The microvascular endothelium in scleroderma

Vascular endothelial injury in SSc leads to a host of pathological changes in the blood vessels that adversely impact the physiology of many organ systems and eventually results in a state of chronic tissue ischaemia. Current hypotheses in SSc vascular disease pathogenesis suggest a possible infectious or chemical trigger(s) that activates both cellular and humoral immunity. Products of immune activation may lead to vascular injury possibly through the production of autoantibodies and the release of products of activated T cells that can directly damage the endothelium. Knowledge of the initial trigger of immune activation in SSc may offer an opportunity to develop a multiple step strategy for therapeutic intervention.

Assessment of vascular involvement

Our objective was to identify a core set of variables for the assessment of vascular involvement in scleroderma that is simple, reproducible, and reflects the presence of vascular disease in SSc. To do so we carried out an extensive literature review of published studies relating to the assessment of vascular involvement in SSc, i.e. studies dealing with clinical parameters, functional vascular studies, cold presser testing, nailfold capillary microscopy and circulating vascular markers. After extensive review of published studies and critical assessment of proposed vascular parameters, the subcommittee endorsed what it considers to be the minimal requirements for the documentation of vascular involvement in SSc. The core set variables include two parameters: Raynaud's phenomenon and digital ulcers. This set is simple, reproducible and should be included in the assessment of SSc patients in clinical investigational studies. The subcommittee also however recognizes that there exists a promising set of vascular variable that still needs further investigation.

Raynaud's phenomenon and systemic sclerosis

In systemic sclerosis, the exaggerated generalized vasospastic tendency is clinically represented by Raynaud's phenomenon as shown by an early digital arterial closure after cold stimulation, and by an inadequate vasodilatory response to heat. The phenomenon is not restricted to the extremities, and can also occur in internal organs. Repeated attacks of Raynaud's phenomenon may contribute to vascular disease in systemic sclerosis by a mechanism of reperfusion injury of the endothelium, and may contribute to tissue fibrosis. Although the aetiology and pathogenesis of Raynaud's phenomenon remain unknown, recent advances in the understanding of mechanisms of vascular tone control provide us with an opportunity to reconsider the pathogenetic process of Raynaud's phenomenon. It is now clear that neuropeptides, the vascular endothelium, and platelets are the three major contributors to the control of vascular tone. Our hypothesis suggests the presence of a sensory nervous system failure, leading to an unopposed endothelial and platelet control of vascular tone. Endothelial injury and platelet activation in systemic sclerosis lead to a shift in vascular function to a pro-vasospastic function not balanced by a vasodilatory sensory input; thus, enhanced vasospasm is generated. The investigation of the role of local vascular mediators in vasospasm may lead to a better understanding of vascular tone control and of Raynaud's phenomenon pathophysiology in systemic sclerosis.

Sarcoidosis in systemic sclerosis: report of 7 cases

OBJECTIVE

To describe the clinical, radiologic, and pathologic features of coexistent systemic sclerosis (SSc) and sarcoidosis, 2 conditions of unknown cause associated with altered cellular immune response.

METHODS

We reviewed clinical information, results from laboratory and radiologic studies, and lung or lymph node biopsy samples of 7 patients with concurrent SSc and sarcoidosis evaluated at 2 academic referral centers between 1989 and 1993.

RESULTS

Each patient fulfilled American College of Rheumatology criteria for the classification of SSc. SSc and sarcoidosis developed simultaneously in 4 patients, whereas in 3 others sarcoidosis was diagnosed more than 6 years after the onset of SSc. The onset of sarcoidosis was characterized by fever, weight loss, or increasing respiratory symptoms. Each patient had radiographic evidence of intrathoracic lymphadenopathy and/or interstitial lung disease. Examination of lung or lymph node biopsies demonstrated noncaseating granulomas. Treatment with corticosteroids was associated with improved lung function.

CONCLUSION

Since sarcoidosis coexists with SSc more frequently than previously suggested, it should be considered in patients with SSc presenting with new pulmonary symptoms. Recognizing sarcoidosis in patients with SSc is important, since these patients may benefit from corticosteroid therapy.

Immunologic aspects of scleroderma

Now that the immune involvement in scleroderma is well established, attention is focused on defining the precise mechanisms in immune activation, the nature of autoantigens, the clinical description of disease subsets as defined by autoantibodies, the cytokine network, and the participation of various immune cells in the disease. Yet the exact trigger of immune involvement is still elusive. Interaction of immune cells with the vascular endothelium, through cell-cell interactions and the effect of cytokines, is one of the earliest changes in scleroderma. It is still unclear whether immune alteration follows or precedes endothelial changes. Nonetheless, involvement of the adhesion molecules cascade is well documented. A nucleolar location has been suggested for all of the major autoantigens in scleroderma, with the nucleolus as the primary autoantigen molecular structure. Topoisomerase-I homology to viral proteins continues to be the focus of investigation; however, molecular mimicry in scleroderma autoimmunity is still unproven. Enhanced expression and responses to interleukin-1 and interleukin-6 by scleroderma fibroblasts emphasize the interactive nature of fibroblasts and demonstrate the ability of nonimmune cells to produce immune mediators. Circulating autoantibodies to interleukin-6 and interleukin-8 add another dimension to our understanding of cytokine network regulation in scleroderma. Circulating markers reflecting T-cell activation in vivo continue to be observed. Adenosine deaminase is the most recent indicator described. Nonetheless, the exact phenotype of the principal effector T cell in scleroderma is still not known. A restricted usage of the V beta gene repertoire of the double-negative alpha/beta T cells propose this cell type as the alloreactive cell in scleroderma.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin converting enzyme: an in vivo and in vitro marker of endothelial injury

An elevated level of von Willebrand factor (vWf) is a well-established marker for both in vivo and in vitro endothelial cell injury. Recent studies indicate that the plasma level of angiotensin-converting enzyme (ACE) in systemic sclerosis is reduced in association with elevated vWf levels. Because the endothelial cell is capable of producing both mediators, and because endothelial cell injury is a fundamental process in systemic sclerosis, we investigated in this study the effect of in vitro endothelial cell injury on the synthesis of both factors. Endothelial cells derived from human umbilical veins, in the second passage, were activated by exposure to interleukin-1 or lymphotoxin or were injured by radiation, actinomycin, or trypsin (each can be shown to induce dose-dependent endothelial cell cytotoxicity). ACE (spectrophotometric method) and vWf levels (enzyme-linked immunosorbent assay method) were determined in the supernatant and in the cell lysate 48 hours after cellular injury and activation. An increase in vWf levels was found in the lysate and in the supernatant from the cells that underwent injury or activation, whereas ACE levels were increased after activation but decreased after injury. Next, and as an in vivo clinical corollary to the in vitro endothelial cell injury, we evaluated ACE and vWf levels in the plasma of seven children in the acute phase of Kawasaki disease, a disorder characterized by widespread vascular injury. Plasma ACE levels were significantly lower than control levels, whereas vWf levels were increased, reflecting the known prominent endothelial cell injury in this disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephelometric detection of soluble immune complexes: methodology and clinical applications

We have developed a method for the detection of immune complexes by laser nephelometry which is simple, reproducible, suitable for automation, and generally adaptable for diagnostic testing. Light dispersion by antigen-antibody complexes in the test samples is measured after addition of polymeric buffer, which enhances the aggregation of complexes but does not significantly affect unbound immunoglobulins. The method was used to measure immune complexes formed in vitro by incubation of tetanus toxoid with serum from a rabbit previously hyperimmunized with the same antigen, and to compare the levels of immune complexes in human sera obtained from normal adults and from 37 patients with collagen vascular diseases or endocarditis. When precautions were taken to avoid interference produced by the presence of lipoproteins or by freezing of the samples, the results obtained with human sera were consistent with those expected for normal controls and for patients with conditions thought to be associated with the presence of soluble immune complexes.