Cardiac surgery increases the activity of matrix metalloproteinases and nitric oxide synthase in human hearts

OBJECTIVES

Heart function is variably impaired after cardiopulmonary bypass. We hypothesized that, similar to other myocardial injury states, cardiopulmonary bypass leads to enhanced activity of nitric oxide synthase and matrix metalloproteinases.

METHODS

We obtained right atrial biopsy specimens and plasma samples at the onset and termination of cardiopulmonary bypass in 10 patients. Biopsy specimens were analyzed for nitric oxide synthase activity by using a citrulline assay, whereas plasma and tissue were analyzed for matrix metalloproteinase-9 and matrix metalloproteinase-2 activity by using zymography. Tissue inhibitor of metalloproteinase-4 was analyzed by means of Western blotting. The cellular expression of inducible nitric oxide, endothelial nitric oxide synthase, matrix metalloproteinase-2, and matrix metalloproteinase-9 was determined in right atrial biopsy samples from 3 additional patients by using the appropriate conjugated antibodies.

RESULTS

Nitric oxide synthase activity increased from the beginning to the end of bypass (4.46 +/- 1.07 vs 16.77 +/- 4.86 pmol citrulline/mg of protein per minute, respectively; P =.018). Pro-matrix metalloproteinase-9 activity increased in hearts (199 +/- 41 vs 660 +/- 177 density units/mg protein; P =.008) and plasma (14.1 +/- 4.6 vs 52.2 +/- 5.9 density units/mg protein; P =.008). Pro-matrix metalloproteinase-2 activity increased in the heart (201 +/- 23 vs 310 +/- 35 density units/mg protein, P <.05) but not in plasma. Tissue inhibitor of metalloproteinase-4 expression in the heart decreased (1574 +/- 280 vs 864 +/- 153 density units, P =.014).

CONCLUSIONS

Cardiopulmonary bypass activates enzymes mediating acute inflammation and organ injury (ie, nitric oxide synthase, matrix metalloproteinase-9, and matrix metalloproteinase-2). Decreased tissue inhibitor of metalloproteinase-4 expression allows relatively unopposed increases in matrix metalloproteinase tissue activity. We postulate that these changes play a role in the pathogenesis of heart dysfunction after bypass surgery.

Ultrastructural and molecular changes in the left and right ventricular myocardium associated with ascites syndrome in broiler chickens raised at low altitude

The present study examines ultrastructural and molecular changes in ventricular myocardium associated with ascites cases in fast-growing broilers raised at low altitude. Extensive ultrastructural lesions were seen in the left and right ventricular myocardium of broilers with fulminant heart failure and ascites. Significant changes included lesions in the myofibril contractile apparatus, altered mitochondria, marked reduction in the myofibril component, and changes in the extracellular matrix (ECM) architecture. No lesions were observed in hearts of slow growing broilers, but mild to moderate changes (predominantly in the left ventriculum) were apparent in the hearts from some clinically normal, fast-growing broilers. SDS-PAGE profiles of washed myofibrils showed several distinctly different bands in preparations from left ventricular myocardium of ascitic birds. Western blot analysis of these samples revealed several fragments of myosin heavy chain, M-protein, and titin. Based on gelatinolytic activity, matrix metalloproteinases (MMP) in the cytosolic fraction of ventricular myocardium homogenates were identified as MMP-2. The relative activity of this enzyme appears to be considerably higher in preparations from broilers, particularly in the preparations from the left ventriculum of fast-growing broilers, in comparison to leghorns or slow growing broilers. The nature and distribution of the changes in the heart indicate that chronic cardiomyopathic process in the left ventricular myocardium occurs during the development of ascites. It is postulated that progressive deterioration of the left heart pump function caused by initial lesions in the left ventricular myocardium is a significant factor in the development of pulmonary hypertension and the pathogenesis of ascites in broilers raised at low altitude.

Villous trophoblasts cultured on semi-permeable membranes form an effective barrier to the passage of high and low molecular weight particles

An effective in vitro model of the placental villous syncytium cultured on semi-permeable substrata is essential for studies of infectious pathogen transmission from mother to fetus. Current models using amniotic membranes or thinner artificial membranes show significant leakage, suggesting disruption of tight junctions or the presence of gaps between syncytial units. Such disruption and discontinuity of trophoblast cultures are probably the result of high stromal cell contamination, poor viability and lack of proliferation in culture. We have successfully cultured confluent layers of tight-junctioned syncytium on semi-permeable insert membranes using highly viable purified cytotrophoblasts and an alternating multiple seeding and differentiation technique. Using criteria including transepithelial diffusion of high and low molecular weight substances, electrical resistance and directional secretion of the matrix metalloproteinase, MMP-9, we demonstrate that these cultures form effective and functional physical barriers that can be maintained for up to 1 month.

Differential expression of matrix metalloproteinases and the tissue inhibitor in human milk

There are differences in the temporal expression of MMP-2 and TIMP-4 in human milk from Day 1 to 30 postpartum in healthy mothers of term pregnancies: (i) MMP-2 activity peaked at Day 1 (colostrum) then exponentially decreased afterwards; and (ii) The expression of TIMP-4 was maximal at Day 7 and persisted thereafter. From our preliminary findings, the differential expression of MMP and the tissue inhibitor in human milk may be related to the protective action of human milk.

Matrix metalloproteinase 2 in tumor cell-induced platelet aggregation: regulation by nitric oxide

A correlation exists between the ability of tumor cells to aggregate platelets and their tendency to metastasize. Tumor cell-induced platelet aggregation (TCIPA) facilitates the embolization of the vasculature with tumor cells and the formation of metastatic foci. It is well documented that matrix metalloproteinases (MMPs) play an integral part in tumor spread and the metastatic cascade. Therefore, we have examined the role of MMPs during TCIPA and its regulation by nitric oxide (NO) in vitro. Human HT-1080 fibrosarcoma and A549 lung epithelial cancer cells induced TCIPA in a concentration-dependent manner that was monitored by aggregometry. This aggregation resulted in the release of MMIP-2 from platelets and cancer cells, as measured by zymography. HT-1080 cells released significantly more MMP-2 than A549 cells and were more efficacious in inducing TCIPA. Inhibition of MMP-2 with phenanthroline (1-1000 microM), a synthetic inhibitor of MMPs, and by neutralizing anti-MMIP-2 antibody (10 microg/ml) reduced TCIPA induced by HT-1080 cells. TCIPA was abolished by simultaneous inhibition of platelet function with acetylsalicylic acid (100 microM; thromboxane pathway inhibitor), apyrase (250 microg/ml; ADP pathway inhibitor), and phenanthroline. NO donors such as S-nitroso-n-acetylpenicillamine and S-nitrosoglutathione (both at 0.01-100 microM) inhibited TCIPA and MMP-2 release from platelets and tumor cells. The inhibitory actions of S-nitroso-n-acetylpenicillamine and S-nitrosoglutathione were reversed by 1H-[1,2,4]oxadiazole[4,3]quinoxalin-1-one (0.01-30 microM), a selective inhibitor of the soluble guanylyl cyclase. We conclude that (a) human fibrosarcoma cells aggregate platelets via mechanism(s) that are mediated, in part, by MMP-2; (b) NO inhibits TCIPA, in part, by attenuating the release of MMP-2; and (c) these effects of NO are cGMP-dependent.

Polarized release of matrix metalloproteinase-2 and -9 from cultured human placental syncytiotrophoblasts

The large increase in placental surface area and fetal villous vascular development in the third trimester of pregnancy requires degradation and reformation of the placental basal lamina. Degradation is carried out by matrix metalloproteinases (MMPs) secreted by adjacent cells. Although the gelatinases, MMP-2 and MMP-9, which are released by extravillous cytotrophoblasts (CTs) are believed to play crucial roles in early placental expansion, neither has been reported in third trimester villous trophoblasts nor has appropriate (basolateral) release of any MMP by the highly polarized syncytiotrophoblast (ST) been demonstrated. We demonstrated villous trophoblast expression of both MMP-2 and MMP-9 by in situ immunohistochemistry and by Western blot analysis and zymography of lysates and culture supernatants of highly purified villous CTs. We also found that epidermal growth factor (EGF)-stimulated CT differentiation into ST and stimulation by the phorbol diester, PMA, both increase MMP-9 secretion. The direction of MMP release was determined with confluent cultures of ST on porous membranes. We found that >90% of MMP-2 and MMP-9 were released from the basolateral surface. We conclude that villous STs express and release gelatinases from their basolateral surfaces in a regulated manner and suggest that such polarized release may be important to villous tissue remodeling.

The mechanisms of platelet dysfunction during extracorporeal membrane oxygenation in critically ill neonates

OBJECTIVE

Although bleeding associated with thrombocytopenia often complicates extracorporeal membrane oxygenation (ECMO), the mechanisms of platelet dysfunction during ECMO remain poorly understood. We investigated the role of matrix metalloproteinase (MMP)-2, which recently has been shown to mediate a novel pathway of platelet aggregation, in the platelet dysfunction induced by ECMO.

DESIGN

Prospective longitudinal case study.

SETTING

Level III neonatal intensive care unit.

PATIENTS

Ten neonates treated with ECMO.

INTERVENTION

ECMO procedure.

MEASUREMENTS

Platelet counts and collagen-induced platelet aggregation ex vivo; plasma markers of platelet (soluble P-selectin) and endothelial (soluble E-selectin and total nitrite/nitrate) activation; plasma MMP-2 and MMP-9 activities; and concentrations of tissue inhibitors of MMPs.

MAIN RESULTS

During ECMO, time-dependent platelet activation, as evidenced by thrombocytopenia, decreased platelet aggregation, and increased plasma soluble P-selectin concentrations were found in the absence of endothelial activation, as shown by normal plasma concentrations of soluble E-selectin and nitric oxide metabolites (nitrite/nitrate). There was a time-dependent increase in plasma MMP-2 but not MMP-9 activity; tissue inhibitors of MMPs were not detected. Plasma soluble P-selectin concentrations significantly correlated with simultaneous plasma MMP-2 (r2 = .37, p < .0001) but not with MMP-9 activities. Platelet dysfunction persisted despite repeated platelet transfusions to maintain platelet counts >100 x 10(9)/L.

CONCLUSIONS

ECMO resulted in the activation of platelets but not endothelial cells. During ECMO, platelet dysfunction persisted despite platelet transfusions. MMP-2 may play a role in the development of platelet dysfunction caused by ECMO.

Matrix metalloproteinase-2 contributes to ischemia-reperfusion injury in the heart

BACKGROUND

Matrix metalloproteinases (MMPs) contribute to collagen degradation and remodeling of the extracellular matrix after myocardial infarction; however, their role in myocardial dysfunction immediately after ischemia and reperfusion is unknown.

METHODS AND RESULTS

We measured the release of MMPs into the coronary effluent of isolated, perfused rat hearts during aerobic perfusion and reperfusion after ischemia. Aerobically perfused control hearts expressed pro-MMP-2 and MMP-2, as well as an unidentified 75-kDa gelatinase. These enzymes were also detected in the coronary effluent. After 20 minutes of global no-flow ischemia, there was a marked increase in pro-MMP-2 in the coronary effluent that peaked within the first minute of reperfusion. The release of pro-MMP-2 into the coronary effluent during reperfusion was enhanced with increasing duration of ischemia and correlated negatively with the recovery of mechanical function during reperfusion (r(2)=0.99). MMP-2 antibody (1.5 to 15 microg/mL) and the inhibitors of MMPs doxycycline (10 to 100 micromol/L) and o-phenanthroline (3 to 100 micromol/L) improved whereas MMP-2 worsened the recovery of mechanical function during reperfusion.

CONCLUSIONS

These results show that acute release of MMP-2 during reperfusion after ischemia contributes to cardiac mechanical dysfunction. The inhibition of MMPs may be a novel pharmacological strategy for the treatment of ischemia-reperfusion injury.

Differential regulation of platelet aggregation by matrix metalloproteinases-9 and -2

We have recently found matrix metalloproteinase-2 (MMP-2) in human platelets and reported that the release of this enzyme during platelet activation stimulates aggregation. We have now identified matrix metalloproteinase-9 (MMP-9) in human platelets and resistance-sized (approximately 200 microm) arteries. Resting platelets released small quantities of pro-MMP-9. Maximal release of MMP-9 was detected during partial (appr. 30% maximum) aggregation with thrombin. However, maximal release of MMP-2 was associated with maximal aggregation. MMP-9 antibodies induced aggregation of resting platelets and potentiated aggregation of platelets induced by thrombin and collagen. Moreover, MMP-9 microisolated from arteries as well as recombinant human MMP-9 (0.1-30 ng/ml) inhibited thrombin and collagen-induced aggregation. We conclude that MMP-9 is an inhibitor of aggregation and in this action opposes the effects of MMP-2. The MMP-2/MMP-9 system may play an important role in the regulation of platelet-platelet and platelet-vessel wall interactions.

Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (Isc). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 µM, and reversibly activated Isc in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 µg/mL) increased whole-cell current and Isc, whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.Key words: matrix metalloproteinases, Cl- current, Calu-3 cells, zymography, phenanthroline.

Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (I(sc)). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 microM, and reversibly activated I(sc) in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 microg/mL) increased whole-cell current and I(sc), whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.

[Elbow contracture: causes, management]

Early results after conservative or operative treatment of 15 patients (6 females, 9 males) for contracture of the elbow are presented. The correction achieved has been evaluated by Mayo Elbow Performance Index and by range of flexion and extension movement. Immobilization of the injured elbow should be as short as possible, fixed deformity is an indication for surgery. Resulting contracture of the elbow depends not only on injury severity but on the type of treatment also. One case has been discussed.

The role of nitric oxide and metalloproteinases in the pathogenesis of hyperoxia-induced lung injury in newborn rats

The effects of nitric oxide (NO) and metalloproteinases (MMP-2 and MMP-9) in the pathogenesis of hyperoxia-induced lung damage in newborn rats were examined. Three-day-old rat pups were subjected to hyperoxia (> or = 95% O2) or room air for 7 and 14 days. Some animals were treated with NG-L-nitro-L-arginine methyl ester (L-NAME, 10 mg kg(-1), s.c., daily). Histology, morphometry, oedema, Ca2+-dependent and -independent NO synthase (NOS) activities, expression of NOS isoforms and the activities of MMP-2 and MMP-9 were measured in lungs of hyperoxic and control animals. Exposure of rats to hyperoxia for 7 days resulted in alveolar sac injury characterized by the presence of cellular debris, red cell extravasation and inflammatory infiltration with mononuclear cells. Lung water content, epithelial, smooth muscle layers and total airway thickness was similar to controls. In contrast, exposure of rats to hyperoxia for 14 days resulted in lung oedema, inflammation and epithelial proliferation. Hyperoxia caused a decrease in Ca2+-dependent NOS activity, an effect that was associated with increased expression of eNOS protein. In control rats, Ca2+-dependent NOS activity and expression of eNOS were reduced at 14 days. Hyperoxia caused 10 fold increase in the activity of Ca2+-independent NOS that remained significantly elevated after 14 days of exposure to hyperoxia. The activity of this enzyme was unchanged in control rats. In lungs of hyperoxic rats, the immunoblot showed time-dependent, biphasic expression (peak at 7 days) of iNOS. The profile of expression of iNOS in control rats was similar. The activities of MMPs were increased in lungs of hyperoxic animals. The L-NAME treatment of hyperoxic animals reduced lung oedema and epithelial proliferation, but enhanced the activities of MMPs. L-NAME exerted no significant effects in control rats. It is concluded that increased generation of NO contributes to the pathogenesis of hyperoxia-induced lung damage in newborn rats.

Localization and translocation of MMP-2 during aggregation of human platelets

We have previously shown that human platelets express matrix metalloproteinase-2 (MMP-2) and that the release of this enzyme during platelet activation mediates the ADP- and thromboxane-independent part of aggregation. We have now used immunogold electron microscopy, flow cytometry. Western blot analysis and zymography methods to study the ultrastructural localization of MMP-2 in human washed platelets. Platelet aggregation was stimulated by collagen and the MMP-2 immunoreactivity of platelets was followed during various stages of aggregation. In resting platelets, MMP-2 was randomly distributed in the platelet cytosol without detectable association with platelet granules. Platelet aggregation caused the translocation of MMP-2 from the cytosol to the extracellular space. During the early stages of aggregation, MMP-2 remained in close association with the platelet plasma membrane. We conclude that the interactions of MMP-2 with platelet surface membranes mediate the aggregatory response induced by this enzyme.

The effects of stress on homeostasis in JCR-LA-cp rats: the role of nitric oxide

We have investigated the effects of early phases of chronic stress on generation and actions of nitric oxide (NO) in JCR:LA-cp rats both lean (+/+) and obese (cp/cp). Restraint stress was carried out for a 15-min single exposure or for 1 hr every day during 4, 9 or 14 days. The stress reaction was evidenced by significant increase in plasma cortisol. The exposure to stress for 14 days led to a neuronal damage in lean rats as evidenced by a decrease in glutamate uptake and an increase in the release of lactate in synaptosomes. This effect was not observed in obese rats. Concomitantly, the levels of glutamate increased in the hippocampus at 14 days in lean, but not obese rats, that showed higher basal levels of glutamate than lean rats. The activity of NO synthase (NOS) and guanosine cyclic monophosphate levels increased in the hippocampus preceding the neuronal damage. The neuronal lesions were prevented by inhibition of NOS without affecting cortisol levels. In the cardiovascular system, chronic stress exerted no significant effect on blood pressure, aortic contractility or platelet aggregation. However, there were significant changes in plasma nitrite/nitrate that reached maximum at 4 to 9 days. It is concluded that the generation of NO contributes to the systemic response to the organism to stress. In the brain, NO appears to be detrimental as this molecule mediates glutamate-dependent hippocampal damage, this effect being cortisol-independent. In contrast, in the vascular system, increased generation of NO may attenuate the vasoconstrictor and platelet aggregatory effects of catecholamines and other mediators of stress.

Expression of the active form of MMP-2 on the surface of leukemic cells accounts for their in vitro invasion

The enhanced expression of matrix metalloproteinases (MMP), especially gelatinases MMP-2 and MMP-9, has been associated with the invasive behavior of tumor cells. Previously we reported that primary acute myelogenous leukemia blasts and human leukemic cultured KG-1 cells but not HEL cells penetrate a reconstituted basement membrane (Matrigel) in an invasion assay. In this study, we investigated the role of MMP-2 and MMP-9 in in vitro invasion by leukemic cells. We found that both recombinant human tissue inhibitor of metalloproteinase-2 (rhTIMP-2) and anti-MMP-2 antibody inhibit the invasiveness of KG-1 cells in the Matrigel assay (by 76% and 51% respectively), while anti-MMP-9 antibody does not, indicating that MMP-2 but not MMP-9 in involved in the invasive process. KG-1 cells were found to secrete constitutively the latent (but not the activated) forms of both MMP-2 and MMP-9 and, after stimulation with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), higher levels of these pro-MMP. TPA stimulation, however, did not increase the in vitro invasiveness of these cells. Analysis by Western blot and flow cytometry revealed the presence of the activated form of MMP-2 (64 kDa) on the surface of KG-1 cells and primary AML blasts, as well as MT-MMP in the homogenates of these cells. This active form of MMP-2 was not detected on the surface of HEL cells, which were non-invasive in vitro, although these cells secreted pro-MMP-2. In conclusion, leukemic KG-1 and primary acute myelogenous leukemia cells, which secrete pro-MMP-2 and pro-MMP-9, were also shown to express the activated form of MMP-2 on their cell surface. We suggest that this active form is essential to the in vitro invasion of leukemic cells.

[Endoprosthetic replacement as an alternative treatment for radial head resection in comminuted fractures]

Indications for radial head endoprosthetic replacement (Link) and early results in 2 patients 52 and 20 years of age are presented. Excellent results were achieved according to Mayo Elbow Performance Index criteria. The authors introduce own dismantable endoprosthesis with moving head.

[Socioeconomic sequelae to hand injuries]

Remote results of hand injuries in 78 patients (93% males, 7% females) aged 16-82 (mean 39 years) were analyzed statistically and economically. Injuries sustained at work constituted 61%. All patients were operated on emergency basis, hospital stay ranged 1-93 days (mean 14 days). Further treatment on an outpatient basis lasted 4.5 months on an average. According to own 3-grade scale 24% results were rated good, 33%-fair and 43%-poor. Fifty-one per cent of patients resumed previous occupation, 17% found less demanding work and 15% were unable to work. Accident compensation fund was granted to 56% of patients. Great social cost of hand injuries is underlined in the paper.

Phenotypic and cytokine analysis of human peripheral blood gamma delta T cells expressing NK cell receptors

The presence of NK receptors (NKR) on populations of T cells has been proposed to play a regulatory role in T cell function, fine tuning the response to Ag, and influencing the nature of the immune response through rapid secretion of large amounts of cytokines. In this study, we assessed the nature and distribution of NKR on human peripheral blood gamma delta T cells and established clones to study cytokine release. In circulating gamma delta T cells, approximately 80% expressed CD94, approximately 25% expressed NKR-P1A, and approximately 20% expressed p58, values substantially higher than those found on alpha beta T cells from the same donors. When cloned for specific NKR expression, most cells in culture were NKR-P1A+ whereas p58 expression was variable, suggesting that the NKR-P1A phenotype can be acquired in culture whereas expression of p58 is more stable. Some clones were triple positive for CD94, NKR-P1A, and p58. V delta 2+ cells generally expressed a wider range of NKR than V delta 1+ cells. Following activation through CD3, all gamma delta T cell clones released large amounts of IFN-gamma, commencing as early as 4 h postactivation. Some clones also released TNF-alpha and IL-4, but no correlation with specific NKR expression was noted. Activation through NKR-P1A induced moderate levels of IFN-gamma without inducing IL-4. The results suggest that activation of most gamma delta T cells is regulated by signaling events occurring via both the TCR and the NKR. They further show that peripheral blood gamma delta T cells may function as a source of the proinflammatory cytokines IFN-gamma and TNF-alpha.

Phenotypic and cytokine analysis of human peripheral blood gamma delta T cells expressing NK cell receptors

The presence of NK receptors (NKR) on populations of T cells has been proposed to play a regulatory role in T cell function, fine tuning the response to Ag, and influencing the nature of the immune response through rapid secretion of large amounts of cytokines. In this study, we assessed the nature and distribution of NKR on human peripheral blood gamma delta T cells and established clones to study cytokine release. In circulating gamma delta T cells, approximately 80% expressed CD94, approximately 25% expressed NKR-P1A, and approximately 20% expressed p58, values substantially higher than those found on alpha beta T cells from the same donors. When cloned for specific NKR expression, most cells in culture were NKR-P1A+ whereas p58 expression was variable, suggesting that the NKR-P1A phenotype can be acquired in culture whereas expression of p58 is more stable. Some clones were triple positive for CD94, NKR-P1A, and p58. V delta 2+ cells generally expressed a wider range of NKR than V delta 1+ cells. Following activation through CD3, all gamma delta T cell clones released large amounts of IFN-gamma, commencing as early as 4 h postactivation. Some clones also released TNF-alpha and IL-4, but no correlation with specific NKR expression was noted. Activation through NKR-P1A induced moderate levels of IFN-gamma without inducing IL-4. The results suggest that activation of most gamma delta T cells is regulated by signaling events occurring via both the TCR and the NKR. They further show that peripheral blood gamma delta T cells may function as a source of the proinflammatory cytokines IFN-gamma and TNF-alpha.

Release of gelatinase A during platelet activation mediates aggregation

Blood platelets limit blood loss at sites of vascular injury by forming a mechanical plug. They are also involved in thrombosis, atherosclerosis, inflammation and metastasis. Platelet activation is essential for these physiological and pathological reactions and depends upon their adhesion to the vessel wall and attachment to each other in the aggregation process. The two known pathways of aggregation are mediated by the release of endoperoxides/thromboxane A2 and ADP which amplify platelet aggregation. Here we report the identification of a new pathway of aggregation which is mediated by the release of a metalloproteinase enzyme, gelatinase A.

Expression of beta 1 integrin mRNAs in human leukemic blasts

Adhesion receptors from the very late activation (VLA) (beta 1) integrin subfamily play a role in the cooperation of hematopoietic progenitors with bone marrow stroma, and the disregulated expression of these molecules, as evaluated by immunophenotyping, has been implicated in the acquisition of the malignant phenotype by hematopoietic cells. In the present study, Northern hybridization was used to determine the pattern of expression of transcripts for VLA subunits in: (i) leukemic blasts obtained from the peripheral blood of ten patients with acute myelogenous leukemia (AML) of different FAB subclasses; (ii) the human leukemic cell lines KG-1, HL-60, K-562, HEL and U-937; and (iii) normal hematopoietic cells. Most of the AML blasts and the cultured leukemic cells expressed mRNAs for the beta 1 and alpha 5 subunits (the only exception among the cell lines was KG-1 cells) and these transcripts were also found in normal bone marrow progenitors, peripheral blood mononuclear cells (PBMNC), and peripheral blood monocytes. While the alpha 4 transcript was detected in all cultured cells but K-562, and in normal circulating monocytes, it occurred in blasts from only two AML patients and was weakly expressed in mature PBMNC. No specific pattern of expression of beta 1, alpha 5, and alpha 4 transcripts could be related to cell differentiation or maturation in the AML blasts and leukemic cell lines tested. None of the primary AML blasts or cultured cells showed mRNA messages for alpha 2, alpha 3 or alpha 6 chains of the beta 1 integrins. The results suggest that, in some cases of AML, the malignant phenotype of leukemic blasts may be associated with down-regulated transcription of the alpha 4 integrin subunit.

Sequence, structure, and expression of a wasp venom protein with a negatively charged signal peptide and a novel repeating internal structure

An expression cDNA library prepared from mRNA from the venom gland of a parasitic wasp, Chelonus sp. near curvimaculatus, was screened with polyclonal antibodies against a 33-kDa venom protein from this wasp. Immunoreactive clones were sequenced, yielding a complete inferred sequence for a protein with an NH2 terminus identical with that of the 33-kDa protein. The structure of the cDNA showed an apparent encoded signal peptide, which was unusual in possessing 2 glutamic acid residues juxtapositioned next to, or replacing, the conventional basic residues. The bulk of the mature protein sequence which follows the NH2-terminal, 5000-kDa hydrophobic domain is composed of a dozen tandem repeats of a highly charged, approximately 14-residue sequence, except for the truncated eighth repeat which terminates in the only proline in this large domain. The primary structure is not closely related to any sequence in the GenBank data bank. Secondary structure analysis identified a turn occurring at or near each of 12 invariantly conserved serine residues. Further, the codon used for this serine was invariant, whereas other serines in the protein (including a nearly invariant serine 2 residues away) used various codons. Results of epitope mapping experiments supported a proposed tertiary structure in which the NH2-terminal 5-kDa forms a hydrophobic core, overlain with the charged repeats. Northern analysis of poly(A) RNA from the venom gland of young adult female wasps showed expression of a single 1-kilobase transcript, for which there is no corresponding message in normal or parasitized host larvae. The remarkable structure of this protein and structural data on other wasp venom proteins suggest an evolutionary pattern in which some proteins critical for venom function evolve by internal tandem duplication, and which are secreted after biosynthesis by a different mechanism from that used for proteins with classical signal peptides containing basic residues.