All-trans retinoic acid at low concentration directly stimulates normal adult megakaryocytopoiesis in the presence of thrombopoietin or combined cytokines

In order to investigate the direct effects of retinoids on normal adult hematopoietic progenitors, purified CD34+ cells were seeded in serum-free cultures in the presence of pharmacological (10(-6)) M or physiological (10(-12)) M concentrations of all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) plus combinations of specific cytokines. 10(-6) M ATRA and 9-cis RA significantly decreased the number of granulomacrophagic, erythroid and megakaryocytic (CFU-meg) progenitors. On the other hand, 10(-12) M ATRA significantly promoted the growth of CFU-meg, in the presence either of thrombopoietin or of IL-3+ GM-CSF, and induced a reproducible stimulation of the immature CD34+DR- subset. In conclusion, our findings suggest that retinoic acids probably play a direct role in normal adult hematopoietic development at both physiological and pharmacological concentrations. The stimulatory effect on megakaryocytopoiesis should be considered in the perspective of a potential use of low-dose ATRA, combined with thrombopoietin or other cytokines, in pathological conditions where the megakaryocytic compartment is impaired and the stimulation of megakaryocytopoiesis is requested.

ACTH and its role in immune-neuroendocrine functions. A comparative study

Adrenocorticotropic hormone (ACTH) belongs to the melanocortine group of related peptides which share a common precursor, the pro-opiomelanocortin (POMC). Melanocortin expresses its functional effects by the stimulation of specific G-protein coupled receptors. To date, five receptor subtypes have been cloned. The POMC gene has been highly conserved during evolution, and ACTH has been found in different cells from invertebrates to vertebrates to vertebrates, including man. With regards the immune system, the presence of melanocortin receptors and the production of ACTH have been reported in invertebrate and vertebrate immuno-competent cells. Among its various physiological effects, ATCH has been shown to play a central role in immmune responses, such as chemotaxis and phagocytosis, in lower and higher forms of life. Moreover, ACTH is a key actor in stress response, and the complex cascade of events observed in vertebrates is reproduced and concentrated in intvertebrate immunocytes. On the basis of the present findings, ACTH should be considered an important immuno-regulator, forming part of the complex mosaic of relationships between the immune and neuroendocrine system which appears to have been substantially maintained over the course of evolution.

3q21 and 3q26 cytogenetic abnormalities in acute myeloblastic leukemia: biological and clinical features

BACKGROUND AND OBJECTIVE

Acute myeloblastic leukemia (AML) with features of myelodysplastic syndrome (MDS) and abnormalities of megakaryocytopoiesis is often characterized by cytogenetic aberrations of the 3q21 and 3q26 bands involving inv(3)(q21q26) and (3;3)(q21;q26). These aberrations have been described in all FAB subtypes with the exception of M3, and in MDS and in megakaryoblastic crisis of chronic myeloid leukemia. We reviewed the biological and clinical features of 10 cases of AML with inv(3)(q21q26) and t(3;3)(q21;q26).

DESIGN AND METHODS

Four hundred and sixteen patients with AML were studied in our Institute by cytogenetic analysis and 10 (2.4%) showed inv(3)(q21q26) (7 patients) or t(3;3)(q21;q26) (3 patients): 7 males, 3 females; median age, 43.5 yrs. We also used RT-PCR to investigate the pattern of expression of the EVI-1 gene in 5 patients.

RESULTS

Additional chromosomal changes were demonstrated in 6 patients. In 5/10 cases a preceding MDS had been observed. A possible occupational exposure was established in 2 patients (a farmer and an histologist employing organic solvents) and another patient had a therapy-related leukemia. AML subtype was M1 in 9 patients and M2 in 1. A variable excess of micromegakaryocytes was observed in all the patients. In 5 patients the platelet count was normal or increased (median number: 172. 5x10(9)/L; range 55-440). Expression of EVI-1 gene was present in all the 5 patients studied. The clinical course and outcome was extremely poor: 9/10 patients were resistant and 1 patient showed a partial remission after induction therapy. Of the 9 patients resistant to the first line chemotherapy, 7 were also resistant to the second line chemotherapy. Three patients obtained a morphologic complete remission after third line chemotherapy (duration 1, 3 and 6 months); 2 of them were submitted to autologous bone marrow transplantation, but relapsed after 1 and 3 months. The median overall survival was 5.5 months.

INTERPRETATION AND CONCLUSIONS

Our findings evidence a strong correlation between 3q21q26 chromosomal aberrations, abnormalities of megakaryocytopoiesis and lack of response to conventional chemotherapy and support the diagnostic and prognostic relevance of chromosome characterization in the classification of AML.

Clinical and molecular follow-up by amplification of the CDR-III IgH region in multiple myeloma patients after autologous transplantation of hematopoietic CD34+ stem cells

BACKGROUND AND OBJECTIVE

Autologous blood stem cell transplantation (ABSCT) using chemotherapy-induced mobilization of peripheral blood stem cells (PBSC) is being increasingly used in the treatment of multiple myeloma (MM). We report the clinical and molecular follow-up of 10 MM patients who underwent autologous stem cell transplantation with peripheral blood selected CD34+ cells, as support therapy following a myeloablative conditioning regimen.

DESIGN AND METHODS

The CDR-III coding region of the IgH gene was studied by a) consensus PCR applied to 8 MM patients, or b) by direct sequencing of PCR product generated by family-specific primers in the remaining two patients (who became immunofixation analysis (IF) negative). In this case, two patient-specific primers were generated, thus obtaining a high PCR assay sensitivity and specificity (ASO PCR).

RESULTS

Seven patients are alive: 4 of them have serum M protein assessable by IF, while 1 was not a secretor and 2 converted from serum IF positivity to negativity 6 and 12 months after ABSCT. Three patients died: 1 from disease progression and 2 from infective complications during clinical remission. The molecular analysis during the follow-up showed that the bone marrow samples from the two patients who obtained IF negativity were persistently PCR positive for the presence of rearranged CDR-III region. Moreover, despite the remarkable reduction of myeloma burden, a minimal level of residual myeloma cells was still detectable by molecular analysis.

INTERPRETATION AND CONCLUSIONS

These results confirm that although positive selection of CD34+ cells markedly reduces the contamination of myeloma cells from apheresis products by up to 3 log, and provides a cell suspension capable of restoring normal hematopoiesis after ablative conditioning regimen, it does not abrogate myeloma cell contamination in most of the apheresis products.

Cytotoxic combination of loxoribine with fludarabine and mafosfamide on freshly isolated B-chronic lymphocytic leukemia cells

Fludarabine has shown a definite clinical activity in B-cell chronic lymphocytic leukemia (B-CLL). Recently it has been demonstrated that loxoribine, a guanine ribonucleotide derivative, is able to increase the cytotoxicity of fludarabine in B-CLL cells, in vitro. We have here extended these findings by testing the activity of loxoribine in combination with fludarabine and mafosfamide. As we have previously demonstrated, loxoribine enhances the activity of fludarabine at all concentrations, while only lower doses of mafosfamide seem to be positively affected by loxoribine. The combination of fludarabine and mafosfamide is synergistic on CLL cells, and the cytotoxic activity is increased by the addition of loxoribine. We have also evaluated the pro-apoptotic activity of each drug, both alone and in combination; these results are concordant with the cytotoxicity data, thus demonstrating that, even though loxoribine is more active in combination with fludarabine than with mafosfamide, the efficacy of the triple combination is higher than that obtained with any other agent alone or in double combination.

In vitro treatment with retinoids decreases bcl-2 protein expression and enhances dexamethasone-induced cytotoxicity and apoptosis in multiple myeloma cells

All-trans retinoic acid (ATRA) has been shown to inhibit in vitro growth of multiple myeloma (MM) cells, and this effect can be further potentiated by the addition of Dexamethasone (DEX). We here extended this study by testing the activity of 9-cis retinoic acid (9-cis RA) and 13-cis retinoic acid (13-cis RA), both alone and in combination with DEX, in two MM cell lines, U266 and RPMI 8226. Furthermore, we aimed at investigating the mechanisms involved in the interactions of retinoids and DEX in this setting. 9-cis RA appeared to be the most active agent in U266 cell line (IC50 = 1.2 mumol/l vs 10.5 and 9.8 mumol/l obtained with ATRA and 13-cis RA, respectively) while, in RPMI 8226 cell line, 9-cis RA and 13-cis RA were almost equally cytotoxic (IC50 = 1 and 0.8 mumol/l) and ATRA was less effective. Co-incubation with DEX resulted in a synergistic cytotoxic activity in both the cell lines except for the combinations DEX + 9-cis RA in U266 cell line and DEX + 13-cis RA in RPMI 8226 cell line, where the effect was merely additive. A synergistic cytotoxic effect of retinoids and DEX was also observed on fresh MM cells obtained from 7 patients. Both retinoids and DEX are known to be inducers of apoptosis; we verified that the combined inhibitory activity of retinoids and DEX could be attributed to an increased induction of apoptosis. This effect may be mediated by a reduced intracellular expression of BCL-2 protein, which indeed observed after prolonged in vitro treatment with retinoids. It has been described recently that an enhanced expression of BCL-2 protein can contribute to the occurrence of early chemoresistance; the downregulation of BCL-2 protein induced by retinoids could thus be exploited, by means of novel chemotherapy plus retinoids combinations, in order to improve the efficacy of conventional chemotherapy in MM.

Autologous peripheral blood stem cell transplantation in acute myeloblastic leukaemia and myelodysplastic syndrome patients: evaluation of tumour cell contamination of leukaphereses by cytogenetic and molecular methods

We evaluated 18 acute myeloblastic leukaemia (AML) and myelodysplastic syndrome (MDS) patients with abnormal karyotype at diagnosis who underwent peripheral blood stem cell (PBSC) transplantation. To evaluate the presence of residual tumour cells, bone marrow (BM) samples and PBSC collections were analysed by cytogenetics and in selected cases also by fluorescence in situ hybridisation (FISH) and molecular studies. All patients were considered to be in morphologic and cytogenetic complete remission (CR) at the time of mobilisation. Seven patients showed neoplastic cells in PBSC harvest and/or BM specimen before reinfusion. Cytogenetic studies revealed contamination in apheretic collections in one patient only, while three patients had BM but not PBSC contamination. Three more patients had leukaemic cells both in the BM and PBSC. All but one (with only BM contamination) of these patients relapsed within 9 months. However, five more patients relapsed after transplantation: in four cases there was no cytogenetic sign of contamination either in PBSC or BM cells and in one case no molecular evidence was revealed either. This study suggests that, whereas the presence of leukaemic cells in autologous grafts correlates with a poor prognosis, the lack of detection of tumour cells is not always predictive of long-term disease-free survival. More importantly, PBSC collections from AML patients are not contaminated by leukaemic cells if the BM is disease-free.

Role of autologous bone marrow transplantation as consolidation therapy in acute promyelocytic leukemia patients in complete remission

Autologous bone marrow transplantation (ABMT), which consents a low mortality rate, has been proposed as an alternative approach to maintenance chemotherapy in patients with acute promyelocytic leukemia (APL) in first complete remission irrespective of the patients' molecular status. Sixteen patients with acute APL in complete remission were submitted to ABMT and were analyzed for the presence of the PML-RARa fusion gene by reverse transcription-polymerase chain reaction (RT-PCR). Our study demonstrated that continued positivity of PCR analysis before ABMT could predict subsequent relapse in patients who undergo un-purged ABMT procedures.

Disappearance of PML/RAR alpha acute promyelocytic leukemia-associated transcript during consolidation chemotherapy

BACKGROUND AND OBJECTIVE

Acute promyelocytic leukemia (APL) (M3 according to FAB classification) is a subtype of acute myelogenous leukemia characterized by a specific t(15;17) (q22;q12) chromosomal translocation. The majority of APL patients achieve morphologic remission after induction chemotherapy. They can be followed from this point by cytogenetic and molecular analysis of the persistence of the PML/RAR alpha transcript. In order to determine the influence of successive courses of consolidation chemotherapy on clinical and molecular outcome, APL patients treated with all-trans retinoic acid (ATRA) and chemotherapy (AIDA-GIMEMA-LAP0493 protocol) were investigated.

DESIGN AND METHODS

Twenty-four APL patients (pts) (15 males; 9 females) were studied by RT-PCR and cytogenetic analysis at diagnosis, after induction chemotherapy, at each point after any of three consolidation courses, and every 3 months during the first years of maintenance therapy. The median follow-up was 24 months (mths) (range 7-40 mths).

RESULTS

All pts achieved hematologic remission after induction chemotherapy. Our results demonstrate that the majority (87%) of APL patients were still molecularly positive for the APL associated transcript after induction chemotherapy, while the majority (80%) of APL patients became PCR-after the second consolidation chemotherapy.

INTERPRETATION AND CONCLUSIONS

The role of the third consolidation chemotherapy course in converting patients with persistent molecular evidence of disease from PCR+ to PCR- was minimal. We confirm the validity of molecular follow-up after single courses of chemotherapy in monitoring the role of molecular remission.

Long-term disease-free acute promyelocytic leukemia patients really can be cured at molecular level

The characteristic t(15;17) translocation involving chromosomes 15 and 17 is specifically associated with both the common and the variant subtypes of acute promyelocytic leukemia (APL) (M3 according to FAB classification). At the molecular level, it fuses genes encoding PML on chromosome 15 and the nuclear retinoic acid receptor-alpha (RAR alpha) on chromosome 17. The subsequent expression of PML/RAR alpha fusion mRNA provides a potential molecular marker that can be detected in leukemic cells taken from patients with APL. Using PML and RARa sequence specific primers, reverse transcription-polymerase chain reaction (RT-PCR) assays have been developed for detection of PML/RAR alpha transcript in leukemic cells obtained from patients; these RT-PCR assays are more sensitive than conventional cytogenetic analysis.

A new theory on the common evolutionary origin of natural immunity, inflammation and stress response: the invertebrate phagocytic immunocyte as an eye-witness

Data in favor of the hypothesis of the common evolutionary origin of natural immunity inflammation and stress response are presented. These phenomena seem to be mediated by a common pool of molecules (POMC-derived peptides, cytokines, biogenic amines, glucocorticoids, and nitric oxide). Macrophages are able to release all the above mentioned molecules. They play a primary role in defence mechanisms. Thus, we argue that this cell can be considered the eye-witness of the common evolutionary origin of the immune and neuroendocrine systems.

Detection of bcr-abl transcript in chronic myelogenous leukemia patients by reverse-transcription-polymerase chain reaction and capillary electrophoresis

BACKGROUND AND OBJECTIVE

Capillary electrophoresis (CE) has become an attractive alternative to SLAB gel analysis for direct and accurate detection of amplified product, and a few cycles of polymerase chain reactions (PCRs) could be sufficient for both quantitative and qualitative analysis. We try to assess: 1) whether CE could be a practical, non-isotopic method for direct detection of the presence of amplified bcr-abl obtained by a reverse transcription (RT)-PCR (qualitative analysis) and 2) whether it is possible to quantify PCR products using a competitive RT-PCR measuring peak areas of CE electropherograms (quantitative analysis).

DESIGN AND METHODS

The two types of bcr-abl chronic myelogenous leukemia (CML) associated transcript products were generated by RT-PCR (qualitative analysis) from 1 microgram of total RNA extracted from bone marrow samples of 34 CML patients at diagnosis (median age 47.5; range 18-65; median Sokal's score 0.9; range 0.53-2.78). The PCR products were analyzed by SLAB-gel electrophoresis (SGE) on 2% agarose gels and by CE (128 runs; median 3.3 times for each sample). Furthermore, we assessed the amount of PCR product (quantitative analysis) by a competitive RT-PCR approach and by CE (bcr-abl transcripts were expressed as transcript per microgram of total RNA examined).

RESULTS

CE separation of PCR products obtained by qualitative RT-PCR showed baseline resolution for the two peaks corresponding to the two types of bcr-abl junctions: the b2-a2 type (343 base pairs, 10 patients) was revealed at 9.33 min [standard deviation (SD) = 0.1] and the b3-a2 type (418 base pair, 24 patients) at 10.03 min (SD = 0.25). By quantitative analysis we found that there is great interpatient variability in bcr-abl expression at diagnosis: the median value of the amount of bcr-abl transcript was 78,000 bcr-abl transcript/microgram total RNA ranging from 17,300 to 750,000. The amount of bcr-abl transcript at diagnosis was related to the number of blast cells (mean value 128,859 vs. 331,722 in patients with 0% blast cells and > 1% blast cells, respectively; p = 0.004) and Sokal's score (mean value 156,865 vs. 408,800 in patients with Sokal's score < 0.8 and > 1.2, respectively; p = 0.003).

INTERPRETATION AND CONCLUSIONS

Our results confirm that CE analysis offers greater resolution and enhanced sensitivity for detection and quantification of bcr-abl PCR product in the study of this leukemia. Qualitative analysis by CE of bcr-abl product provides a rapid technique (less than 20 min) for the analysis of subnanogram amounts of DNA fragments. CE run times are short, the capillary can be re-used and full automation may be feasible with data acquisition by a computer-controlled step. Competitive/quantitative analysis of bcr-abl as analyzed by CE allowed fewer reactions and more precise quantification.

The CRH-ACTH-biogenic amine axis in invertebrate immunocytes activated by PDGF and TGF-beta

In immunocytes from the mollusc Mytilus galloprovincialis, the major pathway followed by platelet-derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1 in provoking the release of norepinephrine, epinephrine and dopamine into cell-free hemolymph (serum) is mediated by a corticotropin-releasing hormone-adrenocorticotropin hormone (CRH-ACTH) biogenic amine axis. This axis not only annulled the inhibiting properties of PDGF-AB, it even reversed the latter's effect, while the inducing effect of TGF-beta1 was amplified. These findings show that non-classical immune-neuroendocrine molecules, such as PDGF-AB and TGF-beta1, are involved in building stress response, using the same conserved mechanisms present from invertebrates to vertebrates.

Neutral endopeptidase-24.11 (NEP) activity in human fibroblasts during development and ageing

Neutral endopeptidase-24.11 (NEP, EC 3.4.24.11) is a cell surface Zn metallopeptidase that hydrolyzes bioactive regulatory peptides. Using a spectrofluorimetric procedure, we assessed NEP activity in plasma membranes of normal human skin and lung fibroblasts. We found a considerable increase in NEP activity during fetal-to-adult transition. Adult skin fibroblasts from an old donor exhibited significantly higher levels of NEP activity than cells from young donors. Interestingly, however, the NEP activity of fibroblasts from a centenarian donor was similar to that of cells from young donors. Increased levels of NEP activity were also found in in vitro aged lung fibroblasts. Finally, adrenocorticotropin hormone (ACTH (1-24)), a regulatory peptide that can be cleaved by NEP, provoked an increase in enzymic activity in fetal and young adult donor fibroblasts and a decrease in this activity in fibroblasts from adult and old donors. This finding suggests that ageing may affect NEP activity.

Naltrexone suppresses the rejection of cardiac tissue transplantation

The present study demonstrates the following: 1. Transplantation of cardiac tissue induces an inflammatory response that ultimately leads to the rejection of the tissue by the host within 9 days; 2. Treatment with the opiate antagonist, naltrexone, significantly increased the survival of the transplanted cardiac tissue to 13 days, suggesting the involvement of opioid signaling molecules in tissue rejection; 3. In further experiments it was demonstrated that in mixed lymphocyte populations from different mice, the DNA synthesis inhibitor, mitomycin C, reduced the lymphocyte proliferative response as did naltrexone; 4. Mice injected with naltrexone for 10 days and given concanavalin A exhibited a suppressed spleen lymphocyte proliferative response compared to controls. Taken together, these data suggest that endogenous opioid signals not only activate immunocytes, but also stimulate DNA synthesis.

The neuro-immunological interface in an evolutionary perspective: the dynamic relationship between effector and recognition systems

The evolutionary perspective indicates that an immune-neuroendocrine effector system integrating innate immunity, stress and inflammation is present in invertebrates. This defense network, centered on the macrophage and exerting primitive and highly promiscuous recognition units, is very effective, ancestral and appears to have been conserved throughout evolution from invertebrates to higher vertebrates. It would seem that there was a "big bang" in the recognition system of lower vertebrates, and T and B cell repertoires, MHC and antibodies suddenly appeared. We argue that this phenomenon is the counterpart of the increasing complexity of the internal circuitry and recognition units in the effector system. The immediate consequences were a progressive enlargement of the pathogen repertoire and new problems regarding self/not-self discrimination. Probably not by chance, a new organ appeared, capable of purging cells able of excessive self recognition. This organ, the thymus, appears to be the result of a well known evolutionary strategy of re-using pre-existing material (neuroendocrine cells and mediators constituting the thymic microenvironment). This bricolage at an organ level is similar to the effect we have already described at the level of molecules and functions of the defense network, and has a general counterpart at genetic level. Thus, in vertebrates, the conserved immune-neuroendocrine effector system remains of fundamental importance in defense against pathogens, while its efficiency has increased through synergy with the new, clonotipical recognition repertoire.

PDGF and TGF-beta induce cell shape changes in invertebrate immunocytes via specific cell surface receptors

The presence of PDGF receptor-alpha- and -beta- and TGF-beta-receptor (type II)-like molecules on the plasma membranes of the immunocytes of the mollusc Mytilus galloprovincialis was demonstrated by an immunocytochemical procedure. Furthermore, the present study provides evidence that PDGF-AB and TGF-beta1 provoke cell shape changes in immunocytes via interactions with the respective receptors and that these extracellular signals are transduced along the phosphoinositide signaling pathway.

Secretion of apoB- and apoA-I-containing lipoproteins by chick kidney

Previous studies showed that chick kidney is a site of synthesis of apolipoprotein (apo) B(B-100) and A-I. Aims of the present study were: a) to compare apoB and apoA-I production in chick kidney and liver; b) to investigate whether kidney apolipoproteins were secreted as constituents of lipoproteins; and c) to define the cellular sites of renal apolipoprotein synthesis. Kidney and liver slices taken from the same animals were incubated with 35S-labeled amino acids and radioactive apoB and apoA-I were immunoprecipitated from cell homogenate and incubation medium. The percentage of total protein radioactivity incorporated into cell plus medium apoB and apoA-I was 0.23+/-0.08 and 0.19+/-0.11 in kidney and 0.38+/-0.05 and 0.38+/-0.07 in liver, respectively (P < 0.05 kidney vs. liver). 35S-labeled medium lipoproteins were separated by density gradient ultracentrifugation and three major classes corresponding to VLDL + IDL, LDL, and HDL were identified. Most of the apoB secreted by the liver was found in VLDL, IDL, and LDL whereas kidney apoB was found in VLDL, LDL and "light" HDL (d 1.070-1.130 g/ml). In both hepatic and renal lipoproteins apoA-I was found not only in HDL but also in the other lipoproteins. Immunohistochemical analysis of kidney sections showed that apoB and apoA-I were present almost exclusively in the epithelial cells of proximal and distal convoluted tubules. Thus apoB and apoA-I synthesized by the epithelial cells of the proximal and distal convoluted tubules of chick kidneys are secreted as constituents of lipoprotein particles floating within the density range of plasma lipoproteins. These observations suggest that in the chick, the kidneys may contribute to the plasma lipoprotein pool.

Inv(16) acute myeloid leukemia cells show an increased sensitivity to cytosine arabinoside in vitro

Karyotype represents the major independent prognostic factor for response and remission duration in acute leukemia. In particular, it has been reported that acute myeloid leukemia (AML) patients with inv(16) abnormality show a better prognosis, especially in case of treatment with high-dose Ara-C (HD Ara-C) containing regimens. In this study we aimed at testing whether leukemic cells from patients showing the inv(16) were more sensitive to Ara-C in vitro, compared to AML blasts from patients with normal karyotype or chromosomal abnormalities other than t(15;17) or t(8;21). We analyzed blast cells from 30 patients who were diagnosed and treated in our institution. The IC50 of Ara-C, as tested by the XTT colorimetric assay, was significantly lower in cases with inv(16) (18.5+/-15.88 micromol/l vs. 38+/-14.6 micromol/l,in cases with other abnormalities, p=0.01). This result was confirmed by a higher incorporation of [3H]-Ara-C into DNA (p=0.02 and p=0.001 compared to samples with normal and abnormal karyotype, respectively). All the same, Ara-C induced apoptosis was significantly increased in cells from patients with inv(16). Our data suggest a possible interaction between the molecular background of inv(16) and a modification of intracellular metabolism of Ara-C, and could thus provide a rationale for HD-Ara-C-based schedules for patients with inv(16) AML.

Characterization of Cyprinus carpio brain nitric oxide synthase

Nitric oxide synthase (NOS) activity is found both in soluble and in particulate fractions of the carp brain. The Km values for arginine are 2.8+/-0.5 and 3.3+/-0.4 microM for the soluble and particulate fractions, respectively. K for NG-monomethyl-L-arginine inhibitor are 2.6+/-0.5 and 2.9+/-0.6 microM, and activation energy for the breakdown of the substrate-enzyme complex 8120+/-710 and 4620+/-450 cal per mole. Carp enzyme shows higher affinity than rat NOS for Ca2+ and for the competitive inhibitor 7-nitroindazole.

In situ localization of ACTH receptor-like mRNA in molluscan and human immunocytes

Adrenocorticotropin hormone (ACTH) receptor-like messenger RNA was localized in molluscan hemocytes and human peripheral blood mononuclear cells by in situ hybridization using a digoxigenin-labelled bovine complementary DNA probe. These findings suggest that the ACTH receptor gene has been highly conserved during evolution. Moreover, these data represent further support for a relationship between the immune and neuroendocrine systems in invertebrates, as documented in our previous studies.

Presence of immunoreactive corticotropin-releasing hormone and cortisol molecules in invertebrate haemocytes and lower and higher vertebrate thymus

Corticotropin-releasing hormone- and cortisol-like molecules are present in the haemocytes of different molluscan species and in the epithelial cells, interdigitating cells and macrophages - but not in the lymphocytes - of fish, frog, chicken and rat thymus. Taking into account the fact that other pro-opiomelanocortin-derived peptides, such as adrenocorticotropin hormone, are present in the haemocytes and thymus of the same species, these results complete the list of stress mediators present in molluscan haemocytes and further support the hypothesis that, although the prototype stress response we have demonstrated in invertebrates is concentrated in a single cell, i.e. the haemocyte, it is similar to the response seen in vertebrates. Moreover, the data presented here are compatible with the hypothesis that an evolutionary, conserved stress response can occur locally with a single organ, e.g. the thymus, in which all the main mediators of this biological response, such as corticotropin-releasing hormone, adrenocorticotropin hormone and glucocorticoids, are present. The implications of these findings for the physiology of thymus and stress response may be far reaching.

Interactions of signaling pathways in ACTH (1-24)-induced cell shape changes in invertebrate immunocytes

ACTH (1-24) induces cell shape changes in the immunocytes of the bivalve mollusc, Mytilus galloprovincialis. Using computer-assisted microscopic image analysis, we have found that the G protein antagonist suramin sodium, the adenylate cyclase inhibitor 2',5'-dideoxyadenosine, and the protein kinase inhibitor staurosporine inhibit this effect. The highly specific inhibitors H-89 (for protein kinase A) and calphostin C (for protein kinase C) only inhibited partially the morphological alterations. In contrast, the simultaneous action of H-89 and calphostin C completely blocked these changes. The above findings indicate that ACTH (1-24) induces cell shape changes in molluscan immunocytes via adenylate cyclase/cAMP/protein kinase A pathway, as well as the activation of protein kinase C.