The IOP-lowering effects and mechanism of action of tafluprost in prostanoid receptor-deficient mice

AIM

To clarify the intraocular pressure (IOP)-lowering profile of tafluprost, a newly synthesised prostaglandin F(2alpha) analogue, in mice.

METHODS

C57BL/6J, and EP1, EP2, EP3 and postaglandin F (FP) receptor-deficient wild-type (WT), EP1KO, EP2KO, EP3KO and FPKO, respectively mice were bred and acclimatised under a 12-h (6:00-18:00) light-dark cycle. To evaluate effects of tafluprost (0.002%) on IOP at night, a single 3 microl drop of tafluprost solution was applied topically at 18:00 once into one eye in each mouse. IOP was measured 3 h after the application with a microneedle method. To clarify whether endogenous prostaglandin is concerned with the tafluprost-induced IOP reduction, we applied 0.1% diclofenac Na, a cyclo-oxygenase inhibitor or PBS 30 min before the application of tafluprost in WT and EP3KO mice and measured IOP 3 h after the tafluprost application. We also determined whether animals responded predictably to 0.1% bunazosin HCl, a drug known to increase uveoscleral outflow.

RESULTS

3 h after the application of 0.0015% tafluprost, mean (SEM) IOP reductions were 25.8 (2.1)% 26.3 (0.8)% 24.2 (1.4)% 16.5 (1.7)% and -0.9 (1.5)% in WT, EP1KO, EP2KO, EP3KO and FPKO mice, respectively. IOP reductions in EP3KO and FPKO mice were significantly smaller than in WT mice. Pretreatment with diclofenac Na significantly attenuated the IOP lowering effect of tafluprost in WT mice but not in EP3KO mice. Bunazosin HCl lowered IOP significantly in all genotypes by the same amount.

CONCLUSION

We conclude that tafluprost lowers IOP through the prostanoid FP receptor. A part of ocular hypotensive effect of tafluprost is attributed to FP receptor-mediated prostaglandin production acting through the prostanoid EP3 receptor.

Gap junctional connexin 37 is expressed in sheep ovaries

The objective of current study was to evaluate the expression of Cx37 in ovarian follicles and in corpora lutea (CL) during the estrous cycle in sheep. Ovine Cx37 was cloned and characterized to design speciesspecific probe and primers. In Exp. 1, ovaries were collected on d 13, 14, 15, and 16 of the estrous cycle, or from FSH-induced ewes at 0, 2, 4, 8, 12, 24, and 48 h after hCG treatment on d 15 of the estrous cycle. In Exps. 2 and 3, CL were collected on d 5, 10, and 15 of the estrous cycle, or at 0, 4, 8, 12, and 24 h after prostaglandin F2alpha (PGF2alpha)-induced luteal regression on d 10 of the estrous cycle, respectively. Ovarian tissues (e.g., granulosa cells, theca cells, ovarian follicles, and /or CL) were used for Cx37 immunostaining followed by image analysis or for determination of Cx37 mRNA expression by real-time RT-PCR. We demonstrated that (1) Cx37 protein was expressed in granulosa and cumulus oocyte complex compartments, ovarian blood vessels, and on the luteal cell borders, (2) expression of Cx37 mRNA was greater in granulosa than in theca cells of preovulatory follicles, (3) Cx37 mRNA expression in granulosa but not theca cells was affected by hCG treatment, (4) Cx37 protein and mRNA expression were dependent on the stage of luteal development, and (5) Cx37 expression changed during PGF2alpha- induced luteal regression. Thus, Cx37 may play a role in follicular development and ovulation as well as in luteal tissue growth, differentiation, and regression.

Endogenous prostaglandins regulate spontaneous contractile activity of uterine strips isolated from non-pregnant pigs

Myometrial strips isolated from non-pregnant pigs show spontaneous contractile activity. In the present study, the involvement of endogenous prostaglandins in regulation of uterine spontaneous contraction was investigated using mechanical, immunohistochemical and biochemical approaches. Immunohistochemical study and Western blot analysis for immunoreactive cyclooxygenase (COX) indicated that COX-1 but not COX-2 was expressed predominantly in the myometrium of non-pregnant pigs in a muscle layer-dependent manner (longitudinal muscle>circular muscle). Pretreatment of uterine strips with indomethacin and selective COX-1 inhibitors (SC-560 and FR122047) significantly reduced both the amplitude and frequency of spontaneous contraction in the longitudinal muscle, but inhibition by COX inhibitors was negligible in the circular muscle. On the other hand, CAY10404, a COX-2 inhibitor, did not change the spontaneous contraction in either of the muscle layers. Pretreatment with SC-560 reduced myometrial PGF(2alpha) and PGE(2) levels. Contractile FP and EP(3) receptors were expressed in a muscle layer-dependent manner (longitudinal muscle>circular muscle), similar to the expression pattern of COX-1. In conclusion, endogenous prostaglandins produced by COX-1 regulate spontaneous contractile activity of non-pregnant porcine uterine longitudinal muscle selectively due to the heterogeneous expression of contractile prostanoid receptors and COX-1.

The effects of ovarian function on estrus synchronization with PGF in dairy cows

Milk progesterone concentration (P4), milk yield, milk composition, ovarian structures and pregnancy status were studied in 108 cows treated with two doses of PGF 14 days apart and inseminated at fixed time (TAI) 80-82 h later. The synchronization protocol was started at 70+/-1.4 days after parturition. Milk P4 profiles revealed that anestrus, failure of luteolysis following treatment with PGF and failure to ovulate following luteolysis were the main reasons for low pregnancy rate with TAI. Anestrous cows had a higher percentage of milk fat (P<0.05) and higher fat to protein ratio (P<0.01), and cows that did not undergo luteolysis had higher milk yield (P<0.05) and lower percentage of milk protein (P<0.05) than cows that responded to PGF treatment. Cows that did not undergo luteolysis and cows that did not ovulate following luteolysis had lower milk P4 during the luteal phase preceding the second PGF injection (P<0.01 and P<0.05, respectively). Pregnancy rates 24 and 47 days after TAI in cows that responded as expected to the synchronization treatment were 62% and 54%, respectively. Pregnancy was precluded in non-responsive cows. The largest follicle at the time of TAI in cows experiencing late embryonic mortality was smaller (P=0.02) than in cows that successfully maintained pregnancy. Results suggest that a primary reason for low pregnancy rate in dairy cows after administration of PGF and TAI is inappropriate ovarian function prior to, or following treatment.

Dissecting why superovulation and embryo transfer usually work on some farms but not on others

Bovine embryo transfer is a well-established commercial industry that is often associated with veterinary practices. Practitioners offering embryo transfer services may possess a very high standard of technical expertise; however, success in the production of embryos and the impregnation of recipients cannot be achieved unless the cattle are healthy and maintained in a well-managed cattle operation. In addition to appropriate gonadotropin treatments of donor cattle, the use of highly fertile semen, known to have been properly stored and handled is required for success. Recipient cattle must be managed with the same attention to detail as donors. Traditionally, PGF has been used for the synchronization of recipients. However, PGF is limited in its effectiveness early and late in the bovine estrus cycle. Recipient estrus synchronization with progesterone releasing intravaginal inserts has been successful and high pregnancy rates have resulted following embryo transfer.

Effect of prostaglandins against alloxan-induced diabetes mellitus

Previously, we observed that alloxan-induced in vitro cytotoxicity and apoptosis in an insulin secreting rat insulinoma, RIN, cells was prevented by prior exposure to prostaglandin (PG) E(1), PGE(2), PGI(2), PGF(1)(alpha), and PGF(3)(alpha) (P<0.05 compared to alloxan), whereas thromboxane B(2) (TXB(2)) and 6-keto-PGF(1)(alpha) were ineffective. In an extension of these studies, we now report that prior intraperitoneal administration of PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) prevented alloxan-induced diabetes mellitus in male Wistar rats, whereas PGI(2), TXB(2), and 6-keto PGF(1)(alpha) were not that effective. PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) not only attenuated chemical-induced diabetes mellitus but also restored the antioxidant status to normal range in red blood cells and pancreas. These results suggest that PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) can abrogate chemically induced diabetes mellitus in experimental animals and attenuate the oxidant stress that occurs in diabetes mellitus.

Prostaglandin analogues and mouse intraocular pressure: effects of tafluprost, latanoprost, travoprost, and unoprostone, considering 24-hour variation

PURPOSE

To establish a mouse model for the pharmacological analysis of antiglaucoma drugs, considering the effect of variations in IOP during 24 hours on the drugs' effects, and to evaluate the effect of a newly developed FP agonist, tafluprost, on mouse IOP, in comparison with three clinically available prostaglandin (PG) analogues.

METHODS

Inbred adult ddY mice were bred and acclimatized under a 12-hour light-dark cycle. With mice under general anesthesia, a microneedle method was used to measure IOP. A single drop of 3 muL of either drug or vehicle solution was topically applied once into one eye in each mouse, in a blinded manner, with the contralateral, untreated eye serving as the control. IOP reduction was evaluated by the difference in IOP between the treated and untreated eyes in the same mouse. First, to determine the period feasible for demonstrating a larger magnitude of ocular hypotensive effect, the 24-hour diurnal variation in mouse IOP was measured, and 0.005% latanoprost was applied at the peak or trough time of variation in 24-hour IOP. The time point of the most hypotensive effect was selected for further studies, to evaluate the effects of PG analogues. Second, mice received tafluprost (0.0003%, 0.0015%, 0.005%, or 0.015%), latanoprost (0.001%, 0.0025%, or 0.005%), travoprost (0.001%, 0.002%, or 0.004%), or isopropyl unoprostone (0.03%, 0.06%, or 0.12%), and each corresponding vehicle solution. IOP was then measured at 1, 2, 3, 6, 9, and 12 hours after drug administration. The ocular hypotensive effects of the other three PG analogues were compared with that of tafluprost. All experiments were conducted in a masked study design.

RESULTS

The IOP in the untreated mouse eye was higher at night than during the day. Latanoprost significantly lowered IOP at night (21.4%), compared with the IOP in the untreated contralateral eye 2 hours after administration. The maximum IOP reduction was 20.2% +/- 2.0%, 18.7% +/- 2.5%, and 11.2% +/- 1.8% of that in the untreated eye 2 hours after administration of 0.005% tafluprost, 0.005% latanoprost, and 0.12% isopropyl unoprostone, respectively, whereas it was 20.8% +/- 4.6% at 6 hours with 0.004% travoprost (n = 7 approximately 17). The order of ocular hypotensive effects of three clinically used PG analogues in mice was comparable to that in humans. Area under the curve (AUC) analysis revealed dose-dependent IOP reductions for each PG analogue. Tafluprost 0.005% decreased IOP more than 0.005% latanoprost at 3, 6, and 9 hours (P = 0.001-0.027) or 0.12% unoprostone at 2, 3, and 6 hours (P = 0.0004-0.01).

CONCLUSIONS

The 24-hour variation in mouse eyes should be taken into consideration when evaluating the reduction of IOP. The mouse model was found to be useful in evaluating the pharmacological response to PG analogues. A newly developed FP agonist, 0.005% tafluprost, lowered normal mouse IOP more effectively than did 0.005% latanoprost.

Effect of prostaglandins against alloxan-induced cytotoxicity to insulin secreting insulinoma RIN cells in vitro

In the present study, we studied the effect of various prostaglandins (PGs) on alloxan-induced cytotoxicity to rat insulinoma (RIN) cells. Of all the PGs tested, PGE(1), PGE(2), PGI(2), PGF(1 alpha), and PGF(3 alpha) protected RIN cells from alloxan-induced cytotoxicity (P<0.05 compared to alloxan), whereas thromboxane B(2) and 6-keto-PGF(1 alpha) were not effective. PGE(1) induces a statistically significant increase in the activities of superoxide dismutase and glutathione peroxidase and decrease in lipid peroxides in alloxan-treated RIN cells (P<0.001). PGE(1) restored nitric oxide/lipid peroxide ratio to normalcy, suggesting that PGE(1) suppresses oxidant stress induced by alloxan in RIN cells in vitro. Furthermore, PGE(1) prevented DNA damage and apoptosis induced by alloxan. These results indicate that PGE(1) prevents alloxan-induced cytotoxicity to RIN cells in vitro.

Pharmacological characteristics of AFP-168 (tafluprost), a new prostanoid FP receptor agonist, as an ocular hypotensive drug

To evaluate the pharmacological characteristics of AFP-168 (tafluprost), a new prostaglandin (PG) F(2alpha) derivative, we examined its receptor-binding affinities, intraocular pressure (IOP)-lowering effect, effects on aqueous humor dynamics, and stimulating effect on melanogenesis. The receptor-binding profile for AFP-172, a carboxylic acid of AFP-168, was determined by measuring muscle contractions in an organ bath, inhibition of platelet aggregation, and competitive binding of a radio-labelled ligand. For the IOP-measurement study, ocular normotensive and laser-induced ocular hypertensive cynomolgus monkeys were used, and IOP was measured using a pneumatonograph. For the studies of aqueous humor dynamics, IOP (Goldmann applanation tonometry), fluorophotometry, two-level constant pressure perfusion, and isotope dilution and accumulation techniques were used in ocular normotensive monkeys. The melanin contents in the medium and in the cell bodies of cultured B16-F0 melanoma cells were measured. The affinity for the FP receptor shown by AFP-172 (Ki : 0.4 nm) was 12 times that of PhXA85 ( Ki : 4.7 nm), a carboxylic acid of latanoprost. A single application of AFP-168 at 0.0025% significantly lowered IOP in both ocular normotensive and hypertensive monkeys (3.1 and 11.8 mmHg, respectively, p < 0.01) and latanoprost at 0.005% significantly lowered IOP (2.1 mmHg, p < 0.01 and 9.5 mmHg, p = 0.059 respectively). Once daily instillation of AFP-168 at 0.001, 0.0025, or 0.005% for 5 days in normotensive monkeys significantly reduced IOP not only for a few hours, but also at the drug-trough time 24hr after application. Latanoprost at 0.005% also reduced IOP, but not at the drug-trough time. AFP-168 decreased IOP mainly by increasing uveoscleral outflow by 65% (p < 0.05) and, as sometimes seen with other prostanoids, also increased total outflow facility (33% increase, p < 0.05). In cultured B16-F0 melanoma cells, AFP-172 (100 microM) did not stimulate melanogenesis, but PhXA85 (100 microM) did. These findings indicate that AFP-168 has a high affinity for the prostanoid FP receptor, has potent IOP-lowering effects in both ocular normotensive and hypertensive monkeys that exceed those of latanoprost, and has less stimulating effect on melanogenesis in melanoma cells.

Human Ciliary Muscle Cell Responses to FP-Class Prostaglandin Analogs: Phosphoinositide Hydrolysis, Intracellular Ca2+ Mobilization and MAP Kinase Activation

Phospholipase C induced phosphoinositide (PI) turnover, intracellular Ca(2+) ([Ca(2+)](i)) mobilization and mitogen-activated protein (MAP) kinase activation by FP-class prostaglandin analogs was studied in normal human ciliary muscle (h-CM) cells. Agonist potencies obtained in the PI turnover assays were: travoprost acid ((+)-fluprostenol; EC(50) = 2.6 +/- 0.8 nM) > bimatoprost acid (EC(50) = 3.6 +/- 1.2 nM) > (+/-)-fluprostenol (EC(50) = 4.3 +/- 1.3 nM) >> prostaglandin F(2 alpha) (PGF(2 alpha)) (EC(50) = 134 +/- 17 nM) > latanoprost acid (EC(50) = 198 +/- 83 nM) > S-1033 (EC(50) = 2930 +/- 1420 nM) > unoprostone (EC(50) = 5590 +/- 1490 nM) > bimatoprost (EC(50) = 9600 +/- 1100 nM). Agonist potencies in h-CM cells correlated well with those previously obtained for the cloned human ciliary body-derived FP receptor (r = 0.96, p< 0.001) and that present on h-TM cells (r = 0.94, p< 0.0001). Travoprost acid, PGF(2 alpha) and unoprostone also stimulated [Ca(2+)](i) mobilization in h-CM cells with travoprost acid being the most potent agonist. MAP kinase activity was stimulated in the h-CM cells with the following rank order of activity (at 100 nM): travoprost acid > PGF(2 alpha) > latanoprost acid > PGD(2) > bimatoprost > latanoprost = bimatoprost acid = fluprostenol > PGE(2) = S-1033 > unoprostone > PGI(2). The PI turnover, [Ca(2+)](i) mobilization and MAP kinase activation induced by several of these agonists was blocked by the FP receptor antagonist, AL-8810 (11 beta-fluoro-15-epiindanyl PGF(2 alpha)) (e.g. K(i) = 5.7 microM versus PI turnover). These studies have characterized the biochemical and pharmacological properties of the native FP prostaglandin receptor present on h-CM cells using three signal transduction mechanism assays and a broad panel of FP-class agonist analogs (including free acids of bimatoprost, travoprost and latanoprost) and the FP receptor antagonist, AL-8810.

Vasodilatory and electrophysiological actions of 8-iso-prostaglandin E2 in porcine coronary artery

We examined the effects of several E-ring and F-ring isoprostanes on mechanical and electrophysiological activity in porcine coronary artery. Several isoprostanes evoked concentration-dependent contractions, with 8-iso-PGE2 being the most potent (-log EC50 of 6.9 +/- 0.1); this excitatory effect has been described in detail elsewhere and was not examined further here. 8-iso-PGE2 evoked dose-dependent relaxations in tissues preconstricted with the thromboxane A2-agonist U46619 (10(-6) M), with a negative log EC50 of 6.0 +/- 0.1 (n = 5). 8-iso-PGE1 and 8-iso-PGF2 beta also evoked relaxations (albeit with lower potency), whereas the other F-ring isoprostanes (8-iso-PGF1 alpha, 8-iso-PGF1 beta, and 8-iso-PGF2 alpha) were largely ineffective in this respect. The potency and efficacy of 8-iso-PGE2 in reversing tone were not dependent upon the concentration of U46619 used to preconstrict the tissues (10(-8) to 10(-6) M), indicating a lack of U46619-induced functional antagonism of these responses. 8-iso-PGE2 was able to completely relax tissues that had been denuded of endothelium (as indicated by loss of responsiveness to bradykinin). 8-iso-PGE2-evoked relaxations were markedly reduced by elevating the K+ equilibrium potential using 30 mM KCl and abolished by 60 mM KCl; they were also sensitive to charybdotoxin (10(-7) M) but not to 4-aminopyridine (1 mM). 8-iso-PGE2 also caused membrane hyperpolarization and augmentation of outward K+ current. We conclude that 8-iso-prostaglandin E2 acts directly on the smooth muscle to increase K+ conductance, leading to membrane hyperpolarization and vasodilation.

The algogenic-induced nociceptive flexion test in mice: studies on sensitivity of the test and stress on animals

Recently we developed a new technique, known as peripheral nociception test or algogenic-induced nociceptive flexion (ANF) test, to study the in vivo signal transduction of pain at the peripheral nerve endings in mice. In the present report, we examined the sensitivity of the method to detect pain signal and the stresses induced by the test on experimental animals. In the algogenic-induced biting and licking (ABL) test, bradykinin could not induce significant biting-licking response even at a dose of 1nmol. It induced significant biting-licking response only at 10nmol. However, with the ANF test, 100fmol of bradykinin was enough to produce sharp and significant nociceptive flexion response. Similarly, substance P, ATP and ONO-54918-07, a stable prostaglandin I(2) agonist, induced nociceptive flexion response in ANF test at much lower doses than needed to induce biting-licking responses in ABL test. Next, we measured the plasma corticosterone level after different nociception tests, which is a measure of stress on animals due to experimental manipulations. However, no significant rise in corticosterone level was observed with ANF test. Altogether, these findings indicate that the ANF test is a highly sensitive and less stressful technique to study in vivo mechanisms of pain at the peripheral nerve ending.

Differential inhibition by botulinum neurotoxin A of cotransmitters released from autonomic vasodilator neurons

The role of the soluble NSF attachment protein receptor (SNARE) protein complex in release of multiple cotransmitters from autonomic vasodilator neurons was examined in isolated segments of guinea pig uterine arteries treated with botulinum neurotoxin A (BoNTA; 50 nM). Western blotting of protein extracts from uterine arteries demonstrated partial cleavage of synaptosomal-associated protein of 25 kDa (SNAP-25) to a NH2-terminal fragment of approximately 24 kDa by BoNTA. BoNTA reduced the amplitude (by 70-80%) of isometric contractions of arteries in response to repeated electrical stimulation of sympathetic axons at 1 or 10 Hz. The amplitude of neurogenic relaxations mediated by neuronal nitric oxide (NO) was not affected by BoNTA, whereas the duration of peptide-mediated neurogenic relaxations to stimulation at 10 Hz was reduced (67% reduction in integrated responses). In contrast, presynaptic cholinergic inhibition of neurogenic relaxations was abolished by BoNTA. These results demonstrate that the SNARE complex has differential involvement in release of cotransmitters from the same autonomic neurons: NO release is not dependent on synaptic vesicle exocytosis, acetylcholine release from small vesicles is highly dependent on the SNARE complex, and neuropeptide release from large vesicles involves SNARE proteins that may interact differently with regulatory factors such as calcium.

Opposite effect of prolactin and prostaglandin F(2 alpha) on the expression of luteal genes as revealed by rat cDNA expression array

It is well established that prolactin (PRL) sustains, while prostaglandin F(2 alpha) (PGF(2 alpha)) curtails, progesterone production by the rat corpus luteum (CL). We have previously shown that the actions of both molecules converge on the 20 alpha-HSD gene and control its expression in a dramatically opposed manner. In this investigation, we have found twelve more genes that are inversely regulated by PRL and PGF(2 alpha). In addition to 20 alpha-HSD, PGF(2 alpha) stimulated and PRL inhibited PGF(2 alpha)-receptor, phospholipase C delta(1) and TGF beta(1) expression. In contrast PRL stimulated and PGF(2 alpha) inhibited the LH receptor, 11 beta-HSD2, sterol carrier protein 2, mitochondrial glutathione S-transferase (GST), GST mu(2), inhibitory DNA-binding proteins 1, 2, and 3, and calcium binding protein 2. We have also identified new target genes for PRL and PGF(2 alpha). PGF(2 alpha) stimulated the expression of genes involved in cell signaling such as cell adhesion kinase-beta, ERK3, FRA2, IL-2 receptor, and 14-3-3 proteins. PGF(2 alpha) also up-regulated the expression of the sodium channel beta(1), Na/K ATPase, annexin IV, GST7pi, and P450 reductase. In contrast PGF(2 alpha) inhibited the expression of two genes involved in cell cycle: cyclin D2 and retinoblastoma related protein (Rb2/p130). It also inhibited genes involved in estradiol (P-450(AROM)) and cholesterol biosynthesis (HMG-CoA synthase), as well as genes involved in tissue remodeling: VEGF and TIMP3. PRL had a profound inhibitory effect on the expression of genes encoding the ADP-ribosylation factor 3, annexin V and c-jun, yet increased the expression of P450scc, 3beta-HSD, and SR-B1 (HDL-receptor), all genes involved in steroidogenesis. PRL also stimulated the expression of beta(2)-microglobulin, TIMP2, cytochrome c oxidase IV, cathepsin H and L, and copper-zinc superoxide dismutase as well as elongation factor SIII, heat shock protein-60 and mitochondrial ATP synthase-D. In conclusion, this investigation has revealed a "yin-yang" relationship between PRL and PGF(2 alpha) in regulating certain critical genes in the rodent CL, and has demonstrated novel regulation by these factors of other important genes involved in luteal function.

Effects of prostaglandin F(2alpha)and carbachol on MAP kinases, cytosolic phospholipase A(2)and arachidonic acid release in cat iris sphincter smooth muscle cells

The signal transduction pathways initiated by Ca(2+)-mobilizing agonists, such as prostaglandin F(2alpha)(PGF(2alpha)) and carbachol (CCh), leading to activation of cytosolic phospholipase A(2)(cPLA(2)) and arachidonic acid (AA) release in a wide variety of tissues remain obscure. To further define the role of protein kinases in receptor mediated stimulation of cPLA(2)and consequently AA release we have investigated the role of mitogen-activated protein (MAP) kinases and protein kinase C (PKC) in PGF(2alpha)- and CCh-induced cPLA(2)phosphorylation and AA release in cat iris sphincter smooth muscle (CISM) cells. The cells were prelabeled with [(3)H]AA for 24 hr and incubated in the absence or presence of the agonist for 5-10 min as indicated. MAP kinases activities and cPLA(2)phosphorylation were determined in immunoprecipitates obtained by using anti-p38 MAP kinase and anti-cPLA(2)antibodies. We found that: (a) PGF(2alpha)and CCh increased p38 MAP kinase activity by 197 and 215%, respectively, and increased p42/p44 MAP kinase activity by 200 and 125%, respectively. (b) SB202190, a p38 MAP kinase specific inhibitor, inhibited PGF(2alpha)- and CCh-induced cPLA(2)phosphorylation by 92 and 85%, respectively, and AA release by 62 and 78%, respectively. (c) PD98059, a p42/p44 MAP kinase inhibitor, inhibited CCh-induced cPLA(2)phosphorylation by 70% and AA release by 71%, but had no effect on that of PGF(2alpha). (d) Inhibition of PKC activity by RO 31-8220 inhibited both PGF(2alpha)- and CCh-stimulation of p38 MAP kinase, p42/p44 MAP kinases and cPLA(2)phosphorylation. We conclude from these results that in CISM cells PGF(2alpha)-induced cPLA(2)phosphorylation and AA release is mediated through p38 MAP kinase, but not through p42/p44 MAP kinases, whereas that of CCh is mediated through both p38 MAP kinase and p42/p44 MAP kinases. These effects of PGF(2alpha)and CCh are regulated by the MAP kinases in a PKC-dependent manner. Studies aimed at elucidating the role of protein kinases in the coupling mechanism between the activation of PGF(2alpha)and muscarinic receptors, and the stimulation of cPLA(2)and AA release in the smooth muscles of the iris-ciliary body will provide important information about the role of protein kinases signaling pathways in smooth muscle function, as well as about the mechanism of the intraocular pressure-lowering effects of PGF(2alpha)and its analog, latanoprost, in glaucoma therapy.

Marked hypotensive and blood flow-increasing effects of a new lipo-PGE(1) (lipo-AS013) due to vascular wall targeting

Lipo-AS013 is being developed as an improved formulation of lipo-PGE(1), which is widely used in clinical practice in Japan and some Asian countries. We have previously reported that lipo-AS013, which is a lipid microsphere (LM) preparation of a chemically stable and lipophilic PGE(1) prodrug (AS013, Fig. 1), slowly releases small amounts of the active ingredient (AS013) in human plasma. In the present study, to estimate the vascular wall targeting ability and efficacy of lipo-AS013, we determined the hypotensive and blood flow-increasing effects of lipo-AS013, lipo-PGE(1), PGE(1)CD, and AS013. Lipo-AS013 was found to have longer-lasting hypotensive and blood flow-increasing effects than the other agents. The two LM preparations, lipo-PGE(1) and lipo-AS013, had a markedly stronger effect than PGE(1)CD and AS013 alone, demonstrating the benefit of drug delivery using LM. In spontaneously hypertensive rats (SHR), lipo-AS013 also had a significant hypotensive effect. To confirm vascular wall targeting by lipo-AS013, the localization of PGE(1) in the aorta and neovascular capillaries of rat was investigated by immunostaining. The results indicated that lipo-AS013 was more efficient at delivering the active ingredient (AS013) to the vessel wall. In conclusion, lipo-AS013 could supersede lipo-PGE(1) and PGE(1)CD in clinical use.

Excitatory and inhibitory actions of isoprostanes in human and canine airway smooth muscle

Isoprostanes are generated nonenzymatically during free radical-mediated lipid peroxidation, and are used clinically and experimentally as markers of oxidative stress. However, their biological effects are poorly understood. We examined the effects of seven different 8-isoprostanes in human and canine airway smooth muscles. In large order airways (carina) of the human, several isoprostanes evoked powerful contractions, with 8-iso-prostaglandin (PG) E(2), 8-iso-PGF(1 alpha), and 8-iso-PGF(2 alpha) being the most efficacious (and with logEC(50) values of 7.0, 5.9, and 6.2 microM, respectively). These contractions were sensitive to the prostanoid TP receptor antagonist ICI 192,605 (0.1-1 microM), but not the EP prostanoid receptor antagonist AH-6809 (50 microM), or the leukotriene receptor antagonists monteleukast or ICI 198,615 (both 1 microM). Qualitatively similar results were obtained in small order human airways (<2 mm o.d.), except that the isoprostanes were generally slightly less potent. None of the isoprostanes had any marked excitatory effect in canine airways. In carbachol-preconstricted tissues (pretreated with ICI 192,605 to block any potential contraction), several isoprostanes completely relaxed canine airways: 8-iso-PGE(1), 8-iso-PGE(2), and 8-iso-PGF(3 alpha) were the most potent, with logIC(50) values of 6.9, 6.9, and 5.7, respectively. Only 8-iso-PGF(3 alpha) relaxed human airways (logIC(50) = 4.9). Our results show that several 8-isoprostanes are highly biologically active in human and canine airways, evoking both excitatory and/or inhibitory effects, and that these effects are compound, species, and tissue dependent.

Exogenous hyaluronidase induces release of nitric oxide from the coronary endothelium

OBJECTIVE

Hyaluronidase, an endogenous enzyme that hydrolyzes mucopolysaccharides, has been shown to enhance myocardial protection when added to preservation solutions. In addition, hyaluronidase infusion reduces injury to ischemic myocardium. Endothelium-derived nitric oxide is an endogenous vasodilator that prevents leukocyte adhesion to the intima and inhibits platelet adhesion and aggregation in the coronary artery. Experiments were undertaken to determine whether the protective action of hyaluronidase could be mediated by the endogenous release of nitric oxide.

METHODS

Segments of coronary artery, with and without endothelium, were placed in organ chambers (25 mL) to measure isometric force. Blood vessel segments were contracted with prostaglandin F(2)(alpha) (2 x 10(-6) mol/L) and exposed to hyaluronidase (3-15 units).

RESULTS

Hyaluronidase induced vasodilation of arteries with intact endothelium but not of arteries without endothelium (n = 6, P<.05). Endothelium-dependent vasodilation to hyaluronidase was blocked by N(G)-monomethyl-L -arginine (10(-5) mol/L), an inhibitor of nitric oxide synthesis from L -arginine (n = 6, P<.05). Inhibition of vasodilation by N(G)-monomethyl-L -arginine was reversed by L -arginine (10(-4) mol/L) but not D -arginine (10(-4) mol/L; n = 6, each group). Vasodilation to hyaluronidase also was inhibited by hemoglobin (2 x 10(-6) mol/L), a scavenger of the nitric oxide radical (n = 6, P<.05).

CONCLUSIONS

Hyaluronidase induces the release of nitric oxide from the coronary endothelium. Because nitric oxide, an endogenous vasodilator, inhibits leukocyte adhesion to the intima in addition to inhibiting platelet adhesion and aggregation, stimulated production of endothelium-derived nitric oxide by exogenous hyaluronidase could be the mechanism of the protective action of hyaluronidase infusion.

Aging reduces the responsiveness of coronary arteries from male Wistar rats to the vasodilatory action of testosterone

This study was performed to examine whether aging affects the vasodilatory effects of testosterone in the coronary arteries of male rats. Isolated coronary arteries from young mature (3-4 months) and elderly (22-26 months) male Wistar rats were studied in a wire myograph. Contractile function and endothelial function were assessed by measuring vasomotor responses to 10-100 mmol/l KCl, 0.1 mmol/l prostaglandin F(2alpha) (PGF(2alpha)) and 10 micromol/l acetylcholine. Sensitivity to the vasodilatory effects of testosterone was assessed by constructing dose-response curves to concentrations between 1 micromol/l and 1 mmol/l testosterone dissolved in water in vessels maximally preconstricted with PGF(2alpha). The compliance characteristics of each vessel and serum testosterone levels from each animal were measured. Histological sections of myocardium were examined for differences in coronary artery morphology. Vessels from elderly animals were significantly more resistant to the vasodilatory effects of testosterone than vessels from young animals (P=0.001 by analysis of covariance). Vessels from elderly animals were also significantly less compliant (7.32+/-0.43 microm/mN, compared with 10.99+/-1.52 microm/mN in young animals; P=0.011), and the levels of circulating testosterone in elderly animals were lower, but not significantly so (2.04+/-0.63 nmol/l compared with 3.88+/-1.7 nmol/l; P=0.32). Vessels from elderly animals were less contractile in response to KCl than those from young animals (P=0.004 by analysis of covariance). There were no significant differences between the two groups in their responses to PGF(2alpha) or acetylcholine. Thus it is concluded that coronary arteries from elderly rats are significantly less sensitive to the vasodilatory effects of testosterone than those from young animals.

Changes in the mechanisms involved in uterine contractions during pregnancy in guinea-pigs

1. The mechanisms involved in contraction in guinea-pig myometrium were compared at mid- and late pregnancy. Tension was recorded simultaneously with either membrane potential or cytoplasmic calcium ([Ca2+]i) in strips exposed briefly to prostaglandin F2alpha (PGF). 2. PGF-induced increases in tension were underpinned by action potentials followed by sustained depolarization and biphasic increases in [Ca2+]i at mid- (peak, 879 +/- 199 nM; sustained, 298 +/- 35 nM, n = 11) and late pregnancy (peak, 989 +/- 302 nM; sustained 178 +/- 33 nM, n = 8). 3. At mid- and late pregnancy, nifedipine (10-6 M) reduced (a) the PGF-induced increase in tension to 84 and 35 %, (b) the level attained during the depolarization by 2 and 12 mV and (c) the peak rise in [Ca2+]i to 42 and 17 %. The sustained rises in [Ca2+]i were resistant to nifedipine. 4. In Ca2+-free solution (containing 1 mM EGTA), PGF elicited an increase in tension that was 26 % of that in 2.5 mM Ca2+ and an increase in [Ca2+]i (24 % of the sustained level) at mid-pregnancy but no increase in tension or [Ca2+]i at term. 5. At both stages of pregnancy, PGF decreased the level of [Ca2+]i required to elicit increases in tension comparable to those evoked by high K+o. The slope of the tension-[Ca2+]i curves were steeper in mid- than in late pregnancy. 6. In conclusion, at mid-pregnancy, the contractile response of the guinea-pig myometrium to PGF involves Ca2+ influx through L-type voltage-operated Ca2+ channels (VOCCs) and by receptor-operated mechanisms, release of Ca2+ from intracellular stores, and an increase in the sensitivity of the contractile apparatus to Ca2+. At term the situation is different: a modest increase in the sensitivity of the contractile apparatus to Ca2+ persists and there is a major reliance on Ca2+ influx through VOCCs.

Design and synthesis of 13,14-dihydro prostaglandin F(1alpha) analogues as potent and selective ligands for the human FP receptor

The in vitro evaluation of a new class of potential bone anabolic agents for the treatment of osteoporosis is described. These compounds are potent and selective ligands for the human prostaglandin F receptor (hFP receptor). The compounds lack the olefin unsaturation required for potency in the natural ligand PGF(2)(alpha) yet retain binding affinity for the hFP receptor in the nanomolar to micromolar range. Removal of the alkenes also results in a better selectivity ratio for the hFP receptor over the other prostaglandin receptors tested. A rationale for the selectivity differences of various analogues, based on ligand docking experiments to a putative hFP receptor model, is also described.

Effects of some isoprostanes on the human umbilical artery in vitro

1. Cumulative concentration-effect curves for the selective prostanoid TP receptor agonist U46619 and six isoprostanes were constructed in the human isolated umbilical artery. 2. All compounds except 8-iso-PGF3 alpha produced concentration-dependent contractions. The contractile response to the isoprostanes increased with each cumulative addition up to a point, after which subsequent addition reduced the contraction below the previous level. This 'downturn' in the concentration-effect curve did not occur with U46619. 3. The potencies of the compounds tested were as follows (pEC50 +/- s.e.mean): U46619, 6.7 +/- 0.2; 8-iso-PGE2, 6.5 +/- 0.1; 8-iso-PGF2 alpha, 5.8 +/- 0.2; 8-iso-PGE1, 5.4 +/- 0.1; 8-iso-PGF1 alpha, 5.0 +/- 0.1; 8-iso-PGF2 beta > 4.8; 8-iso-PGF3 alpha >> 4.8 (n = 4-17). Neither 8-iso-PGF2 beta nor 8-iso-PGF3 alpha at 44 microM had a significant effect on cumulative concentration-effect curves to U46619. 4. The selective TP receptor antagonist GR32191 (0.1 microM) caused rightward shifts in the concentration-effect curves to all the active compounds. pA2 values for GR32191 against U46619, 8-iso-PGE2, 8-iso-PGF2 alpha, 8-iso-PGE1 were 7.6 +/- 0.2, 9 +/- 1, 8.2 +/- 0.3 and 7.7 +/- 0.3, respectively (n = 4). 5. Neither N omega-nitro-L-arginine methyl ester (100 microM) nor the selective DP receptor antagonist BW A868C (50 nM) affected the complex concentration-effect curve to 8-iso-PGE2 (n = 3). 6. Stable contractions to U46619 (1-3 microM) were unaffected by anandamide at concentrations up to 60 microM.

Effects of lysophosphatidic acid on proliferation and cytosolic Ca++ of human adult vascular smooth muscle cells in culture

Lysophosphatidic acid (LPA) is a lipid mediator generated by activated platelets and having various effects on numerous cell types. We investigated some effects of 1-oleyl LPA on vascular smooth muscle cells cultured from adult human normal arteries. At micromolar concentrations, LPA induced a mitogenic effect ([3H]-thymidine incorporation and cell proliferation) on quiescent cells, without an additional growth factor being required. This effect was equipotent to that of 10% fetal calf serum, and it was accompanied by early (5 minutes) and late (1-3 hours) phosphorylation of mitogenactivated protein kinase. LPA inhibited cell migration through collagen coated membranes, with or without platelet-derived growth factor BB as chemoattractant. LPA induced a typical biphasic Ca2+ signal response made up of a rapid first phase due to Ca2+ release from intracellular stores followed by a second wave due to external Ca2+ influx. These findings support the proposal that LPA released from activated platelets is a mediator for smooth muscle cell response at the site of vessel injury in humans.

Prostaglandin E2 and I2 regulate intercellular adhesion molecule-1 expression in interleukin-1 beta-stimulated human gingival fibroblasts

The present study investigated the effect of prostaglandin (PG) E2 and PGI2 on intercellular adhesion molecule-1 (ICAM-1) expression in interleukin-1 beta (IL-1 beta)-stimulated human gingival fibroblasts (HGF). IL-1 beta potently induced ICAM-1 expression in HGF and indomethacin, a cyclooxygenase inhibitor, enhanced ICAM-1 expression in the cells. These data showed that endogenous PGs generated by HGF stimulated with IL-1 beta downregulated ICAM-1 expression. IL-1 beta significantly increased the levels of PGE2 and, to a lesser extent, those of 6-keto-PGF1 alpha (a stable metabolite of PGI2) in the culture media of HGF. Indomethacin completely inhibited the production of PGE2 and 6-keto-PGF1 alpha in IL-1 beta-stimulated HGF. Exogenous PGE2 and carbacyclin (a stable derivative of PGI2) in the presence of indomethacin dose-dependently suppressed ICAM-1 expression in IL-1 beta-challenged HGF. Since PGE2 and PGI2 are known to elevate intracellular cyclic AMP (cAMP) levels, we examined the effect of dibutyryl cAMP, a cAMP analogue, and isobutylmethylxanthine, a phosphodiesterase inhibitor, on ICAM-1 expression. Both agents downregulated ICAM-1 expression in IL-1 beta-stimulated HGF. These results suggest that PGE2 and PGI2 downregulate ICAM-1 expression in IL-1 beta-stimulated HGF through a cAMP-dependent mechanism and that intracellular cAMP elevation in HGF may control inflammatory and immune responses in periodontal disease.

Different contractile properties between intralobar and extralobar pulmonary arteries of the rabbit

In pulmonary circulation, small muscular resistance arteries are known to have different receptor properties and sensitivity to neurotransmitters from those of large elastic conduit arteries. It is, however, not yet certain whether the different properties are primarily due to the diameter or the location of arteries. In the present study, we compared the contractile responses to various agonists among large extralobar (ELPA, diameter: 2-3 mm), large intralobar (ILPA, diameter: 2-3 mm), and small intralobar pulmonary arteries (SPA, diameter: 300-500 microm) of the rabbit. There were no differences in normalized dose-response curves to KCl among three groups. Half maximum doses (EC50 in mM) were 38.0+/-2.0 (n=8, mean+/-SEM) in ELPA, 36.9+/-2.4 (n=10) in ILPA, and 39.0+/-0.9 (n=12) in SPA. Responses to phenylephrine, epinephrine, histamine, serotonin, and PGF2alpha were normalized and expressed as a relative contraction against maximum tension to KCl. In ELPA, the contractile responses to various agents showed the following sequence: KCl>epinephrine>phenylephrine>serotonin>PGF2alpha>histamine. In ILPA and SPA, the sequence was: KCl>histamine>PGF2alpha>serotonin. There was little response to phenylephrine and epinephrine in ILPA and SPA. These results demonstrate that the difference of contractile responses between ELPA and ILPA was more prominent than that between ILPA and SPA, suggesting that the location is more important than the diameter itself in determining the characteristic contractile responses of pulmonary arteries.