Bombesin: an activator of specific Aeromonas antibody secretion in rat intestine

Gut Lymphocyte Phenotype Changes After Parenteral Nutrition and Neuropeptide Administration

OBJECTIVE

To define gut-associated lymphoid tissue (GALT) phenotype changes with parenteral nutrition (PN) and PN with bombesin (BBS).

BACKGROUND

PN reduces respiratory tract (RT) and GALT Peyer patch and lamina propria lymphocytes, lowers gut and RT immunoglobulin A (IgA) levels, and destroys established RT antiviral and antibacterial immunity. BBS, an enteric nervous system neuropeptide, reverses PN-induced IgA and RT immune defects.

METHODS

Experiment 1: Intravenously cannulated ICR mice received chow, PN, or PN + BBS injections for 5 days. LSR-II flow cytometer analyzed Peyer patches and lamina propria isolated lymphocytes for homing phenotypes (L-selectin and LPAM-1) and state of activation (CD25, CD44) in T (CD3)-cell subsets (CD4 and CD8) along with homing phenotype (L-selectin and LPAM-1) in naive B (IgD) and antigen-activated (IgD or IgM) B (CD45R/B220) cells. Experiment 2: Following the initial experiment 1 protocol, lamina propria T regulatory cell phenotype was evaluated by Foxp3 expression.

RESULTS

Experiment 1: PN significantly reduced lamina propria (1) CD4CD25 (activated) and (2) CD4CD25LPAM-1 (activated cells homed to the lamina propria) T cells, whereas PN-BBS assimilated chow levels. PN significantly reduced lamina propria (1) IgD (naive), (2) IgDLPAM (antigen-activated homed to the lamina propria) and CD44 memory B cells, whereas PN-BBS assimilated chow levels. Experiment 2: PN significantly reduced lamina propria CD4CD25Foxp3 T regulatory cells compared with chow-fed mice, whereas PN + BBS assimilated chow levels.

CONCLUSIONS

PN reduces lamina propria activated and T regulatory cells and also naive and memory B cells. BBS addition to PN maintains these cell phenotypes, demonstrating the intimate involvement of the enteric nervous system in mucosal immunity.

Current aspects of mucosal immunology and its influence by nutrition

BACKGROUND

A significant body of clinical literature demonstrates that enteral feeding significantly reduces the incidence of pneumonia compared to patients fed parenterally. An immunologic link between the gastrointestinal tract and respiratory tract is postulated via the common mucosal immune hypothesis. This hypothesis states that cells are sensitized within the Peyer's patches of the small intestine and are subsequently distributed to submucosal locations in both intestinal and extra intestinal sites. This system is exquisitely sensitive to route and type of nutrition.

DATA SOURCE

This review examines the laboratory data regarding cell numbers, cell phenotypes, cytokine profile, and immunologic function in both intestinal and extra intestinal sites in animals that have been administered either parenteral feeding or various types of enteral feeding. It also establishes links between a specific nutrient, glutamine, the enteric nervous system, by way of neuropeptides, and mucosal immunity.

CONCLUSION

Progress in understanding relationships between nutrient availability, enteric nervous system stimulation, and nutrient delivery on mucosal immunity offers opportunities to explore immune systems previously not appreciated by clinicians and basic scientists. These opportunities offer new challenges to the physician scientist, basic scientist, and clinician to understand, manipulate, and apply these concepts to the critically ill patient population by favorably influencing immunologic barriers and the inflammatory response.

The neuropeptide bombesin improves IgA-mediated mucosal immunity with preservation of gut interleukin-4 in total parenteral nutrition-fed mice

BACKGROUND

The Th2 cytokines, interleukin-4 (IL-4) and interleukin-10 (IL-10), stimulate IgA production. Total parenteral nutrition (TPN) reduces IL-4 and IL-10 messenger RNA in gut lamina propria lymphocytes, total IL-4 and IL-10 in gut homogenates, and IgA-mediated mucosal immunity. Bombesin (BBS) can maintain mucosal immunity in TPN-fed mice, but the effects of BBS on gut IL-4 and IL-10 levels and their mRNA expression in the lamina propria are unknown.

METHODS

In experiment 1, mice that were fed chow, TPN, or TPN + BBS (15 microg/kg intravenously-three times a day) for 5 days were killed, and respiratory tract IgA and intestinal IgA, IL-4, and IL-10 levels were measured. In experiment 2, IL-4 and IL-10 mRNA were measured in isolated lamina propria lymphocytes from chow-, TPN-, and TPN+BBS-fed mice by reverse transcriptase-polymerase chain reaction. Intestines were harvested 1 hour after injection of 100 7 microg of lipopolysaccharide intraperitoneally. Samples were standardized to beta-actin.

RESULTS

TPN-fed mice had significantly lower respiratory tract IgA levels than chow- or TPN + BBS-fed mice. TPN+BBS did not increase intestinal IL-10 or IL-10 lamina propria mRNA levels but maintained intestinal IL-4 levels and lamina propria IL-4 mRNA expression equal to those of chow-fed mice.

CONCLUSIONS

BBS reverses the effects of TPN on intestinal and respiratory tract IgA levels and most effects on gut cytokines. Lamina propria cytokine mRNA levels reflect total gut cytokine concentration.

Bombesin recovers gut-associated lymphoid tissue and preserves immunity to bacterial pneumonia in mice receiving total parenteral nutrition

OBJECTIVE

To study the ability of bombesin (BBS) to recover gut-associated lymphoid tissue (GALT) and preserve immunity in a lethal model of Pseudomonas aeruginosa (Ps) pneumonia in mice receiving total parenteral nutrition (TPN).

SUMMARY BACKGROUND DATA

TPN causes depression of mucosal immunity compared with enterally fed animals, which may explain the increased incidence of pneumonia in parenterally fed trauma patients. BBS prevents this TPN-induced GALT atrophy, depressed gastrointestinal and respiratory tract IgA levels, and impaired antiviral IgA-mediated mucosal immunity. The authors examined whether some supplement could be added to TPN to avoid this GALT atrophy and lower the incidence of infectious complications in the parenterally fed animal.

METHODS

Male mice were randomized to chow or intravenous (IV) TPN. After 5 days of IV TPN, mice received 0, 1, 2, or 3 days of BBS IV three times a day and then were killed to harvest Peyer's patch, intraepithelium, and lamina propria for cell yields. Gastrointestinal and respiratory tract IgA levels were analyzed by enzyme-linked immunosorbent assay. Next, mice underwent intranasal inoculation with liposomes alone (nonimmune) or liposome-containing Ps polysaccharide. Ps immune mice were catheterized and randomized to chow, IV TPN, or IV TPN + BBS. The liposome group received chow but no IV catheter. These mice were given an LD90 dose of intratracheal Ps, and death rates were recorded.

RESULTS

GALT and gastrointestinal and respiratory tract IgA levels improved to those in chow-fed mice after 3 days of BBS. Immunization reduced the death rate from 92% in chow-fed liposome-only animals to 20% in immunized animals. TPN-fed animals lost their mucosal immunity, with a death rate of 86% compared with 21% in the TPN + BBS group.

CONCLUSION

The results demonstrate that BBS reverses TPN-induced changes in GALT and preserves mucosal immunity. Ps immunization reduces the death rate in a gram-negative pneumonia model and maintains gastrointestinal and respiratory immunity in Ps immune mice receiving IV TPN.

Cholecystokinin modulates mucosal immunoglobulin A function

BACKGROUND

We have established that mucosal immunoglobulin A (IgA) production is highly dependent on cholecystokinin release and is markedly suppressed by glucocorticoids. The purpose of the present study was to examine the role of cholecystokinin on the functional responsiveness of the mucosal IgA system in glucocorticoid treated rats.

METHODS

A total of 24 Fischer rats were assigned to three groups of 8 animals each. Animals were injected with vehicle (CON), dexamethasone (DEX) (0.08 mg/150 g), or DEX (0.08 mg/150 gm) and ARL1294KF (500 ng twice daily), a novel and potent long-acting cholecystokinin agonist (DEX+CCK). Animals were treated for 48 hours and killed. Duodenum was harvested, and the total mucosal concentration of cholecystokinin was measured by radioimmunoassay. Mucosal IgA was assayed by quantitation of immunoreactive cells in the ileum. Bacterial adherence was evaluated by quantitative culture of vigorously washed stripped cecal mucosa. Transepithelial electrical resistance, a measure of tight junction permeability, was assessed by mounting strips of adjacent cecal mucosa in Ussing chambers.

RESULTS

Glucocorticoid administration resulted in a statistically significant (p < 0.001) decrease in duodenal cholecystokinin, decreased IgA, and impaired mucosal immunity (increased bacterial adherence and decreased tissue resistance). Cholecystokinin administration preserved mucosal immune function in DEX-treated rats.

CONCLUSIONS

Cholecystokinin may play an important role in maintaining the functional responsiveness of mucosal immunity during catabolic stress.

Calmodulin binds to the basolateral targeting signal of the polymeric immunoglobulin receptor

We have identified a major calmodulin (CaM)-binding protein in rat liver endosomes using 125I-CaM overlays from two-dimensional protein blots. Immunostaining of blots demonstrates that this protein is the polymeric immunoglobulin receptor (pIgR). We further investigated the interaction between pIgR and CaM using Madin-Darby canine kidney cells stably expressing cloned wild-type and mutant pIgR. We found that detergent-solubilized pIgR binds to CaM-agarose in a Ca(2+)-dependent fashion, and binding is inhibited by the addition of excess free CaM or the CaM antagonist W-13 (N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide), suggesting that pIgR binding to CaM is specific. Furthermore, pIgR is the most prominent 35S-labeled CaM-binding protein in the detergent phase of Triton X-114-solubilized, metabolically labeled pIgR-expressing Madin-Darby canine kidney cells. CaM can be chemically cross-linked to both solubilized and membrane-associated pIgR, suggesting that binding can occur while the pIgR is in intact membranes. The CaM binding site is located in the membrane-proximal 17-amino acid segment of the pIgR cytoplasmic tail. This region of pIgR constitutes an autonomous basolateral targeting signal. However, binding of CaM to various pIgR mutants suggests that CaM binding is not necessary for basolateral targeting. We suggest that CaM may be involved in regulation of pIgR transcytosis and/or signaling by pIgR.

Stimulation of natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities in murine leukocytes by bombesin-related peptides requires the presence of adherent cells

Bombesin and the two mammalian bombesin-related peptides, gastrin-releasing peptide (GRP) and neuromedin C, at physiological concentrations have been previously shown to stimulate significantly in vitro the antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activities in BALB/c mouse leukocytes from axillary nodes, spleen and thymus. In the present work we have shown that adherent cells are required in leukocyte samples for stimulation of cytotoxicity by the neuropeptides, which suggests that this effect may be mediated by those cells. Here we demonstrate the specificity of the effects by reversing them in the presence of the bombesin-antagonist (Leu13-psi CH2NH-Leu14)-BN, and by detecting specific receptors for GRP on macrophages of high and low affinity. Using the same binding technics, no receptors for this neuropeptide were found in non-adherent leukocytes.

Effects of parenteral and enteral nutrition on gut-associated lymphoid tissue

Changes in mucosal defense have been implicated as important factors affecting infections complications in critically ill patients. To study the effects of nutrient administration on gut-associated lymphatic tissue (GALT), ICR mice were randomized to receive chow plus intravenous saline, intravenous feeding of a total parenteral nutrition (TPN) solution, or enteral feeding of the same TPN solution. In a second series of experiments, a more complex enteral diet (Nutren) was compared with chow feeding and enteral TPN. After 5 days of feeding with experimental diets, lymphocytes were harvested from the mesenteric lymph nodes (MLNs), Peyer's patches (PPs), lamina propria (LP) cells, and intraepithelial (IE) spaces of the small intestine to determine cell yields and phenotypes. Small intestinal washings, gallbladder contents, and sera were collected and analyzed for immunoglobulin A (IgA) levels. In both series of experiments, there were no significant changes within the MLNs. There were significant decreases in total cell yields from the PPs, IE spaces, and LP in animals fed with TPN solution, either enterally or parenterally, as compared with chow-fed mice. Total T cells were decreased in both TPN-fed groups in the PPs and LP, whereas total B cells were decreased in the PP, IE, and LP populations. Total cell numbers remained normal in the Nutrenfed group, except for a decrease in LP T cells. CD4+ LP cells decreased significantly with a reduction in the CD4/CD8 ratio in mice fed TPN solution either intravenously or enterally, whereas IgA recovery from small intestinal washings was significantly decreased in the same groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Bombesin improves survival from methotrexate-induced enterocolitis

OBJECTIVE

The authors determined whether bombesin could improve survival from methotrexate (MTX)-induced enterocolitis.

SUMMARY BACKGROUND DATA

Bombesin prevents gut mucosal atrophy, which is produced by feeding rats an elemental diet. Administration of MTX produces a lethal enterocolitis in rats fed an elemental diet.

METHODS

On treatment day 0, 60 rats were divided randomly into three groups and fed an elemental diet (Vivonex TEN, Sandoz, Minneapolis, MN) as the only source of nutrition. Groups were subdivided further to receive either saline or bombesin (10 micrograms/kg, subcutaneously, three times a day) beginning either on day 0 or day 14. Methotrexate (20 mg/kg, intraperitoneally) was given to all rats 14 days after the start of an elemental diet.

RESULTS

Bombesin prevented the mucosal atrophy in the ileum produced by the elemental diet and significantly decreased mortality in rats given MTX (whether given as a pretreatment or at the time of MTX administration).

CONCLUSION

Bombesin significantly improved survival in a lethal model of MTX-induced enterocolitis, possibly by maintaining gut mucosal structure. Administration of bombesin to patients receiving chemotherapy may be clinically useful in preventing the severe enterocolitis induced by various chemotherapeutic agents.

Gs alpha stimulates transcytosis and apical secretion in MDCK cells through cAMP and protein kinase A

Recent evidence suggests a role for heterotrimeric G proteins in vesicular transport. Cholera toxin, which activates Gs alpha by ADP-ribosylation, has been reported to stimulate both apical secretion (Pimplikar, S.W., and K. Simons. 1993. Nature (Lond.). 352:456-458) and apically directed transcytosis (Bomsel, M., and K.E. Mostov. 1993. J. Biol. Chem. 268:25824-25835) in MDCK cells, via a cAMP-independent mechanism. Here, we demonstrate that apical secretion and apically directed transcytosis are significantly stimulated by agents that elevate cellular cAMP. Forskolin, which activates adenylyl cyclase directly, and 8BrcAMP augment both transport processes in MDCK cells. The increase is not limited to receptor-mediated transport (polymeric Ig receptor), since transcytosis of ricin, a galactose-binding lectin, is similarly stimulated. The effects of elevated cellular cAMP on apical secretion and transcytosis are apparently mediated via protein kinase A (PKA), as they are inhibited by H-89, a selective PKA inhibitor. Experiments employing a 17 degrees C temperature block indicate that cAMP/PKA acts at a late, possibly rate-limiting stage in the transcytotic pathway, after translocation of internalized markers into the apical cytoplasm. However, no significant stimulus of apical recycling was observed in the presence of FSK, suggesting that cAMP/PKA either affects transcytosis at a level proximal to apical early endosomes and/or specifically increases the efficiency by which transcytosing molecules are delivered to the apical plasma membrane. Finally, we overexpressed wild-type Gs alpha and a mutant, Q227L, which constitutively activates adenylyl cyclase, in MDCK cells. Although Q227L increased transcytosis more than wild-type Gs alpha, neither construct was as effective as FSK in stimulating transcytosis, arguing against a significant role of Gs alpha in transcytosis independent of cAMP and PKA.

Phorbol myristate acetate-mediated stimulation of transcytosis and apical recycling in MDCK cells

We observed that phorbol myristate acetate (PMA) stimulates transcytosis of the polymeric immunoglobulin receptor (pIgR) in MDCK cells. Apical release of pre-endocytosed ligand (dimeric IgA) bound to the pIgR can be stimulated twofold within 7 min of addition of PMA while recycling of the ligand from the basal surface is not affected. In addition, apical surface delivery of pIgR and cleavage of its ectodomain to secretory component (SC) is also stimulated by PMA. The recycling of apically internalized ligand back to the apical surface is similarly stimulated. These results suggest that the stimulation of apical delivery is from an apical recycling compartment. The effect of PMA suggests that protein kinase C (PKC) is involved in the regulation of pIgR trafficking in MDCK cells. To test this we down regulated PKC activity by pre-treating cells with PMA for 16 h and observed that transcytosis could no longer be stimulated by PMA. Western blots show that the PKC isozymes alpha and to a lesser extent epsilon, are depleted from MDCK cells which have been pre-treated with PMA for 16 h and that treatment of MDCK cells with PMA for 5 min causes a dramatic translocation of the PKC alpha isozyme and a partial translocation of the epsilon isozyme from the cytosol to the membrane fraction of cell homogenates. This translocation suggests that the alpha and/or epsilon isozymes may be involved in PMA mediated stimulation of transcytosis. A mutant pIgR in which serines 664 and 726, the major sites of phosphorylation, are replaced by alanine is stimulated to transcytose by PMA, suggesting that phosphorylation of pIgR at these sites is not required for the effect of PMA. These results suggest that PMA-mediated stimulation of pIgR transcytosis may involve the activation of PKC alpha and/or epsilon, and that this stimulation occurs independently of the major phosphorylation sites on the pIgR. Finally, PMA stimulates transcytosis of basolaterally internalized transferrin, suggesting that PMA acts to generally stimulate delivery of endocytosed proteins to the apical surface.

The modulatory role of gut hormones in elemental diet and intravenous total parenteral nutrition-induced bacterial translocation in rats

We have previously shown that parenteral and certain elemental diets promote bacterial translocation and that this diet-induced bacterial translocation can be prevented by the provision of bulk-forming dietary fiber. The goal of the current study was to test the hypothesis that fiber's protective effect on diet-induced bacterial translocation was mediated by trophic gut hormones. This hypothesis was tested by using bombesin (which stimulates gut hormone release) or the somatostatin analog Sandostatin (which inhibits gut hormone release) to modulate gut hormone release in rats receiving rat food, intravenous total parenteral nutrition, or an elemental diet. Both bombesin and fiber were effective in preventing elemental diet-induced bacterial translocation, whereas octreotide acetate abrogated the protective effect of fiber. Bombesin was also effective in limiting bacterial translocation in parenterally fed rats. Although both enteral (elemental diet) and parenteral diet-induced bacterial translocation were associated with cecal bacterial overgrowth, loss of small-bowel weight, and loss of mucosal protein content, none of these factors seemed to be primarily responsible for bacterial translocation. Because bombesin decreased the incidence of villous injury in the elemental diet-fed rats and decreased the incidence of villous injury and prevented loss of intestinal barrier function to horseradish peroxidase in the parenterally fed rats, it is possible that bombesin exerted its protective effect by limiting mucosal injury and preserving barrier function.

Chemoattractant capacity of bombesin, gastrin-releasing peptide and neuromedin C is mediated through PKC activation in murine peritoneal leukocytes

Bombesin-like peptides have been recently shown to regulate immune functions. In the present work, we have studied their action as chemoattractants for murine peritoneal macrophages and lymphocytes. The results showed a significant increase in the number of cells that migrate when they are exposed to a gradient of bombesin, gastrin-releasing peptide (GRP) or neuromedin C (from 10(-8) to 10(-12) M). The most effective of the three neuropeptides studied was GRP, even more than formyl-Met-Leu-Phe peptide (FMLP), an established leukocyte chemoattractant. GRP action was mediated through specific cell receptors as it was significantly reduced in presence of a competitive and specific bombesin receptor antagonist. In the presence of retinal, a protein kinase C (PKC) inhibitor, the chemoattractant capacity of GRP was considerably reduced. In order to investigate further the mechanism of action involved in the GRP effect, we measured PKC activity. Peritoneal cells incubated with GRP experimented an increase in PKC activity to the same extent of that produced by the PKC activator phorbol myristate acetate (PMA). These data prove that bombesin-like peptides are potent chemoattractants for murine peritoneal macrophages and lymphocytes, and that their action is at least in part mediated through PKC activation.

Bombesin, gastrin-releasing peptide, and neuromedin C modulate murine lymphocyte proliferation through adherent accessory cells and activate protein kinase C

Recent data have shown the ability of bombesin-related peptides to stimulate murine macrophage functions. In the present study, we have investigated the effect of bombesin, gastrin-releasing peptide (GRP), and neuromedin C on the proliferative response of lymphocytes from murine axillary nodes, spleen, and thymus. The results show that these neuropeptides at 10(-9), 10(-10), and 10(-11) M concentrations modulate the lymphoproliferative response, stimulating to a small but significant extent the spontaneous proliferation and inhibiting to a great extent the lymphoproliferative response to the mitogen concanavalin A (Con A). This regulation is probably mediated through adherent accessory cells, since their presence for the neuropeptides to produce their effect. The increased interleukin-1 beta production by Con A in cultures of peritoneal macrophages (a model of adherent accessory cells) decreased after the addition of bombesin, GRP, and neuromedin C; this diminution is a possible mechanism for their inhibitory action on the lymphoproliferative response to Con A. In addition, these neuropeptides caused a significant protein kinase C activation in total leukocyte population and T-enriched lymphocytes from axillary nodes, as well as in peritoneal macrophages.

Stimulation of natural killer and antibody-dependent cellular cytotoxicity activities in mouse leukocytes by bombesin, gastrin-releasing peptide and neuromedin C: involvement of cyclic AMP, inositol 1,4,5-trisphosphate and protein kinase C

Bombesin and the two mammalian bombesin-related peptides, gastrin-releasing peptide (GRP) and neuromedin C, at physiological concentrations ranging from 10(-11) M to 10(-9) M have been shown in this study to significantly stimulate in vitro the antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activities in BALB/c mouse leukocytes from axillary nodes, spleen and thymus. The three neuropeptides studied induced no change in interleukin-2 production. In addition, these neuropeptides induced in leukocytes from axillary nodes a rapid, transient and significant decrease of intracellular cyclic AMP at 30 s, but a significant transient increase of inositol 1,4,5-trisphosphate levels at 30 and 60 s and a stimulation of protein kinase C activity in membrane fractions after 5 min incubation. These results suggest that inositol phospholipid signalling and cAMP messenger systems are involved in the increase of NK and ADCC activities when leukocytes are incubated in the presence of bombesin, GRP or neuromedin C.

Elemental diet-induced bacterial translocation can be hormonally modulated

BACKGROUND

The authors have previously documented that feeding mice an elemental diet resulted in bacterial translocation (BT) that could be prevented by the provision of dietary fiber. To test whether the protective effect of fiber was related to the stimulation of trophic gut hormones, the effects of sandostatin and bombesin were tested.

METHODS

Mice fed either chow or the elemental diet were stratified into several groups and the ability of bombesin (10 micrograms/kg, tid) or sandostatin (100 micrograms/kg bid) to modulate BT was examined. After 14 days, mice were sacrificed and BT, cecal bacterial population levels, mucosal protein, and small bowel weight was measured. Segments of the ileum and jejunum were examined histologically.

RESULTS

Incidence of elemental diet-induced BT (75%) was reduced by fiber (9%) or the administration of bombesin (13%) (p < 0.01). Although sandostatin did not promote BT in chow-fed mice, it reversed the protective effect of fiber on BT (75%) (p < 0.01).

CONCLUSION

Elemental diet-induced bacterial translocation can be modulated hormonally and the beneficial effects of fiber on diet-induced BT appears to be hormonally mediated.

Immunologic structure and function of the gastrointestinal tract

Host defenses within the gastrointestinal tract exclude bacteria and other intraluminal substances, which if released into the systemic circulation, would be toxic to the body. This is accomplished via complex interactions between these external pathogens and local immune responses and nonimmunologic processes. In addition to the mechanical and chemical barriers of the nonimmunologic defense system within the gastrointestinal tract, there is an effective immunologic barrier composed of aggregated and nonaggregated lymphoid cells. Gut-associated lymphoid tissue protects the intestinal mucosa from invading pathogens by intricate pathways of antigen processing. Gut-associated lymphoid tissue also transfers protection to other secretory sites within the body through the common mucosal immune system. The integrity of both the immunologic and nonimmunologic barriers may be affected by any number of pathologic insults as well as by nutritional influences. This article reviews the structural and functional characteristics of this complex and critically important host defense system. Specific nutrient requirements of the immunologic processes are discussed.

Bombesin-related peptides modulate interleukin-1 production by alveolar macrophages

We have tested the effect of bombesin (BN) and BN-related peptides on the production of interleukin-1 (IL-1) by rat alveolar macrophages. BN incubated with AM alone had no direct effect on IL-1 release. However, at concentrations ranging from 10(-11) M to 10(-6) M, BN significantly enhanced IL-1 release by AM activated with lipopolysaccharide (LPS). A typically U-shaped dose-response relationship was observed with maximal effect obtained between 10(-9) M and 10(-8) M. BN also potentiated the stimulatory effects of other IL-1 inducers including muramyl dipeptide (MDP) and granulocyte-macrophage colony stimulating factor (GM-CSF). The 2- to 3-fold enhancement in IL-1 production seen with BN was blocked by the bombesin receptor antagonist [Leu13,-psi(CH2NH)Leu14]-Bombesin. Furthermore, bombesin-related peptides, gastrin-releasing peptides, (GRP)-27 and GRP-10 also potentiated the stimulatory effects of LPS whereas Neuromedin B (NeB) had no effect. These results suggest that BN-related peptides might play an important role as local modulator(s) of cytokine production and inflammatory reactions in the lung.

Verapamil and furosemide prevent cholecystokinin-induced translocation of immunoglobulins in rat intestine

Our previous studies have shown that cholecystokinin and pilocarpine are known to be extracellular messengers promoting the release of immunoglobulins A and G antibody activity in the lumen of the rat intestine. In the present study, which was also performed in rats, we show that CCK also promotes the translocation of albumin, electrolytes, and water into the lumen of the intestine. The effect of CCK on the translocation of immunoglobulins, albumin, and electrolytes is reduced by the prior injection of the calcium-channel blocker verapamil and the chloride-channel blocker furosemide. Taken together, the above observations suggest that the translocation of immunoglobulins, albumin, and electrolytes in the intestine appears to be stimulated by identical mechanisms and to proceed simultaneously.

Intravenous administration of bombesin in man stimulates natural killer cell activity against tumour cells

Peptides from both the nervous and endocrine system have been shown to influence immune functions. This study describes the stimulatory effect of bombesin on natural killer cell activity of peripheral blood mononuclear cells. The stimulation of cytotoxicity by bombesin in vivo was much higher than found in vitro. In vitro studies with bombesin and gastrin revealed that the stimulatory effect of bombesin in vivo can for a major part be attributed to other stimulatory mediators which are released by BBS. These results indicate that neuropeptide release might rapidly interfere, both directly and indirectly, with natural killer activity of peripheral blood mononuclear cells.

The effect of bombesin-related peptides on the phagocytic function of mouse phagocytes in vitro

Bombesin (BBS) at doses of 0.1, 1.0, 10.0 and 100.0 nM stimulated chemiluminescence (CL) production by phagocytic cells (monocytes, macrophages and polymorphonuclear leucocytes) in mice in the presence of ZAP (opsonized zymosan particles containing luminol). These data suggest that BBS increased the phagocytic function of mouse phagocytes. BBS-related peptides, gastrin-releasing peptides (GRP)-27, GRP-14, GRP-10 and neuromedin B, also induced similar CL responses compared with BBS. The CL response elicited by BBS was depressed dramatically by various concentrations of EGTA (a Ca++ chelator), indicating that a Ca++ pathway may play a key role in the BBS-stimulated CL response.