The evolving treatment of ANCA-associated vasculitides.

Prevention of organ damage and maintenance of long-term remission are the principal goals for treatment of ANCA-associated vasculitides. This can be accomplished by early diagnosis and swift initiation of remission-inducing agents. Outcome has improved but relapses and glucocorticoid- and cyclophosphamide-related toxicity are still major concerns. For remission induction in generalized disease a combination of glucocorticoids and cyclophosphamide or rituximab is used. Rituximab is suitable especially for younger patients with fertility concerns and when cyclophosphamide avoidance otherwise is desirable. In the treatment of relapses and refractory disease, rituximab has proved effective. As maintenance treatment rituximab prevents relapses more effectively than azathioprine.

[Hepatopulmonary syndrome]. / Hepatopulmonaalinen oireyhtymä.

Hepatopulmonary syndrome (HPS) is characterized by the triad of liver disease, intrapulmonary vascular dilatation and arterial deoxygenation. Mediating factors are tumor necrosis factor a, endothelin 1 and nitric oxide. Typical symptom is an increase in dyspnea while in standing position, orthodeoxia. In orthodeoxia hypoxemia accentuates while the partial pressure of oxygen in arterial blood decreases by 5% or more. The blood flow distribution to the lungs is changed as the pulmonary vascular tone is altered. Diagnosis is based on the evidence of liver disease, hypoxemia and pulmonary vascular shunt detected by the so-called bubble test. Liver transplantation is currently the only efficient therapeutic option.

[Diffuse alveolar damage DAD and organizing pneumonia OP]. / Diffuusi alveolivaurio ja organisoituva pneumonia.

Acute or subactute pulmonary damage can be either idiopathic or resulting from a known cause. The most common histologic types are diffuse acute alveolar damage (DAD) and organizing pneumonia (OP). Various kinds of infection, pulmonary drug reactions or acute exacerbations of interstitial lung diseases may cause DAD, often requiring intensive care. High-resolution computed tomography (HRTT) of the lungs is the most important diagnostic examination. Surgical lung biopsy is performed for few patients.

Ultrastructural and chromosomal studies on manganese superoxide dismutase in malignant mesothelioma.

Mesothelioma represents an aggressive tumor type with high resistance to all treatment modalities. Its pathogenesis is strongly associated with exposure to asbestos fibers and probably with free radicals. One of the most important free radical scavenging enzymes, mitochondrial manganese superoxide dismutase (MnSOD), has been shown to be elevated in mesothelioma (K. Kahlos et al., 1998, Am. J. Respir. Cell Mol. Biol. 18:570-580). In the present study, we could detect intense ultrastructural accumulation of MnSOD in the mitochondrial compartment of malignant mesothelioma cells. There was no association between the immunohistochemical reactivity and the most common and functional polymorphic variant of MnSOD, the Ala to Val amino acid change at 9 position (16th amino acid from the beginning of the signal sequence), in the 31 mesothelioma cases investigated. Comparative genomic hybridization and fluorescence in situ hybridization did not reveal any changes in chromosome 6, where the MnSOD gene is located. Sequencing of the MnSOD promoter region in four mesothelioma cell lines showed similar nucleotide variables in the malignant and nonmalignant cells. Therefore, the intense expression of MnSOD in the mitochondria of mesothelioma cells does not appear be associated with any major chromosomal alterations or the polymorphism of MnSOD gene. Association with oxidative/nitrosative stress in mesothelioma using nitrotyrosine immunostaining pointed to a tendency for more intense reactivity in those mesotheliomas with higher MnSOD expression (P = 0.069).

Thioredoxin restores nitric oxide-induced inhibition of protein kinase C activity in lung endothelial cells.

We previously reported that exposure to exogenous nitric oxide (NO) causes diminished expression of thioredoxin/thioredoxin reductase, a critical component of the redox system that regulates the functions of redox-sensitive enzymes, receptors, and transcription factors. Here we examined the role of thioredoxin in NO-induced inhibition of protein kinase C (PKC) isoform(s) and potential interaction of PKC and thioredoxin in pulmonary artery endothelial cells (PAEC) in culture. Exposure to NO gas (8 ppm) significantly diminished the catalytic activity of the representative isoforms of the conventional, novel, and atypical PKCs alpha, epsilon, and zeta, respectively, in PAEC. Further examination of NO's effect on PKC-zeta revealed that NO-induced inhibition of the catalytic activity of PKC-zeta was time-dependent and regulated by a posttranscriptional mechanism. NO-induced loss of the catalytic activity of PKC-zeta was restored by incubation with the disulfide reducing agent dithiothreitol (DTT) as well as by purified thioredoxin or thioredoxin reductase. Confocal imaging studies revealed co-localization of PKC and thioredoxin in PAEC. These results indicate that: (1) NO-induced inhibition of PKC isoforms is associated with S-nitrosylation-mediated disulfide formation of active site thiols in PKC-zeta as the disulfide reducing agent DTT and/or the thioredoxin enzyme system restore PKC-zeta catalytic activity and (2) NO causes oxidation of endogenous thioredoxin as exogenous reduced thioredoxin or thioredoxin reductase are required to reduce thioredoxin and to restore the catalytic activity of PKC-zeta in PAEC.

Overexpression of gamma-glutamylcysteine synthetase in human malignant mesothelioma.

Mesothelioma is a fatal tumor resistant to all treatment modalities for reasons that are still unresolved. Glutathione (GSH)-associated pathways are induced by oxidants and cytotoxic drugs, and they are also involved in the progression and resistance of some tumor cells in vitro. The rate-limiting enzyme in GSH biosynthesis is gamma-glutamylcysteine synthetase (gamma GCS). However, the expression of this enzyme has not been systematically investigated in malignant tumors, and there are no studies of gamma GCS in biopsy specimens of malignant mesothelioma. We investigated the immunohistochemical distribution and expression of both subunits of gamma GCS in healthy pleural mesothelium, pleural mesothelioma tumor biopsy samples (34 cases), and mesothelioma cells in culture (7 cell lines). Nonmalignant mesothelium showed no immunoreactivity for either subunit in any of the cases. The heavy (catalytic) subunit of gamma GCS was highly immunostained in 29 and weakly positive in 5 cases. High-moderate and weak immunoreactivity of the light (regulatory) subunit of gamma GCS was found in 15 and 7 tumors, respectively, whereas 12 cases showed no reactivity. There was no correlation with either catalytic or regulatory subunit expression and patient survival. There was, however, a significant correlation between the heavy chain and multidrug resistance protein (MRP) 2 (P =.048), whereas no correlation was observed between the light chain and MRP1 or MRP2. Treatment of cultured mesothelioma cells with buthionine sulfoximine (BSO), to inhibit gamma GCS, significantly potentiated cisplatin-induced cytotoxicity mainly by nonapoptotic mechanism when assessed by counting the living cells, TUNEL (terminal deoxytransferase-mediated dUTP nick-end labeling) assay, and caspase-3 cleavage. In conclusion, gamma GCS is highly positive in most cases of malignant mesothelioma and may play an important role in the primary drug resistance of this tumor in vivo.

Modulation of DNA single-strand breaks by intracellular glutathione in human lung cells exposed to asbestos fibers.

We investigated the role of glutathione and nitric oxide synthase (NOS) in fiber-induced cell and DNA toxicity using alkaline (pH 13) single-cell gel electrophoresis (the Comet assay). Transformed cultured human pleural mesothelial (MeT-5A) cells and alveolar epithelial cells (A549) were exposed to crocidolite asbestos fibers (1-10 microg/cm(2)) in the presence of buthionine sulfoximine (BSO) or L-arginine-methyl ester (L-NAME). BSO inhibits gamma-glutamylcysteine synthetase (gamma-GCS) and causes glutathione depletion, and L-NAME inhibits nitric oxide generation. Studies were also conducted to assess the expression of the heavy and light subunits of gamma-GCS in human pleural mesothelium and bronchial epithelium in vivo and the induction of inducible NOS (iNOS) by asbestos fibers. Asbestos fibers caused DNA single-strand breaks, and the process was significantly enhanced by BSO (69% compared to the non-treated cells). A549 cells had a 3.5-fold glutathione content compared to MeT-5A cells, which was consistent with the higher resistance of these cells against oxidants and fibers. Flow cytometry of iNOS showed no change of iNOS by the fibers in either cell type in vitro. L-NAME had no effects on the DNA single-strand breaks in the Comet assay, either. Studies on lung biopsies showed that the immunoreactivities of both gamma-GCS subunits were very low in healthy human mesothelium in vivo. We conclude that glutathione may play an essential role in protecting intact cells against fiber-induced oxidative DNA alterations, and low gamma-GCS reactivity in pleural mesothelium may be associated with the high sensitivity of mesothelial cells to fiber-induced toxicity.