Oncocytic mania: a review of oncocytic lesions throughout the body.

Oncocytic lesions are characterized pathologically by an abundance of oncocytes, that is by enlarged, eosinophilic, and finely granular cells enriched in mitochondria. They can arise in numerous organs and tissues, often in endocrine glands, and have been associated with hyperplasia, autoimmunity, and neoplasia. The causes and mechanisms that transform a normal cell into an oncocyte remain to be elucidated. Aim of this article is to review the most common oncocytic lesions, highlighting their key pathological features and clinical significance.

Thirty robotic adrenalectomies: a single institution's experience.

BACKGROUND: Robotic adrenalectomy is a minimally invasive alternative to traditional laparoscopic adrenalectomy. To date, only case reports and small series of robotic adrenalectomies have been reported. This study presents a single institution's series of 30 robotic adrenalectomies, and evaluates the procedure's safety, efficacy, and cost. METHODS: Thirty patients underwent robotic adrenalectomy at the Johns Hopkins Hospital between April 2001 and January 2004. Patient morbidity, hospital length of stay, operative time, and conversion rate to traditional laparoscopic or open surgery are presented. Improvement in operative time with surgeon experience is evaluated. Hospital charges are compared to charges for traditional laparoscopic and open adrenalectomies performed during the same time period. RESULTS: Median operative time was 185 min. Patient morbidity was 7%. There were no conversions to traditional laparoscopic or open surgery. The median hospital stay was 2 days. Operative time improved significantly by 3 min with each operation. Hospital charges for robotic adrenalectomy (12,977 dollars) were not significantly different than charges for traditional laparoscopic (11,599 dollars) or open adrenalectomy (14,600 dollars). CONCLUSIONS: Robotic adrenalectomy is a safe and effective alternative to traditional laparoscopic adrenalectomy.

Antioxidants increase lipopolysaccharide-stimulated TNF alpha release in murine macrophages: role for altered TNF alpha mRNA stability.

Through their effects on gene activation, antioxidants have been reported to modulate cellular expression of several proinflammatory cytokines and adhesion molecules, an effect mediated by preventing translocation of the transcription factor nuclear factor-kappa B (NF-kappa B) into the nucleus. In addition, modulation of the intracellular redox state may have profound effects on cell activation and subsequent gene expression distinct from effects on NF-kappa B; these effects may account for the divergent effects of antioxidants on cytokine gene expression in various reports. In the present studies, we evaluated the effect of the antioxidant, pyrrolidine dithiocarbamate (PDTC), on murine and human myeloid cell tumor necrosis factor alpha (TNF alpha) gene and protein expression. PDTC-enhanced LPS-induced TNF alpha secretion in cells derived from a murine macrophage cell line (J774.1), as well as in primary murine peritoneal macrophages by 4-fold. The effect was both stimulus and species dependent, as TNF alpha secretion was attenuated by PDTC in human THP-1 cells and in murine cells stimulated with zymosan. Northern analysis demonstrated that these effects were evident at the level of mRNA expression. Electrophoretic mobility shift assays confirmed the down-regulatory effect of PDTC on human myeloid NF-kappa B activation, whereas in murine cells no such inhibitory effect was evident. Evaluation of TNF alpha mRNA stability in murine cells demonstrated that the potentiating effect of PDTC on TNF alpha mRNA expression was due to an increase in mRNA half-life from 37 to 93 min. Together, these data suggest that the effect of antioxidants on gene expression are both stimulus and species dependent and illustrate a novel mechanism whereby redox manipulation might modulate TNF alpha expression in vivo.

Adrenal cortical carcinoma.

Adrenal cortical carcinoma is a rare endocrine tumor for which complete surgical resection is the only potentially curative treatment. Accurate preoperative evaluation (biochemical and radiographic) of the patient who presents with an adrenal mass maximizes the opportunity for the patient to undergo a complete, margin-negative resection of the primary tumor, which is the most powerful prognostic variable for long-term survival. The response to chemotherapy or mitotane is modest in patients with advanced disease. Hopefully, an improved understanding of the molecular pathogenesis of this challenging tumor will lead to the development of more effective therapies in the future.

Neoadjuvant chemoradiotherapy for adenocarcinoma of the pancreas: treatment variables and survival duration.

BACKGROUND: For patients with potentially resectable pancreatic cancer, the poor outcome associated with resection alone and the survival advantage demonstrated for combined-modality therapy have stimulated interest in preoperative chemoradiotherapy. The goal of this study was to analyze the effects of different preoperative chemoradiotherapy schedules, intraoperative radiation therapy, patient factors. and histopathologic variables on survival duration and patterns of treatment failure in patients who underwent pancreaticoduodenectomy for adenocarcinoma of the pancreatic head. METHODS: Data on 132 consecutive patients who received preoperative chemoradiation followed by pancreaticoduodenectomy for adenocarcinoma of the pancreatic head between June 1990 and June 1999 were retrieved from a prospective pancreatic tumor database. Patients received either 45.0 or 50.4 Gy radiation at 1.8 Gy per fraction in 28 fractions or 30.0 Gy at 3.0 Gy per fraction in 10 fractions with concomitant infusional chemotherapy (5-fluorouracil, paclitaxel, or gemcitabine). If restaging studies demonstrated no evidence of disease progression, patients underwent pancreaticoduodenectomy. All patients were evaluated with serial postoperative computed tomography scans to document first sites of tumor recurrence. RESULTS: The overall median survival from the time of tissue diagnosis was 21 months (range 19-26, 95%CI). At last follow-up, 41 patients (31%) were alive with no clinical or radiographic evidence of disease. The survival duration was superior for women (P = .04) and for patients with no evidence of lymph node metastasis (P = .03). There was no difference in survival duration associated with patient age, dose of preoperative radiation therapy, the delivery of intraoperative radiotherapy, tumor grade, tumor size, retroperitoneal margin status, or the histologic grade of chemoradiation treatment effect. CONCLUSION: This analysis supports prior studies which suggest that the survival duration of patients with potentially resectable pancreatic cancer is maximized by the combination of chemoradiation and pancreaticoduodenectomy. Furthermore, there was no difference in survival duration between patients who received the less toxic rapid-fractionation chemoradiotherapy schedule (30 Gy, 2 weeks) and those who received standard-fractionation chemoradiotherapy (50.4 Gy, 5.5 weeks). Short-course rapid-fractionation preoperative chemoradiotherapy combined with pancreaticoduodenectomy, when performed on accurately staged patients, maximizes survival duration and is associated with a low incidence of local tumor recurrence.

Adrenal cortical carcinoma.

Adrenal cortical carcinoma is a rare endocrine tumor, and complete surgical resection is the only potentially curative treatment. Accurate preoperative biochemical and radiographic evaluation of the patient who presents with an adrenal mass optimizes patient management and facilitates a complete margin-negative resection of the primary tumor--the most important prognostic variable for long-term survival. Response to mitotane or chemotherapy is modest in patients with advanced disease. It is hoped that an improved understanding of the molecular pathogenesis of this challenging tumor will lead to the development of novel treatment strategies.

Limitations of size as a criterion in the evaluation of adrenal tumors.

BACKGROUND: Size has been considered to be the single best predictor of malignancy in adrenal neoplasms that have been identified incidentally. However, small adrenal cortical cancers have been reported from multiple centers. METHODS: We retrospectively evaluated the value of tumor size and other clinical parameters in the prediction of the presence of adrenal malignancy. RESULTS: The records of 117 patients who underwent evaluation for tumors of the adrenal gland were reviewed. The median tumor size of the adrenal cortical carcinomas (n = 38 carcinomas) was 9.2 cm (range, 1.7-30 cm); 5 cancers (13.5%) were smaller than 5.0 cm. The median overall size of the benign tumors, excluding pheochromocytomas, was 4.0 cm (n = 38 carcinomas); 10 benign tumors (26%) were larger than 5.0 cm. The imaging features of 4 of 5 small adrenal cancers predicted malignancy; the remaining patients had hormonally functioning tumors. The imaging features of 7 of 10 large benign adrenal tumors predicted benign histologic features, including 5 of 5 myelolipomas. CONCLUSIONS: Although size remains a good predictor of the histologic features and clinical behavior of adrenal neoplasms, both small adrenal cortical cancers and large benign tumors occur with measurable frequency. High-quality imaging studies may be helpful in the identification of relatively small adrenal cancers and of characteristic benign lesions that may be selectively followed.

Relative contributions of technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay to the surgical management of hyperparathyroidism.

HYPOTHESIS: Technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay have been used to permit a directed operation in patients with hyperparathyroidism. We hypothesized that the coordinated use of these techniques might be particularly useful in patients who require a second operation for hyperparathyroidism. DESIGN: Retrospective analysis was performed to determine the specific contribution of these technologies to the surgical management of patients with hyperparathyroidism who underwent evaluation by at least 2 of these techniques between April 1996 and October 1999. SETTING: Patients were evaluated and treated by an endocrine tumor surgery group within a tertiary care referral center. PATIENTS: Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and/or the rapid parathyroid hormone assay was performed in 32 patients. RESULTS: Twenty-eight of 32 patients had primary hyperparathyroidism, 3 had multiple endocrine neoplasia type 1, and 1 had secondary hyperparathyroidism. The surgical procedure was an initial cervical exploration in 19 and a second operative procedure in 13. Parathyroidectomy was successful in all patients. A directed anatomic operation was performed in 24 patients, including 11 patients who underwent second operative procedures and 9 patients who underwent minimally invasive procedures under local anesthesia. A directed operation was facilitated by sestamibi scan in 22 of 24 patients, intraoperative gamma probe detection in 5 of 23 patients, and the rapid parathyroid hormone assay in 15 of 15 patients. CONCLUSIONS: Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay allows for successful directed reoperative parathyroidectomy; a minimally invasive procedure may be performed in selected patients.

Screening for MEN1 mutations in patients with atypical endocrine neoplasia.

BACKGROUND: Most patients from typical multiple endocrine neoplasia type 1 (MEN1) kindreds harbor mutations in the MEN-1 gene, MEN1. We hypothesized that some patients with atypical endocrine neoplasia would also have mutations in MEN1. METHODS: DNA sequencing analysis of mutations in the coding region of MEN1 was performed with genomic DNA obtained from peripheral blood lymphocytes in a total of 21 patients who had: typical MEN1 (n = 8), clinical features suggestive of MEN1 but without a family history of endocrinopathy (n = 7), and atypical endocrine neoplasia and a family history of endocrinopathy suggestive of MEN1 (n = 6). RESULTS: All 8 patients with typical MEN1 had mutations in MEN1. None of the 7 patients with features of MEN1, but without a family history of endocrinopathy, had a MEN1 mutation. In contrast, 4 of 6 patients with atypical endocrine neoplasia that included components of MEN1 and a family history of endocrinopathy had mutations in MEN1, including 2 patients with pheochromocytoma. CONCLUSIONS: Genomic mutations in MEN1 may frequently be identified in patients with atypical endocrine neoplasia, especially in the setting of a family history of endocrinopathy. Atypical presentations of MEN1 may include pheochromocytoma.

Murine hepatitis virus strain 3 induces the macrophage prothrombinase fgl-2 through p38 mitogen-activated protein kinase activation.

The clinical syndrome of acute liver failure produced by fulminant viral hepatitis can be reproduced in mice by infection with murine hepatitis virus strain 3 (MHV-3). Although it is clear that MHV-3-induced hepatitis depends upon macrophage activation and the expression of a specific prothrombinase, fgl-2, the signaling pathways involved in virally stimulated cell activation are unclear. Since we had previously found that MHV-3 induces the tyrosine phosphorylation of cellular proteins, we investigated the roles of the mitogen-activated protein kinase (MAPK) proteins. In a series of Western blots, immunoprecipitation and in vitro kinase assay studies, we found that both the extracellular signal-related kinase (ERK) and p38 MAPK proteins are tyrosine-phosphorylated and activated following exposure of murine peritoneal exudative macrophages (PEM) to MHV-3. Although p38 phosphorylation and activity are induced soon after MHV-3 exposure, peaking by 1-5 min, ERK phosphorylation and activity increase more gradually, peaking at 20-30 min and gradually fading thereafter. Interestingly, whereas selective p38 inhibition with SB203580 (1-20 microM) abolished the virally stimulated induction of fgl-2 mRNA, protein, and functional activity, selective ERK inhibition with PD98059 (1-50 microM) limited fgl-2 functional activity but had little to no effect on fgl-2 mRNA or protein levels. Moreover, whereas inhibition of ERK had no effect on p38 activity, p38 inhibition consistently increased MHV-3-induced ERK activity. To ensure that these pathways were relevant in vivo, MHV-3 was injected intraperitoneally, and peritoneal exudative macrophages were collected. Again, MHV-3 exposure led to increased p38 and ERK tyrosine phosphorylation. These data argue that MHV-3 induces tightly interconnected ERK and p38 MAPK cascades in the macrophage both in vitro and in vivo. Although the ERK and p38 MAPK proteins have discordant effects at the level of fgl-2 expression, both converge at the level of its activity, suggesting that targeted MAPK inhibition may ultimately be useful in the modulation of viral hepatitis.

The glutathione depleting agent diethylmaleate prolongs renal allograft survival.

INTRODUCTION: Intercellular adhesion molecule 1 (ICAM-1) plays an important role in mediating allograft rejection through its role in cellular trafficking and as an important costimulatory signal mediating T cell activation. We have previously reported that systemic administration of the glutathione (GSH) depleting agent diethylmaleate (DEM) prevents upregulation of ICAM-1 in various inflammatory models, suggesting that this agent may offer benefit in preventing allograft rejection. Thus we evaluated the effects of DEM in a murine model of renal transplantation. METHODS: Kidneys from C57BL/6 mice were transplanted into MHC incompatible C3H mice. Donors were treated with DEM 1 h prior to sacrifice, whereas recipients received DEM 1 h following transplantation. Animals were followed until the time of death. In separate studies, renal ICAM-1 mRNA expression was evaluated by polymerase chain reaction and the CD4(+) T cell cytokine profile evaluated in a mixed lymphocyte reaction using C3H responder splenocytes and C57BL/6 stimulator cells. RESULTS: Pretreatment with DEM increased survival from 18.9 +/- 3.6 to 30.6 +/- 10 days (P < 0.05). This increase in survival was associated with a reduction in renal ICAM-1 mRNA expression. Mixed lymphocyte cultures derived from animals pretreated with DEM demonstrated a reduction in the Th1 cytokines IFN-gamma and IL-2 and an increase in the Th2 cytokines IL-4 and IL-10. CONCLUSION: Administration of DEM with consequent systemic GSH depletion significantly reduces allograft ICAM-1 expression and prolongs graft survival. Although speculative, a shift from a Th1 to a Th2 cytokine response raises the possibility that tolerance induction plays a role in prolonged allograft survival.

Thiol-mediated regulation of ICAM-1 expression in endotoxin-induced acute lung injury.

The intracellular redox state regulates several aspects of cell function, suggesting that strategies directed toward altering the cellular redox state may modulate cell activation in inflammatory states. As the most abundant intracellular thiol, glutathione plays a critical role as an intracellular redox buffer. Using diethylmaleate (DEM) as a glutathione-depleting agent, we evaluated the effects of GSH depletion in a rodent model of polymorphonuclear neutrophil (PMN)-dependent acute lung injury. Rats received 500 microg of LPS by intratracheal challenge, inducing a 5.5-fold increase in lung permeability and sixfold increase in lung PMN content. Pretreatment with DEM prevented the LPS-induced increase in lung PMN influx and lung permeability. Northern analysis and immunohistochemical studies suggest that this effect may be mediated by preventing up-regulation of lung ICAM-1 mRNA and protein expression. This effect is specific to ICAM-1, because lung cytokine-induced neutrophil chemoattractant and TNF-alpha mRNA levels are unaffected. This finding is not unique to the lung, because a similar effect on PMN influx was recapitulated in a rodent model of chemical peritonitis. Further, in vitro studies demonstrated that pretreatment of HUVEC monolayers with DEM prevented both ICAM-1 up-regulation and PMN transendothelial migration. These data indicate the presence of a thiol-sensitive mechanism for modulating ICAM-1 gene expression and suggest a potential novel therapeutic strategy for diseases characterized by PMN-mediated tissue injury.

Pyrrolidine dithiocarbamate attenuates endotoxin-induced acute lung injury.

Lung injury in the acute respiratory distress syndrome (ARDS) is in part due to polymorphonuclear leukocyte (PMN)-mediated oxidative tissue damage. By means of nuclear factor-kappaB (NF-kappaB) activation, oxidants may also induce several genes implicated in the inflammatory response. The dithiocarbamates are antioxidants with potent inhibitory effects on NF-kappaB. We postulated that the pyrrolidine derivative pyrrolidine dithiocarbamate (PDTC) would attenuate lung injury following intratracheal challenge with endotoxin (lipopolysaccharide; LPS) through its effect as an antioxidant and inhibitor of gene activation. Rats were given PDTC (1 mmole/kg) by intraperitoneal injection, followed by intratracheal administration of LPS. The transpulmonary flux of [125I] albumin (permeability index; PI) was used as a measure of lung injury. Northern blot analysis of total lung RNA was performed to assess induction of tumor necrosis factor-alpha (TNF-alpha) and intercellular adhesion molecule-1 (ICAM-1) messenger RNA (mRNA) as markers of NF-kappaB activation. The effect of in vivo treatment with PDTC on LPS-induced NF-kappaB DNA binding activity in macrophage nuclear extracts was evaluated with the electrophoretic mobility shift assay (EMSA). PDTC administration attenuated LPS-induced increases in lung permeability (PI = 0.16 +/- 0.02 for LPS versus 0.06 +/- 0.01 for LPS + PDTC; P < 0.05). TNF-alpha levels and PMN counts in bronchoalveolar lavage fluid (BALF) were unaffected, as were whole-lung TNF-alpha and ICAM-1 mRNA expression. PDTC had no effect on NF-kappaB activation as evaluated with EMSA. PDTC reduced lung lipid peroxidation as assessed by levels of malondialdehyde, without reducing neutrophil oxidant production. We conclude that PDTC attenuates LPS-induced acute lung injury. This effect occurs independently of any effect on NF-kappaB. PDTC reduces oxidant-mediated cellular injury, as demonstrated by a reduction in the accumulation of malondialdehyde. Administration of PDTC may represent a novel approach to limiting neutrophil-mediated oxidant injury.

The role of tyrosine phosphorylation in lipopolysaccharide- and zymosan-induced procoagulant activity and tissue factor expression in macrophages.

The expression of surface procoagulants by exudative macrophages represents an important mechanism underlying local fibrin deposition at sites of extravascular inflammation. The present studies investigated the contribution of tyrosine phosphorylation to the generation of macrophage procoagulant activity (PCA) and tissue factor expression in response to proinflammatory stimuli. Both lipopolysaccharide (LPS) and zymosan rapidly stimulated tyrosine phosphorylation in elicited murine peritoneal macrophages. This effect was prevented by the tyrosine kinase inhibitors genistein and herbimycin and augmented by the addition of the phosphotyrosine phosphatase inhibitor vanadate. The vanadate-mediated rise in phosphotyrosine accumulation was abrogated by the use of diphenylene iodonium, an inhibitor of the respiratory burst oxidase, suggesting a role for peroxides of vanadate as contributors to the tyrosine phosphorylation. This notion was supported by the finding that vanadyl hydroperoxide markedly increased the accumulation of phosphotyrosine residues. To define the role of tyrosine phosphorylation in the induction of macrophage PCA by LPS, the effects of tyrosine kinase inhibition by genistein and herbimycin were investigated. Both agents inhibited the expression of macrophage PCA. Further, Northern blot analysis with the cDNA probe for murine tissue factor indicated that the inhibition occurred at the mRNA level or earlier. Since vanadate augmented phosphotyrosine accumulation, it was hypothesized that it might enhance generation of macrophage products. However, vanadate reduced induction of PCA in response to LPS. By contrast, vanadate augmented basal prostaglandin E2 (PGE2) release and stimulated PGE2 release by macrophages. Indomethacin prevented the increase in PGE2 but only partially restored normal levels of PCA. The effect of vanadate on tissue factor expression appeared to be posttranscriptional. These studies thus demonstrate, by functional Western blotting and Northern blotting techniques, that tyrosine phosphorylation plays a role in the regulation of macrophage PCA and tissue factor expression in response to proinflammatory stimuli.

VLA-4 integrin cross-linking on human monocytic THP-1 cells induces tissue factor expression by a mechanism involving mitogen-activated protein kinase.

Adhesion molecules such as VLA-4 are important not only for monocyte adhesion to extracellular matrix proteins, but also for subsequent cell activation. Monocyte adherence to fibronectin or engagement of VLA-4 has been demonstrated to stimulate production of potent inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1, and the procoagulant tissue factor protein. However, the intracellular signaling cascades leading to gene expression have not been elucidated. Using the human monocytic THP-1 cell line, VLA-4 cross-linking by monoclonal antibodies directed against its alpha4 and beta1 subunits produced a time-dependent increase in tyrosine phosphorylation of a broad range of cellular proteins. Using Western blot analysis directed against the phosphorylated form of the extracellular signal-related kinase (ERK) mitogen-activated protein (MAP) kinase proteins, as well as immunoprecipitation and in vitro kinase assays, we found that VLA-4 cross-linking increased ERK1/ERK2 tyrosine phosphorylation and activity. In conjunction, integrin cross-linking also increased NF-kappaB nuclear translocation and 4-h expression of tissue factor. Inhibition of tyrosine kinase activity with genistein (10 microg/ml) as well as selective MAP kinase inhibition with the MEK-1 inhibitor PD98059 abolished the VLA-4-dependent ERK tyrosine phosphorylation, inhibited NF kappaB nuclear binding, and abrogated tissue factor expression induced by both VLA-4 cross-linking and adhesion to fibronectin in THP-1 cells and human peripheral blood monocytes. These studies point to the involvement of the MAP kinase pathway in the activation of monocytic cells during transmigration to inflammatory sites.

Prevention of endotoxin-induced mortality by antitissue factor immunization.

BACKGROUND: Microvascular thrombosis with intravascular fibrin deposition is a characteristic pathologic alteration during endotoxic shock. This effect is predominantly mediated by expression of the cellular procoagulant tissue factor by endothelial cells and cells of monocyte or macrophage lineage, resulting in acceleration of the coagulation cascade and fibrin deposition. OBJECTIVE: To determine whether modulation of this response by treatment with an antitissue factor antibody might have beneficial effects. DESIGN: A polyclonal antibody to murine tissue factor was prepared by injecting rabbits with a synthesized peptide sequence of murine tissue factor. To determine the activity of the antibody, elicited murine peritoneal macrophages were treated for 4 hours with 10-micrograms/mL lipopolysaccharide (LPS), and procoagulant activity was determined via a clotting assay (milliunits of activity per 10(6) macrophages). RESULTS: The tissue factor antibody abrogated LPS-induced macrophage procoagulant activity, confirming activity of the antibody (macrophages, 236 +/- 28 mU/10(6) macrophages; macrophages/LPS, 3801 +/- 190* mU/10(6) macrophages; macrophages/LPS/alpha-tissue factor, 753 +/- 92* mU/10(6) macrophages; n = 3; the asterisk indicates P < .05 by an analysis of variance). Additionally, antibody-protein affinity was confirmed by Western blot analysis. Having determined the activity of the antibody in vitro, we tested its efficacy in vivo in a lethal endotoxemia model. Mice were immunized with 200 microL of antiserum intraperitoneally 2 hours before injection with 250 micrograms of LPS intraperitoneally and 24 hours later. Control animals received 200 microL of saline solution. All animals initially exhibited lethargy and piloerection, characteristic of the predicted response to LPS. However, immunized animals had a significantly (P < .05) reduced mortality compared with control animals. Fibrinogen levels were significantly (P < .05) higher in the immunized mice, suggesting decreased consumption of coagulation factors, a finding consistent with an antitissue factor effect. Further, plasma tumor necrosis factor levels 90 minutes after LPS injection were similar in both groups, suggesting normal induction of the cytokine cascade. CONCLUSIONS: Modulation of microvascular fibrin deposition by abrogating tissue factor-mediated coagulation significantly (P < .05) improved survival in this model without attenuating the initiation of the cytokine cascade. These findings suggest a pathogenic role for coagulation in the induction of acute organ injury during sepsis.

Integrin engagement induces monocyte procoagulant activity and tumor necrosis factor production via induction of tyrosine phosphorylation.

The specific interactions of monocytes with the endothelial cell surface and underlying extracellular matrix proteins are mediated via surface adhesion molecules, particularly those of the integrin family. Recent studies have suggested that these interactions may be important in modulating gene expression and thus cell function. We tested the hypothesis that engagement of surface integrins on monocytes, simulating integrin/ligand interactions, might modulate monocyte procoagulant activity (PCA) and tumor necrosis factor (TNF) production. Mononuclear cells from pooled rat blood were incubated with a mouse anti-rat VLA-4 (beta1 integrin) antibody (20 microg/ml), or a mouse anti-rat Mac-1 (beta2 integrin) antibody (20 microg/ml), washed, and then cell surface integrins were crosslinked with a goat anti-mouse IgG antibody (20 microg/ml). After incubation at 37 degrees C for 4 hr, supernatants were aspirated and tested for TNF by ELISA and cell pellets were freeze-thawed for measurement of PCA in a one-stage clotting assay. Crosslinking of the beta1 integrin VLA-4 or the beta2 integrin Mac-1 on monocytes significantly increased cellular procoagulant activity and TNF production (PCA mU/10(6) cells: control, 30 +/- 3; anti-VLA-4, 131 +/- 33; anti-Mac-1, 152 +/- 29; TNF pg/ml: control, 60 +/- 4; anti-VLA-4, 548 +/- 38; anti-Mac-1, 701 +/- 134). Since tyrosine phosphorylation participates in macrophage signaling, we studied whether integrin ligation might stimulate this pathway. By Western blot analysis, crosslinking of the integrin VLA-4 was shown to induce the accumulation of tyrosine phosphorylated proteins, an effect which was inhibited by the tyrosine kinase inhibitor genistein. In parallel studies, genistein inhibited cellular PCA. Considered together, these studies suggest that monocyte activation following integrin engagement is induced by stimulation of tyrosine kinase activity. Thus, in addition to mediating cell adhesion, surface integrins may play a role in modulating cell function at sites of inflammation.

Thiol-mediated redox regulation of neutrophil apoptosis.

BACKGROUND: Intracellular glutathione, an endogenous antioxidant, protects cellular function against oxidative stress. Because oxidative stress has been implicated in neutrophil apoptosis, we hypothesized that reduced thiol levels may induce apoptosis through an alteration in cellular redox state. METHODS: Human polymorphonuclear leukocytes (PMNs), were incubated with medium or with increasing concentrations of the reduced glutathione (GSH)-depleting agents diethylmaleate and diamide and buthionine sulfoximine, an inhibitor of GSH synthesis. Apoptosis was assessed by means of flow cytometry with propidium iodide DNA staining and confirmed morphologically. GSH was measured colorimetrically, and tyrosine phosphorylation was assessed by means of immunoblotting. RESULTS: Diethylmaleate and diamide induced a dose-dependent reduction in GSH and a corresponding increase in PMN apoptosis. This effect could be reversed with N-acetylcysteine, suggesting that diethylmaleate induces apoptosis through the depletion of GSH. The antioxidant pyrolidine dithiocarbamate had no effect. Because oxidants can mediate intracellular signaling via tyrosine phosphorylation, we therefore evaluated the effects of the tyrosine kinase inhibition on diethylmaleate-induced PMN apoptosis. Both genistein and herbimycin A reduced diethylmaleate-induced apoptosis and tyrosine phosphorylation. CONCLUSIONS: Sulfhydryl oxidation by diethylmaleate alone induces apoptosis, providing evidence of a redox-sensitive, thiol-mediated pathway of apoptosis. Furthermore, tyrosine phosphorylation appears to play an important role in this process. Because apoptosis is a critical mechanism regulating PMN survival in vivo, manipulation of PMN intracellular thiols may represents a novel therapeutic target for the regulation of cellular function.

Diethylmaleate attenuates endotoxin-induced lung injury.

BACKGROUND: Alterations in the cellular redox state play a critical role in cell signaling and cell activation, suggesting that administration of sulfhydryl-reactive agents may have important modulatory effects on the inflammatory response. We postulated that intracellular thiol depletion may attenuate the pulmonary inflammatory response after intratracheal administration of endotoxin (LPS) and that this attenuation would supersede the reduction in antioxidant defenses associated with depletion of the endogenous antioxidant, glutathione. METHODS: Sprague Dawley rats were administered diethylmaleate (6 mmol/kg intraperitoneally), a rapidly acting glutathione-depleting agent, followed by intratracheal administration of LPS. Lung injury was assessed by measuring the transpulmonary flux of 125-I albumin and expressed as a permeability index. RESULTS: Administration of diethylmaleate reduced lung glutathione levels from 1310 +/- 114 to 185 +/- 48 nmol/gm. This was associated with a reduction in the permeability index after LPS treatment (LPS, 0.22 +/- 0.03 versus LPS + diethylmaleate, 0.03 +/- 0.01). Bronchoalveolar lavage fluid polymorphonuclear neutrophil counts were markedly reduced in animals pretreated with diethylmaleate (LPS, 90.5 +/- 24 x 10(6) versus LPS + diethylmaleate, 1.9 +/- 0.4 x 10(6)). Peripheral blood polymorphonuclear neutrophils isolated from animals treated with diethylmaleate had equivalent chemotactic responses to n-formyl-methionyl-leucyl-phenylalanine and normal up-regulation of CD11b as determined by flow cytometry. Levels of bronchoalveolar lavage fluid tumor necrosis factor-alpha were unaffected. CONCLUSIONS: Diethylmaleate attenuates LPS-induced lung injury through a reduction in lung polymorphonuclear neutrophil sequestration. Normal peripheral blood neutrophil chemotactic responses and CD11b expression suggest that thiol depletion might mediate this effect through inhibition of endothelial cell adhesion molecule activity.

Induction of macrophage procoagulant activity by murine hepatitis virus strain 3: role of tyrosine phosphorylation.

The induction of a unique macrophage procoagulant molecule by murine hepatitis virus strain 3 correlates with the severity of viral hepatitis. The role of tyrosine phosphorylation in the signalling pathway leading to procoagulant expression was studied. Murine hepatitis virus strain 3 initiated a rapid increase in phosphotyrosine accumulation. Tyrosine kinase inhibition precluded this increase and abrogated expression of the virus-induced procoagulant mouse fibrinogen-like protein (musfiblp) gene. These findings suggest that manipulation of this signalling pathway in vivo might represent a novel approach to treating this disease.