Suppression of β1-adrenoceptor autoantibodies is involved in the antiarrhythmic effects of omega-3 fatty acids in male and female hypertensive rats

The arrhythmogenic potential of β1-adrenoceptor autoantibodies (β1-AA), as well as antiarrhythmic properties of omega-3 in heart diseases, have been reported while underlying mechanisms are poorly understood. We aimed to test our hypothesis that omega-3 (eicosapentaenoic acid-EPA, docosahexaenoic acid-DHA) may inhibit matrix metalloproteinase (MMP-2) activity to prevent cleavage of β1-AR and formation of β1-AA resulting in attenuation of pro-arrhythmic connexin-43 (Cx43) and protein kinase C (PKC) signaling in the diseased heart. We have demonstrated that the appearance and increase of β1-AA in blood serum of male and female 12-month-old spontaneously hypertensive rats (SHR) was associated with an increase of inducible ventricular fibrillation (VF) comparing to normotensive controls. In contrast, supplementation of hypertensive rats with omega-3 for two months suppressed β1-AA levels and reduced incidence of VF. Suppression of β1-AA was accompanied by a decrease of elevated myocardial MMP-2 activity, preservation of cardiac cell membrane integrity and Cx43 topology. Moreover, omega-3 abrogated decline in expression of total Cx43 as well as its phosphorylated forms at serine 368 along with PKC-ε, while decreased pro-fibrotic PKC-δ levels in hypertensive rat heart regardless the sex. The implication of MMP-2 in the action of omega-3 was also demonstrated in cultured cardiomyocytes in which desensitization of β1-AR due to permanent activation of β1-AR with isoproterenol was prevented by MMP-2 inhibitor or EPA. Collectively, these data support the notion that omega-3 via suppression of β1-AA mechanistically controlled by MMP-2 may attenuate abnormal of Cx43 and PKC signaling; thus, abolish arrhythmia substrate and protect rats with an advanced stage of hypertension from malignant arrhythmias

Activation of JNK Triggers Release of Brd4 from Mitotic Chromosomes and Mediates Protection from Drug-Induced Mitotic Stress

Some anti-cancer drugs, including those that alter microtubule dynamics target mitotic cells and induce apoptosis in some cell types. However, such drugs elicit protective responses in other cell types allowing cells to escape from drug-induced mitotic inhibition. Cells with a faulty protective mechanism undergo defective mitosis, leading to genome instability. Brd4 is a double bromodomain protein that remains on chromosomes during mitosis. However, Brd4 is released from mitotic chromosomes when cells are exposed to anti-mitotic drugs including nocodazole. Neither the mechanisms, nor the biological significance of drug-induced Brd4 release has been fully understood. We found that deletion of the internal C-terminal region abolished nocodazole induced Brd4 release from mouse P19 cells. Furthermore, cells expressing truncated Brd4, unable to dissociate from chromosomes were blocked from mitotic progression and failed to complete cell division. We also found that pharmacological and peptide inhibitors of the c-jun-N-terminal kinases (JNK) pathway, but not inhibitors of other MAP kinases, prevented release of Brd4 from chromosomes. The JNK inhibitor that blocked Brd4 release also blocked mitotic progression. Further supporting the role of JNK in Brd4 release, JNK2–/– embryonic fibroblasts were defective in Brd4 release and sustained greater inhibition of cell growth after nocodazole treatment. In sum, activation of JNK pathway triggers release of Brd4 from chromosomes upon nocodazole treatment, which mediates a protective response designed to minimize drug-induced mitotic stress

Pentoxifylline influences drug transport activity of P-glycoprotein and decreases mdr1 gene expression in multidrug resistant mouse leukemic L1210/VCR cells

The effects of pentoxifylline (PTX) on intracellular accumulation of doxorobicin (DOX), DOX cytotoxicity and expression of Pgp in multidrug resistant L1210/VCR cell line were investigated. PTX (100 mg/l) was able to enhance the DOX accumulation in resistant cells. The maximum intracellular levels of DOX were reached after treatment with PTX for 24 hours (total duration of PTX-treatment was 72 hours). The levels of mdrl mRNA (measured by RT-PCR method) were decreased 2-fold in the presence of 100 mg/l PTX (minimum reached within 48 hours) in comparison to control cells

Involvement of the fibroblast growth factor system in adaptive and chemokine-induced arteriogenesis

Fibroblast growth factors (FGFs) have been applied in a variety of therapeutic and experimental studies to improve collateral blood flow. However, the pathophysiological role and the temporospatial expression of the FGFs and their receptors during arteriogenesis have never been elucidated in vivo. Here, we report that collateral artery growth in its early phase is associated with an increased expression of FGF receptor-1 (FGFR-1) and syndecan-4 on mRNA and protein levels as well as with an increased kinase activity of FGFR-1 in a rabbit model of arteriogenesis. However, the mRNA levels of FGF-1 and -2 remained constant. Our data suggest that these growth factors are supplied by endothelial attracted monocytes that, in turn, produce and deliver the FGFs to growing collateral arteries. Monocyte chemoattractant protein-1-stimulated arteriogenesis was strongly reduced in rabbits by application of the FGF inhibitor polyanetholesulfonic acid, indicating that the monocyte-related arteriogenesis (as well as the unstimulated adaptation proper) is promoted by FGFs. In summary, this study shows that arteriogenesis is associated with an increased expression of the FGFRs at the site of the vessel, whereas the growth-promoting ligands are supplied by monocytes in a paracrine way

Regulation of tight junction proteins and cell death by peroxisome proliferator-activated receptor γ agonist in brainstem of hypertensive rats

The decrease in tight junction proteins and their adapter proteins in the hypertensive brain is remarkable. Here, we aimed to investigate tight junction proteins and peroxisome proliferator-activated receptor (PPARγ) activation as well as inflammation factors and cell death proteins in the brainstem of hypertension models, namely spontaneously hypertensive rats (SHR) and borderline hypertensive rats (BHR). At first, SHR and BHR groups were treated with PPARγ agonist, pioglitazone. Then, occludin, claudin-1, claudin-2, claudin-12, ZO-1, and NF-κB p65 gene expression levels; pIKKβ, NF-κB p65, TNF, IL-1β, caspase-3, caspase-9 levels, and PARP-1 cleavage were evaluated. Significantly lower pIKKβ, NF-κB p65, TNF, and IL-1β levels were measured in pioglitazone-treated SHR. Results from this study confirm higher occludin (1.35-fold), claudin-2 (7.45-fold), claudin-12 (1.12-fold), and NF-κB p65 subunit (4.76-fold) expressions in the BHR group when compared to the SHR group. Pioglitazone was found effective in terms of regulating gene expression in SHR. Pioglitazone significantly increased occludin (8.17-fold), claudin-2 (2.41-fold), and claudin-12 (1.85-fold) mRNA levels, which were accompanied by decreased cleaved caspase-3, caspase-9 levels, PARP-1 activation, and proinflammatory factor levels in SHR (p ˂ 0.05). Our work has led us to conclude that alterations in tight junction proteins, particularly occludin, and cell death parameters in the brainstem following PPARγ activation may contribute to neuroprotection in essential hypertension. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.This research was funded by the Ege University Research Foundation (BAP) under grant number TYL-2020–21726 and VEGA 2/0158/20.Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 2/0158/20; Ege University Research Foundation; Bilimsel Araştırma Projeleri Birimi, İstanbul Teknik Üniversitesi, BAP: TYL-2020–2172