Disruption of dopamine D1/D2 receptor complex is involved in the function of haloperidol in cardiac H9c2 cells.

AIMS: Haloperidol is an antipsychotic agent and acts as dopamine D2 receptor (D2R) antagonist, as a prototypical ligand of sigma1 receptors (Sig1R) and it increases expression of type 1 IP3 receptors (IP3R1). However, precise mechanism of haloperidol action on cardiomyocytes through dopaminergic signaling was not described yet. This study investigated a role of dopamine receptors in haloperidol-induced increase in IP3R1 and Sig1R, and compared physiological effect of melperone and haloperidol on basic heart parameters in rats. MATERIALS AND METHODS: We used differentiated NG-108 cells and H9c2 cells. Gene expression, Western blot and immunofluorescence were used to evaluate haloperidol-induced differences; proximity ligation assay (PLA) and immunoprecipitation to determine interactions of D1/D2 receptors. To evaluate cardiac parameters, Wistar albino male rats were used. KEY FINDINGS: We have shown that antagonism of D2R with either haloperidol or melperone results in upregulation of both, IP3R1 and Sig1R, which is associated with increased D2R, but reduced D1R expression. Immunofluorescence, immunoprecipitation and PLA support formation of heteromeric D1/D2 complexes in H9c2 cells. Treatment with haloperidol (but not melperone) caused decrease in systolic and diastolic blood pressure and significant increase in heart rate. SIGNIFICANCE: Because D1R/D2R complexes can engage Gq-like signaling in other experimental systems, these results are consistent with the possibility that disruption of D1R/D2R complex in H9c2 cells might cause a decrease in IP3R1 activity, which in turn may account for the increase expression of IP3R and Sig1R. D2R is probably not responsible for changes in cardiac parameters, since melperone did not have any effect.

Nilotinib induces ER stress and cell death in H9c2 cells.

Tyrosine kinases inhibitors (TKi) represent a relatively novel class of anticancer drugs that target cellular pathways overexpressed in certain types of malignancies, such as chronic myeloid leukaemia (CML). Nilotinib, ponatinib and imatinib exhibit cardiotoxic and vascular effects. In this study, we focused on possible cardiotoxicity of nilotinib using H9c2 cells as a suitable cell model. We studied role of endoplasmic reticulum (ER) stress and apoptosis in nilotinib toxicity using a complex approach. Nilotinib impaired mitochondrial function and induced formation of ROS under clinically relevant concentrations. In addition, ability of nilotinib to induce ER stress has been shown. These events result in apoptotic cell death. All these mechanisms contribute to cytotoxic effect of the drug. In addition, involvement of ER stress in nilotinib toxicity may be important in co-treatment with pharmaceuticals affecting ER and ER stress, e.g. beta-blockers or sartans, and should be further investigated.

Epigenetic modification of Rta (ORF50) promoter is not responsible for distinct reactivation patterns of murine gammaherpesviruses.

Gammaherpesviruses-encoded replication and transcription activator (Rta) (ORF50) plays an essential role in the initiation of viral lytic gene expression and reactivation from latency. The Rta expression is influenced by many viral and cellular factors, including epigenetic modifications, mainly DNA methylation and histone modifications. Murine gammaherpesvirus 68 (MHV-68), belonging to the species Murid herpesvirus (MuHV-4), is widely used as a model to study human gammaherpesvirus infections in vitro as well as in vivo. Recent studies of the MHV-68 Rta promoter revealed the effect of DNA demethylation and histone acetylation, induced by the inhibitor of histone deacetylase trichostatin A (TSA), on the MHV-68 reactivation from latency. Two other strains of MuHV-4, MHV-72 and MHV-4556, possess several unique properties, which distinguish them from strain MHV-68. Recently discovered reduced capacity of MHV-72 and MHV-4556 to reactivate from latency may be related to different methylation/demethylation patterns of the promoter regulatory region of the Rta. Here, we investigated the epigenetic regulation of the Rta promoter of three murine gammaherpesvirus strains, MHV-68, MHV-72 and MHV-4556, during latency and reactivation in vivo. However, we did not find any differences between Rta of MHV-68, MHV-72 and MHV-4556 and its epigenetic regulation during lytic infection, latency and de novo infection after ex vivo and in vivo reactivation induced by TSA. We confirmed that the treatment with TSA successfully induced demethylation of the Rta promoter regions of all three studied strains. Moreover, we have shown that the primary sequence of Rta and its promoter is identical for all three strains.

Interferon lambda induces antiviral response to herpes simplex virus 1 infection.

Lambda interferons (IFN-λ) are known to induce potent antiviral response in a wide variety of target cells. They activate the same intracellular signalling pathways and have similar biological activities as IFN-α/ß, including antiviral activity, but signal via distinct receptor complex, which is expressed in a cell- and species-specific manner. IFN-λ was reported to induce in vitro marked antiviral activity against various RNA viruses, but corresponding data on DNA viruses are sparse. Therefore we examined the IFN-λ1 induced antiviral activity against two strains of herpes simplex virus 1, a highly pathogenic ANGpath and moderately pathogenic KOS. The antiviral response was determined in vitro in Vero cells, known as deficient in production of type I IFNs and in Vero E6 cells, responding to viral infection with abundant IFN-λ production, although deficient in production of type I IFNs. The results showed that IFN-λ1 induced in Vero cells higher antiviral activity against ANGpath strain than against KOS strain. In Vero E6 cells endogenous IFN-λ induced higher antiviral activity against ANGpath strain than against KOS strain, but because of the virus induction of IFN-λ expression the antiviral activity was detected later. The observed differences between the IFN-λ1-induced antiviral activities against viral strains of various pathogenicity suggest that virus attributes may play role in the antiviral state of cells induced by IFN-λ.

Interferons lambda, new cytokines with antiviral activity.

Interferons (IFNs) are key cytokines in the establishment of a multifaceted antiviral response. Three distinct types of IFNs are now recognized (type I, type II, and type III) based on their receptor usage, structural features and biological activities. Although all IFNs are important mediators of antiviral protection, their roles in antiviral defence vary. Interferon lambda (IFN-λ) is a recently discovered group of small helical cytokines capable of inducing an antiviral response both in vitro as well as in vivo. They were discovered independently in 2003 by the groups of Sheppard and Kotenko. This family consists of three structurally related IFN-λ subtypes called IFN-λ1 (IL-29), IFN-λ2 (IL-28A), and IFN-λ3 (IL-28B). In this study we investigate the antiviral activities of IFN-λ1, λ2, and λ3 on some medically important viruses, influenza viruses, herpes viruses and lymphocytic choriomeningitis virus.