Venodilation in Raynaud's disease

ADRA2A and IRX1 are putative risk genes for Raynaud's phenomenon

Raynaud's phenomenon (RP) is a common vasospastic disorder that causes severe pain and ulcers, but despite its high reported heritability, no causal genes have been robustly identified. We conducted a genome-wide association study including 5,147 RP cases and 439,294 controls, based on diagnoses from electronic health records, and identified three unreported genomic regions associated with the risk of RP (p < 5 × 10-8). We prioritized ADRA2A (rs7090046, odds ratio (OR) per allele: 1.26; 95%-CI: 1.20-1.31; p < 9.6 × 10-27) and IRX1 (rs12653958, OR: 1.17; 95%-CI: 1.12-1.22, p < 4.8 × 10-13) as candidate causal genes through integration of gene expression in disease relevant tissues. We further identified a likely causal detrimental effect of low fasting glucose levels on RP risk (rG = -0.21; p-value = 2.3 × 10-3), and systematically highlighted drug repurposing opportunities, like the antidepressant mirtazapine. Our results provide the first robust evidence for a strong genetic contribution to RP and highlight a so far underrated role of α2A-adrenoreceptor signalling, encoded at ADRA2A, as a possible mechanism for hypersensitivity to catecholamine-induced vasospasms.

Modulation of fibrosis in systemic sclerosis by nitric oxide and antioxidants

Systemic sclerosis (scleroderma: SSc) is a multisystem, connective tissue disease of unknown aetiology characterized by vascular dysfunction, autoimmunity, and enhanced fibroblast activity resulting in fibrosis of the skin, heart, and lungs, and ultimately internal organ failure, and death. One of the most important and early modulators of disease activity is thought to be oxidative stress. Evidence suggests that the free radical nitric oxide (NO), a key mediator of oxidative stress, can profoundly influence the early microvasculopathy, and possibly the ensuing fibrogenic response. Animal models and human studies have also identified dietary antioxidants, such as epigallocatechin-3-gallate (EGCG), to function as a protective system against oxidative stress and fibrosis. Hence, targeting EGCG may prove a possible candidate for therapeutic treatment aimed at reducing both oxidant stress and the fibrotic effects associated with SSc.

Botulinum toxin A treatment of Raynaud's phenomenon: a review

OBJECTIVES

Botulinum toxin A has conventionally been used in the upper extremity to treat spasticity resulting from stroke, paraplegia, and dystonia. Recently, it has been used to relieve symptoms of vasospasm in Raynaud's phenomenon. This review summarizes the current literature on botulinum toxin A in the treatment of Raynaud's phenomenon and examines the proposed mechanisms of action, suggested techniques of administration, and clinical efficacy.

METHODS

An Ovid MEDLINE search from 1950 to September 2010 was performed to identify any reports on the use of Botulinum toxin in the treatment of Raynaud's disease or associated vasoconstrictive disorders. All studies pertaining to "Raynaud's disease," "Raynaud's," or "vasoconstriction" were queried and meshed with a secondary search of studies pertaining to "botox" or "botulinum toxin type A." These reports were meshed and subsequently limited to human studies. All studies that met criteria were included and their outcomes evaluated and summarized.

RESULTS

Since 2004, there have been 5 studies that have evaluated the use of Botulinum Toxin A for the treatment of Raynaud's. In each study, patients received a range of botulinum toxin injections (10-100 units) in their fingers and hands. The studies have many limitations (lack of controls, variable severity of disease, variability of dosing) but all report favorable clinical results. All showed overall improvement in patient pain as well as a reduction in soft tissue ulceration.

CONCLUSIONS

Initial reports on the use of botulinum toxin A for Raynaud's phenomenon are promising. Larger controlled trials with improved study design are warranted. A better understanding of the mechanism of action, appropriate dose and dose frequency, and the efficacy relative to other medical and surgical treatments requires investigation.

The Effects of Tadalafil on Cold-induced Vasoconstriction in Patients with Raynaud's Phenomenon

Raynaud's phenomenon (RP) is a disorder characterized by episodic periods of vasoconstriction typically provoked by exposure to cold. Phosphodiesterase 5 (PDE5) inhibitors may improve digital blood flow and clinical symptoms in patients with RP, but the mechanisms are unknown. We examined the hypothesis that a PDE5 inhibitor, tadalafil, attenuates cold-induced vasoconstriction. Additionally, we examined whether tadalafil reduced vascular dysfunction following ischemia, thus altering the response to repeated cooling. We conducted a double-blind, placebo-controlled crossover study in 20 subjects with RP on two separate study days, when subjects received either placebo or tadalafil (10 mg). Digital blood flow (flux) was measured by laser Doppler flowmetry at rest and during two graduated local heat and cold exposure cycles. Temperature-response curves were evaluated by E(max) (maximal flux during heating), E(min) (minimal flux during cooling), and ET(50) and ET(90) (the local temperature at which flux decreased by 50% and 90% of E(max)-E(min), respectively). Tadalafil did not increase baseline flux (81.0+/-73.0 vs 91.3+/-114.0 arbitrary unit (AU), P=0.57), E(max) (280.0+/-107.6 vs 279.5+/-119.8 AU, P=0.94), ET(50) (25.4+/-4.4 vs 26.6+/-5.7 degrees C, P=0.62), or ET(90) (21.2+/-3.9 vs 21.8+/-5.0 degrees C, P=0.78), (cycle 1 values presented). There were no differences between cycles on either study day. In conclusion, in patients with RP, single-dose tadalafil does not increase digital blood flow at baseline or in response to heating, nor does it attenuate cold-induced vasoconstriction. Furthermore, it does not precondition the endothelium to resist a second cooling challenge. The clinical benefit in patients with RP treated with PDE5 inhibitors probably involves mechanisms other than acute inhibition of cold-induced vasoconstriction.

Mechanisms of Raynaud's disease

Raynaud's phenomenon is due to transient cessation of blood flow to the digits of the hands or feet. An attack of Raynaud's phenomenon is classically manifested as triphasic color changes. The white phase is due to excessive vasoconstriction and cessation of regional blood flow. This phase is followed by a cyanotic phase, as the residual blood in the finger desaturates. The red phase is due to hyperemia as the attack subsides and blood flow is restored. An attack is frequently associated with pain and/or paresthesia due to sensory nerve ischemia. Variants of Raynaud's phenomenon include acrocyanosis and primary livedo reticularis, each of which is associated with reduced skin blood flow, exacerbated by cold or emotional upset. Raynaud's phenomenon in the absence of other disorders is primary Raynaud's phenomenon, or Raynaud's disease. The mechanisms of Raynaud's disease include increased activation of the sympathetic nerves, in response to cold or emotion; an impaired habituation of the cardiovascular response to stress may contribute. In addition, there appears to be a local fault, which is likely multifactorial. This local fault is due to an alteration in vascular function rather than vascular structure. The alteration in vascular function may be related to increased sensitivity to cold of the adrenergic receptors on the digital artery vascular smooth muscle. In some cases, locally released or systemically circulating vasoconstrictors may participate, including endothelin, 5-hydroxytryptamine and thromboxane. A deficiency or increased degradation of nitric oxide, possibly due to increased oxidative stress, may be involved in some cases. These recent pathophysiological insights may lead to new therapeutic options.

Endothelin-1 response to mental stress in early ischemic lesions of the extremities due to systemic sclerosis

We studied circulating levels of endothelin-1, catecholamines and nitric oxide after a mental arithmetic test in 14 patients with early ischemic lesions of the extremities due to systemic sclerosis and slightly impaired peripheral vascular flow. The test induced an increase (P<0.01) in blood pressure, heart rate, endothelin-1 and catecholamine levels, whereas it did not change the low basal levels of nitric oxide. In healthy subjects (n=20) the test significantly (P<0.01) decreased endothelin-1 without affecting nitric oxide. The low basal levels of nitric oxide and the high plasma concentration of endothelin-1 after psychological stress cannot be explained by an impaired release from the limited ischemic lesions alone. This suggests a diffuse microvascular derangement that aggravates the course of peripheral microvascular ischemic lesions.

Pathogenesis of Raynaud's phenomenon

The pathogenesis of Raynaud's phenomenon is not fully understood. However, the last 20 yr have witnessed enormous increases in our understanding of different mechanisms which, singly or in combination, may contribute. A key point is that Raynaud's phenomenon can be either primary (idiopathic) or secondary to a number of underlying conditions, and that the pathogenesis and pathophysiology vary between these conditions. This review concentrates upon those subtypes of Raynaud's phenomenon of most interest to rheumatologists: systemic sclerosis-related Raynaud's phenomenon, primary Raynaud's phenomenon and Raynaud's phenomenon secondary to hand-arm vibration syndrome. In this review, I shall discuss the main mechanisms thought to be important in pathophysiology under the three broad headings of 'vascular', 'neural' and 'intravascular'. While these are false distinctions because all interrelate, they facilitate discussion of the key elements: the blood vessel wall (particularly the endothelium), the neural control of vascular tone, and the many circulating factors which can impair blood flow and/or cause endothelial injury. Vascular abnormalities include those of both structure and function. Neural abnormalities include deficiency of the vasodilator calcitonin gene-related peptide (released from sensory afferents), alpha(2)-adrenoreceptor activation (possibly with up-regulation of the normally 'silent' alpha(2C)-adrenoreceptor) and a central nervous system component. Intravascular abnormalities include platelet activation, impaired fibrinolysis, increased viscosity and probably oxidant stress. As our understanding of the pathophysiology of Raynaud's phenomenon increases, so do our possibilities for identifying effective treatments.

The vasculopathy of Raynaud's phenomenon and scleroderma

The scleroderma (SSc) disease process involves dramatic dysfunction in acute and chronic vascular regulatory mechanisms; it presents initially with heightened vasoconstrictor or vasospastic activity and progresses to structural derangement or vasculopathy of the microcirculation. This article discusses the regulatory mechanisms that contribute to this dysfunction and the vascular changes in the context of the other aspects of the SSc disease process in a novel attempt to integrate the individual pathologies of the disease process.

Raynaud's phenomenon

Many persons are affected by the phenomenon known as Raynaud's. Raynaud's is classified in 2 ways-as Raynaud's disease or Raynaud's syndrome. Classification is based on the presence of associated conditions. Raynaud's is characterized by vasospasm-induced color changes of the fingers, toes, and ears. The fingers are most commonly affected. Studies involving cause, diagnosis, and treatment have been instituted with varied results. Diagnosis is primarily based on clinical symptoms involving digital color changes. Treatment is aimed at prevention of attacks and includes medication, stress reduction, and avoidance of vasoconstricting agents. Whether the phenomenon will develop into a more serious condition with which Raynaud's is associated is important. This article describes the etiology, pathophysiology, diagnosis, treatment, and nursing implications with regard to Raynaud's.

Seasonal differences in finger skin temperature and microvascular blood flow in healthy men and women are exaggerated in women with primary Raynaud's phenomenon

AIMS

Patients with primary Raynaud's phenomenon (PRP) have more severe symptoms in the winter. The aetiology of this is more complex than simply increased vasoconstriction in response to the immediate ambient temperature. The aim of this study was to investigate differences in skin temperature (Tsk), microvascular blood flow and responses to endothelium-dependent and independent vasodilators in healthy controls, and women with PRP under identical environmental temperatures but in different seasons.

METHODS

Ten women with PRP were compared with age matched women (10) and men (10). Finger skin responses were recorded immediately on arrival, after stabilizing in a temperature regulated laboratory at 22-24 degrees C, and at matched warm (35 degrees C) and cold (15 degrees C) Tsk in the winter and summer. Baseline red blood cell flux (r.b.c. flux), and the change in flux in response to iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) were recorded by laser Doppler fluxmetry at the warm and cold Tsk.

RESULTS

Arrival Tsk were significantly cooler for all subjects during the winter (mean seasonal difference -2.6 degrees C, P < 0.0001), and markedly colder in subjects with PRP (mean seasonal difference -3.5 degrees C, P < 0.0005). Statistically significant seasonal differences persisted in all subjects at stable Tsk despite an identical laboratory temperature (mean difference 1.3 degrees C, P < 0.0001). To achieve comparable controlled finger Tsk a significantly colder local environment was required for male controls (mean of -2.1 degrees C, P < 0.0001), and a significantly warmer environment for subjects with PRP (mean of + 2.4 degrees C, P < 0.0001) compared with female controls. This needed to be warmer in the winter, by a mean of 2.4 degrees C, than the summer for all subjects. Vasodilatation in response to ACh, but not SNP, was significantly smaller (P < 0.0001) in the PRP group compared with the female controls for all visits, with most of this difference arising in the winter visits (P < 0.01).

CONCLUSIONS

There is a seasonal and persistent influence on finger Tsk, and microvascular blood flow in healthy men and women, which modifies the observed responses to immediate changes in finger Tsk. The seasonal differences are greater in women than men, and are further exaggerated in women with PRP, in whom this is associated with reduced endothelium-dependent vasodilatation.

Vascular function in systemic sclerosis

Raynaud phenomenon is often the earliest manifestation of systemic sclerosis. This fact highlights the role of vascular dysfunction early on in the disease process. Although this review deals primarily with digital vasculature, recent research confirms that vascular dysfunction is widespread, and affects large as well as small vessels. Abnormalities of vascular function and structure are interdependent, and together result in the ischemic atrophy so characteristic of SSc. Key areas of research include the pathophysiology of the imbalance between vasodilation and vasoconstriction, with particular interest in understanding the relative contributions of endothelial-dependent and endothelial-independent vasodilation, and the development of new methodologies by which to quantify vascular function.

Autoimmunity and vascular involvement in systemic sclerosis (SSc)

Endothelial injury, obliterative microvascular lesions, and increased vascular wall thickness are present in all involved organs in scleroderma. The vascular pathology is associated with altered vascular function with increased vasospasm, reduced vasodilatory capacity and increased adhesiveness of the blood vessels to platelets and lymphocytes. The extent of injury and dysfunction is reflected by changes in the circulating levels of vascular markers. The initial triggers for the vascular pathology are not known. Possible viral triggers are visited here, including cytomegalovirus in view of increased levels of anti-CMV antibodies in scleroderma, and the remarkable similarities between CMV vasculopathies and scleroderma vascular disease. Endothelial apoptosis in scleroderma may be related to viral infection, immune reactions to viral or environmental factors, reperfusion injury or to anti-endothelial antibodies. The impact of the vascular pathology on the evolution of tissue fibrosis is not known; still, cytokines (TGFbeta, IL4), vascular factors (endothelin), and growth factors (PDGF) are possibly crucial signals that link the vascular disease to tissue fibrosis. Knowledge of the regulation of these and other factors will provide the opportunity to develop more rational therapeutic approaches to the disease.

Why study vascular factors in glaucoma?

There is clinical and experimental evidence that both increased intraocular pressure and disturbed circulation are involved in the pathogenesis of glaucomatous damage. Among the many factors discussed, decreased blood pressure and vasospasm are the most important, and these factors may, at least in part, be therapeutically influenced. The basic underlying disorder might be a vascular dysfunction leading to local vasospasm and to systemic hypotension.

Effect of nitric-oxide-generating system on microcirculatory blood flow in skin of patients with severe Raynaud's syndrome: a randomised trial

BACKGROUND

Patients with Raynaud's syndrome have abnormal digital vasoconstriction, which may be secondary to impaired synthesis of, or impaired sensitivity to, nitric oxide. We studied the effect on microcirculation of a nitric-oxide-generating system applied topically to the finger and forearm of healthy volunteers and patients with primary Raynaud's syndrome.

METHODS

We did a single-blind, randomised, placebo controlled, cross-over study of the microcirculatory response to topical application of a nitric-oxidegenerating gel in 20 patients with severe Raynaud's syndrome, and ten healthy volunteers. We prepared the nitric-oxide-generating system by mixing a solution of KY jelly and sodium nitrite (5% weight/volume), with a solution of KY jelly and ascorbic acid (5% weight/volume). About 0.5 mL of each solution was separately applied to the skin of the forearm (3 cm2), and then mixed with a sterile cotton bud. A similar procedure was done simultaneously on the other arm with KY jelly only (placebo). The procedure was then repeated on the finger pulps. Changes in skin microcirculatory volume and flux were measured bilaterally by infrared photoplethysmography and laser doppler fluxmetry, respectively.

FINDINGS

In the forearm, blood flow increased significantly after application of the active gel both in patients with Raynaud's syndrome (microcirculatory volume from mean area under the curve 98 [SE 14] to 1024 [130]; microcirculatory flux from 5060 [462] to 74,800 [3940]) and in healthy controls (volume from 85 [19] to 1020 [60]; flux from 4420 [435] to 84,500 [7000]). In the fingers, although baseline blood flow was lower in patients than in controls, both groups showed increases with application of active gel (volume from 1100 [194] to 3280 [672] and 2380 [441] to 6160 [1160], respectively; flux from 33,400 [4200] to 108,000 [13,600] and 52,000 [8950] to 185,000 [19,500]). Increases in blood flow with placebo gel were not significant. No adverse effects were reported.

INTERPRETATION

In primary Raynaud's syndrome, topical application of a nitric-oxide-generating system can stimulate an increase in both microcirculatory volume and flux.

A case-control study of candidate vasoactive mediator genes in primary Raynaud's phenomenon

OBJECTIVES

To elucidate possible genetic factors involved in the pathogenesis of primary Raynaud's phenomenon (RP) and to determine the demographic features.

METHODS

The allele frequencies of known polymorphisms in four vasoactive candidate genes, eNOS, BKRG, ET-1 and the ETA receptor genes, were compared in a phenotypically homogeneous group of patients with primary RP and a normal control population.

RESULTS

In patients with primary RP, there was a higher reporting of both a family history of RP than in controls (45.3% vs 3.1%; P<0.0001) and a personal history of migraine (32.6% vs 7.2%; P<0.0001). No significant differences in allele frequencies of the candidate genes were found.

CONCLUSIONS

These findings support the concept that genetic susceptibility exists in primary RP. The high prevalence of migraine suggests that primary RP is part of a more widespread disorder of vascular tone. These findings do not suggest that common molecular variants of these candidate genes are involved in primary RP.

Impaired cholinergic dilator response of resistance arteries isolated from patients with Raynaud's disease

AIMS

We examined the effect of cooling on the response to the endothelium-dependent and -independent dilators, acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, in human microvessels in vitro, and compared the responses between Raynaud's disease (RD) patients and controls, in order to assess the pathogenic role of the endothelium in RD.

METHODS

Subcutaneous resistance arteries were dissected from gluteal fat biopsies taken from patients with RD (n=18) and from age-and sex-matched control subjects (n=17). Vessels were cannulated in a small vessel arteriograph, in which a pressure of 50 mmHg was maintained across the vessel wall. Cumulative concentration-response curves for ACh (10-10-10-4 m ) and SNP (10-10-10-3 m ) were generated in vessels at either 37 degrees C or 24 degrees C, with endothelium intact for ACh and removed for SNP (n=6 per group).

RESULTS

Neither dilator showed significant differences in sensitivity when comparing responses between vessels from RD patients and controls, at either temperature, but the maximal relaxation to ACh was depressed in vessels from RD patients compared with controls at 37 degrees C (Emax=45+/-13 in RD vs 89+/-4 in controls; P=0.004).

CONCLUSIONS

These results support the hypothesis that impaired endothelium-dependent vasodilatation is involved in the pathophysiology of RD.

The effects of iloprost infusion on microcirculation is independent of nitric oxide metabolites and endothelin-1 in chronic peripheral ischaemia

BACKGROUND

Endothelial vascular tone modulators are thought to be involved in aetiopathogenesis of systemic sclerosis (SS) and of peripheral artery occlusive disease (PAOD). Iloprost, a prostacyclin (PGI2) analogue, induces clinical benefit in patients suffering from peripheral ischaemia. This study was performed to investigate the effect of this drug on endothelial function in vivo to elucidate the role of vascular tone modulators.

METHODS

Fourteen PAOD and 15 SS patients were treated for 24 and 10 days respectively. On the first day, before and after therapy, nitric oxide metabolites (NO2-/NO3-) and endothelin-1 (ET-1) plasma concentrations were detected; moreover, the endothelium-dependent vasodilatation in response to artificial ischaemia was evaluated by means of an echo-Doppler device.

RESULTS

The echo-Doppler evaluation showed that the percentage of arterial reactive dilatation was not modified by placebo or by iloprost, and that the increase in blood velocity flow lasted for a significant longer time after drug infusion (226.79 +/- 17.49 vs. 310.71 +/- 36.32 s; P > 0.04). NO2-/NO3- and ET-1 plasma concentration were higher in patients than in control subjects (P < 0.004). After 6 h of iloprost infusion, no significant modifications were detected.

CONCLUSION

This study provides evidence that iloprost enhances the microvascular functional capacity and clinical benefit for patients. The effects of the drug seem to be independently or not directly correlated with its interactions with vascular tone modulators such as NO2-/NO3- or ET-1.

Hemodynamics in nailfold capillaries of patients with systemic scleroderma: synchronous measurements of capillary blood pressure and red blood cell velocity

There is increasing evidence that endothelial damage occurs at a very early stage during the course of systemic scleroderma. Endothelial damage is accompanied by impaired microvascular function, which has clearly failed in patients with systemic scleroderma, as evidenced by necrosis of the fingertips in severe cases. We investigated two important determinants of microvascular function, namely capillary blood pressure and capillary red blood cell velocity, simultaneously in the same capillary. In patients with systemic scleroderma and in healthy volunteers matched for age and sex, capillary blood pressure was measured by direct cannulation and capillary red blood cell velocity by video microscopy. Capillary blood pressure and capillary red blood cell velocity were significantly lower in patients (14.27 +/- 4.34 mmHg, 230 +/- 310 microm per s) than in healthy controls (19.06 +/- 3.69 mmHg, p < 0.008, and 910 +/- 240 microm per s, p < 0.003) at an ambient temperature of 22 degrees C, whereas no significant difference in skin temperature was observed (23.7 +/- 0.9 degrees C vs 24.7 +/- 1.9 degrees C) and no occlusion of finger arteries was detected. Capillary blood pressure in enlarged capillaries did not differ from that in normal-shaped capillaries in the patients (correlation of diameter and capillary blood pressure, R2 = 0.04), which was also the case with capillary red blood cell velocity (R2 = 0.13). Capillary pulse pressure amplitude and capillary red blood cell velocity showed a strong correlation (R2 = 0.81), suggesting that the pressure gradient across the capillary loop, which is the driving force for capillary red blood cell velocity, was mainly dependent on precapillary resistance. These observations reflect the inadequate microvascular function in systemic scleroderma, which may be due mainly to a pathophysiologic functional increase in precapillary resistance, even at comfortable ambient temperatures.

The endothelin system in cardiovascular physiology and pathophysiology

Endothelin-1, a member of a novel family of regulatory peptides, is the most potent vasoconstrictor and pressor substance known. Endothelin-1 is a 21-amino-acid endothelium-derived peptide causing uniquely sustained vasoconstriction. In addition, endothelin-1 has pronounced effects on the coronary, renal and cerebral circulations, enhances responses to other vasoconstrictors, and is comitogenic. Recent studies have shown that the endothelins are essential for normal fetal development, and that endothelin-1 plays an important physiological role in the regulation of basal vascular tone and blood pressure in healthy humans. There is now also a wealth of evidence suggesting that endothelin-1 is a key mediator in a range of cardiovascular diseases associated with sustained vasoconstriction, such as chronic heart failure, and with vasospasm, such as subarachnoid haemorrhage. In addition, endothelin-1 appears to act in opposition to nitric oxide to promote the atherosclerotic process. There are a large number of oral and intravenously active endothelin antagonists entering clinical development and a number of clinical studies, particularly with endothelin receptor antagonists, are now under way. Such studies are beginning to define the role of the endothelins in cardiovascular disease and to confirm the potential of the endothelin system as an important new therapeutic target.

Decrease in the concentrations of transforming growth factor-beta 1 in the sera of patients with Kawasaki disease

Kawasaki disease (KD) is one of the most important forms of vasculitis, and is characterized by the initiation of a proinflammatory cytokine cascade. To further characterize the immunological profile of KD, we measured the serum levels of transforming growth factor-beta 1 (TGF-beta 1) as a regulatory cytokine. We determined the concentration of TGF-beta 1 in the sera of the patients with KD, anaphylactoid purpura (AP), and scarlet fever, using a sandwich enzyme linked immunosorbent assay. The serum levels of TGF-beta 1 were decreased in patients with KD, but not in patients with AP or scarlet fever during the acute stage. We found an inverse correlation between TGF-beta 1 and soluble tumor necrosis factor (TNF) receptor levels in KD patients during the acute and subacute stage. Decreased levels of TGF-beta 1, in particular to suppress TNF alpha (TNF-alpha) production, is an important part of the regulatory system of increased TNF-alpha production which cause vasculitis.

Inverse correlation between endothelin-1-induced peripheral microvascular vasoconstriction and blood pressure in glaucoma patients

BACKGROUND

The potent vasoconstrictor peptide endothelin-1 has been shown to participate in the control of peripheral vascular tone and in the regulation of ocular perfusion. In glaucoma patients vasospasms and arterial hypotension have been identified as risk factors for the progression of glaucomatous damage, and the regulation of endothelin-1 release is disturbed in some of these patients. The aim of this study was to assess the relationship between resting blood pressure and cutaneous vascular responsiveness to endothelin-1 and phenylephrine in patients with glaucoma and in matched controls.

METHODS

In 9 patients with primary open-angle glaucoma (POAG), 7 patients with normal tension glaucoma (NTG), and 16 age- and sex-matched controls, endothelin-1 and phenylephrine responses were assessed in the human forearm microcirculation using laser Doppler flowmetry during intra-arterial drug administration. Blood pressure was measured intra-arterially.

RESULTS

In contrast to alpha 1-adrenergic effects, endothelin-1 responses were inversely correlated to both systolic (r2 = 0.27, P = 0.05) and diastolic (r2 = 0.54, P = 0.001) blood pressure in glaucoma patients, whereas there was no such correlation in controls. Patients with lower blood pressure values were more sensitive to the vasoconstrictor effects of endothelin-1. Cutaneous responsiveness to endothelin-1 and phenylephrine was similar in glaucoma patients and in controls.

CONCLUSION

These results reveal that glaucoma patients appear to have peripheral microvascular abnormalities which are exhibited as altered responsiveness to endothelin-1. Thus, this study supports the hypothesis that endothelin-1-related microvascular dysfunction may be involved in the pathogenesis of glaucomatous damage.

Plasma nitric oxide metabolite in women with primary Raynaud's phenomenon and in healthy subjects

Primary Raynaud's phenomenon (PRP) is characterized by cold- or stress-induced transient attacks of impaired skin circulation in fingers and/or toes. PRP displays seasonal variation with less severe symptoms in the summer. The aetiology has not been clarified. The aims of the present study were (a) to assess the influence of cold exposure on the plasma levels of the nitric oxide (NO) metabolite, nitrate, in patients with PRP and in healthy control subjects; and (b) to investigate whether there is a seasonal variation in these plasma levels. In a group of women with PRP and matched control subjects, venous blood was sampled before and at the end of a 40-min period of whole-body cooling. The study was performed with the same protocol on two occasions; once in the winter and once in the summer. A seasonal variation was detected with higher plasma levels of nitrate in the winter than in the summer, both in PRP and in control subjects. However, the plasma level of nitrate was not changed in response to cold exposure on any occasion, either in the patient or in the control group. Our study indicates that NO formation is up-regulated in response to cold weather in both study groups. However, NO formation does not seem to be increased in response to whole-body cooling, either in PRP patients or in healthy subjects. Further investigations are required to reveal whether the observed seasonal variation in NO formation is a universal phenomenon in man.

Oral L-arginine supplementation and cutaneous vascular responses in patients with primary Raynaud's phenomenon

OBJECTIVE

To assess the effects of oral L-arginine supplementation on cutaneous vascular responses in patients with primary Raynaud's phenomenon (RP).

METHODS

Double-blind, crossover comparison of placebo versus L-arginine (8 gm/day for 28 days). Cutaneous vascular responses in the fingers were assessed during iontophoresis of acetylcholine and sodium nitroprusside, which are endothelium-dependent and endothelium-independent vasodilators.

RESULTS

In comparison with control subjects, patients with primary RP had diminished endothelium-dependent and -independent vasodilatation (P < 0.05, and P < 0.005, respectively, by analysis of variance). At the 3 doses used, vascular responses to acetylcholine were reduced by 71%, 64%, and 63%, respectively, and responses to sodium nitroprusside were reduced by 67%, 73%, and 66%, respectively. L-arginine had no significant effect on cutaneous vascular responses to acetylcholine or sodium nitroprusside in control subjects or patients with primary RP.

CONCLUSION

Reduced vasodilator ability in primary RP is unlikely to be due to an impairment in the L-arginine/nitric oxide pathway.

Raynaud's phenomenon

Raynaud's phenomenon is a common clinical problem occurring in 3% to 5% of the general population. The first symptom of scleroderma is often Raynaud's phenomenon, which is associated with a diffuse small vessel vasculopathy and ischemia and reperfusion injury to skin and other organs targeted in this disease. Current studies support the concept that Raynaud's phenomenon is secondary to a local defect in the regulation of regional blood flow. New evidence demonstrates that there is a profound sensitivity to alpha 2-adrenoceptors mediated vasoconstriction in scleroderma vessels. Traditional treatment of Raynaud's phenomenon is cold avoidance and the use of vasodilators. Oral prostaglandins have shown promise as therapeutic agents.

The endothelin system and its potential as a therapeutic target in cardiovascular disease

Endothelin (ET)-1, an endothelium-derived peptide, is the most potent vasoconstrictor agent described to date. ET-1 also has positive inotropic and chronotropic effects in the heart and is a co-mitogen in both cardiac and vascular myocytes. The major elements of the system involved in formation of ET-1 and its isopeptides, as well as the receptors mediating their effects, have been cloned and characterised. Antagonists of the ET receptors are now available, and selective inhibitors of the ET-converting enzymes are being developed. Early studies using receptor antagonists support the involvement of ET-1 in the pathophysiology of several cardiovascular diseases. The relative merits of ET-converting enzyme inhibitors and receptor antagonists for the treatment of cardiovascular disease are discussed.

Cold exposure increases cyclic guanosine monophosphate in healthy women but not in women with Raynaud's phenomenon

OBJECTIVE

To investigate influence of whole-body cooling on cyclic GMP (cGMP) in women with Raynaud's phenomenon and in healthy women.

DESIGN

The study was performed as an open, parallel-group comparison between women with Raynaud's phenomenon and healthy women during the winter month of February.

SETTING

The municipality of Västerås (Sweden).

PARTICIPANTS

The Raynaud group comprised 24 female patients. The control group consisted of 21 healthy females.

MAIN OUTCOME MEASURE

The venous levels of cGMP were measured on three different occasions: just before and after 40 min of whole-body cooling and after 20 min rest at room temperature (21 degrees C).

RESULTS

Venous cGMP increased significantly in the control group after cold exposure (mean difference 0.43 pmol mL-1; 95% CI, 0.018-0.848; t = 2.18; df = 20; P = 0.02) and remained at a high level after 20 min rest (mean difference 0.58 pmol mL-1; 95% CI, 0.063-1.108; t = 2.34; df = 20; P = 0.015). In contrast, the levels of venous cGMP in the Raynaud group did not change significantly. The difference in increase between the two groups was significant (P < 0.02). The diastolic blood pressure in the Raynaud group increased after 40 min of whole-body cooling and was still significantly increased (P < 0.001) after 20 min rest at room temperature (21 degrees C).

CONCLUSION

These results indicate that women suffering from Raynaud's phenomenon lack the physiological response of cGMP to cold exposure, which may explain their increased vasospastic response.

Response of digital arteries to endothelium dependent and independent vasodilators in patients with Raynaud's phenomenon

The cause of the digital artery spasm seen in Raynaud's phenomenon (RP) is unclear. A dysfunction of endothelium-dependent vasodilation might contribute to the development of this spasm. We studied the digital artery responses to endothelium-dependent and independent vasodilators in eight Raynaud's phenomenon patients and eight sex-matched controls. A sequential series of infusions alternating with physiological saline were administered at a rate of 1 mL min-1 via the radial artery. The infusions contained acetylcholine chloride (ACh) 110 nm mL-1 and 550 nm mL-1, L-arginine 50 mumol mL-1, prostacyclin (PGI2) 2.5 ng mL-1 and glyceryl trinitrate (GTN) 4.5 nm mL-1. Digital artery diameter (DAD) and cutaneous temperature were measured. DAD was measured using a high frequency A-mode ultrasound scanner. There was no significant difference in mean brachial artery pressure, digital cutaneous temperature and DAD between the two groups at the start of the study. Comparing responses in the groups, there was a significantly greater increase in DAD and cutaneous temperature to Ach (endothelium-dependent vasodilator) at both concentrations in controls. A significantly greater increase in DAD was obtained in response to GTN (endothelium-independent vasodilator) in the RP subjects. There was no significant difference in response to L-arginine and PGI2 between the groups. These results suggest that a dysfunction of endothelium-dependent vasodilation is present in RP patients.

Plasma TGF beta in systemic sclerosis: a cross-sectional study

OBJECTIVES

To determine whether the active 25 kDa form of the fibrogenic cytokine transforming growth factor beta (TGF beta) can be detected in plasma from patients with systemic sclerosis and to examine the relationship between plasma TGF beta and clinical markers of disease severity and serum concentrations of the aminoterminal peptide of type III procollagen (PIIINP) (a laboratory marker of the fibrotic process).

METHODS

A cross sectional study was made of 39 patients with systemic sclerosis (11 diffuse and 28 limited), nine patients with primary Raynaud's disease and 60 healthy controls. TGF beta 1 and TGF beta 2 were measured by enzyme linked immunosorbent assay (ELISA) (sensitivity 100 pg/ml) and PIIINP by radioimmunoassay.

RESULTS

TGF beta 1 was detected in plasma from six of 39 patients with systemic sclerosis but not in any patient with primary Raynaud's disease or healthy controls. TGF beta 2 was not detected in plasma from patients or controls. No clear relationship was demonstrated between TGF beta 1, clinical features or PIIINP concentrations.

CONCLUSIONS

The 25 kDa form of TGF beta 1 can be detected in the plasma of some patients with systemic sclerosis. This provides limited support for the hypothesis that this cytokine plays a role in the pathogenesis of this disease. However, longitudinal studies, particularly in early diffuse disease, are required to clarify the relationship between circulating TGF beta 1 and disease activity.

Direct and sympathetically mediated venoconstriction in essential hypertension. Enhanced responses to endothelin-1

Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide. Although circulating concentrations are not increased in essential hypertension, enhanced sensitivity to endothelin-1 has been observed in animal models of hypertension. We investigated dorsal hand vein responses to local infusion of endothelin-1 and norepinephrine in 12 patients with essential hypertension who had never received treatment and in 12 age and sex matched normotensive control subjects. The maximal venoconstriction and the geometric mean of the dose of norepinephrine that caused 50% of maximal venoconstriction were similar in hypertensive (mean +/- SE; 80 +/- 4%; 31 +/- 8 pmol/min) and normotensive subjects (87 +/- 5%, 22 +/- 9 pmol/min). In contrast, mean venoconstriction to endothelin-1 was significantly greater in hypertensive (49 +/- 5%) than in normotensive subjects (27 +/- 2%; P = 0.004). Sympathetically mediated venoconstriction elicited by deep breath was substantially potentiated by endothelin-1 in hypertensive (67 +/- 7% at 90 min) but not normotensive subjects (11 +/- 3% at 90 min; P = 0.001). Venoconstriction to endothelin-1 correlated positively with mean arterial pressure in the hypertensive subjects (r = 0.82; p = 0.001) but negatively in the normotensive subjects (r = -0.58; p = 0.047). Endothelin-1 may contribute to the reduction of venous compliance occurring in the early stages of essential hypertension and to the altered systemic hemodynamics in this condition.