The expression of the thyroid-stimulating hormone (TSH) receptor and the cAMP-dependent protein kinase RII beta regulatory subunit confers TSH-cAMP-dependent growth to mouse fibroblasts.

TSH activates its specific receptor in thyroid cells and induces cAMP, a robust stimulator of thyroid cell proliferation. Conversely, cAMP is a potent inhibitor of growth in mouse fibroblasts. To dissect the signals mediating cAMP-dependent growth, we have expressed in mouse fibroblasts the human thyrotropin receptor (TSHR) or a constitutively active mutant, under the control of the tetracyclin promoter. Both TSHR and cAMP levels were modulated by tetracyclin. In the presence of serum, activation of TSHR by TSH induced growth arrest. In the absence of serum, cells expressing TSHR stimulated with TSH, replicated their DNA, but underwent apoptosis. Co-expression of cAMP-dependent protein kinase (PKA) regulatory subunit type II (RIIbeta) inhibited apoptosis and stimulated the growth of cells only in the presence of TSH. Expression of RIIbeta-PKA, in the absence of TSHR, induced apoptosis, which was reversed by cAMP. Growth, stimulated by TSHR-RIIbeta-PKA in mouse fibroblasts, was also dependent on Rap1 activity, indicating cAMP-dependent growth in thyroid cells. As for the molecular mechanism underlying these effects, we found that in normal fibroblasts, TSH induced AKT and ERK1/2 only in cells expressing TSHR and RII. Similarly, activation of TSHR increased cAMP levels greatly, but was unable to stimulate CREB phosphorylation and transcription of cAMP-induced genes in the absence of RII. These data provide a simple explanation for the anti-proliferative and proliferative effects of cAMP in different cell types and indicate that RII-PKAII complements TSHR action by stably propagating robust cAMP signals in cell compartments

Role of G Protein-coupled Receptor Kinase 4 and β-Arrestin 1 in Agonist-stimulated Metabotropic Glutamate Receptor 1 Internalization and Activation of Mitogen-activated Protein Kinases

The metabotropic glutamate 1 (mGlu(1)) receptor in cerebellar Purkinje cells plays a key role in motor learning and motor coordination. Here we show that the G protein-coupled receptor kinases (GRK) 2 and 4, which are expressed in these cells, regulate the mGlu(1) receptor by at least in part different mechanisms. Using kinase-dead mutants in HEK293 cells, we found that GRK4, but not GRK2, needs the intact kinase activity to desensitize the mGlu(1) receptor, whereas GRK2, but not GRK4, can interact with and regulate directly the activated Galpha(q). In cells transfected with GRK4 and exposed to agonist, beta-arrestin was first recruited to plasma membranes, where it was co-localized with the mGlu(1) receptor, and then internalized in vesicles. The receptor was also internalized but in different vesicles. The expression of beta-arrestin V53D dominant negative mutant, which did not affect the mGlu(1) receptor internalization, reduced by 70-80% the stimulation of mitogen-activated protein (MAP) kinase activation by the mGlu(1) receptor. The agonist-stimulated differential sorting of the mGlu(1) receptor and beta-arrestin as well as the activation of MAP kinases by mGlu(1) agonist was confirmed in cultured cerebellar Purkinje cells. A major involvement of GRK4 and of beta-arrestin in agonist-dependent receptor internalization and MAP kinase activation, respectively, was documented in cerebellar Purkinje cells using an antisense treatment to knock down GRK4 and expressing beta-arrestin V53D dominant negative mutant by an adenovirus vector. We conclude that GRK2 and GRK4 regulate the mGlu(1) receptor by different mechanisms and that beta-arrestin is directly involved in glutamate-stimulated MAP kinase activation by acting as a signaling molecule

Seroprevalence of Bartonella henselae in patients awaiting heart transplant in Southern Italy

Background Bartonella henselae is the etiologic agent of cat-scratch disease. B. henselae infections are responsible for a widening spectrum of human diseases, although often symptomless, ranging from self-limited to life-threatening and show different courses and organ involvement due to the balance between host and pathogen. The role of the host immune response to B. henselae is critical in preventing progression to systemic disease. Indeed in immunocompromised patients, such as solid organ transplant patients, B. henselae results in severe disseminated disease and pathologic vasoproliferation. The purpose of this study was to determine the seroprevalence of B. henselae in patients awaiting heart transplant compared to healthy individuals enrolled in the Regional Reference Laboratory of Transplant Immunology of Second University of Naples. Methods Serum samples of 38 patients awaiting heart transplant in comparison to 50 healthy donors were examined using immunfluorescence assay. Results We found a B. henselae significant antibody positivity rate of 21% in patients awaiting heart transplant ( p = 0.002). There was a positive rate of 8% ( p > 0.05) for immunoglobulin (Ig)M and a significant value of 13% ( p = 0.02) for IgG, whereas controls were negative both for IgM and IgG antibodies against B. henselae . The differences in comorbidity between cases and controls were statistically different (1.41 ± 0.96 vs 0.42 ± 0.32; p = 0.001). Conclusions Although this study was conducted in a small number of patients, we suggest that the identification of these bacteria should be included as a routine screening analysis in pretransplant patients

Pathogenic mechanisms of tissue damage mediated by Bartonella henselae in preclinical models and in patients with advanced heart failure awaiting transplantation

Heart transplantation outcome is related to effects of immunological and no immunological factors. The major immunological factors are the HLA, the autoimmunity and the inflammation, while the non-immunological factors include among other the hypertension, diabetes, immunosuppressive therapies, cancer and infections. Infectious complications represent a significant source of morbidity and mortality in heart transplantation recipients. However, few studies have been focused on the incidence and the types of infection in patients awaiting heart transplantation and the impact of pre-transplantation infections on the early post-transplantation period. Often these are opportunistic infections due to virus, bacteria and fungi that can be difficult to identify, to treat, and can be lethal in the immunosuppressed patients. Most post-transplantation infections represent reactivation of latent or quiescent infections that had been contracted prior to transplantation. Recently, several evidences have showed the incidence of B. henselae infections in solid organ transplantation recipients. B. henselae infections are responsible for a widening spectrum of human diseases, ranging from self-limited to life-threatening and show different course and organ involvement due to the balance between host and pathogen. The role of the host immune response to B. henselae is critical in preventing progression to systemic disease. Indeed, in immunocompromised patients, such as solid organ transplanted subjects, B. henselae infection results in severe disseminated disease and pathologic vasoproliferation with involvement of different organs mainly due to vasoproliferative lesions. Furthermore, B. henselae can persist in primary niche prior to blood-stage infection. In vitro and in vivo studies have demonstrated that endothelial progenitor cells are able to internalize B. henselae and they are eligibile as primary niche. Susceptibility to infections and many other human diseases arises through the complex interaction between environmental and host genetic factors including the HLA molecules. In our study, we have found a B. henselae significant antibody positivity rate of 21% in patients awaiting heart transplantation enrolled in our Regional Reference list for organ transplantation. We have demonstrated a significant correlation between the B. henselae infection and the presence of HLA-B*35 allele and a significant impairment of number of circulating endothelial progenitor cells in patients with advanced heart failure. In addition, we have also evaluated the tissue damage in a model of immunocompromised mice infected with B. henselae by revealing a strong deposition of collagen after B. henselae infection and an increase of endothelial progenitor cell number that can suggest an involvement of these cells in the immune response of mice infected but also in the triggering the vasoproliferative process. Our retrospective observational study, although performed on a small number of patients only in pre-transplantation time suggests that B. henselae, together with other emerging bacteria, should be included as a routine analysis in the list of opportunistic infections

From HLA typing to anti-HLA antibody detection and beyond: The road ahead

The complex polymorphism of the HLA genes and the need of a proper identification of anti-HLA antibodies have led to continuously develop novel practical and feasible technologies in the field of organ and tissue transplantation. Technologies to identify HLA molecules have evolved from the serological to the molecular methods and a true innovation in the DNA sequencing has taken place with the development of next generation sequencing. An interesting field to explore is how the information resulting from the HLA-DNA sequencing can be applied in the clinical setting by including the alloimmunization assessment. Indeed, a good characterization of anti-HLA antibody at epitope level can reduce the risk of immunization. Many anti-HLA antibodies are specific for epitopes rather than for HLA antigens and the knowledge of unacceptable epitopes allows to reduce the number of mismatched antigens. Furthermore, high resolution HLA allele typing could help to understand the epitopes against which antibodies are developed. However, the improvements should not only concern the diagnostic tools in the pre-transplantation phase, but also the monitoring of post transplantation outcome. There is a growing interest in developing new non-invasive biomarkers to monitor the rejection. Currently, increasing evidence has focused on miRNAs, epigenetic markers emerged as regulators of molecular events that are differently expressed in biopsies and blood as well as in urinary samples of transplanted recipients. The implementation of next generation sequencing and genome-wide expression analysis together with functional assays may provide useful tools to evaluate the epigenetic modulation in transplantation biology but many efforts are requested for translating in the clinical arena the results obtained in experimental models

Comprehensive assessment of sensitizing events and anti-HLA antibody development in women awaiting kidney transplantation

Background: Alloimmunization remains a critical factor which affects the success of kidney transplantation. Patients awaiting solid organ transplantation may develop anti-HLA antibodies after pregnancies, transfusions and previous events of transplantations. Aim: We evaluated the effects of different sensitizing events on the anti-HLA antibody production and the potential role of patient HLA alleles in the context of antibody development in both the overall and pregnancy sensitized groups. Material and methods: We retrospectively stratified 411 women on waiting list for kidney transplantation by route of sensitization. The presence of anti-HLA antibodies was evaluated by Solid Phase Assay and HLA typing was performed by serological and molecular methods. Results: In our study population, 54% of women had anti-HLA antibodies. We found that the 51.6% of women with pregnancy only, 44% of women with transfusion only and 100% of women with a history of transplantation only developed anti-HLA antibodies. Pregnancy only resulted significantly associated with all anti-HLA antibody development such as anti-A, -B, -C, -DR, -DP as well as anti-DQB and -DQA antibodies. We investigated the influence of patient HLA alleles on the antibody development in the overall study population. Patients expressing HLA A*32 (p = 0.024, OR = 0.42), B*14 (p = 0.035, OR = 0.44), HLA-B*44 (p = 0.026, OR = 0.51) and DRB1*01 (p = 0.029, OR = 0.55) alleles produced anti-HLA antibodies less frequently compared to subjects with other alleles. In the pregnancy only group, B*14 (p = 0.010, OR = 0.12) and B*51 (p = 0.005, OR = 0.24) alleles were associated with a low risk of anti-HLA antibody development, while A*11 (p = 0.033, OR = 3.56) and DRB1*04 (p = 0.022, OR = 3.03) alleles seem to represent a higher risk. Conclusions: Pregnancy still remains a strong sensitizing event in women awaiting kidney transplantation. The anti-HLA antibody development in pregnancy appears to be associated with the expression of particular HLA alleles

Innate and adaptive immune response in stroke: Focus on epigenetic regulation

Inflammation and immune response play a pivotal role in the pathophysiology of ischemic stroke giving their contribution to tissue damage and repair. Emerging evidence supports the involvement of epigenetic mechanisms such as methylation, histone modification and miRNAs in the pathogenesis of stroke. Interestingly, epigenetics can influence the molecular events involved in ischemic injury by controlling the switch from pro- to anti-inflammatory response, however, this is still a field to be fully explored. The knowledge of epigenetic processes could to allow for the discovery of more sensitive and specific biomarkers for risk, onset, and progression of disease as well as further novel tools to be used in both primary prevention and therapy of stroke. Indeed, studies performed in vitro and in small animal models seem to suggest a neuroprotective role of HDAC inhibitors (e.g. valproic acid) and antagomir (e.g. anti-miR-181a) in ischemic condition by modulation of both immune and inflammatory pathways. Thus, the clinical implications of altered epigenetic mechanisms for the prevention of stroke are very promising but clinical prospective studies and translational approaches are still warranted

The epigenetic promise to improve prognosis of heart failure and heart transplantation

Heart transplantation is still the only possible life-saving treatment for end-stage heart failure, the critical epilogue of several cardiac diseases. Epigenetic mechanisms are being intensively investigated because they could contribute to establishing innovative diagnostic and predictive biomarkers, as well as ground-breaking therapies both for heart failure and heart transplantation rejection. DNA methylation and histone modifications can modulate the innate and adaptive immune response by acting on the expression of immune-related genes that, in turn, are crucial determinants of transplantation outcome. Epigenetic drugs acting on methylation and histone-modification pathways may modulate Treg activity by acting as immunosuppressive agents. Moreover, the identification of non-invasive and reliable epigenetic biomarkers for the prediction of allograft rejection and for monitoring immunosuppressive therapies represents an attractive perspective in the management of transplanted patients. MiRNAs seem to fit particularly well to this purpose because they are differently expressed in patients at high and low risk of rejection and are detectable in biological fluids besides biopsies. Although increasing evidence supports the involvement of epigenetic tags in heart failure and transplantation, further short and long-term clinical studies are needed to translate the possible available findings into clinical setting