit, and they remain worldwide health concerns. The initial host defense against bacterial infections involves Toll-like receptors (TLRs), which detect and respond to microbial ligands. In addition, a coordinated response of the adrenal and immune systems is crucial for survival during severe inflammation. Previously, we demonstrated a link between the innate immune system and the endocrine stress response involving TLR-2. Like TLR-2, TLR-4 is also expressed in human and mouse adrenals. In the present work, by using a low dose of LPS to mimic systemic inflammatory response syndrome, we have revealed marked cellular alterations in adrenocortical tissue and an impaired adrenal corticosterone response in TLR-4-/- mice. Our findings demonstrate that TLR-4 is a key mediator in the crosstalks between the innate immune system and the endocrine stress response. Furthermore, TLR polymorphisms could contribute to the underlying mechanisms of impaired adrenal stress response in patients with bacterial sepsis.