The Met66 allele of the functional Val66Met polymorphism in the brain-derived neurotrophic factor gene confers protection against neurocognitive dysfunction in systemic lupus erythematosus.

BACKGROUND: A common functional polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met) was previously associated with diminished episodic memory performance in healthy people. As cognitive function is commonly impaired in patients with systemic lupus erythematosus (SLE), the association of the BDNF Val66Met with neurocognitive function was studied. OBJECTIVE: To study the association of the BDNF Val66Met with neurocognitive function in a cohort of patients with SLE. METHODS: Cognitive function was assessed in 59 patients with SLE with no previous or current central nervous system involvement. Cognitive tests were grouped into five domains (memory, attention/executive function, visuospatial skills, motor function and psychomotor speed) and used to obtain domain Z scores, reflecting the difference between averaged scores of performance on individual tests and published norms in each domain. Genotyping was carried out using a 5'-nuclease assay with 99.9% accuracy. Unpaired t test was used to assess the relationship between genotypes and cognitive function, whereas the effect of possible confounders was assessed in a multivariate analysis. RESULTS: Patients carrying the Met66 allele scored significantly higher on psychomotor, attention/executive and motor function tests, resulting in significantly higher domain Z scores for the psychomotor (p = 0.005) and motor (p = 0.002) domains. CONCLUSIONS: The BDNF Met66 allele was associated with better cognitive functioning in the psychomotor and motor domains, even after controlling for differences in ethnicity, sex, depression status and prednisone treatment. These data suggest that the BDNF Met66 allele confers protection against the decline of motor and psychomotor cognitive functions in patients with longstanding SLE.

Anti-inflammatory effect of synthetic somatostatin analogues in the rat.

1. Somatostatin (6.11 nmol kg(-1) i.p.) inhibited neurogenic plasma extravasation evoked by 1% mustard oil and non-neurogenic oedema induced by 5% dextran in the rat skin. 2. Cyclic synthetic octapeptide (TT-248 and TT-250) and heptapeptide (TT-232) somatostatin analogues proved to be more effective in reducing neurogenic and non-neurogenic inflammatory reactions but octreotide had no influence on either neurogenic or non-neurogenic inflammation. 3. TT-232 administered i.p. or i.v. (1.06 - 42.40 nmol kg(-1)) inhibited in a dose-dependent manner the plasma extravasation evoked by mustard oil in the rat's paw. Neither diclofenac (15.78 - 315.60 micromol kg(-1)) nor the selective COX-2 inhibitor meloxicam (2.95 - 569.38 micromol kg(-1)) attenuated the mustard oil-induced neurogenic plasma extravasation. 4. TT-232, diclofenac and meloxicam dose-dependently diminished non-neurogenic dextran-oedema of the paw the ED(35) values were 1.73 nmol kg(-1) for TT-232 and 34.37 micromol kg(-1) for diclofenac. 5. TT-232 inhibited in the dose range of 1.06 - 21.21 nmol kg(-1) the bradykinin-induced plasma extravasation in the skin of the chronically denervated paw. 6. Mustard oil-induced cutaneous plasma extravasation was dose-dependently diminished by s.c. TT-232 1, 2, 4, 6 or 16 h after the treatment. TT-232 (2 x 106, 2 x 212 and 2 x 530 nmol kg(-1) per day s.c. for 18 days) caused dose-dependent inhibition of chronic Freund adjuvant-induced arthritis during the experimental period. 7. TT-232 (200 and 500 nM) inhibited the release of SP, CGRP and somatostatin from the rat isolated trachea induced by electrical field stimulation (40 V, 0.1 ms, 10 Hz, 120 s) or by capsaicin (10(-7) M), but did not influence the basal, non-stimulated peptide release. 8. It is concluded that somatostatin analogues without endocrine functions as TT-232 are promising compounds with a novel site of action for inhibition of non-neurogenic and neurogenic inflammatory processes.

Functional and biochemical evidence for capsaicin-induced neural endothelin release in isolated working rat heart.

In isolated working rat heart, capsaicin elicited a concentration-dependent constriction of coronary arteries accompanied by decline of all cardiac parameters recorded (heart rate, coronary and aortic flow, left ventricular developed pressure, and first derivative of left ventricular developed pressure). The following evidence suggests that capsaicin-induced changes are mediated by endothelin of neural origin: (1) the capsaicin (10 nM)-evoked decrease in coronary flow resulting in deterioration of cardiac functions was mimicked by endothelin (0.1 nM); (2) the selective endothelin ET(A) receptor antagonist, cyclo (D-alpha-aspartyl-L-propyl-D-valyl-L-leucyl-D-tryptophyl) (1 microM), abolished the cardiac effects provoked by capsaicin (10 nM); (3) reduction of extracellular Ca2+ concentration from 2.4 to 1.2 or 0.6 mM inhibited the cardiac effects of capsaicin (10 nM) but not those induced by endothelin (0.1 nM); (4) perfusion of the heart with 0.1% (v/v) Triton X-100 damaged the endothelium and reversed the enhancement of coronary flow evoked by bethanechol (1 microM), decreased the basal flow, but was without effect on capsaicin-induced coronary constriction; (5) in response to capsaicin challenge (10-100 nM), the endothelin concentration measured in coronary effluent by means of radioimmunoassay increased up to sevenfold but remained unchanged in the presence of 0.6 mM Ca2+; (6) no reduction of coronary flow was induced by capsaicin (100 nM) applied to the heart of rats which were desensitised by capsaicin (150 mg/kg). It is concluded that, in the rat heart, capsaicin acting on VR1 capsaicin receptors elicits a release of endothelin from the sensory nerve terminals.

Impaired capsaicin-induced decrease in heart rate and coronary flow in isolated heart of diabetic rats.

The effect of capsaicin (0.1 microM) on heart rate and coronary flow was studied in Langendorff-perfused heart from streptozotocin-induced (50 mg/kg i.v.) diabetic rats where sensory neuropathy developed. In hearts from animals 4- and 8-week diabetes baseline heart rate and coronary flow decreased from 317.9 +/- 2.9 b.p.m. and 13.4 +/- 0.7 m/min to 255.1 +/- 12.7 and 219.8 +/- 2.8 b.p.m. and 8.9 +/- 0.6 and 10.0 +/- 0.1 ml/min (P<0.05), respectively. Capsaicin significantly decreased both variables in either normal or 4-week diabetic animals its effects, however, on coronary flow or heart rate were missing in preparations from 8-week diabetic rats. Endothelin-1 (0.1 nM), the putative mediator of the capsaicin effect, significantly decreased heart rate and coronary flow irrespective of the presence or absence of diabetes. In the femoral nerve of streptozotocin-treated animals conduction velocity involving both fast conducting A- and slow-conducting C-fibres was decreased proportional to the duration of the pre-existing diabetic state. It is concluded that in insulin deficient diabetes the diminished responses evoked by capsaicin on heart rate and coronary flow are signs of sensory neuropathy. This is related to a feeble endothelin release from sensory nerve endings without changes in post-receptor mechanisms mediating the endothelin effects.

Anti-nociceptive effect induced by somatostatin released from sensory nerve terminals and by synthetic somatostatin analogues in the rat.

In rats anaesthetized with urethan and pretreated with pipecuronium bromide nocifensive reaction of blood pressure elevation evoked by intraarterial capsaicin injection was inhibited over 40 min by bilateral antidromic stimulation of the sensory fibres of the sciatic nerves. Rise in blood pressure, heart rate and respiratory frequency evoked by capsaicin were markedly diminished after smearing 1% mustard oil on the acutely denervated hindpaws indicating a release of mediators with anti-nociceptive action from cutaneous nociceptors. Intravenous injection of the putative mediator somatostatin (10 microg/kg) or its analogues RC-160 and TT-232, but not octreotide inhibited the cardiorespiratory and blood pressure responses evoked by topical cutaneous application of mustard oil or capsaicin instillation into the eye. It is concluded, that the endocrine and the anti-nociceptive effects of somatostatin are mediated through distinct receptor subtypes and therefore, TT-232, a novel heptapeptide analogue without endocrine action, is a promising analgesic compound.

Impairment of neurogenic inflammatory and anti-inflammatory responses in diabetic rats.

The effect was studied of a primary (preconditioning) neurogenic inflammatory challenge induced by electrical stimulation of the peripheral stump of the sciatic nerve (20 V, 0.5 ms, 5 Hz, for 5 min) on neurogenic oedema (5 min later) induced by stimulation of the contralateral sciatic nerve. Plasma extravasation due to the second stimulation was decreased by 52.7+/-3.1% (P<0.01) in normal animals and by 29.7+/-2.2 and 18.1+/-1.5% with 50 mg/kg streptozotocin pretreatment i.v. 4 and 8 weeks previously, respectively. Subsequently, bilateral sciatic nerve stimulation increased baseline plasma somatostatin levels from 6.4+/-0.3, 11. 7+/-1.4, and 16.8+/-3.8 to 28.3+/-2.9 (P<0.01), 17.9+/-3.7, and 25. 1+/-1.7 pmol/l in normal, and 4- and 8-week diabetic animals, respectively. We conclude that experimental diabetes impairs the capability of a preconditioning neurogenic inflammatory episode to elicit a systemic anti-inflammatory effect. This is accompanied by a deficiency in elevation of the plasma somatostatin level in response to nerve stimulation, although the baseline plasma somatostatin level increases proportionally to the duration of experimental diabetes.

Endothelin release by capsaicin in isolated working rat heart.

Capsaicin (1 nM-1 microM) induced a concentration-dependent decrease in heart rate, coronary flow, aortic flow, left ventricular developed pressure and its first derivative, dP/dt(max) in isolated working rat heart. The effect of 10 nM capsaicin was mimicked by 0.1 nM endothelin. PD142893 (200 nM), a non-selective endothelin receptor blocking agent antagonized the effect of either endothelin (0.1 nM) or capsaicin (10 nM). We conclude that the majority of the effects of capsaicin in the rat heart are mediated by neural endothelin release.

Interplay between nitric oxide and CGRP by capsaicin in isolated guinea-pig heart.

Capsaicin at a concentration of 10(-7)m induced a significant increase in heart rate and increased coronary flow in isolated Langendorff-perfused guinea-pig hearts. This effect was completely blocked by 30 microm of N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase. Additional incubation with 3 m m L-Arg antagonized the inhibitory effect of L-NAME. In the presence of 1 microm of a human calcitonin gene-related peptide fragment (hCGRP 8-37), a CGRP-receptor antagonist, L-Arg was without effect. We conclude that a capsaicin-induced increase in coronary flow and heart rate is dependent from an interplay between CGRP and NO in guinea-pig hearts. 1999 Academic Press.

Interaction between capsaicin and nitrate tolerance in isolated guinea-pig heart.

Capsaicin-induced increases in heart rate and coronary flow were blocked by N(G)-nitro-L-Arg-methyl ester (30 mM) in Langendorff-perfused guinea-pig hearts. Neither heart rate nor coronary flow changed by capsaicin in hearts from animals made tolerant to the hypotensive effect of 30 microg/kg nitroglycerin by the administration of 50 mg/kg nitroglycerin subcutaneously 4 times a day over 3 days. We conclude that the effector function of sensory nerves may deteriorate in nitrate tolerance.

Decreased sensory neuropeptide release from trachea of rats with streptozotocin-induced diabetes.

We studied the release of somatostatin, calcitonin gene-related peptide (CGRP) and substance P in response to electrical field stimulation from isolated tracheas of rats following 4 weeks of streptozotocin (50 mg/kg i.v.)-induced diabetes. Field stimulation (40 V, 0.1 ms, 10 Hz for 120 s) increased the release of somatostatin, CGRP and substance P from the baseline 0.18+/-0.029, 0.17+/-0.027, and 1.77+/-0.086 to 0.51+/-0.022, 0.69+/-0.115, and 5.96+/-0.377 in control preparations and 0.31+/-0.081, 0.41+/-0.142, and 3.14+/-0.443 fmol/mg wet tissue weight in preparations from diabetic rats as measured by radioimmunoassay (control vs. diabetic P<0.01 for each). The results show a simultaneous decrease in release of the three sensory neuropeptides and an enhanced plasma somatostatin level in rats with streptozotocin-induced diabetes.

Substance P radioimmunoassay for quantitative characterization of sensory neurotransmitter release.

In the present work we report the development of a new radioimmunoassay method for measuring the substance P content liberated from isolated rat tracheae in response to electrical or chemical (capsaicin, resiniferatoxin, piperine) stimulation. The amount of substance P released by electrical stimulation has been found to be dependent on the number of pulses and chemically elicited substance P release also proved to be dose-dependent. Our findings reinforce previous data that resiniferatoxin is approximately 100 times more potent than capsaicin and the potency ratio between piperine and capsaicin is 1/50.

Systemic anti-inflammatory effect induced by counter-irritation through a local release of somatostatin from nociceptors.

1. Neurogenic plasma extravasation evoked by topical application of 1% vv(-1) mustard oil on the skin of the acutely denervated rat hindleg (primary reaction) inhibited the development of a subsequent oil-induced plasma extravasation induced in the skin of the contralateral hindleg by 49.3+/-7.06% (n=9) and in the conjunctival mucosa due to 0.1% wv(-1) capsaicin instillation by 33.5+/-10.05% (n=6). The primary reaction also inhibited the non-neurogenic hindpaw oedema evoked by s.c. injection of 5% wv(-1) dextran into the chronically denervated hindpaw by 48.0+/-4.6% (n= 5). 2. Capsaicin injection (100 microg ml(-1) in 50 microl, s.c.) into the acutely denervated hindleg caused 56.5+/-4.0% (n=5) inhibition in the intensity of plasma extravasation elicited by 1% vv(-1) mustard oil smearing on the contralateral side. After chronic denervation, subplantar injection of 5% wv(-1) dextran elicited a non-neurogenic inflammatory response with intensive tissue oedema without causing any systemic anti-inflammatory effect. Bilateral adrenalectomy did not inhibit the mustard oil-induced anti-inflammatory effect in the contralateral hindleg. 3. Pretreating the rats with polyclonal somatostatin antiserum (0.5 ml rat(-1), i.v.) or with the somatostatin depleting agent cysteamine (280 mg kg(-1), s.c.) prevented the inhibitory action of mustard oil-induced inflammation on subsequent neurogenic plasma extravasation and strongly diminished the inhibition of non-neurogenic oedema formation evoked by dextran. 4. Exogenous somatostatin (10 microg kg(-1), i.p.) caused a 30.3+/-8.3% (n=6) inhibition of plasma extravasation caused by mustard oil smearing on the acutely denervated hindleg and this inhibitory effect was abolished by somatostatin antiserum (0.5 ml rat(-1), i.v.). The plasma level of somatostatin-like immunoreactivity (SST-LI) increased by 40.03+/-6.8% (n= 6) 10 min after topical application of 1% vv(-1) mustard oil on the acutely denervated hindpaws compared to the paraffin oil treated control group. Chronic denervation of the hindlegs or cysteamine (280 mg kg(-1), s.c.) pretreatment prevented the mustard oil-induced elevation of SST-LI in plasma. 5. It is concluded that chemical excitation of the capsaicin-sensitive sensory receptors not only induces local neurogenic plasma extravasation but also inhibits the development of a subsequent inflammatory reaction at remote sites of the body in the rat. A role for somatostatin in this systemic anti-inflammatory effect is suggested.

Inhibition of nociceptin on sensory neuropeptide release and mast cell-mediated plasma extravasation in rats.

Nociceptin (20 microg/kg i.p.) strongly inhibited cutaneous Evans blue accumulation in the chronically denervated hindpaw of the rat in response to mast cell degranulating peptide (MCDP, 0.25 microg in 100 microl) but it had no and marginal effect on plasma extravasation induced by 5-hydroxytryptamine (5-HT, 0.5 microg in 100 microl) and histamine (0.1 microg in 100 microl), respectively. Release of sensory neuropeptides such as substance P, calcitonin gene-related peptide (CGRP) and somatostatin from the rat isolated trachea in response to capsaicin (10(-8) M) or bradykinin (10(-7) M) were also attenuated by nociceptin (100 and 300 nM). It is concluded that chemically induced discharge of mediators from mast cells and from capsaicin-sensitive afferent nerve terminals are both inhibited by nociceptin that participates in the anti-inflammatory effect of the peptide.

Release of somatostatin and its role in the mediation of the anti-inflammatory effect induced by antidromic stimulation of sensory fibres of rat sciatic nerve.

1. The effect of antidromic stimulation of the sensory fibres of the sciatic nerve on inflammatory plasma extravasation in various tissues and on cutaneous vasodilatation elicited in distant parts of the body was investigated in rats pretreated with guanethidine (8 mg kg(-1), i.p.) and pipecuronium (200 microg kg(-1), i.v.). 2. Antidromic sciatic nerve stimulation with C-fibre strength (20 V, 0.5 ms) at 5 Hz for 5 min elicited neurogenic inflammation in the innervated area and inhibited by 50.3 +/- 4.67% the development of a subsequent plasma extravasation in response to similar stimulation of the contralateral sciatic nerve. Stimulation at 0.5 Hz for 1 h also evoked local plasma extravasation and inhibited the carrageenin-induced (1%, 100 microl s.c.) cutaneous inflammation by 38.5 +/- 10.0% in the contralateral paw. Excitation at 0.1 Hz for 4 h elicited no local plasma extravasation in the stimulated hindleg but still reduced the carrageenin-induced oedema by 52.1 +/- 9.7% in the paw on the contralateral side. 3. Plasma extravasation in the knee joint in response to carrageenin (2%, 200 microl intra-articular injection) was diminished by 46.1 +/- 12.69% and 40.9 +/- 4.93% when the sciatic nerve was stimulated in the contralateral leg at 0.5 Hz for 1 h or 0.1 Hz for 4 h, respectively. 4. Stimulation of the peripheral stump of the left vagal nerve (20 V, 1 ms, 8 Hz, 10 min) elicited plasma extravasation in the trachea, oesophagus and mediastinal connective tissue in rats pretreated with atropine (2 mg kg(-1), i.v.), guanethidine (8 mg kg(-1), i.p.) and pipecuronium (200 microg kg(-1), i.v.). These responses were inhibited by 37.8 +/- 5.1%, 49.7 +/- 9.9% and 37.6 +/- 4.2%, respectively by antidromic sciatic nerve excitation (5 Hz, 5 min) applied 5 min earlier. 5. Pretreatment with polyclonal somatostatin antiserum (0.5 ml/rat, i.v.) or the selective somatostatin depleting agent cysteamine (280 mg kg(-1), s.c.) prevented the anti-inflammatory effect of sciatic nerve stimulation (5 Hz, 5 min) on a subsequent neurogenic plasma extravasation of the contralateral paw skin. The inhibitory effect of antidromic sciatic nerve excitation on plasma extravasation in response to vagal nerve stimulation was also prevented by somatostatin antiserum pretreatment. 6. Cutaneous blood flow assessment by laser Doppler flowmetry indicated that antidromic vasodilatation induced by sciatic nerve stimulation was not inhibited by excitation of the sciatic nerve of the contralateral leg (1 Hz, 30 min) or by somatostatin (10 microg/rat, i.v.) injection. 7. Plasma levels of somatostatin increased more than 4 fold after stimulation of both sciatic nerves (5 Hz, 5 min) but the stimulus-evoked increase was not observed in cysteamine (280 mg kg(-1), s.c.) pretreated rats. 8. These results suggest that somatostatin released from the activated sensory nerve terminals mediates the systemic anti-inflammatory effect evoked by stimulating the peripheral stump of the sciatic nerve.