Degradation of elastic fiber and elevated elastase expression in long head of biceps tendinopathy

Tendinopathy of the long head of the biceps (TLHB) involves various types of extracellular matrix degeneration, but previous studies have not evaluated elastic fibers. The purpose of this study was to investigate elastic fiber distribution in long head of the biceps (LHB). The TLHB tendons of 16 consecutive patients (eight men and eight women; average age of 55.75 years; age range of 40-71 years) were transected and harvested. Three cadaveric LHB tendons were used as the control group. The expression of collagen type I was decreased, but type III was increased in TLHB. Disruption of elastic fibers was particularly observed in grade II specimens where the level of elastase-positive staining was significantly higher than in grade I specimens. Elastic fibers were not observed in the grade III area, implying a higher expression of elastase than in the grade I area. Results of Western blotting showed that the expression of elastin was higher in the control group and the levels of elastin significantly decreased in grades II and III of TLHB. Levels of osteopontin and elastase were increased in primary culture of human tenocytes after experiencing elastic derived peptide treatment. These results suggested that elastase may be caused by the disruption of elastic fibers in the development of chronic tendinopathy and that elastic derived peptide may enhance elastase and osteopontin expression. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1919-1926, 2017.

Fibrillin-2 Degradation by Matrix Metalloproteinase-2 in Periodontium

Elastic system fibers, comprised of microfibrils and tropoelastin, are extracellular components of periodontal tissue. During development, the microfibrils act as a template on which tropoelastin is deposited. However, the process of elastic system fiber remodeling is not fully understood. Therefore, we examined whether matrix metalloproteinases (MMPs) are involved in the remodeling of fibrillins (major components of microfibrils) by human gingival fibroblasts and periodontal ligament (PDL) fibroblasts. Gingival and PDL fibroblasts were cultured for 6 weeks. In some cultures, MMP inhibitor or tissue inhibitor of matrix metalloproteinsase-2 (TIMP-2) was added to the medium for an additional 2 weeks. Active MMP-2 (62 kDa) appeared as cell-membrane-associated or in extracellular matrix only in PDL fibroblast cell layers. The addition of MMP inhibitor or TIMP-2 significantly increased fibrillin-2 accumulation in PDL fibroblast cell layers, and decreased the amount of fibrillin-2 fragments, suggesting that active MMP-2 may degrade fibrillin-2, and that MMPs may play a role in the remodeling of elastic system fibers in PDL.

Altered vascular activation due to deficiency of the NADPH oxidase component p22phox

BACKGROUND

Reactive oxygen species generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase play important roles in vascular activation. The p22(phox) subunit is necessary for the activity of NADPH oxidase complexes utilizing Nox1, Nox2, Nox3, and Nox4 catalytic subunits.

METHODS

We assessed p22(phox)-deficient mice and human tissue for altered vascular activation.

RESULTS

Mice deficient in p22(phox) were smaller than their wild-type littermates but showed no alteration in basal blood pressure. The wild-type littermates were relatively resistant to forming intimal hyperplasia following carotid ligation, and the intimal hyperplasia that developed was not altered by p22(phox) deficiency. However, at the site of carotid artery ligation, the p22(phox)-deficient mice showed significantly less vascular elastic fiber loss compared with their wild-type littermates. This preservation of elastic fibers was associated with a reduced matrix metallopeptidase (MMP) 12/tissue inhibitor of metalloproteinase (TIMP) 1 expression ratio. A similar decrease in the relative MMP12/TIMP1 expression ratio occurred in human coronary artery smooth muscle cells upon knockdown of the hydrogen peroxide responsive kinase CK1αLS. In the ligated carotid arteries, the p22(phox)-deficient mice showed reduced expression of heterogeneous nuclear ribonucleoprotein C (hnRNP-C), suggesting reduced activity of CK1αLS. In a lung biopsy from a human patient with p22(phox) deficiency, there was also reduced vascular hnRNP-C expression.

CONCLUSIONS

These findings indicate that NADPH oxidase complexes modulate aspects of vascular activation including vascular elastic fiber loss, the MMP12/TIMP1 expression ratio, and the expression of hnRNP-C. Furthermore, these findings suggest that the effects of NADPH oxidase on vascular activation are mediated in part by protein kinase CK1αLS.

Emphysema in an adult with galactosialidosis linked to a defect in primary elastic fiber assembly

Galactosialidosis is a lysosomal storage disorder caused by loss of function of protective protein cathepsin A, which leads to secondary deficiencies of β-galactosidase and neuraminidase-1. Emphysema has not been previously reported as a possible complication of this disorder, but we now describe this condition in a 41-year-old, non-smoking male. Our patient did not display deficiency in α-1-antitrypsin, the most common cause of emphysema in non-smokers, which brings about disseminated elastolysis. We therefore hypothesized that loss of cathepsin A activity was responsible because of previously published evidence showing it is prerequisite for normal elastogenesis. We now present experimental evidence to support this theory by demonstrating impaired primary elastogenesis in cultures of dermal fibroblasts from our patient. The obtained data further endorse our previous finding that functional integrity of the cell surface-targeted molecular complex of cathepsin A, neuraminidase-1 and the elastin-binding protein (spliced variant of β-galactosidase) is prerequisite for the normal assembly of elastic fibers. Importantly, we also found that elastic fiber production was increased after exposure either to losartan, spironolactone, or dexamethasone. Of immediate clinical relevance, our data suggest that surviving patients with galactosialidosis should have periodic assessment of their pulmonary function. We also encourage further experimental exploration of therapeutic potential of the afore-mentioned elastogenesis-stimulating drugs for the alleviation of pathological processes in galactosialidosis that could be mechanistically linked to impaired deposition of elastic fibers.

Metalloproteinase-2 and -9 in giant cell arteritis: involvement in vascular remodeling

BACKGROUND

Both matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) have been postulated to play roles in the pathophysiology of giant cell arteritis (GCA) because of their ability to degrade elastin. Understanding the specific mediators of arterial damage in GCA could lead to new therapeutic targets in this disease.

METHODS AND RESULTS

Temporal artery biopsy specimens were obtained from 147 consecutive patients suspected of GCA. Clinical and histopathological data were collected according to protocol. Using immunohistochemistry, we compared the expression of MMP-2 and MMP-9 in the temporal artery biopsies of both GCA cases (n=50) and controls (n=97). MMP-9 was found more frequently in positive than in negative temporal artery biopsies (adjusted odds ratio [OR], 3.20; P=0.01). In contrast, the frequency of MMP-2 was not significantly different between positive and negative biopsies (adjusted OR, 2.18; P=0.22). Both MMP-2 and MMP-9 were found in macrophages and giant cells near the internal elastic lamina and in smooth muscle cells and myofibroblasts of the media and intima. MMP-9 was also found in the vasa vasorum. MMP-9 but not MMP-2 was associated with internal elastic lamina degeneration, intimal hyperplasia, and luminal narrowing, even after adjustment for possible confounding variables.

CONCLUSIONS

MMP-9 appears more likely than MMP-2 to be involved in the pathophysiology of GCA. MMP-9 not only participates in the degradation of elastic tissue but also is associated with intimal hyperplasia, subsequent luminal narrowing, and neoangiogenesis. The expression of MMP by smooth muscle cells implicates these cells as potential secretory cells in GCA.

The Pathogenesis of Floppy Eyelid SyndromeInvolvement of matrix metalloproteinases in elastic fiber degradation

OBJECTIVE

To investigate histopathologic alterations of eyelid biopsy specimens from patients with floppy eyelid syndrome (FES) with special regard to elastic fiber content and ultrastructure as well as to the expression of elastin-degrading enzymes to elucidate the pathogenesis of this disorder.

DESIGN

Retrospective, interventional case series.

PARTICIPANTS AND CONTROLS

Eleven consecutive patients with FES and 10 age-matched control patients with basal cell carcinoma of the eyelid.

METHODS

Horizontal pentagonal eyelid resections of 16 upper lids were performed in 11 patients with FES. Full-thickness eyelid biopsy specimens from study and control patients were examined by light and transmission electron microscopy, semiquantitative morphometry, and immunohistochemistry using antibodies against matrix metalloproteinase (MMP)-2, MMP-7, MMP-9, and MMP-12 and neutrophil elastase.

RESULTS

All patients treated with surgical horizontal eyelid shortening were asymptomatic at follow-up. Histopathologic analysis of the surgical specimens showed, apart from unspecific signs of chronic inflammation, a significant decrease in the amount of elastin within the tarsal plate and eyelid skin as compared with controls. Residual elastic fibers revealed an abnormal ultrastructure with a diminished elastin core. Immunohistochemistry demonstrated an increased immunoreactivity for elastolytic proteases, particularly MMP-7 and MMP-9, in areas of elastin depletion in FES specimens as compared with controls.

CONCLUSIONS

The findings indicate that upregulation of elastolytic enzymes, most probably induced by repeated mechanical stress, participates in elastic fiber degradation and subsequent tarsal laxity and eyelash ptosis in FES.

Protective effect of a vegetable extract from Lupinus albus (LU 105) on human gingival elastic fibers degradation by human leukocyte elastase

The aim of this study was to determine if a vegetable extract from seeds of Lupinus albus (LU 105) has the capacity to inhibit human leukocyte elastase and/or protect gingival elastic fibers against proteolytic degradation. LU105 was extracted from seeds of L albus and is freely soluble in water. In this study the ex-vivo elastolytic activity of human leukocyte elastase and the potential inhibitory effect of LU 105 were determined using human gingival cryostat tissue sections and computerized morphometric analysis. The gingival tissue sections pre-treated or not with LU 105 were submitted to the action of human leukocyte elastase or submitted to the simultaneous action of human leukocyte elastase and LU 105, and then analyzed using automated image analysis. In such conditions, LU 105 at 0.1%, 0.01%, and 0.001% developed a dose dependent protection of gingival elastic fibers against enzymatic proteolysis due to human leukocyte elastase, and LU 105 at 0.1% or 0.01% was able to inhibit the elastolytic activity of leukocyte elastase itself. It is proposed that LU 105 is an option for the treatment of gingival inflammation in which leukocyte elastase is involved.

Inactivation of human beta-defensins 2 and 3 by elastolytic cathepsins

beta-Defensins are antimicrobial peptides that contribute to the innate immune responses of eukaryotes. At least three defensins, human beta-defensins 1, 2, and 3 (HBD-1, -2, and -3), are produced by epithelial cells lining the respiratory tract and are active toward Gram-positive (HBD-3) and Gram-negative (HBD-1, -2, and -3) bacteria. It has been postulated that the antimicrobial activity of defensins is compromised by changes in airway surface liquid composition in lungs of patients with cystic fibrosis (CF), therefore contributing to the bacterial colonization of the lung by Pseudomonas and other bacteria in CF. In this report we demonstrate that HBD-2 and HBD-3 are susceptible to degradation and inactivation by the cysteine proteases cathepsins B, L, and S. In addition, we show that all three cathepsins are present and active in CF bronchoalveolar lavage. Incubation of HBD-2 and -3 with CF bronchoalveolar lavage leads to their degradation, which can be completely (HBD-2) or partially (HBD-3) inhibited by a cathepsin inhibitor. These results suggest that beta-defensins are susceptible to degradation and inactivation by host proteases, which may be important in the regulation of beta-defensin activity. In chronic lung diseases associated with infection, overexpression of cathepsins may lead to increased degradation of HBD-2 and -3, thereby favoring bacterial infection and colonization.

Impaired elastic-fiber assembly by fibroblasts from patients with either Morquio B disease or infantile GM1-gangliosidosis is linked to deficiency in the 67-kD spliced variant of beta-galactosidase

We have previously shown that intracellular trafficking and extracellular assembly of tropoelastin into elastic fibers is facilitated by the 67-kD elastin-binding protein identical to an enzymatically inactive, alternatively spliced variant of beta-galactosidase (S-Gal). In the present study, we investigated elastic-fiber assembly in cultures of dermal fibroblasts from patients with either Morquio B disease or GM1-gangliosidosis who bore different mutations of the beta-galactosidase gene. We found that fibroblasts taken from patients with an adult form of GM1-gangliosidosis and from patients with an infantile form, carrying a missense mutations in the beta-galactosidase gene-mutations that caused deficiency in lysosomal beta-galactosidase but not in S-Gal-assembled normal elastic fibers. In contrast, fibroblasts from two cases of infantile GM1-gangliosidosis that bear nonsense mutations of the beta-galactosidase gene, as well as fibroblasts from four patients with Morquio B who had mutations causing deficiency in both forms of beta-galactosidase, did not assemble elastic fibers. We also demonstrated that S-Gal-deficient fibroblasts from patients with either GM1-gangliosidosis or Morquio B can acquire the S-Gal protein, produced by coculturing of Chinese hamster ovary cells permanently transected with S-Gal cDNA, resulting in improved deposition of elastic fibers. The present study provides a novel and natural model validating functional roles of S-Gal in elastogenesis and elucidates an association between impaired elastogenesis and the development of connective-tissue disorders in patients with Morquio B disease and in patients with an infantile form of GM1-gangliosidosis.

Increased fibroblast elastase activity in acquired cutis laxa

BACKGROUND

Acquired cutis laxa is a rare disease characterized by sagging skin, premature wrinkling and reduced skin elasticity.

OBSERVATION

We report a 21-year-old woman, who presented with acquired cutis laxa on the face and the ear lobes. Urticarial papules had preceded for 6 years. There was no systemic involvement. Skin specimens were obtained from lax skin and urticarial papules, and from healthy controls. Histology showed only few perivascular lymphocytes in lax ear skin and a dense inflammatory infiltrate in urticarial skin. In both biopsies elastic fibres were decreased as demonstrated by computerized morphometric analyses. Elastase activities of fibroblasts in culture were evaluated. There was a 2- to 3-fold increase in elastase activity in urticarial skin fibroblasts, contrasting with a normal elastase activity in lax ear skin.

CONCLUSION

Our findings suggest that the inflammatory cells could play a significant role in the destruction of elastic fibres.

[The species characteristics of the elastolytic system of the arteries and veins in the early stages of experimental tunica media calcinosis and atherosclerosis]

The role of the elastolytic system arterial and venous tissues in pathogenesis of vascular pathology was investigated on rabbits and rats in experimental arterio-atherosclerosis. The obtained results indicate that elastase activity in aortic homogenates was significant higher in normal and pathological condition in rats than in rabbits. Elastase inhibitors (alpha 2-macroglobulin and alpha 1-proteinase inhibitor) also respond on angiosclerotic agent and level of alpha 2-macroglobulin increased significant in resistant animals (rats) but not in rabbits. In venous vessels determined more higher level of antielastase potential that may be explain its phenomenal resistance to different damage factors. The presented result confirm the importance of balance elastase and it inhibitors in pathogenesis of arterio-atherosclerosis.

Ultrastructural changes of the external elastic lamina in experimental hypercholesterolemic porcine coronary arteries

The external elastic lamina (EEL) serves as a barrier for cells and macromolecules between the media and adventitia in the vascular wall. We evaluated the morphological changes and quantitative assessments of the EEL architecture in the coronary circulation of pigs fed with a high cholesterol diet. Confocal microscopy analysis of the EEL from hypercholesterolemic coronary arteries revealed an altered pattern characterized by fragmentation and disorganization of the EEL associated with an increase in the thickness. Computerized digital analysis of the images obtained by confocal scanning microscopy demonstrated that compared to normal coronary arteries, the EEL of hypercholesterolemic coronary arteries decreased in the percentage of their elastin content (30.80 +/- 1.64% vs. 47.85 +/- 1.82%, p = 0.001). The percentage of elastin content was negatively correlated with the vessel wall area (r = -0.82, p = 0.001). The immunoreactivity for matrix metalloproteinase-3 (MMP-3) increased in cholesterol-fed coronary arteries, predominantly in the neointima and adventitia. This study demonstrates that experimental hypercholesterolemia induced ultrastructural changes of the EEL in coronary circulation. The EEL may also be an atherosclerosis-prone area compared with the intima. The EEL may play an important role in the development of structural changes which characterizes the early phase of coronary atherosclerosis and vascular remodeling.

Adventitial delivery minimizes the proinflammatory effects of adenoviral vectors

PURPOSE

Adenovirus-mediated arterial gene transfer is a promising tool in the study of vascular biology and the development of vascular gene therapy. However, intraluminal delivery of adenoviral vectors causes vascular inflammation and neointimal formation. Whether these complications could be avoided and gene transfer efficiency maintained by means of delivering adenoviral vectors via the adventitia was studied.

METHODS

Replication-defective adenoviral vectors encoding a beta-galactosidase (beta-gal) gene (AdRSVnLacZ) or without a recombinant gene (AdNull) were infused into the lumen or the adventitia of rabbit carotid arteries. Two days after infusion of either AdRSVnLacZ (n = 8 adventitial, n = 8 luminal) or AdNull (n = 4 luminal), recombinant gene expression was quantitated by histochemistry (performed on tissue sections) and with a beta-gal activity assay (performed on vessel extracts). Inflammation caused by adenovirus infusion was assessed 14 days after infusion of either AdNull (n = 6) or vehicle (n = 6) into the carotid adventitia. Inflammation was assessed by means of examination of histologic sections for the presence of neointimal formation and infiltrating T cells and for the expression of markers of vascular cell activation (ICAM-1 and VCAM-1). To measure the systemic immune response to adventitial infusion of adenovirus, plasma samples (n = 3) were drawn 14 days after infusion of AdNull and assayed for neutralizing antibodies.

RESULTS

Two days after luminal infusion of AdRSVnLacZ, approximately 30% of luminal endothelial cells expressed beta-gal. Similarly, 2 days after infusion of AdRSVnLacZ to the adventitia, approximately 30% of adventitial cells expressed beta-gal. beta-gal expression was present in the carotid adventitia, the internal jugular vein adventitia, and the vagus nerve perineurium. Elevated beta-gal activity (50- to 80-fold more than background; P <.05) was detected in extracts made from all AdRSVnLacZ-transduced arteries. The amount of recombinant protein expression per vessel did not differ significantly between vessels transduced via the adventitia (17.1 mU/mg total protein [range, 8.1 to 71.5]) and those transduced via a luminal approach (10.0 mU/mg total protein [range, 3.9 to 42.6]). Notably, adventitial delivery of AdNull did not cause neointimal formation. In addition, vascular inflammation in arteries transduced via the adventitia (ie, T-cell infiltrates and ICAM-1 expression) was confined to the adventitia, sparing both the intima and media. Antiadenoviral neutralizing antibodies were present in all rabbits after adventitial delivery of AdNull.

CONCLUSION

Infusion of adenoviral vectors into the carotid artery adventitia achieves recombinant gene expression at a level equivalent to that achieved by means of intraluminal vector infusion. Because adventitial gene transfer can be performed by means of direct application during open surgical procedures, this technically simple procedure may be more clinically applicable than intraluminal delivery. Moreover, despite the generation of a systemic immune response, adventitial infusion had no detectable pathologic effects on the vascular intima or media. For these reasons, adventitial gene delivery may be a particularly useful experimental and clinical tool.

Ultrastructural changes of the internal elastic lamina in experimental hypercholesterolemic porcine coronary arteries

The internal elastic lamina (IEL) serves as a barrier for cells and macromolecules between the intima and media in the vascular wall. We evaluated the morphological changes and quantitative assessments of the IEL architecture in the coronary circulation of pigs fed with a high cholesterol diet. Transmission electron microscopy (TEM) analysis of the IEL from hypercholesterolemic coronary arteries revealed fragmentation of the IEL associated with a decrease in the thickness. Confocal microscopy and scanning electron microscopy (SEM) revealed an altered pattern characterized by a large oval fenestration in the IEL of hypercholesterolemic vessels. Morphometric analysis of confocal microscopy images demonstrated that the IEL of cholesterol-fed animals were characterized by an increase in the minor diameter of the fenestrae (2.16+/-0.04 microm vs 3.32+/-0.06 microm, p=0.003) and a decrease in the fenestrae density (22,333+/-1,334/mm2 vs 17,552+/-931/mm2, p=0.015) compared to controls. The percentage of the IEL area covered by the fenestrae correlated with the intimal thickness (r=0.79, p=0.004). The immunoreactivity for matrix metalloproteinase-3 (MMP-3) increased in cholesterol-fed coronary arteries, predominantly in the neointima. This study demonstrates experimental hypercholesterolemia induced ultrastructural changes of the IEL in the coronary circulation. The IEL may play an important role in the development of structural changes which characterize the early phase of coronary atherosclerosis.

Increased expression of gelatinases A and B by skin explants from patients with anetoderma

The extent of alterations to the elastic fibre network in lesional skin areas of three patients with anetoderma was assessed by quantitative image analysis of tissue sections and compared with morphometric parameters from unaffected sites of the same individuals. In the anetodermic skins pre-elastic fibres were undetectable or extremely rare: the volume fraction (Vv%) occupied by these pre-elastic fibres was 0-0.3%, while in unaffected skins the Vv% occupied by pre-elastic fibres was 0.5-0.8%. A nearly complete absence of dermal elastic fibres in lesional skins from the three patients was evidenced (Vv% = 0.2-0.3%). Organ cultures were performed using explants from skin with or without anetodermic lesions to quantify the expressions of elastase-type proteinases. All tissues from anetodermic lesions expressed proforms of gelatinases A and B and the activated form of gelatinase A; their levels increased with the culture time. In comparison, enzymatic activities on oligopeptide substrates specific for leucocyte elastase and fibroblast plasma membrane-associated metalloelastase were not detected in the conditioned media of any explants at any time of culture from 1 to 5 days. Increased production of progelatinases A and B and activation of progelatinase A could be mainly responsible for the degradation of skin elastic fibres demonstrated in anetodermic skins.

Elastin degradation in the superficial temporal arteries of patients with intracranial aneurysms reflects changes in plasma elastase

OBJECTIVE

alpha 1-Antitrypsin (AAT) and alpha 2-macroglobulin (AMG) are elastase inhibitors that bind the enzyme and reduce measured levels of free elastase. It was recently demonstrated that some patients with intracranial aneurysms have significantly elevated plasma elastase (PE) levels. Although this elevation is unrelated to plasma AAT, it is unknown whether abnormal AAT phenotypes or reduced AMG levels play a role. Moreover, the pathological significance of this elevation is not understood.

METHODS

Plasma from 24 patients with aneurysms (ruptured, n = 15; unruptured, n = 9) and 10 age-matched patients who comprised a control group was analyzed for PE and AMG levels by enzyme-linked immunosorbent assay and for AAT phenotype by isoelectric focusing. Sections of superficial temporal temporal artery obtained from these patients at the time of surgery were examined for evidence of elastin degradation by using a van Gieson stain, with scoring on a nine-point quantitative scale.

RESULTS

Patients with aneurysms showed significantly elevated PE levels (119 +/- 28 versus 17 +/- 7 micrograms/ml, P < 0.05), but AMG levels were not decreased. AAT phenotypic abnormalities were observed in 10% (2 of 20) of the patients with aneurysms, but this was not different from the expected population incidence (7%). Elastin degradation scores were significantly higher in patients with aneurysms than in patients control group (4.26 +/- 0.54 versus 1.21 +/- 0.43, P < 0.05). In addition, patients with higher elastase levels (> 80 micrograms/ml) demonstrated 55% higher degradation scores than did those with lower elastase levels (< 80 micrograms/ml).

CONCLUSION

These data suggest that high PE levels may play a role in systemic arterial elastin degradation seen in patients with intracranial aneurysms. These data also support the contention that elevated elastase levels are not the result of decreased protease inhibitor levels. Although PE levels were significantly higher for the entire group of patients with aneurysms, this assay has relatively low sensitivity for predicting the presence of unruptured aneurysms. Additional study is necessary to determine whether serum elastase levels greater than 80 micrograms/ml, in the setting of other risk factors, are useful in identifying asymptomatic patients for additional screening.

Macrophages contain 92-kd gelatinase (MMP-9) at the site of degenerated internal elastic lamina in temporal arteritis

Inflammation precedes erosion and rupture of atherosclerotic atheromas and aneurysms. Inflammatory infiltrates of macrophages have been shown to secrete proteolytic enzymes, including matrix metalloproteinases (MMPs), that weaken the arterial wall. The effect of inflammation on arterial structure and remodeling can be studied in primary vascular inflammatory diseases such as in temporal arteritis. We examined the 72-kd gelatinase (MMP-2) and the 92-kd gelatinase (MMP-9) in inflamed and uninvolved temporal arteries from 10 patients with temporal arteritis and 5 controls by immunohistochemistry. The substrates of these enzymes, type IV collagen and elastin, were detected by immunohistochemistry and histochemical staining, respectively. Both diseased and normal artery specimens had moderate staining for immunoreactive MMP-2. Temporal arteritis specimens had clearly enhanced immunostaining for MMP-9 compared with normal arteries. MMP-9 was specifically localized to macrophages in regions of internal elastic lamina disruption, which may thus be of pathological significance.

"Aberrant elastic" in elastofibroma: an immunohistochemical and ultrastructural study

Elastofibroma is a rare lesion characterized by the presence of abundant abnormal elastic fibers with a unique morphology, fibroblastic proliferation, and collagen deposition. Whether the altered morphology of the elastic fibers is a degenerative phenomenon or is due to abnormal elastogenesis is controversial. We studied fetal skin and three cases of elastofibroma by light microscopy and immunohistochemistry using an antibody to lysozyme, and one case of elastofibroma by electron microscopy (EM). Our previous studies have shown that normal elastic fibers in adult skin do not stain for lysozyme whereas abnormal elastic fibers in solar elastosis and pseudoxanthoma elasticum react positively for lysozyme. In the fetal skin and all three cases of elastofibroma the elastic fibers were negative for lysozyme. EM showed the abnormal flowerlike configuration of the elastic fibers, which consisted of a central core of normal or degenerating elastin surrounded by radiating spokes of granular and filamentous material of variable electron densities, suggesting that the structure and organization of the microfibrils is abnormal. The absence of lysozyme in the aberrant elastic did not differentiate whether there was excessive production of fetal or adult elastic. However, the excessive amount of microfibrils seen at the ultrastructural level suggests that there may be excessive fetal elastic production. The elastic fibers were intimately related to the fibroblasts and were often present within their caveolae, suggesting that the abnormal elastic fibers are produced by the fibroblast. Our study suggests that abnormal elastogenesis with subsequent degeneration plays a role in the production of the abnormal elastic fibers in elastofibroma.

Immunohistochemical localization of lysyl oxidase in normal human skin

Lysyl oxidase (EC 1.4.3.13), a copper-dependent enzyme which catalyses the formation of aldehyde cross-links, and acts primarily on collagen and elastin, is known to be increased during wound healing and in fibrotic disorders including liver cirrhosis and atherosclerosis, and to be decreased in some hereditary connective tissue diseases and in malignant cell lines. A recent study showed that lysyl oxidase might possess tumour suppressor activity as an antioncogene for ras. Little is known about the localization of this enzyme in human skin. In this study, we determined immunohistochemically the localization of lysyl oxidase in normal skin of young and elderly subjects obtained from sun-exposed and unexposed regions of the body. All skin samples tested had similar distributions of lysyl oxidase. The enzyme was present both extracellularly and intracellularly. Extracellularly, a few granular aggregates of immunoreactants were observed along collagen and elastic fibres. These granules were more common in the adventitial portion of the dermis than in the reticular portion. Of all sun-exposed and unexposed regions studied, the skin of the face displayed the greatest amount of extracellular immunoreactants. Immunopositive granules were observed intracellularly in fibroblasts, vascular endothelial cells, sweat glands, sebaceous glands, arrector pili muscles and some keratinocytes. These findings provide evidence that, as suggested in recent reports, lysyl oxidase may have a variety of intracellular functions.

Damaging role of neutrophil elastase in the elastic fiber and basement membrane in human emphysematous lung

The immunolocalization of human neutrophil elastase (HNE) in the alveolar interstitium of 6 patients with emphysema was investigated by immunochemical electron microscopy. The results showed that HNE is localized in the azurophil granules of neutrophils, and extracellularly on the elastic fibers of alveolar interstitium and basement membranes of epithelium and endothelium. The damage of elastic fibers and basement membranes could be observed. The HNE level of the alveolar interstitium was obviously elevated and closely related to the severity of emphysematous lesions as shown by measuring the mean linear intercept (MLI) in 4 emphysematous lungs with chronic bronchitis (r = 0.84). This suggests that HNE might play an important role in the pathogenesis of emphysema. Although enlarged airspace and increased MLI data were observed in 2 patients, one with asthma and the other, an elderly patient, without lung diseases, the HNE level of alveolar interstitium is much less than that of the other 4 chronic obstructive pulmonary disease patients. This implies that the mechanism of the the airspace enlargement occurring in the 2 patients may be different from that of others. These findings support the hypothesis of elastase-antielastase imbalance on the pathogenesis of pulmonary emphysema.

Is neutrophil elastase associated with elastic tissue in emphysema?

To test the role of elastase in the pathogenesis of emphysema human neutrophil elastase (HNE) was localised by electron microscopy using an immunogold staining technique. Specific localisation of HNE to elastic tissue in emphysema did not occur, but non-specific binding of immunoglobulin G (IgG) to elastic tissue in emphysematous and normal lung tissue, which was completely blocked by the non-immune serum that was homologous to the gold labelled second antibody, was found. HNE was also present, however, in the granules of neutrophils in the same sections. Non-specific labelling associated with elastin was probably due to binding of IgG to the high numbers of hydrophobic and charged regions known to be present in this molecule, and it is concluded that our findings do not support the existence of high concentrations of elastase in association with elastin in emphysematous lung tissue.

Different distribution of two types of angiotensin II-generating enzymes in the aortic wall

Dog, monkey and human aortic tissues contained two distinct types of angiotensin II-generating enzymes; angiotensin converting enzyme (ACE) and chymostatin-sensitive angiotensin II-generating enzyme (CAGE). Endothelium, media and adventitia of canine thoracic aortae were separated using collagenase digestion, and determined for their ACE and CAGE activity. ACE activity was assayed by hippuryl-His-Leu cleavage. CAGE activity was estimated with ANG I as substrate in the presence of inhibitors of ACE and angiotensinases. His-Leu, the common product of both enzyme reactions, was fluorimetrically quantified after o-phthalaldehyde condensation. ACE localized mainly in endothelium, while CAGE distributed predominantly in adventitia. Similar results were obtained with human and monkey aortae. Such a contrasting distribution may indicate the distinct functional role of these two enzymes.

Elastosis in breast carcinoma: II. Association of protease inhibitors with immature elastic fibres

The elastosis of 11 invasive ductal and infiltrative lobular carcinomas of the breast was specifically immunostained for the plasma protease inhibitors alpha-1 antitrypsin, alpha-1 antichymotrypsin, alpha-2 macroglobulin, inter alpha trypsin inhibitor and C1 esterase inhibitor. None of these components was detected in the elastic fibres of normal ducts or blood vessels in the breast. The elastosis in breast carcinomas was also stained by Concanavalin A and Triticum vulgaris lectins. Such lectin staining probably represents binding to the microfibrillar component of elastic fibres, which is increased in immature elastic fibres, thus suggesting that the elastotic fibres of breast carcinoma are recently synthesised. It is suggested that the presence of protease inhibitors may influence the metabolism of elastic fibres, facilitating elastic fibre proliferation by the inhibition of elastinolytic enzymes.

Ultrastructural immunolocalization of lysyl oxidase in vascular connective tissue

The localization of lysyl oxidase was examined in calf and rat aortic connective tissue at the ultrastructural level using polyclonal chicken anti-lysyl oxidase and gold conjugated rabbit anti-chicken immunoglobulin G to identify immunoreactive sites. Electron microscopy of calf aortic specimens revealed discrete gold deposits at the interface between extracellular bundles of amorphous elastin and the microfibrils circumferentially surrounding these bundles. The antibody did not react with microfibrils which were distant from the interface with elastin. There was negligible deposition of gold within the bundles of amorphous elastin and those few deposits seen at these sites appeared to be associated with strands of microfibrils. Lysyl oxidase was similarly localized in newborn rat aorta at the interface between microfibrils and nascent elastin fibers. Gold deposits were not seen in association with extracellular collagen fibers even after collagen-associated proteoglycans had been degraded by chondroitinase ABC. However, the antibody did recognize collagen-bound lysyl oxidase in collagen fibers prepared from purified collagen to which the enzyme had been added in vitro. No reaction product was seen if the anti-lysyl oxidase was preadsorbed with purified lysyl oxidase illustrating the specificity of the antibody probe. The present results are consistent with a model of elastogenesis predicting the radial growth of the elastin fiber by the deposition and crosslinking of tropoelastin units at the fiber-microfibril interface.

Enzymatic destruction of the elastic lamella at the mouth of cerebral berry aneurysm? An ultrastructural study with special regard to the elastic tissue

Destruction of the elastic tissue is probably an acquired lesion and is decisive for the appearance of cerebral arterial aneurysms at the sites of congenital media defects. The elastic component in the mouths of aneurysms has therefore been studied by electron microscopy, using two new staining methods, i.e. ruthenium-red staining and prolonged osmium-tetroxide treatment. The hypertrophic, duplicated, elastic lamellae showed a disintegration of their luminal portions not earlier described. In close connection with the disintegrated portions, extracellular lysosome-like granules were observed. It is hypothesized that discharged leucocyte grannules containing elastase help to destroy the elastic lamellae.

Elastolytic enzymes and elastin in the aging rat. II. Antielastoproteinase, antitrypsin and antichymotrypsin levels in serum

The age-relationship of antielastoproteinase, antitrypsin, and antichymotrypsin activity of rat serum was studied using alkali-treated elastin as substrate for measuring elasto-proteinase activity and synthetic substrates for measuring trypsin and chymotrypsin activity (trypsin substrate: benzoyl-arginine- <i>p</i>-nitroanalide; chymotrypsin substrate: acetyl-tyrosine-hydrazide). Serum antielastoproteinase levels in both male and female rats increased with age, whereas the levels for ântitrypsin and antichymotrypsin decreased with age. These findings support the hypothesis that the serum contains separate inhibitors for elastoproteinase and trypsin. The effect of age on the antielastoproteinase activity of rat serum was compared with data found in the literature for human serum. Rat serum showed highly significant age-related ‘tryptic and chymotryptic activities’ (both ‘enzyme activities’ increasing with age in both sexes). That these enzymatic activities represent real trypsin and chymotrypsin activities is questioned. Serum amidases and thrombin may be responsible for the measured activities.

Studies on the cathepsins in elastic cartilage

1. The presence of several enzymes in rabbit ear cartilage was examined by a quantitative method that permits the incubation of a fixed weight of cartilage sections (18mum.) with an appropriate exogeneous substrate. 2. As the presence of cathepsins B and D in cartilage has already been established, evidence is now provided to show that cathepsins A and C are also present and are maximally active at pH5. 3. Cathepsin A was recognized by its hydrolysis of benzyloxycarbonyl-glutamyl-tyrosine and cathepsin C by its hydrolysis of glycyl-tyrosine amide; the cartilage also hydrolysed benzyloxycarbonyl-glutamyl-phenylalanine and benzoyl-dl-phenylalanine 2-naphthyl ester at pH5. 4. The acid phosphatase activity and the DNA content of cartilage have also been measured to provide a basis for comparison with the cathepsin activity of cartilage obtained from other sites and species.