Unexpected Absence of Skeletal Responses to Dietary Magnesium Depletion: Basis for Future Perspectives?

It’s known that a magnesium (Mg)-deficient diet is associated with an increased risk of osteoporosis. The aim of this work is to investigate, by a histological approach, the effects of a Mg-deprived diet on the bone of 8-weeks-old C57BL/6J male mice. Treated and control mice were supplied with a Mg-deprived or normal diet for 8 weeks, respectively. Body weight, serum Mg concentration, expression of kidney magnesiotropic genes, and histomorphometry on L5 vertebrae, femurs, and tibiae were evaluated. Body weight gain and serum Mg concentration were significantly reduced, while a trend toward increase was found in gene expression in mice receiving the Mg-deficient diet, suggesting the onset of an adaptive response to Mg depletion. Histomorphometric parameters on the amount of trabecular and cortical bone, number of osteoclasts, and thickness of the growth plate in femoral distal and tibial proximal metaphyses did not differ between groups; these findings partially differ from most data present in the literature showing that animals fed a Mg-deprived diet develop bone loss and may be only in part explained by differences among the experimental protocols. However, the unexpected findings we recorded on bones could be attributed to genetic differences that may have developed after multiple generations of inbreeding.

Endoplasmic reticulum localization of phosphoinositide specific phospholipase C enzymes in U73122 cultured human osteoblasts

<abstract> <p>Different signal transduction pathways contribute to the differentiation and metabolic activities of osteoblasts, with special regard to the calcium-related pathway of phosphoinositide specific phospholipase C (PLC) enzyme family. PLC enzymes were demonstrated to be involved in the differentiation of osteoblasts and differently localize in the nucleus, cytoplasm or both depending on the isoform. The amino-steroid molecule U-73122 inhibits the enzymes belonging to the PLC family. In addition to the temporary block of the enzymatic activity, U-73122 promotes off-target effects, including modulation of the expression of selected <italic>PLC</italic> genes and different localization of PLC enzymes, depending on the cell line, in different cell lines.</p> <p>In order to evaluate possible off-target effects of the molecule in human osteoblasts, we investigated the expression of <italic>PLC</italic> genes and the localization of PLC enzymes in cultured human osteoblasts (hOBs) in the presence of low dose U-73122.</p> <p>Our results confirm that all <italic>PLC</italic> genes are transcribed in hOBs, that probably splicing variants of selected <italic>PLC</italic> genes are expressed and that all PLC enzymes are present in hOBs, except for PLC δ3 in quiescent hOBs at seeding. Our results confirm literature data excluding toxicity of U-73122 on cell survival. Our results indicate that U-73122 did not significantly affect the transcription of <italic>PLC</italic> genes. It acts upon the localization of PLC enzymes, as PLC enzymes are detected in cell protrusions or pseudopodia-like structures, at the nuclear or the plasma membrane, in membrane ruffles and/or in the endoplasmic reticulum.</p> </abstract>

Phosphoinositide-specific phospholipase C in normal human liver and in alcohol abuse

The phosphoinositide (PI) signal transduction pathway participates in liver metabolism. Abnormal activity or expression of PI-specific phospholipase C (PLC) enzymes has been described in different liver diseases. We resume the role of the PI metabolism in liver and PLC abnormalities in different liver diseases. Moreover, we present the results of PLC analyses in a normal human liver and an alcohol-damaged liver. PLC enzymes and the expression of the corresponding genes in liver biopsies from individuals deceased for complications of the alcoholic liver disease (ALD) at different stages compared with normal controls (deceased individuals with histologically normal livers without alcohol addiction anamnesis) were analyzed by using immunohistochemistry and molecular biology techniques. The expression panel of PLCs was described in normal and alcohol abuse liver. Our observations suggest that the regulation of PLC expression might be due to posttranscriptional events and that alcohol affects the epigenetic control of PLC expression belonging to PI signaling. We also describe the alternate expression of PLCB1 and PLCH1 genes in liver. Our results corroborate literature data suggesting that PLC enzymes are differently expressed in normal versus pathological liver, playing a role in the histopathogenesis of liver tissue damage. The expression and/or localization of selected PLC isoforms is especially affected in alcohol-related liver tissue histopathology. Our present observations confirm that the modulation of protein synthesis plays a role in the regulation of PLC enzymes. We also suggest that this modulation might act at the transcription level. Further studies are required to investigate related epigenetic mechanisms.

Wounds Difficult to Heal: An Effective Treatment Strategy

OBJECTIVE

Treatment of wounds difficult to heal concerns 50% of the elderly population in Italy and is therefore a relevant social burden. The present study shows how the treatment with autologous leuco-platelets reduces the healing time of wounds improving the functional recovery.

PATIENTS AND METHODS

Patients (n=100) with ulcers of the legs were divided in two groups: 1) 50 patients treated with conventional therapies; 2) 50 patients treated with autologous leuco-platelet concentrate (LPC) and hyaluronic acid (HIAFF, Hyalofill-F® ) as a scaffold.

RESULTS

After 2 months, a 49% reduction in wound area was observed in the second group and in about 65% wound reduction was achieved in 15 days (4 LPC dressings). In contrast, patients treated by conventional therapies, showed a longer healing time and a greater percentage of failures. Morphometric analysis of biopsy samples obtained from the edge as well as from the bottom of the lesions obtained from the LPC group, detected an abundant presence of neoformed capillaries, characterized by a cubic, "reactive endothelium", close to the site of LPC infiltration.

CONCLUSION

These results suggest that healing was promoted not only by limiting bacterial infections but also by the release of chemotactic and proangiogenic factors from leukocytes and platelets, improving the neoformation of capillaries.

The Phosphoinositide Signal Transduction Pathway in the Pathogenesis of Alzheimer’s Disease

Background:

During aging and in age-associated disorders, such as Alzheimer's Disease (AD), learning abilities decline. Probably, disturbances in signal transduction in brain cells underlie the cognitive decline. The phosphorylation/dephosphorylation imbalance occurring in degenerating neurons was recently related to abnormal activity of one or more signal transduction pathways. AD is known to be associated with altered neuronal Ca²⁺ homeostasis, as Ca²⁺ accumulates in affected neurons leading to functional impairment. It is becoming more and more evident the involvement of signal transduction pathways acting upon Ca²⁺ metabolism and phosphorylation regulation of proteins. A growing interest raised around the role of signal transduction systems in a number of human diseases including neurodegenerative diseases, with special regard to the systems related to the phosphoinositide (PI) pathway and AD. The PI signal transduction pathway plays a crucial role, being involved in a variety of cell functions, such as hormone secretion, neurotransmitter signal transduction, cell growth, membrane trafficking, ion channel activity, cytoskeleton regulation, cell cycle control, apoptosis, cell and tissue polarity, and contributes to regulate the Ca²⁺ levels in the nervous tissue.

Conclusion:

A number of observations indicated that PI-specific phospholipase C (PLC) enzymes might be involved in the alteration of neurotransmission. To understand the role and the timing of action of the signalling pathways recruited during the brain morphology changes during the AD progression might help to elucidate the aetiopathogenesis of the disease, paving the way to prognosis refinement and/or novel molecular therapeutic strategies.

Different Expression and Localization of Phosphoinositide Specific Phospholipases C in Human Osteoblasts, Osteosarcoma Cell Lines, Ewing Sarcoma and Synovial Sarcoma

Background: Bone hardness and strength depends on mineralization, which involves a complex process in which calcium phosphate, produced by bone-forming cells, was shed around the fibrous matrix. This process is strictly regulated, and a number of signal transduction systems were interested in calcium metabolism, such as the phosphoinositide (PI) pathway and related phospholipase C (PLC) enzymes. Objectives: Our aim was to search for common patterns of expression in osteoblasts, as well as in ES and SS. Methods: We analysed the PLC enzymes in human osteoblasts and osteosarcoma cell lines MG-63 and SaOS-2. We compared the obtained results to the expression of PLCs in samples of patients affected with Ewing sarcoma (ES) and synovial sarcoma (SS). Results: In osteoblasts, MG-63 cells and SaOS-2 significant differences were identified in the expression of PLC δ4 and PLC η subfamily isoforms. Differences were also identified regarding the expression of PLCs in ES and SS. Most ES and SS did not express PLCB1, which was expressed in most osteoblasts, MG-63 and SaOS-2 cells. Conversely, PLCB2, unexpressed in the cell lines, was expressed in some ES and SS. However, PLCH1 was expressed in SaOS-2 and inconstantly expressed in osteoblasts, while it was expressed in ES and unexpressed in SS. The most relevant difference observed in ES compared to SS regarded PLC ε and PLC η isoforms. Conclusion: MG-63 and SaOS-2 osteosarcoma cell lines might represent an inappropriate experimental model for studies about the analysis of signal transduction in osteoblasts

U-73122 reduces the cell growth in cultured MG-63 ostesarcoma cell line involving Phosphoinositide-specific Phospholipases C

The definition of the number and nature of the signal transduction pathways involved in the pathogenesis and the identification of the molecules promoting metastasis spread might improve the knowledge of the natural history of osteosarcoma, also allowing refine the prognosis and opening the way to novel therapeutic strategies. Phosphatydil inositol (4,5) bisphosphate (PIP2), belonging to the Phosphoinositide (PI) signal transduction pathway, was related to the regulation of ezrin, an ezrin-radixin-moesin protein involved in metastatic osteosarcoma spread. The levels of PIP2 are regulated by means of the PI-specific Phospholipase C (PLC) enzymes. Recent literature data suggested that in osteosarcoma the panel of expression of PLC isoforms varies in a complex and unclear manner and is related to ezrin, probably networking with Ras GTPases, such as RhoA and Rac1. We analyzed the expression and the subcellular localization of PLC enzymes in cultured human osteosarcoma MG-63 cells, commonly used as an experimental model for human osteoblasts, using U-73122 PLC inhibitor, U-73343 inactive analogue, and by silencing ezrin. The treatment with U-73122 significantly reduces the number of MG-63 viable cells and contemporarily modifies the expression and the subcellular localization of selected PLC isoforms. U-73122 reduces the cell growth in cultured MG-63 ostesarcoma cell line involving PI-specific Phospholipases C.

Relapsing polychondritis: A clinical update

Relapsing polychondritis (RP) is a rare connective tissue disease in which recurrent bouts of inflammation, involve the cartilage of the ears, nose, larynx, tracheobronchial tree and cardiovascular system. RP is generally observed in the fourth and fifth decades of life and occurs with equal frequency in both sexes. The cause of RP is still unknown. It is considered an immune-mediated disease, as there is an overlap between well documented RP with other rheumatic and autoimmune diseases. There is a significant association of RP with the antigen HLA-DR4. RP includes loss of basophilic staining of cartilage matrix perichondral accompanied by inflammation of the cartilage. Cells are present perivascular mononuclear and polymorphonuclear cells infiltrated. The chondrocytes become vacuolated and necrotic and are replaced by fibrous tissue. Common symptoms are often absent in the early stages of the disease in almost half the cases, resulting in delay in diagnosis. The development of chondrite allows the diagnosis of RP in patients initially evaluated for joint abnormalities, ocular, cutaneous, or audio-vestibular. Diagnostic criteria for RP are based on characteristic clinical manifestations. According to Damiani and Levine, the diagnosis can be considered final when one or more of the clinical features are present in conjunction with biopsy confirmation. The course of symptoms for patients with relapsing polychondritis is often unpredictable. Patients with mild signs of acute inflammation are usually treated with non-steroidal anti-inflammatory drugs and small doses of prednisone. Patients with severe manifestations, such as airway compromise may require high doses of prednisone or even intravenous pulse methyl-prednisone.

Impairment and reorganization of the phosphoinositide-specific phospholipase C enzymes in suicide brains

A number of studies suggested that suicide may be associated with specific neurobiological abnormalities. Neurobiology studies focused upon abnormalities of signalling mechanisms with special regard to the serotonin system and the related Phosphoinositide (PI) signalling system. Previous data suggested the involvement of the PI-specific phospholipase C (PLC) family in neuropsychiatric disorders. By using PCR and morphological microscopy observation we examined the whole panel of expression of PLC isoforms in the brains of 28 individuals who committed suicide and in normal controls in order to evaluate the involvement of specific PLC isoforms. The overall PLC expression was reduced and a complex reorganization of the isoforms was observed. The knowledge of the complex network of neurobiological molecules and interconnected signal transduction pathways in the brain of suicide victims might be helpful to understand the natural history and the pathogenesis of the suicidal behavior. That might lead to obtain prognostic suggestions in order to prevent suicide and to new therapeutic agents targeting specific sites in this signalling cascade.

Silencing of phosphoinositide-specific phospholipase C ε remodulates the expression of the phosphoinositide signal transduction pathway in human osteosarcoma cell lines

BACKGROUND

Ezrin, a member of the ezrin-radixin-moesin family, is involved in the metastatic spread of osteosarcoma. Ezrin binds phosphatydil inositol-4,5-bisphosphate (PIP2), a crucial molecule of the phosphoinositide signal transduction pathway. PIP2 levels are regulated by phosphoinositide-specific phospholipase C (PI-PLC) enzymes. PI-PLCε isoform, a well-characterized direct effector of rat sarcoma (RAS), is at a unique convergence point for the broad range of signaling pathways that promote RAS GTPase-mediated signalling.

MATERIALS AND METHODS

By using molecular biology methods and microscopic analyses, we analyzed the expression of ezrin and PLC genes after silencing of PLCE (OMIM *608414) in 143B and Hs888 cell lines.

RESULTS

The growth rate of the cells was slowed, and the expression of ezrin, PLCB1, PLCG2 and PLCD4 was significantly modified. Ezrin displacement from the plasma membrane was observed.

CONCLUSION

The present results corroborate the hypothesis that ezrin and the PI signal transduction system are involved in a common network.

Is Montgomery tracheal Safe-T-Tube clinical failure induced by biofilm?

OBJECTIVES

Montgomery Safe-T-Tube deterioration and early biofilm colonization may explain the discomfort claimed by many patients and clinical failures. The aim of the study was to analyze the deterioration of Montgomery Safe-T-Tube morphological and mechanical properties in vivo in 16 patients by using microbiological methods, optical and electron microscopy, and engineering tests.

STUDY DESIGN

Prospective controlled study at a single medical center.

SETTING

University hospital.

SUBJECTS AND METHODS

The study, conducted from April 2007 to February 2012 at the "Sapienza" University of Rome, was designed to collect 2 Montgomery Safe-T-Tubes from each patient. The first was removed 3 to 15 days after insertion (group A) and the second at least 90 days after (group B). Specimens underwent microbiologic assays, electron microscopic analysis, immunocytologic analysis, and mechanical tests.

RESULTS

Microorganisms were not isolated in 2 group A cases (12%), whereas they were in all group B cases. Biofilm was identified in 11 of 16 (69%) group A samples and in 16 of 16 (100%) group B samples (P = .0149) using scanning electron microscopy. Immunohistochemistry showed monocyte-granulocyte line cells producing interleukin-1β on the external surfaces of Montgomery Safe-T-Tubes. The tensile test showed that the wear related to the longer period of use makes Montgomery Safe-T-Tubes more rigid than newer ones.

CONCLUSION

Early biofilm colonization takes place in Montgomery Safe-T-Tubes in most cases. The mechanical decay could be justified in part by the destructive biofilm activity and by the release of inflammatory effectors and enzymes.

Phosphoinositide-specific Phospholipase C β1 gene deletion in bipolar disorder affected patient

The involvement of phosphoinositides (PI) signal transduction pathway and related molecules, such as the Phosphoinositide-specific Phospholipase C (PI-PLC) enzymes, in the pathophysiology of mood disorders is corroborated by a number of recent evidences. Our previous works identified the deletion of PLCB1 gene, which codifies for the PI-PLC β1 enzyme, in 4 out 15 patients affected with schizophrenia, and no deletion both in major depression affected patients and in normal controls. By using interphase fluorescent in situ hybridization methodology, we analyzed PLCB1 in paraffin embedded samples of orbito-frontal cortex of 15 patients affected with bipolar disorder. Deletion of PLCB1 was identified in one female patient.

Phosphoinositide pathway and the signal transduction network in neural development

The development of the nervous system is under the strict control of a number of signal transduction pathways, often interconnected. Among them, the phosphoinositide (PI) pathway and the related phospholipase C (PI-PLC) family of enzymes have been attracting much attention. Besides their well-known role in the regulation of intracellular calcium levels, PI-PLC enzymes interact with a number of molecules belonging to further signal transduction pathways, contributing to a specific and complex network in the developing nervous system. In this review, the connections of PI signalling with further transduction pathways acting during neural development are discussed, with special regard to the role of the PI-PLC family of enzymes.

Deletion of PLCB1 gene in schizophrenia-affected patients

A prevalence of 1% in the general population and approximately 50% concordance rate in monozygotic twins was reported for schizophrenia, suggesting that genetic predisposition affecting neurodevelopmental processes might combine with environmental risk factors. A multitude of pathways seems to be involved in the aetiology and/or pathogenesis of schizophrenia, including dopaminergic, serotoninergic, muscarinic and glutamatergic signalling. The phosphoinositide signal transduction system and related phosphoinositide-specific phospholipase C (PI-PLC) enzymes seem to represent a point of convergence in these networking pathways during the development of selected brain regions. The existence of a susceptibility locus on the short arm of chromosome 20 moved us to analyse PLCB1, the gene codifying for PI-PLC β1 enzyme, which maps on 20p12. By using interphase fluorescent in situ hybridization methodology, we found deletions of PLCB1 in orbito-frontal cortex samples of schizophrenia-affected patients.

Fetal aorta wall inflammation in ultrasound-detected aortic intima/media thickness and growth retardation

Several studies have reported that fetuses with intrauterine growth restriction (IUGR) and infants with low birth weight present increased intima/media thickness (aIMT) of the abdominal aorta wall compared with fetuses and infants appropriate for gestational age (AGA). Evidence suggested that aIMT might be related to inflammation, probably indicating a very early stage of future adulthood disease, such as atherosclerosis. We aimed to investigate histological findings in the abdominal aorta wall of one IUGR stillbirth in which ultrasound had detected aIMT. Microscopy observations of the abdominal aorta wall confirmed the intima thickening and detected condensation of the elastic fibers forming an evident internal elastic membrane and presence of inflammatory elements, such as macrophages, activated endothelial cells, and fibroblastoid cells. The present study highlights that IUGR associated with aIMT is related to inflammation, which might represent a very early sign of future adult lesions.

Role of phosphoinositide-specific phospholipase C η2 in isolated and syndromic mental retardation

Deletions in the distal region of the short arm of chromosome 1 (1p36) are widely diffuse, both as somatic abnormalities in tumors and as constitutive in the congenital 1p36 deletion syndrome. The deletion size varies from 1.5 to 10 Mb, with common breakpoints located from 1p36.13 to 1p36.33. Patients bearing constitutional deletion of a smaller region, 1p36.3, present with a number of features, including mental retardation. The gene PLCH2, codifying for the phosphoinositide-specific phospholipase C (PI-PLC) η2, maps on the 1p36.32 region. PI-PLC η2, expressed in the brain after birth, is a key enzyme in cellular calcium mobilization. In the brain, calcium plays a role in axon growth and retraction, growth cone guidance, synapse formation, and responses to various neurotransmitters. For its role in the nervous system, PI-PLC η2 might be a putative candidate gene for the neurodevelopmental delay observed in patients bearing 1p36.3 deletions.

Expression pattern and sub-cellular distribution of phosphoinositide specific phospholipase C enzymes after treatment with U-73122 in rat astrocytoma cells

Phosphoinositide specific phospholipase C (PI-PLC) enzymes interfere with the metabolism of inositol phospholipids (PI), molecules involved in signal transduction, a complex process depending on various components. Many evidences support the hypothesis that, in the glia, isoforms of PI-PLC family display different expression and/or sub cellular distribution under non-physiological conditions such as the rat astrocytes activation during neurodegeneration, the tumoural progression of some neoplasms and the inflammatory cascade activation after lipopolysaccharide administration, even if their role remains not completely elucidated. Treatment of a cultured established glioma cell line (C6 rat astrocytoma cell line) induces a modification in the pattern of expression and of sub cellular distribution of PI-PLCs compared to untreated cells. Special attention require PI-PLC beta3 and PI-PLC gamma2 isoforms, whose expression and sub cellular localization significantly differ after U-73122 treatment. The meaning of these modifications is unclear, also because the use of this N-aminosteroid compound remains controversial, inasmuch it has further actions which might contribute to the global effect recorded on the treated cells.

Expression of phosphoinositide-specific phospholipase C isoenzymes in cultured astrocytes activated after stimulation with lipopolysaccharide

Signal transduction pathways, involved in cell cycle and activities, depend on various components including lipid signalling molecules, such as phosphoinositides and related enzymes. Many evidences support the hypothesis that inositol lipid cycle is involved in astrocytes activation during neurodegeneration. Previous studies investigated the pattern of expression of phosphoinositide-specific phospholipase C (PI-PLC) family isoforms in astrocytes, individuating in cultured neonatal rat astrocytes, supposed to be quiescent cells, the absence of some isoforms, accordingly to their well known tissue specificity. The same study was conducted in cultured rat astrocytoma C6 cells and designed a different pattern of expression of PI-PLCs in the neoplastic counterpart, accordingly to literature suggesting a PI signalling involvement in tumour progression. It is not clear the role of PI-PLC isoforms in inflammation; recent data demonstrate they are involved in cytokines production, with special regard to IL-6. PI-PLCs expression in LPS treated neonatal rat astrocytes performed by using RT-PCR, observed at 3, 6, 18 and 24 h intervals, expressed: PI-PLC beta1, beta4 and gamma1 in all intervals analysed; PI-PLC delta1 at 6, 18 and 24 h; PI-PLC delta3 at 6 h after treatment. PI-PLC beta3, delta4 and epsilon, present in untreated astrocytes, were not detected after LPS treatment. Immunocytochemical analysis, performed to visualize the sub-cellular distribution of the expressed isoforms, demonstrated different patterns of localisation at different times of exposure. These observations suggest that PI-PLCs expression and distribution may play a role in ongoing inflammation process of CNS.

Signalling in the genomic era

For a complex organism, short range signalling is not sufficient to coordinate the behaviour of all cells composing itself. The response to stimuli is the reprogramming of cell activity (resulting in differentiation, proliferation, stand by or apoptosis depending on the set of signals). Cells own elaborate and complex systems of proteins that enable them to communicate, including both secreted signalling molecules and related factors, deriving from relic mechanisms. The intra and intercellular signalling are actively studied not only to comprehend the basic mechanisms that allowed the evolution of mammals species on earth, but also because the alteration of one or more of these pathways is recognized to be involved in a crescent number of human diseases, both degenerative and tumoural. That is, a growing body of evidences suggest that every human disease may be analyzed and classified by a "signalling disease" point of view. This approach opens new therapeutic perspectives, virtually amplifying for every single disease the number of therapeutic targets (in terms of both genes and proteins) to upstream and/or downstream, short and/or long distance proteins interacting with the altered molecule, thus individuating many other targets to which act upon.

Immunohistochemical profile of various neurotransmitters, neurotrophins and MIB-1 in cholesteatomas of the petrous bone

Compared to the normal epidermal epithelium, cholesteatomas have altered growth properties characterized by the excessive growth of keratinocytes leading to mucosal destruction. Either congenital or acquired, these lesions, which grow in the middle ear space, the petrous apex or the mastoid of temporal bones, are mostly considered benign skin tumoral lesions. However, many questions remain concerning their pathophysiology. Numerous studies have been proposed to identify those cholesteatoma lesions at risk of recurrence, a possible event that may cause hearing loss. We examined patients with petrous apex or mastoid cholesteatoma in order to analyze the expression of various neurotransmitters, neurotrophins and their receptors and the Ki-67 antigen for identification of a possible relationship between clinical outcome and histopathological behaviour in terms of the proliferative activity of cholesteatomas. Expression of the analyzed molecules was studied using immunohistochemical methods in seven adult patients with petrous apex cholesteatoma who underwent surgical removal of the lesion. Our results, in accordance with published data, confirm that Molecular Immunology Borstel-1 (MIB-1) and certain neurotransmitters could be useful in the prognostic evaluation of the risk of recurrence of aggressive forms of cholesteatoma.

Expression of phosphoinositide-specific phospholipase C isoenzymes in cultured astrocytes

Signal transduction from plasma membrane to cell nucleus is a complex process depending on various components including lipid signaling molecules, in particular phosphoinositides and their related enzymes, which act at cell periphery and/or plasma membrane as well as at nuclear level. As far as the nervous system may concern the inositol lipid cycle has been hypothesized to be involved in numerous neural as well as glial functions. In this context, however, a precise panel of glial PLC isoforms has not been determined yet. In the present experiments we investigated astrocytic PLC isoforms in astrocytes obtained from foetal primary cultures of rat brain and from an established cultured (C6) rat astrocytoma cell line, two well known cell models for experimental studies on glia. Identification of PLC isoforms was achieved by using a combination of RT-PCR and immunocytochemistry experiments. While in both cell models the most represented PI-PLC isoforms were beta4, gamma1, delta4, and epsilon, isoforms PI-PLC beta2 and delta3 were not detected. Moreover, in primary astrocyte cultures PI-PLC delta3 resulted well expressed in C6 cells but was absent in astrocytes. Immunocytochemistry performed with antibodies against specific PLC isoforms substantially confirmed this pattern of expression both in astrocytes and C6 glioma cells. In particular while some isoenzymes (namely isoforms beta3 and beta4) resulted mainly nuclear, others (isoforms delta4 and epsilon) were preferentially localized at cytoplasmic and plasma membrane level.

Peribronchial innervation of the rat lung

Mammalian peribronchial tissue is supplied by several peptide-containing nerve fibers. Although it is well established that different neuropeptides exert significant effects on bronchial and vascular tone in the lungs, the role played by some neuromediators on the general regulation, differentiation and release of locally active substances is still controversial. We studied the innervation of rat peribronchial tissue by immunohistochemical techniques. The immunoperoxidase method with nickel amplification was applied to detect the distribution of nerve fibers using antibodies against the general neuronal marker PGP 9.5 (neuron-specific cytoplasmic protein), while the cholinacetyltransferase immunoreactivity was studied by immunohistochemistry. A slight immunoreactivity for NT receptors is observed in lung bronchial epithelium. There is increasing evidence that NTs may act with a paracrine mechanism regulating functional activity of neuronal and non-neuronal structures. A specific immunoreactivity for NTs and NT receptors was also demonstrated within different layers of large, medium and small sized intrapulmonary arteries and veins, according to a recent study of our group. Moreover our data describe the expression of NTs and NT receptors in lymphoid aggregates of the lung (BALT) in which both lymphocytes and macrophages express TrkA receptor and synthesize NTs. Our results show the presence of an extensive network of innervation in the rat peribronchial tissue, confirming a morphological basis for a possible neural modulation of the respiratory mucosa and the physiological/pathophysiological mechanisms of the lung.

Expression of phospholipase C beta family isoenzymes in C2C12 myoblasts during terminal differentiation

In the present work, we have analyzed the expression and subcellular localization of all the members of inositide-specific phospholipase C (PLCbeta) family in muscle differentiation, given that nuclear PLCbeta1 has been shown to be related to the differentiative process. Cell cultures of C2C12 myoblasts were induced to differentiate towards the phenotype of myotubes, which are also indicated as differentiated C2C12 cells. By means of immunochemical and immunocytochemical analysis, the expression and subcellular localization of PLCbeta1, beta2, beta3, beta4 have been assessed. As further characterization, we investigated the localization of PLCbeta isoenzymes in C2C12 cells by fusing their cDNA to enhanced green fluorescent protein (GFP). In myoblast culture, PLCbeta4 was the most expressed isoform in the cytoplasm, whereas PLCbeta1 and beta3 exhibited a lesser expression in this cell compartment. In nuclei of differentiated myotube culture, PLCbeta1 isoform was expressed at the highest extent. A marked decrease of PLCbeta4 expression in the cytoplasm of differentiated C2C12 cells was detected as compared to myoblasts. No relevant differences were evidenced as regards the expression of PLCbeta3 at both cytoplasmatic and nuclear level, whilst PLCbeta2 expression was almost undetectable. Therefore, we propose that the different subcellular expression of these PLC isoforms, namely the increase of nuclear PLCbeta1 and the decrease of cytoplasmatic PLCbeta4, during the establishment of myotube differentiation, is related to a spatial-temporal signaling event, involved in myogenic differentiation. Once again the subcellular localization appears to be a key step for the diverse signaling activity of PLCbetas.