Orally administered FPRL1 receptor agonist peptide MMK-1 inhibits etoposide-induced alopecia by a mechanism different from intraperitoneally administered MMK-1

Oral administration for 6 days of 100 mg/kg MMK-1, an agonist peptide selective for the FPRL1 receptor, suppressed alopecia induced by the anticancer drug etoposide in neonatal rats. The anti-alopecia effect of orally administered MMK-1 was not inhibited by pyrilamine or cimetidine, antagonists for histamine H1 and H2 receptors, respectively, which blocked the anti-alopecia effect of intraperitoneally administered MMK-1 at a dose of 10 mg/kg for 4 days. However, the anti-alopecia effect of orally administered MMK-1 was inhibited by indomethacin, an inhibitor of cyclooxygenase (COX), or AH-23848B, an antagonist of the EP4 receptor for prostaglandin (PG) E2, suggesting involvement of PGE2 release and the EP4 receptor in the oral MMK-1 anti-alopecia mechanism. The anti-alopecia effect of orally administered MMK-1 was also blocked by an inhibitor of nuclear factor-kappaB (NF-kappaB), pyrrolidine dithiocarbamate, suggesting that the oral anti-alopecia effect of MMK-1 may be mediated by activation of NF-kappaB. These results suggest that MMK-1 bound to FPRL1 receptor might suppress etoposide-induced apoptosis of hair follicle cells and alopecia by way of PGE2 release and NF-kappaB activation.     

Design of soymetide-4 derivatives to potentiate the anti-alopecia effect

Previously, we found that soymetide-4 (MITL), an N-formyl-methionyl-leucyl-phenylalanine (fMLP) agonist peptide derived from soybean beta-conglycinin alpha' subunit, stimulated phagocytosis of human polymorphonuclear leukocytes, and inhibited alopecia induced by etoposide, an anticancer drug, in neonatal rats after oral administration. We found that the fMLP receptor affinity and phagocytosis-stimulating activity of soymetide-4 was potentiated by replacement of Thr(3) with hydrophobic residues. Among the derivatives synthesized, [Trp](3)-soymetide-4 (MIWL) was the most potent, stronger by 180 and 130 times than soymetide-4 in receptor affinity and phagocytosis-stimulating activity, respectively. The anti-alopecia effect of [Trp](3)-soymetide-4 was about 3 times larger than that of soymetide-4 after oral administration.     

Mechanism of the protective effect of intraperitoneally administered agonists for formyl peptide receptors against chemotherapy-induced alopecia

Previously, we found that an intraperitoneally administered chemotactic peptide, N-formyl-Met-Leu-Phe (fMLP), and MMK-1, a selective agonist of formyl peptide receptor-like 1 (FPRL1) receptor, the low affinity subtype of the fMLP receptor, prevented the alopecia in neonatal rats induced by the anticancer agent etoposide. The anti-alopecia effect of fMLP was not inhibited at all by Boc-FLFLF, a selective antagonist of formylpeptide receptor (FPR), which is the high affinity subtype of the fMLP receptor, but it was partly inhibited by Trp-Arg-Trp-Trp-Trp-Trp-NH(2) (WRW(4)), an antagonist of FPRL1 receptor. On the other hand, the anti-alopecia effect of MMK-1 was completely abolished by WRW(4). The anti-alopecia effects of fMLP and MMK-1 were also inhibited by Lys-D-Pro-Thr (K(D)PT) and pyrrolidine dithiocarbamate, which are inhibitors of interleukin-1 (IL-1) and nuclear factor-kappaB (NF-kappaB) respectively. Hence, we suggest that the anti-alopecia mechanisms of intraperitoneally administered fMLP and MMK-1 include activation of NF-kappaB via IL-1 release downstream of the FPRL1 receptor homolog in rats.     

Anti-alopecia effect of Gly-Leu-Phe, an immunostimulating peptide derived from alpha-lactalbumin

Gly-Leu-Phe (GLF), an immunostimulating peptide derived from alpha-lactalbumin, prevented alopecia induced by an anticancer agent etoposide in a neonatal rat model after intraperitoneal injection at a dose of 100 mg/kg for 4 d or oral administration at a dose of 300 mg/kg for 6 d. By microscopic analysis of skin sections, GLF proved to inhibit etoposide-induced loss of hair, thickening of the epidermis, and thinning of the adipocyte layer. The anti-alopecia effect of GLF was inhibited by pyrilamine, a histamine H1 receptor antagonist, suggesting that the anti-alopecia effect is mediated by histamine release.     

Mechanism of the Protective Effect of Intraperitoneally Administered Agonists for Formyl Peptide Receptors against Chemotherapy-Induced Alopecia

Previously, we found that an intraperitoneally administered chemotactic peptide, N-formyl-Met-Leu-Phe (fMLP), and MMK-1, a selective agonist of formyl peptide receptor-like 1 (FPRL1) receptor, the low affinity subtype of the fMLP receptor, prevented the alopecia in neonatal rats induced by the anticancer agent etoposide. The anti-alopecia effect of fMLP was not inhibited at all by Boc-FLFLF, a selective antagonist of formylpeptide receptor (FPR), which is the high affinity subtype of the fMLP receptor, but it was partly inhibited by Trp-Arg-Trp-Trp-Trp-Trp-NH₂ (WRW⁴), an antagonist of FPRL1 receptor. On the other hand, the anti-alopecia effect of MMK-1 was completely abolished by WRW⁴. The anti-alopecia effects of fMLP and MMK-1 were also inhibited by Lys-D-Pro-Thr (K(D)PT) and pyrrolidine dithiocarbamate, which are inhibitors of interleukin-1 (IL-1) and nuclear factor-κB (NF-κB) respectively. Hence, we suggest that the anti-alopecia mechanisms of intraperitoneally administered fMLP and MMK-1 include activation of NF-κB via IL-1 release downstream of the FPRL1 receptor homolog in rats.     

Soymetide,an immunostimulating peptide derived from soybean beta-conglycinin,is an fMLP agonist

A tridecapeptide (MITLAIPVNKPGR) that stimulates phagocytosis of human neutrophils was isolated from a trypsin digest of soybean proteins. This peptide is derived from the soybean β-conglycinin ′ subunit and was named soymetide-13. The N-terminal methionine residue of soymetide-13 is essential for its activity, and removal of C-terminal residues revealed that soymetide-4 (MITL) is the minimal structure required for phagocytosis stimulation. Although they are not formylated at their N-termini, soymetides have a weak affinity for the N-formyl-methionyl-leucyl-phenylalanine (fMLP) receptor and their phagocytosis-stimulating activity is inhibited by the fMLP antagonist Boc-MLP. Interestingly, soymetide-4 promotes tumor necrosis factor production at a higher level than soymetide-13 following oral administration in mice.     

Histamine directly and synergistically with lipopolysaccharide stimulates cyclooxygenase-2 expression and prostaglandin I(2) and E(2) production in human coronary artery endothelial cells

Although histamine plays an essential role in inflammation, its influence on cyclooxygenases (COX) and prostanoid homeostasis is not well understood. In this study, we investigated the effects of histamine on the expression of COX-1 and COX-2 and determined their contribution to the production of PGE(2), prostacyclin (PGI(2)), and thromboxane A(2) in human coronary artery endothelial cells (HCAEC). Incubation of HCAEC monolayers with histamine resulted in marked increases in the expression of COX-2 and production of PGI(2) and PGE(2) with no significant change in the expression of COX-1. Histamine-induced increases in PGI(2) and PGE(2) production were due to increased expression and function of COX-2 because gene silencing by small interfering RNA or inhibition of the catalytic activity by a COX-2 inhibitor blocked prostanoid production. The effects of histamine on COX-2 expression and prostanoid production were mediated through H(1) receptors. In addition to the direct effect, histamine was found to amplify LPS-stimulated COX-2 expression and PGE(2) and PGI(2) production. In contrast, histamine did not stimulate thromboxane A(2) production in resting or LPS-activated HCAEC. Histamine-induced increases in the production of PGE(2) and PGI(2) were associated with increased expression of mRNA encoding PGE(2) and PGI(2) synthases. The physiological role of histamine on the regulation of COX-2 expression in the vasculature is indicated by the findings that the expression of COX-2 mRNA, but not COX-1 mRNA, was markedly reduced in the aortic tissues of histidine decarboxylase null mice. Thus, histamine plays an important role in the regulation of COX-2 expression and prostanoid homeostasis in vascular endothelium.     

Streptococcus pneumoniae induced p38 MAPK- and NF-kappaB-dependent COX-2 expression in human lung epithelium

Streptococcus pneumoniae is a major cause of community-acquired pneumonia and death from infectious diseases in industrialized countries. Lung airway and alveolar epithelial cells comprise an important barrier against airborne pathogens. Cyclooxygenase (COX)-derived prostaglandins, such as PGE(2), are considered to be important regulators of lung function. Herein, we tested the hypothesis that pneumococci induced COX-2-dependent PGE(2) production in pulmonary epithelial cells. Pneumococci-infected human pulmonary epithelial BEAS-2B cells released PGE(2). Expression of COX-2 but not COX-1 was dose and time dependently increased in S. pneumoniae-infected BEAS-2B cells as well as in lungs of mice with pneumococcal pneumonia. S. pneumoniae induced degradation of IkappaBalpha and DNA binding of NF-kappaB. A specific peptide inhibitor of the IkappaBalpha kinase complex blocked pneumococci-induced PGE(2) release and COX-2 expression. In addition, we noted activation of p38 MAPK and JNK in pneumococci-infected BEAS-2B cells. PGE(2) release and COX-2 expression were reduced by p38 MAPK inhibitor SB-202190 but not by JNK inhibitor SP-600125. We analyzed interaction of kinase pathways and NF-kappaB activation: dominant-negative mutants of p38 MAPK isoforms alpha, beta(2), gamma, and delta blocked S. pneumoniae-induced NF-kappaB activation. In addition, recruitment of NF-kappaB subunit p65/RelA and RNA polymerase II to the cox2 promoter depended on p38 MAPK but not on JNK activity. In summary, p38 MAPK- and NF-kappaB-controlled COX-2 expression and subsequent PGE(2) release by lung epithelial cells may contribute significantly to the host response in pneumococcal pneumonia.     

Effect of histamine and histamine antagonists on the glycogen content of Tetrahymena

The glycogen content of Tetrahymena pyriformis was analysed by a cytophotometric method. Histamine and histamine antagonists were found to influence the glycogen content. It increases after acute histamine treatment, while it decreases after 4 days incubation with histamine. The H2 receptor antagonist methiamide was more effective than histamine, while the H1 receptor antagonist phenindamine had no effect on the glycogen content. The effect reflects the similarity or dissimilarity of the chemical structure of the antagonists and of histamine. Subdivision of the cytophotometric results indicated that all of the protozoa react to histamine or to its antagonists, but all agents increased the number of glycogen-rich Tetrahymena.     

Regulation and function of COX-2 gene expression in isolated gastric parietal cells

We examined expression, function, and regulation of the cyclooxygenase (COX)-2 gene in gastric parietal cells. COX-2-specific mRNA was isolated from purified (>95%) canine gastric parietal cells in primary culture and measured by Northern blots using a human COX-2 cDNA probe. Carbachol was the most potent inducer of COX-2 gene expression. Gastrin and histamine exhibited minor stimulatory effects. Carbachol-stimulated expression was inhibited by intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM (90%), protein kinase C (PKC) inhibitor GF-109203X (48%), and p38 kinase inhibitor SB-203580 (48%). Nuclear factor (NF)-kappaB inhibitor 1-pyrrolidinecarbodithioic acid inhibited carbachol-stimulated expression by 80%. Similar results were observed in the presence of adenoviral vector Ad.dom.neg.IkappaB, which expresses a repressor of NF-kappaB. Addition of SB-203580 with Ad.dom.neg.IkappaB almost completely blocked carbachol stimulation of COX-2 gene expression. We examined the effect of carbachol on PGE(2) release by enzyme-linked immunoassay. Carbachol induced PGE(2) release. Ad.dom.neg.IkappaB, alone or with SB-203580, produced, respectively, partial (70%) and almost complete (>80%) inhibition of carbachol-stimulated PGE(2) production. Selective COX-2 inhibitor NS-398 blocked carbachol-stimulated PGE(2) release without affecting basal PGE(2) production. In contrast, indomethacin inhibited both basal and carbachol-stimulated PGE(2) release. Carbachol induces COX-2 gene expression in the parietal cells through signaling pathways that involve intracellular Ca(2+), PKC, p38 kinase, and activation of NF-kappaB. The functional significance of these effects seems to be stimulation of PGE(2) release.     

NADPH oxidase NOX5-S mediates acid-induced cyclooxygenase-2 expression via activation of NF-kappaB in Barrett's esophageal adenocarcinoma cells

We have shown that the NADPH oxidase NOX5-S may play an important role in the progression from Barrett's esophagus to esophageal adenocarcinoma (EA) by increasing cell proliferation and decreasing apoptosis. However, the mechanism of the acid-induced NOX5-S-mediated increase in cell proliferation is not known. We found that, in SEG1 EA cells, the acid-induced increase in prostaglandin E2 (PGE2) production was mediated by activation of cyclooxygenase-2 (COX2) but not by COX1. Acid treatment increased intracellular Ca2+, and a blockade of intracellular Ca2+ increase inhibited the acid-induced increase in COX2 expression and PGE2 production. Knockdown of NOX5-S or NF-kappaB1 p50 by their small interfering RNA significantly inhibited acid-induced COX2 expression and PGE2 production in SEG1 cells. Acid treatment significantly decreased IkappaBalpha and increased luciferase activity when SEG1 cells were transfected with an NF-kappaB in vivo activation reporter plasmid, pNF-kappaB-Luc. In a novel Barrett's cell line overexpressing NOX5-S, IkappaBalpha was significantly reduced, and luciferase activity increased when these Barrett's cells were transfected with pNF-kappaB-Luc. Overexpression of NOX5-S in Barrett's cells significantly increased H2O2 production, COX2 expression, PGE2 production, and thymidine incorporation. The increase in thymidine incorporation occurring in NOX5-S-overexpressing Barrett's cells or induced by acid treatment in SEG1 EA cells was significantly decreased by COX2 inhibitors or small interfering RNA. We conclude that acid-induced COX2 expression and PGE2 production depend on an increase in cytosolic Ca2+ and sequential activation of NOX5-S and NF-kappaB in SEG1 cells. COX2-derived PGE2 production may contribute to NOX5-S-mediated cell proliferation in SEG1 cells.     

Prostaglandins mediate tonic contraction of the guinea pig and human gallbladder

The gallbladder (GB) maintains tonic contraction modulated by neurohormonal inputs but generated by myogenic mechanisms. The aim of these studies was to examine the role of prostaglandins in the genesis of GB myogenic tension. Muscle strips and cells were treated with prostaglandin agonists, antagonists, cyclooxygenase (COX) inhibitors, and small interference RNA (siRNA). The results show that PGE2, thromboxane A2 (TxA2), and PGF(2alpha) cause a dose-dependent contraction of muscle strips and cells. However, only TxA2 and PGE2 (E prostanoid 1 receptor type) antagonists induced a dose-dependent decrease in tonic tension. A COX-1 inhibitor decreased partially the tonic contraction and TxB2 (TxA2 stable metabolite) levels; a COX-2 inhibitor lowered the tonic contraction partially and reduced PGE2 levels. Both inhibitors and the nonselective COX inhibitor indomethacin abolished the tonic contraction. Transfection of human GB muscle strips with COX-1 siRNA partially lowered the tonic contraction and reduced COX-1 protein expression and TxB2 levels; COX-2 siRNA also partially reduced the tonic contraction, the protein expression of COX-2, and PGE2. Stretching muscle strips by 1, 2, 3, and 4 g increased the active tension, TxB2, and PGE2 levels; a COX-1 inhibitor prevented the increase in tension and TxB2; and a COX-2 inhibitor inhibited the expected rise in tonic contraction and PGE2. Indomethacin blocked the rise in tension and TxB2 and PGE2 levels. We conclude that PGE2 generated by COX-2 and TxA2 generated by COX-1 contributes to the maintenance of GB tonic contraction and that variations in tonic contraction are associated with concomitant changes in PGE2 and TxA2 levels.     

Prostaglandin E2 aggravates gastric mucosal injury induced by histamine in rats through EP1 receptors

We demonstrated that prostaglandin (PG) E2 aggravates gastric mucosal injury caused by histamine in rats, and investigated using various EP agonists which EP receptor subtype is involved in this phenomenon. Rats were used after 18 hr fasting. Histamine (80 mg/kg) dissolved in 10% gelatin, was given s.c., either alone or in combination with i.v. administration of PGE2 or various EP agonists such as 17-phenyl PGE2 (EP1), butaprost (EP2), sulprostone (EP1/EP3), ONO-NT012 (EP3) and ONO-AE1-329 (EP4). The animals were killed 4 hr later, and the mucosa was examined for lesions. The mucosal permeability was determined using Evans blue (1%). Histamine alone induced few lesions in the gastric mucosa within 4 hr. PGE2 dose-dependently worsened the lesions induced by histamine, the response being inhibited by tripelennamine but not cimetidine. The effect of PGE2 was mimicked by 17-phenyl PGE2 and sulprostone, but not other EP agonists, including EP2, EP3, and EP3/EP4 agonists. The mucosal vascular permeability was slightly increased by histamine, and this response was markedly enhanced by co-administration of 17-phenyl PGE2 as well as PGE2. The mucosal ulcerogenic and vascular permeability responses induced by histamine plus PGE2 were both suppressed by pretreatment with ONO-AE829, the EP1 antagonist. These results suggest that PGE2 aggravates histamine-induced gastric mucosal injury in rats. This action of PGE2 is mediated by EP1 receptors and functionally associated with potentiation of the increased vascular permeability caused by histamine through stimulation of H1-receptors.     

Prophylactic and therapeutic benefits of COX-2 inhibitor on motility dysfunction in bowel obstruction: roles of PGE₂ and EP receptors

We reported previously that mechanical stretch in rat colonic obstruction induces cyclooxygenase (COX)-2 expression in smooth muscle cells. The aims of the present study were to investigate whether in vivo treatment with COX-2 inhibitor has prophylactic and therapeutic effects on motility dysfunction in colon obstruction, and if so what are the underlying mechanisms. Partial colon obstruction was induced with a silicon band in the distal colon of 6-8-wk-old Sprague-Dawley rats; obstruction was maintained for 3 days or 7 days. Daily administration of COX-2 inhibitor NS-398 (5 mg/kg) or vehicle was started before or after the induction of obstruction to study its prophylactic and therapeutic effects, respectively. The smooth muscle contractility was significantly suppressed, and colonic transit rate was slower in colonic obstruction. Prophylactic treatment with NS-398 significantly prevented the impairments of colonic transit and smooth muscle contractility and attenuated fecal collection in the occluded colons. When NS-398 was administered therapeutically 3 days after the initiation of obstruction, the muscle contractility and colonic transit still improved on day 7. Obstruction led to marked increase of COX-2 expression and prostaglandin E(2) (PGE(2)) synthesis. Exogenous PGE(2) decreased colonic smooth muscle contractility. All four PGE(2) E-prostanoid receptor types (EP1 to EP4) were detected in rat colonic muscularis externa. Treatments with EP1 and EP3 antagonists suppressed muscle contractility in control tissue but did not improve contractility in obstruction tissue. On the contrary, the EP2 and EP4 antagonists did not affect control tissue but significantly restored muscle contractility in obstruction. We concluded that our study shows that COX-2 inhibitor has prophylactic and therapeutic benefits for motility dysfunction in bowel obstruction. PGE(2) and its receptors EP2 and EP4 are involved in the motility dysfunction in obstruction, whereas EP1 and EP3 mediate PGE(2) regulation of colonic smooth muscle contractile function in normal state.     

Retinoic acid increases hypoxia-inducible factor-1α through intracrine prostaglandin E(2) signaling in human renal proximal tubular cells HK-2

We have previously shown in HK-2 cells that ATRA (all-trans-retinoic acid) up-regulates HIF-1α (hypoxia-inducible factor-1α) in normoxia, which results in increased production of renal protector VEGF-A (vascular endothelial growth factor-A). Here we investigated the role of COXs (cyclooxygenases) in these effects and we found that, i) ATRA increased the expression of COX-1 and COX-2 mRNA and protein and the intracellular levels (but not the extracellular ones) of PGE(2). Furthermore, inhibitors of COX isoenzymes blocked ATRA-induced increase in intracellular PGE(2), HIF-1α up-regulation and increased VEGF-A production. Immunofluorescence analysis found intracellular staining for EP1-4 receptors (PGE(2) receptors). These results indicated that COX activity is critical for ATRA-induced HIF-1α up-regulation and suggested that intracellular PGE(2) could mediate the effects of ATRA; ii) Treatment with PGE(2) analog 16,16-dimethyl-PGE(2) resulted in up-regulation of HIF-1α and antagonists of EP1-4 receptors inhibited 16,16-dimethyl-PGE(2)- and ATRA-induced HIF-1α up-regulation. These results confirmed that PGE(2) mediates the effects of ATRA on HIF-1α expression; iii) Prostaglandin uptake transporter inhibitor bromocresol green blocked the increase in HIF-1α expression induced by PGE(2) or by PGE(2)-increasing cytokine interleukin-1β, but not by ATRA. Therefore only intracellular PGE(2) is able to increase HIF-1α expression. In conclusion, intracellular PGE(2) increases HIF-1α expression and mediates ATRA-induced HIF-1α up-regulation.     

Mechanisms of histamine-induced relaxation in bovine small adrenal cortical arteries

Adrenal steroidogenesis is closely correlated with increases in adrenal blood flow. Many reports have studied the regulation of adrenal blood flow in vivo and in perfused glands, but until recently few studies have been conducted on isolated adrenal arteries. The present study examined vasomotor responses of isolated bovine small adrenal cortical arteries to histamine, an endogenous vasoactive compound, and its mechanism of action. In U-46619-precontracted arteries, histamine (10(-9)-5 x 10(-6) M) elicited concentration-dependent relaxations. The relaxations were blocked by the H(1) receptor antagonists diphenhydramine (10 microM) or mepyramine (1 microM) (maximal relaxations of 18 +/- 6 and 22 +/- 6%, respectively, vs. 55 +/- 5% of control) but only partially inhibited by the H(2) receptor antagonist cimetidine (10 microM) and the H(3) receptor antagonist thioperamide (1 microM). Histamine-induced relaxations were also blocked by the nitric oxide synthase inhibitor N-nitro-L-arginine (L-NA, 30 microM; maximal relaxation of 13 +/- 7%) and eliminated by endothelial removal or L-NA combined with the cyclooxgenase inhibitor indomethacin (10 microM). In the presence of adrenal zona glomerulosa (ZG) cells, histamine did not induce further relaxations compared with histamine alone. Histamine (10(-7)-10(-5) M) concentration-dependently increased aldosterone production by adrenal ZG cells. Compound 48/80 (10 microg/ml), a mast cell degranulator, induced significant relaxations (93 +/- 0.6%), which were blocked by L-NA plus indomethacin or endothelium removal, partially inhibited by the combination of the H(1), H(2), and H(3) receptor antagonists, but not affected by the mast cell stabilizer sodium cromoglycate (1 mM). These results demonstrate that histamine causes direct relaxation of small adrenal cortical arteries, which is largely mediated by endothelial NO and prostaglandins via H(1) receptors. The potential role of histamine in linking adrenal vascular events and steroid secretion requires further investigation.     

Properties of histamine-induced suppressor factor in the regulation of lymphocyte response to PHA in mice

Splenic T lymphocytes release a suppressor factor into the culture supernatant when incubated for 24 hr with histamine (10^?4M). Histamine-induced suppressor factor (HISF) inhibits lymphocyte response to PHA; it is released by T lymphocytes (either nylon-nonadherent or nylon-adherent lymphocytes) and not by B-cells or macrophages; its production is not observed after depletion of histamine receptor-bearing lymphocytes and is blocked by the H2 receptor antagonist (cimetidine) but not by the H1 receptor antagonist (diphenhydramine). Gel filtration by Sephadex G100 chromatography indicates that HISF had an approximate MW of 45,000 to 68,000. Its inhibitory activity was removed by passage over a histamine RSA-Sepharose column, but not by passage over rabbit anti-mouse Ig-Sepharose column; it was blocked by prostaglandin synthetase inhibitor (PGS) (Ro 205720) indicating that this activity is mediated by a prostaglandin (PG) synthesis.     

Sensitivity difference to the suppressive effect of prostaglandin E2 among mouse strains: a possible mechanism to polarize Th2 type response in BALB/c mice

PGE2 has been shown to play a prominent role in regulating Th1 and Th2 type responses. We studied the role of PGE2 in IFN-gamma production by Staphylococcus aureus Cowan I-stimulated spleen cells from several mouse strains such as BALB/c, C3H/HeN, and C57BL/6. When spleen cells were pretreated with indomethacin (cyclooxygenase (COX)-1 and COX-2 inhibitor) or NS-398 (COX-2-specific inhibitor), S. aureus Cowan I -induced IFN-gamma production was increased more markedly in spleen cells from BALB/c mice than from C3H/HeN and C57BL/6 mouse. However, PGE2 production was not significantly different among spleen cells from three mouse strains. When various concentrations of PGE2 were exogeneously added to spleen cells, PGE2 showed a stronger suppressive effect on IFN-gamma production in spleen cells from BALB/c mice than from other strains of mice. This suppressive effect of PGE2 in BALB/c mice mainly depended on IL-12p70 production by APCs. More PGE2 binding sites were found in BALB/c spleen cells than in C3H/HeN spleen cells, indicating that the sensitivity difference to the suppressive effect of PGE2 was due to the difference of the number of PGE2 receptors. The administration of NS-398 into BALB/c mice enhanced Ag-specific IFN-gamma production, but not IL-4 production. This effect is the same as IL-12 administration in vivo. From these results, we propose that the modulation of PGE2 is important for Th1 activation via IFN-gamma and IL-12p70 production in vitro and in vivo and that PGE2 is one of the pivotal factors in the Th2-dominant immune response in BALB/c mice.     

Antinociceptive activity of impentamine, a histamine congener, after CNS administration

The brain neuromodulator histamine induces antinociception when administered directly into the rodent CNS. However, several compounds derived from H2 and H3 antagonists also produce antinociception after central administration. Pharmacological studies have shown that a prototype of these agents, improgan, induces analgesia that is not mediated by actions on known histamine receptors. Presently, the antinociceptive properties of a compound that chemically resembles both improgan and histamine were investigated in rats. Intraventricular (i.v.t.) administration of impentamine (4-imidazolylpentylamine) induced reversible, near-maximal antinociception on the hot plate and tail flick tests (15 microg, 98 nmol). The dose-response function was extremely steep, however, since other doses showed either no effect or behavioral toxicity. On the tail flick test, impentamine antinociception was resistant to antagonism by blockers of H1, H2, or H3 receptors, similar to characteristics previously found for improgan. In contrast, histamine antinociception was highly attenuated by H1 and H2 antagonists. These findings suggest that: 1) the histamine congener impentamine may induce antinociception by a mechanism similar to that produced by improgan, and 2) additional histamine receptors may be discovered that are linked to pain-attenuating processes.