NK1 receptors mediate tachykinin-induced plasma extravasation in the rat knee joint

The effect of adrenergic compounds on neurogenic dural vasodilatation

The pharmacology of neurogenic trigeminovascular vasodilator responses in the dura mater is of interest for understanding the pathophysiology of migraine and to develop new therapies for this disabling common condition. Aminergic mechanisms have been implicated in migraine through direct study of amines in patients, and by inference from the pharmacology of many effective anti-migraine compounds, particularly preventative agents. This study used intravital microscopy to assess the role of aminergic transmission in neurogenic dural vasodilatation (NDV) by measuring directly the diameter of dural arteries in sodium pentobarbitone anaesthetised rats. Electrical stimulation of a closed cranial window produces, by local depolarisation of nerves, dural vessel dilation that is monitored continuously on-line using video-microscopy and a video dimension analyser. This dural vasodilatation was not affected by pre-treatment with an alpha1-adrenoceptor agonist (phenylephrine, 1 and 5 microg/kg), or antagonist (corynanthine, 1 and 2 mg/kg), nor by an alpha2-adrenoceptor agonist (UK14,304, 5 microg/kg) or antagonist (yohimbine, 1 and 3 mg/kg). Similarly, we saw no effect of beta-adrenoceptor blockade (propranolol, 1 and 3 mg/kg). The lack of an inhibitory effect of UK14,304 the model of neurogenic dural vasodilation contrasts with its effect in neurogenic dural plasma protein extravasation model. The lack of inhibition of beta-adrenoceptor antagonists in the neurogenic vasodilatation model contrasts with their usefulness as migraine prophylactics, and suggests that their mechanism of action in migraine is unlikely to be through sensory trigeminal fibre terminals at the neurovascular junction. Moreover, the data indicate that the adrenergic system does not play a significant role in neurogenic dural vasodilation.

Release of neutrophil elastase and its role in tissue injury in acute inflammation: effect of the elastase inhibitor, FR134043

Neutrophil elastase degrades extracellular matrix components and is involved in tissue destruction in several inflammatory states. We examined the inhibition of the elastase activity derived from activated neutrophils in vitro and in vivo by FR134043, disodium-(Z,1S,15S,18S,24S,27R,29S,34S,37R)-29-b enzyl-21-ethylidene-27-hydroxy-15-isobutyrylamino-34-isopropyl-31, 37-dimethyl-10,16,19,22,30,32,35,38-octaoxo-36-oxa-9,11,17,20,23,2 8,31,33-octaazatetracyclo[16.13.6.1(24,28).0(3,8)]octatriconta+ ++-3,5,7-trien-5,6-diyl disulfate, an elastase inhibitor with broad specificity, and elucidated the role of neutrophil elastase in pathogenesis of acute inflammation. In a culture of human neutrophils, phorbol myristate acetate (PMA) and calcium ionophore increased elastase activity in the supernatants, which was amplified by co-existing mononuclear leukocytes. Formyl-Met-Leu-Phe stimulated elastase release in the presence of, not without, mononuclear leukocytes. Intratracheal injection of lipopolysaccharide elevated the elastase activity in bronchoalveolar lavage fluid of rats. These elastase activities were significantly inhibited by FR134043. Intratracheal treatment with FR134043 in rats also inhibited the enzyme induced by lipopolysaccharide, though the maximum inhibition was 52%. Ear edema elicited by topical application of PMA in mice was significantly suppressed by pretreatment with FR134043 (38% inhibition at 1 mg/ear). In carrageenan-induced joint injury in rats, plasma extravasation into the synovial cavity was partially and significantly inhibited by FR134043 at 1 mg/knee, while an elastase-specific inhibitor showed no effect. These results suggest that neutrophil elastase is partially involved in tissue damage in acute inflammation provoked by irritants, but not in carrageenan-induced hyperpermeability.

Release of substance P, calcitonin gene-related peptide and prostaglandin E2 from rat dura mater encephali following electrical and chemical stimulation in vitro

Neurogenic inflammation of the dura, expressed in plasma extravasation and vasodilatation, putatively contributes to different types of headache. A novel in vitro preparation of the fluid-filled skull cavities was developed to measure mediator release from dura mater encephali upon antidromic electrical stimulation of the trigeminal ganglion and after application of a mixture of inflammatory mediators (serotonin, histamine and bradykinin, 10(-5) M each, pH 6.1) to the arachnoid side of rat dura. The release of calcitonin gene-related peptide, substance P and prostaglandin E2 from dura mater was measured in 5-min samples of superfusates using enzyme immunoassays. Orthodromic chemical and antidromic electrical stimulation of dural afferents caused significant release of calcitonin gene-related peptide (2.8- and 4.5-fold of baseline). The neuropeptide was found to be increased during the 5-min stimulation period and returned to baseline (20.9 +/- 12 pg/ml) in the sampling period after stimulation. In contrast, release of substance P remained at baseline levels (19.3 +/- 11 pg/ml) throughout the experiment. Prostaglandin E2 release was elevated during chemical and significantly also after antidromic electrical stimulation (6- and 4.2-fold of baseline, which was 305 +/- 250 pg/ml). Prostaglandin E2 release outlasted the stimulation period for at least another 5 min. The data support the hypothesis of neurogenic inflammation being involved in headaches and provide new evidence for prostaglandin E2 possibly facilitating meningeal nociceptor excitation and, hence, pain.

The tachykinin NK1 receptor. Part II: Distribution and pathophysiological roles

The tachykinin NK1 receptor is widely distributed in both the central and peripheral nervous system. In the CNS, NK1 receptors have been implicated in various behavioural responses and in regulating neuronal survival and degeneration. Moreover, central NK1 receptors regulate cardiovascular and respiratory function and are involved in activating the emetic reflex. At the spinal cord level, NK1 receptors are activated during the synaptic transmission, especially in response to noxious stimuli applied at the receptive field of primary afferent neurons. Both neurophysiological and behavioural evidences support a role of spinal NK1 receptors in pain transmission. Spinal NK1 receptors also modulate autonomic reflexes, including the micturition reflex. In the peripheral nervous system, tachykinin NK1 receptors are widely expressed in the respiratory, genitourinary and gastrointestinal tracts and are also expressed by several types of inflammatory and immune cells. In the cardiovascular system, NK1 receptors mediate endothelium-dependent vasodilation and plasma protein extravasation. At respiratory level, NK1 receptors mediate neurogenic inflammation which is especially evident upon exposure of the airways to irritants. In the carotid body, NK1 receptors mediate the ventilatory response to hypoxia. In the gastrointestinal system, NK1 receptors mediate smooth muscle contraction, regulate water and ion secretion and mediate neuro-neuronal communication. In the genitourinary tract, NK1 receptors are widely distributed in the renal pelvis, ureter, urinary bladder and urethra and mediate smooth muscle contraction and inflammation in response to noxious stimuli. Based on the knowledge of distribution and pathophysiological roles of NK1 receptors, it has been anticipated that NK1 receptor antagonists may have several therapeutic applications at central and peripheral level. At central level, it is speculated that NK1 receptor antagonists could be used to produce analgesia, as antiemetics and for treatment of certain forms of urinary incontinence due to detrusor hyperreflexia. In the peripheral nervous system, tachykinin NK1 receptor antagonists could be used in several inflammatory diseases including arthritis, inflammatory bowel diseases and cystitis. Several potent tachykinin NK1 receptor antagonists are now under evaluation in the clinical setting, and more information on their usefulness in treatment of human diseases will be available in the next few years.

Characterization of tachykinin receptors mediating plasma extravasation and vasodilatation in normal and acutely inflamed knee joints of the rat

1. Inflammatory actions of tachykinins in normal rat knee joints were compared with those of animals with acutely inflamed joints induced by intra-articular injection of 2% carrageenan. Plasma protein extravasation in rat knee joints, measured by protein micro-turbidimetry, was induced by intra-articular perfusion of selective tachykinin receptor agonists. Changes in joint blood flow, measured by laser Doppler perfusion imaging, were produced by topical applications of selective tachykinin receptor agonists to the joint capsule. 2. Carrageenan-injected rat knee joints showed significantly higher (P < 0.001) basal plasma extravasation (56 +/- 4 micrograms ml-1, n = 5) than normal rat knee joints (10 +/- 4 micrograms ml-1, n = 6). Intra-articular perfusion of the selective neurokinin1 (NK1) receptor agonist [Sar9, Met(O2)11]-substance P (0.8 nmol min-1) for 60 min elevated the basal plasma extravasation to 90 +/- 17 micrograms ml-1 (n = 6, P < 0.001) in normal joints, and to 150 +/- 14 micrograms ml-1 (n = 5, P < 0.001) in inflamed joints. Perfusion of the selective NK1 receptor antagonist N2-[(4R)-4-hydroxy-1-(1-methyl-1H- indol-3-yl)carbonyl-L-prolyl]-N-methyl-N-phenylmethyl-3-(2-naphthyl)- L-alaninamide (FK888; 0.8 nmol min-1) for 20 min followed by co-perfusion with the NK1 receptor agonist (0.8 nmol min-1) produced complete inhibition of the NK1 receptor agonist-induced plasma extravasation in the two groups of animals (for both groups; n = 3, P < 0.001). 3. Intra-articular perfusion of the selective NK receptor agonist [Nle10]-neurokinin A4-10 (0.8 nmol min-1) and the selective NK3 receptor agonist [MePhe7]-neurokinin B (0.8 nmol min1) produced no increase in plasma extravasation in normal or in inflamed rat knee joints (n = 4 and 11, P > 0.05). 4. Topical bolus applications of the NK1 receptor agonist [Sar9, Met(O2)11]-substance P onto normal joint capsules produced dose-dependent vasodilatation expressed as a voltage increase from control level. The maximum increase in blood flow was 2.05-0.21 V from a basal voltage of 3.42 +/- 0.07 V (n = 13, P < 0.001). To a much lesser extent, administration of the NK2 receptor agonist [Nle10]-neurokinin A4-10 also produced dose-dependent vasodilatation with maximum increase of 0.46 +/- 0.08 V from a basal level of 3.38 +/- 0.1 V (n = 7, P < 0.01). Animals with acutely inflamed joints showed enhanced vasodilator responses to the NK1 and NK2 receptor agonists (for both: P vs non-inflamed joints < 0.001). Thus, the NK1 and NK2 receptor agonists produced maximum increases of 2.56 +/- 0.19 V (basal level = 5.84 +/- 0.07 V; n = 7, P < 0.001) and 1.97 +/- 0.26 V (basal level = 6.31 +/- 0.23 V; n = 11, P < 0.001), respectively. The NK3 receptor agonist [MePhe7]-neurokinin B produced no change in blood flow in normal or in inflamed rat knee joints (n = 7 and 5, P > 0.05). 5. Bolus administration of the NK1 receptor antagonist FK888 (10 pmol) alone followed 5 min later by another dose of 10 pmol FK888 (i.e. total dose of 2 x 10 pmol) applied together with the NK1 receptor selective agonist [Sar9, Met(O2)11]-substance P produced partial, but significant inhibition of the NK1 receptor agonist-induced vasodilatation in both normal (maximum response reduced by 51.9 +/- 5.4%; n = 6, P < 0.001) and inflamed rat knee joints (maximum response reduced by 49.3 +/- 6.1%; n = 5, P < 0.001). The NK2 receptor agonist [Nle10]-neurokinin A4-10-induced vasodilator responses in inflamed joints were not affected by this treatment (n = 6, P > 0.05). However, with two higher doses of FK888 (both 1 nmol), the NK1 and the NK2 receptor agonist-induced vasodilator responses were abolished in the two groups of animals (n = 6-8, P < 0.005). 6. Administration of two doses of the selective NK2 receptor antagonist (S)-N-methyl-N-[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) -butyl]benzamide (SR48968;...

Involvement of tachykinin receptors in oedema formation and plasma extravasation induced by substance P, neurokinin A, and neurokinin B in mouse ear

The involvement of tachykinin receptors in skin inflammation induced by substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) was investigated in mouse ears. Intradermal injection of tachykinins (0.1-100 pmol/site) into the ear skin produced oedema formation. RP 67580 (ED50: 0.34 mg/kg, i.v.) and SR 140333 (ED50: 0.19 mg/kg, i.v.), the non-peptide NK1 receptor antagonists, inhibited SP-induced oedema. SR 140333 was also effective in preventing NKA- and NKB-induced oedema. SR 48968 (1 mg/kg, i.v.), a non-peptide NK2 antagonist, induced a significant inhibition of NKA-induced oedema but had no effect on the response to SP and NKB. SR 142801 (3 mg/kg, i.v.), a non-peptide NK3 antagonist, prevented only NKB-induced oedema. In contrast, phosphoramidon (0.1 and 0.5 mg/kg, i.v.), an endopeptidase inhibitor, enhanced the oedema response to tachykinins. SR 140333, SR 48968, and SR 142801 blocked the enhancement by phosphoramidon of the response to SP, NKA, and NKB, respectively. Plasma extravasation in ear skin was induced by i.v. injection of tachykinins (0.7-17.6 nmol/kg). RP 67580 (ED50: 0.15 mg/kg, i.v. for SP) and SR 140333 (ED50: 14.3 micrograms/kg, i.v. for SP) inhibited tachykinin-induced plasma extravasation in ear skin. However, SR 48968 and SR 140281 had no effect on the vascular response to tachykinins. Chlorpheniramine (4 mg/kg, i.v.), a histamine H1 blocker, inhibited the response to local SP but not to i.v. SP. These results suggest that in addition to the NK1 receptors, functional NK2 and NK3 receptors may participate in the oedema response to local NKA and NKB in the ear skin. However, it appears that NK1 receptors on blood vessels are involved predominantly in plasma extravasation induced by i.v. tachykinins in the ear.

Involvement of substance P as a mediator in capsaicin-induced mouse ear oedema

We examined the involvement of substance P (SP) in mouse ear oedema induced by topical application of capsaicin (250 micrograms/ear). Reapplication of capsaicin at 4 h, 24 h, and 48 h after initial treatment did not induce a second oedema response. Oedema induced after the second application was significantly (p < 0.01 or p < 0.001) suppressed for up to 30 days but was observed when capsaicin was applied 40 days after initial treatment. Topical pretreatment of ears with capsaicin at 4 h, 24 h and 48 h before i.v. injection of SP (5 micrograms/kg) did not cause a significant inhibition of plasma extravasation in ear skin. NK1 receptor antagonists such as RP 67580 (ED50:0.19 mg/kg, i.v.), spantide II (ED50:0.33 mg/kg, i.v.), and GR 82334 (ED50:0.26 mg/kg, i.v.), inhibited capsaicin-induced ear oedema, whereas SR 48968 (2.0 mg/kg, i.v.), a NK2 receptor antagonist, had no effect. Furthermore, RP 67580 (0.5 kg/mg, i.v.) inhibited the oedema response induced by reapplication of capsaicin at 50 days after initial treatment. These results indicate that tachyphylaxis of capsaicin-induced oedema is reversible and suggest that this response may be due mainly to a reduction of SP in sensory neurones but not to any loss of responsiveness of NK1 receptors. We also conclude that SP and NK1 receptors are involved predominantly in the development of capsaicin-induced mouse ear oedema.

Role of nitric oxide in the actions of substance P and other mediators of inflammation in rat skin microvasculature

The role of nitric oxide in inflammatory responses to substance P and other mediators of inflammation was examined in rat skin microvasculature in a blister base raised on the hind footpad. Superfusion of substance P (1 microM) over the blister base caused an increase in plasma extravasation and a vasodilator response which was not maintained. N(G)-Nitro-L-arginine (100 microM), an inhibitor of nitric oxide biosynthesis, attenuated vasodilatation and plasma extravasation due to substance P. The inactive isomer N(G)-nitro-D-arginine was without effect. Neurokinin A (1 microM), 5-hydroxytryptamine (1 microM), ATP (50 microM) and vasoactive intestinal polypeptide (1 microM) elicited vasodilation, which for vasoactive intestinal polypeptide was maintained even after washout. 5-Hydroxytryptamine and neurokinin A, but not ATP or vasoactive intestinal polypeptide, significantly increased plasma extravasation. Vasodilatation to neurokinin A, 5-hydroxytryptamine and ATP, and the increase in plasma extravasation due to neurokinin A and 5-hydroxytryptamine were unaffected by N(G)-nitro-L-arginine (100 microM), whereas vasodilation due to vasoactive intestinal polypeptide was significantly attenuated. These findings suggest that in rat skin microvasculature in vivo, nitric oxide is involved in vasodilator responses due to substance P and vasoactive intestinal polypeptide, and plasma extravasation due to substance P, but does not contribute significantly to vasodilatation induced by neurokinin A, 5-hydroxytryptamine or ATP, or the plasma extravasation induced by neurokinin A or 5-hydroxytryptamine.