Serum endothelin concentrations in workers exposed to vibration

Blood biomarkers for occupational hand-arm vibration exposure

Hand-arm vibration is a common occupational exposure that causes neurological impairment, myalgia, and vibration-induced Raynaud's phenomena or vibration white fingers (VWF). The pathological mechanism is largely unknown, though several mechanisms have been proposed, involving both immunological vascular damage and defective neural responses. The aim of this study was to test whether the substances interleukin-33 (IL-33), macrophage-derived chemokine (MDC), interleukin-10 (IL-10), endothelin-1 (ET-1), C-C motif chemokine ligand 20 (CCL20), calcitonin, and thromboxane (TXA2) changed before and after occupational hand-arm vibration exposure. 38 full-time shift workers exposed to hand-arm vibration were recruited. All the participants underwent medical examinations regarding symptoms of Raynaud's phenomena. In 29 of the participants, the concentration of IL-33, MDC, IL-10, ET-1, CCL20, calcitonin, and TXA2 was measured before and after a workday. There was a significant increase in ET-1 and calcitonin concentration and a decrease in the CCL20 concentration after the work shift in all participants. In the group suffering from VWF, but not in the non-VWF group, MDC was statistically significantly lower before the work shift (p = .023). The VWF group also showed a significant increase in MDC after the work shift. Exposure to occupational hand-arm vibration is associated with changes in ET-1, calcitonin, and MDC concentration in subjects suffering from vibration white fingers, suggesting a role of these biomarkers in the pathophysiology of this condition.

Blood biomarkers for vibration-induced white fingers. A case-comparison study

BACKGROUND

Vibration induced white fingers (VWF) is one form of secondary Raynaud's phenomenon (RP).

METHODS

Vibration exposed workers with RP and vibration exposed controls without RP participated. Blood samples were collected before and after cold challenge exposure (COP). The concentration of von Willebrand factor (vonWf), thrombomodulin (TM), serotonin (SER), endothelin-1 (ET₁ ), calcitonin gene-related peptide, or thromboxane A₂ was calculated. The diagnostic usefulness of the substances for ruling in the diagnosis of Raynaud's was evaluated.

RESULTS

The cases showed a significant lower concentration of vonWf before and after COP, a significant increase of ET₁  and a decrease of TM after COP. The diagnostic usefulness of vonWf showed a likelihood of defining a true case by 35%.

CONCLUSIONS

vonWf, TM, SER, or ET₁ are suggested biomarkers for VWF. Diagnostic evaluation of vonWf showed a likelihood of defining a true case by 35% in the diagnosis of RP related to vibration.

Organische und funktionelle Durchblutungsstörungen der Hand – differenzialdiagnostische Aspekte

Die Abklärung von venösen und arteriellen Durchblutungsstörungen sowie Lymphödemen gehört zur täglichen Praxisroutine des Gefäßmediziners. Nicht selten werden von chirurgischen Kollegen Patienten mit Beschwerden im Schulter-, Arm- und Handbereich zum Ausschluss einer vaskulären Ursache vorgestellt. Der wohl häufigste Abklärungsgrund im Handbereich ist das Raynaud-Phänomen. Neben arteriosklerotischen Durchblutungsstörungen und der Thrombangiitis obliterans sind das Hypothenar-/Thenar-Hammer-Syndrom und das Vibrationssyndrom in den Fingern eher wenig bekannte Entitäten, deren Kenntnis jedoch neben dem medizinischen Vorgehen auch versicherungsrelevante Konsequenzen haben kann. Während beim Hypothenar-/Thenar-Hammer-Syndrom eine organische Durchblutungsstörung vorliegt, beinhaltet das Vibrationssyndrom der Finger eine funktionell vaskuläre sowie eine nervale Komponente, die eine Trennung vom Karpaltunnelsyndrom erschwert. Bei beiden Entitäten ist eine Berufsanamnese häufig hilfreich. Schon der Verdacht auf eine Berufskrankheit muss nach Gesetzeslage zur Anzeige gebracht werden. Der Artikel beschreibt die wesentlichen pathophysiologischen Mechanismen beider Entitäten und stellt diagnostische und therapeutische Optionen dar. Die Kenntnis beider Erkrankungen erweitert die differenzialdiagnostische Vorgehensweise in der täglichen Praxisroutine bei Patienten mit Schulter-Arm-Hand-Beschwerden und bei Patienten mit Raynaud-Phänomen.

Analysis of long-term stored plasma samples for investigation into the pathophysiology of vibration-induced white finger: preliminary results

Blood samples were collected 25 yr ago from hand-arm vibration syndrome patients with vibration-induced white finge/VWF (VWF+ group) and without it (VWF- group), and healthy controls (n=12 in each group), and stored at -80 °C. The subjects provided venous blood twice: at baseline, and after cold exposure at 7 °C for 25 min. Blood specimens were analyzed for plasma endothelin-1 (ET-1) by an enzyme-linked immunosorbent assay. Baseline concentration of plasma ET-1 was found to be significantly larger in the VWF- group than the control group, whereas no such difference was observed for the VWF+ group. However, the %change was larger in the VWF+ group (107.73 ± 30.49%) than the other two groups, and more subjects in the VWF+ group showed the maximum increase in ET-1 than the other two groups. In conclusion, ET-1 appears to have a role in the pathophysiology of VWF.

The association between vibration and vascular injury in rheumatic diseases: a review of the literature

Vascular manifestations can be seen early in the pathogenesis of inflammatory rheumatic diseases. Animal experiments, laboratory and clinical findings indicated that acute or long-term vibration exposure can induce vascular abnormalities. Recent years, in addition to Raynaud's phenomenon (RP), vibration as a risk factor for other rheumatic diseases has also received corresponding considered. This review is concentrated upon the role of vibration in the disease of systemic sclerosis (SSc). In this review, we are going to discuss the main mechanisms which are thought to be important in pathophysiology of vascular injury under the three broad headings of "vascular", "neural" and "intravascular". Aspects on the vibration and vascular inflammation are briefly discussed. And the epidemiological studies related to vibration studies in SSc and other rheumatic diseases are taken into account.

Raynaud's phenomenon: from molecular pathogenesis to therapy

Raynaud's phenomenon (RP) is a well defined clinical syndrome characterized by recurrent episodes of digital vasospasm triggered by exposure to physical/chemical or emotional stress. RP has been classified as primary or secondary, depending on whether it occurs as an isolated condition (pRP) or is associated to an underlying disease, mainly a connective tissue disease (CTD-RP). In both cases, it manifests with unique "triple" (pallor, cyanosis and erythema), or "double" color changes. pRP is usually a benign condition, while sRP can evolve and be complicated by acral digital ulcers and gangrene, which may require surgical treatment. The pathogenesis of RP has not yet been entirely clarified, nor is it known whether autoantibodies have a role in RP. Even so, recent advances in our understanding of the pathophysiology have highlighted novel potential therapeutic targets. The aim of this review is to discuss the etiology, epidemiology, risk factors, clinical manifestations, recently disclosed pathogenic mechanisms underlying RP and their correlation with the available therapeutic options, focusing primarily on pRP and CTD-RP.

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.

Laser Doppler anemometry distinguishes primary Raynaud phenomenon from VWF syndrome

OBJECTIVES

We evaluated two microcirculatory function-tests, the Laser Doppler (LD)-Anemometry and the Laser Doppler Imager (LDI)-Flowmetry in their value to further elucidate functional behavior of the "Vibration-induced white finger syndrome" (VWF) and to distinguish between Raynaud's phenomenon (RP) of idiopathic or vibration origin.

PARTICIPANTS AND METHODS

Ninety-four patients, suffering from RP were studied (78 patients with primary RP and 16 patients with VWF). Measurement of blood cell velocity (BCV) before and after provocation was obtained by nailfold capillary microscopy and an included Laser detector ("Anemometry"). Digital blood flux was recorded by LDI-Flowmetry during a standardized cooling and rewarming thermal challenge.

RESULTS

"Time to peak" of BCV, a measure of maximal reactive hyperemia was longer in VWF in comparison to primary RP (30.37 versus 19.29 sec P < 0.02), respectively.

CONCLUSION

Based on the fact, that prolongation of reactive hyperemia, an indicator of impaired endothelium-dependent vasodilation is also frequently found in peripheral arterial occlusive disease, it is hypothesized that VWF is not only a microcirculatory vasospastic disorder, but may also be related to atherosclerosis. Anemometry, in association with an appropriate provocation-test, could represent a useful non-invasive method for objectifying diagnosis of VWF in patients with RP.

Extracellular signal-regulated kinase activation and endothelin-1 production in human endothelial cells exposed to vibration

Hand-arm vibration syndrome is a vascular disease of occupational origin and a form of secondary Raynaud's phenomenon. Chronic exposure to hand-held vibrating tools may cause endothelial injury. This study investigates the biomechanical forces involved in the transduction of fluid vibration in the endothelium. Human endothelial cells were exposed to direct vibration and rapid low-volume fluid oscillation. Rapid low-volume fluid oscillation was used to simulate the effects of vibration by generating defined temporal gradients in fluid shear stress across an endothelial monolayer. Extracellular signal-regulated kinase (ERK1/2) phosphorylation and endothelin-1 (ET-1) release were monitored as specific biochemical markers for temporal gradients and endothelial response, respectively. Both vibrational methods were found to phosphorylate ERK1/2 in a similar pattern. At a fixed frequency of fluid oscillation where the duration of each pulse cycle remained constant, ERK1/2 phosphorylation increased with the increasing magnitude of the applied temporal gradient. However, when the frequency of flow oscillation was increased (thus decreasing the duration of each pulse cycle), ERK1/2 phosphorylation was attenuated across all temporal gradient flow profiles. Fluid oscillation significantly stimulated ET-1 release compared to steady flow, and endothelin-1 was also attenuated with the increase in oscillation frequency. Taken together, these results show that both the absolute magnitude of the temporal gradient and the frequency/duration of each pulse cycle play a role in the biomechanical transduction of fluid vibrational forces in endothelial cells. Furthermore, this study reports for the first time a link between the ERK1/2 signal transduction pathway and transmission of vibrational forces in the endothelium.

Risk of hand-arm vibration syndrome according to occupation and sources of exposure to hand-transmitted vibration: A national survey

BACKGROUND

Although some occupational sources of hand-transmitted vibration (HTV) have been extensively investigated, the risks associated with others are poorly characterized.

METHODS

A questionnaire was mailed to a community sample of 12,240 men aged 16- 64 years and 906 men from the armed forces. Questions covered current occupation, sources of HTV, numbness or tingling in the fingers in the past week, and finger blanching. In the 5,364 respondents who had been at work in the past week, associations between symptoms and exposures were examined by logistic regression, with odds ratios converted into prevalence ratios (PRs).

RESULTS

Altogether, 513 men (10%) reported cold-induced finger blanching and 769 (14%) sensory symptoms in the fingers. The risk of blanching was increased in builders (PR 2.4, 95% CI 1.0-5.2), carpenters and joiners (PR 1.9, 95% CI 1.0-3.4), motor mechanics (PR 2.3, 95% CI 1.1-4.6), and laborers (PR 2.8, 95% CI 1.3-6.0); while the risk of sensory symptoms was elevated in laborers (PR 4.0, 95% CI 2.3-6.6) and plant operatives (PR 3.5, 95% CI 1.9-5.9). Use of hand-guided mowers, concrete breakers, chain saws, and jig saws was significantly associated with symptoms.

CONCLUSIONS

Little attention has been paid to the risks of vibration injury in construction workers, woodworkers, motor mechanics, and laborers, or to the risks from mowers, jig saws and several other common vibratory tools. These should be a focus for further investigation and preventive measures.

Response of finger circulation to energy equivalent combinations of magnitude and duration of vibration

OBJECTIVES

To investigate the acute response of finger circulation to vibration with different combinations of magnitude and duration but with the same "energy equivalent" acceleration magnitude according to current standards for hand transmitted vibration.

METHODS

Finger skin temperature (FST) and finger blood flow (FBF) were measured in the middle fingers of both hands of 10 healthy men who had not used hand held vibrating tools regularly. With a static load of 10 N, the right hand was exposed to 125 Hz vibration with the following unweighted root mean square (rms) acceleration magnitudes and durations of exposure: 44 m/s(2) for 30 minutes; 62 m/s(2) for 15 minutes; 88 m/s(2) for 7.5 minutes; 125 m/s(2) for 3.75 minutes; and 176 m/s(2) for 1.88 minutes. These vibration exposures produce the same 8 hour energy equivalent frequency weighted acceleration magnitude (approximately 1.4 m/s(2) rms) according to international standard ISO 5349 (1986). Finger circulation was measured in both the right (vibrated) and the left (non-vibrated) middle fingers before application of the vibration, and at fixed intervals during exposure to vibration and during a 45 minute recovery period.

RESULTS

The FST did not change during exposure to vibration, whereas vibration with any combination of acceleration magnitude and duration produced significant percentage reductions in the FBF of the vibrated finger compared with the FBF before exposure (from -40.1% (95% confidence interval (95% CI) -24.3% to -57.2%) to -61.4% (95% CI -45.0% to -77.8%). The reduction in FBF during vibration was stronger in the vibrated finger than in the non-vibrated finger. Across the five experimental conditions, the various vibration stimuli caused a similar degree of vasoconstriction in the vibrated finger during exposure to vibration. There was a progressive decrease in the FBF of both fingers after the end of exposure to vibration with acceleration magnitudes of 44 m/s(2) for 30 minutes and 62 m/s(2) for 15 minutes. Significant vasoconstrictor after effects were not found in either finger after exposure to any of the other vibration stimuli with greater acceleration magnitudes for shorter durations.

CONCLUSIONS

For the range of vibration magnitudes investigated (44 to 176 m/s(2) rms unweighted; 5.5 to 22 m/s(2) rms when frequency weighted according to ISO 5349), the vasoconstriction during exposure to 125 Hz vibration was independent of vibration magnitude. The after effect of vibration was different for stimuli with the same energy equivalent acceleration, with greater effects after longer durations of exposure. The energy equivalent acceleration therefore failed to predict the acute effects of vibration both during and after exposure to vibration. Both central and local vasoregulatory mechanisms are likely to be involved in the response of finger circulation to acute exposures to 125 Hz vibration.

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.

Haemodynamic changes in ipsilateral and contralateral fingers caused by acute exposures to hand transmitted vibration

OBJECTIVES

To investigate changes in digital circulation during and after exposure to hand transmitted vibration. By studying two frequencies and two magnitudes of vibration, to investigate the extent to which haemodynamic changes depend on the vibration frequency, the vibration acceleration, and the vibration velocity.

METHODS

Finger skin temperature (FST), finger blood flow (FBF), and finger systolic pressure were measured in the fingers of both hands in eight healthy men. Indices of digital vasomotor tone-such as critical closing pressure and vascular resistance-were estimated by pressure-flow curves obtained with different hand heights. With a static load of 10 N, the right hand was exposed for 30 minutes to each of the following root mean squared (rms) acceleration magnitudes and frequencies of vertical vibration: 22 m.s-2 at 31.5 Hz, 22 m.s-2 at 125 Hz, and 87 m.s-2 at 125 Hz. A control condition consisted of exposure to the static load only. The measures of digital circulation and vasomotor tone were taken before exposure to the vibration and the static load, and at 0, 20, 40, and 60 minutes after the end of each exposure.

RESULTS

Exposure to static load caused no significant changes in FST, FBF, or indices of vasomotor tone in either the vibrated right middle finger or the non-vibrated left middle finger. In both fingers, exposure to vibration of 125 Hz and 22 m.s-2 produced a greater reduction in FBF and a greater increase in vasomotor tone than did vibration of 31.5 Hz and 22 m.s-2. In the vibrated right finger, exposure to vibration of 125 Hz and 87 m.s-2 provoked an immediate vasodilation which was followed by vasoconstriction during recovery. The non-vibrated left finger showed a significant increase in vasomotor tone throughout the 60 minute period after the end of vibration exposure.

CONCLUSIONS

The digital circulatory response to acute vibration depends upon the magnitude and frequency of the vibration stimulus. Vasomotor mechanisms, mediated both centrally and locally, are involved in the reaction of digital vessels to acute vibration. The pattern of the haemodynamic changes in the fingers exposed to the vibration frequencies used in this study do not seem to support the frequency weighting assumed in the current international standard ISO 5349.