Laszlo Deres

Diastolic dysfunction in prediabetic male rats: Role of mitochondrial oxidative stress

Although incidence and prevalence of prediabetes are increasing, little is known about its cardiac effects. Therefore, our aim was to investigate the effect of prediabetes on cardiac function and to characterize parameters and pathways associated with deteriorated cardiac performance. Long-Evans rats were fed with either control or high-fat chow for 21 wk and treated with a single low dose (20 mg/kg) of streptozotocin at week 4 High-fat and streptozotocin treatment induced prediabetes as characterized by slightly elevated fasting blood glucose, impaired glucose and insulin tolerance, increased visceral adipose tissue and plasma leptin levels, as well as sensory neuropathy. In prediabetic animals, a mild diastolic dysfunction was observed, the number of myocardial lipid droplets increased, and left ventricular mass and wall thickness were elevated; however, no molecular sign of fibrosis or cardiac hypertrophy was shown. In prediabetes, production of reactive oxygen species was elevated in subsarcolemmal mitochondria. Expression of mitofusin-2 was increased, while the phosphorylation of phospholamban and expression of Bcl-2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP3, a marker of mitophagy) decreased. However, expression of other markers of cardiac auto- and mitophagy, mitochondrial dynamics, inflammation, heat shock proteins, Ca2+/calmodulin-dependent protein kinase II, mammalian target of rapamycin, or apoptotic pathways were unchanged in prediabetes. This is the first comprehensive analysis of cardiac effects of prediabetes indicating that mild diastolic dysfunction and cardiac hypertrophy are multifactorial phenomena that are associated with early changes in mitophagy, cardiac lipid accumulation, and elevated oxidative stress and that prediabetes-induced oxidative stress originates from the subsarcolemmal mitochondria.

PARP-Inhibitor Treatment Prevents Hypertension Induced Cardiac Remodeling by Favorable Modulation of Heat Shock Proteins, Akt-1/GSK-3β and Several PKC Isoforms

Spontaneously hypertensive rat (SHR) is a suitable model for studies of the complications of hypertension. It is known that activation of poly(ADP-ribose) polymerase enzyme (PARP) plays an important role in the development of postinfarction as well as long-term hypertension induced heart failure. In this study, we examined whether PARP-inhibitor (L-2286) treatment could prevent the development of hypertensive cardiopathy in SHRs. 6-week-old SHR animals were treated with L-2286 (SHR-L group) or placebo (SHR-C group) for 24 weeks. Wistar-Kyoto rats were used as aged-matched, normotensive controls (WKY group). Echocardiography was performed, brain-derived natriuretic peptide (BNP) activity and blood pressure were determined at the end of the study. We detected the extent of fibrotic areas. The amount of heat-shock proteins (Hsps) and the phosphorylation state of Akt-1Ser473, glycogen synthase kinase (GSK)-3βSer9, forkhead transcription factor (FKHR)Ser256, mitogen activated protein kinases (MAPKs), and protein kinase C (PKC) isoenzymes were monitored. The elevated blood pressure in SHRs was not influenced by PARP-inhibitor treatment. Systolic left ventricular function and BNP activity did not differ among the three groups. L-2286 treatment decreased the marked left ventricular (LV) hypertrophy which was developed in SHRs. Interstitial collagen deposition was also decreased by L-2286 treatment. The phosphorylation of extracellular signal-regulated kinase (ERK)1/2Thr183-Tyr185, Akt-1Ser473, GSK-3βSer9, FKHRSer256, and PKC εSer729 and the level of Hsp90 were increased, while the activity of PKC α/βIIThr638/641, ζ/λ410/403 were mitigated by L-2286 administration. We could detect signs of LV hypertrophy without congestive heart failure in SHR groups. This alteration was prevented by PARP inhibition. Our results suggest that PARP-inhibitor treatment has protective effect already in the early stage of hypertensive myocardial remodeling.

A quinazoline-derivative compound with PARP inhibitory effect suppresses hypertension-induced vascular alterations in spontaneously hypertensive rats

AIMS Oxidative stress and neurohumoral factors play important role in the development of hypertension-induced vascular remodeling, likely by disregulating kinase cascades and transcription factors. Oxidative stress activates poly(ADP-ribose)-polymerase (PARP-1), which promotes inflammation and cell death. We assumed that inhibition of PARP-1 reduces the hypertension-induced adverse vascular changes. This hypothesis was tested in spontaneously hypertensive rats (SHR). METHODS AND RESULTS Ten-week-old male SHRs and wild-type rats received or not 5mg/kg/day L-2286 (a water-soluble PARP-inhibitor) for 32 weeks, then morphological and functional parameters were determined in their aortas. L-2286 did not affect the blood pressure in any of the animal groups measured with tail-cuff method. Arterial stiffness index increased in untreated SHRs compared to untreated Wistar rats, which was attenuated by L-2286 treatment. Electron and light microscopy of aortas showed prominent collagen deposition, elevation of oxidative stress markers and increased PARP activity in SHR, which were attenuated by PARP-inhibition. L-2286 treatment decreased also the hypertension-activated mitochondrial cell death pathway, characterized by the nuclear translocation of AIF. Hypertension activated all three branches of MAP-kinases. L-2286 attenuated these changes by inducing the expression of MAPK phosphatase-1 and by activating the cytoprotective PI-3-kinase/Akt pathway. Hypertension activated nuclear factor-kappaB, which was prevented by PARP-inhibition via activating its nuclear export. CONCLUSION PARP-inhibition has significant vasoprotective effects against hypertension-induced vascular remodeling. Therefore, PARP-1 can be a novel therapeutic drug target for preventing hypertension-induced vascular remodeling in a group of patients, in whom lowering the blood pressure to optimal range is harmful or causes intolerable side effects.

Doxycycline protects against ROS-induced mitochondrial fragmentation and ISO-induced heart failure

In addition to their anti-bacterial action, tetracyclines also have complex biological effects, including the modification of mitochondrial protein synthesis, metabolism and gene-expression. Long-term clinical studies have been performed using tetracyclines, without significant side effects. Previous studies demonstrated that doxycycline (DOX), a major tetracyclin antibiotic, exerted a protective effect in animal models of heart failure; however, its exact molecular mechanism is still unknown. Here, we provide the first evidence that DOX reduces oxidative stress—induced mitochondrial fragmentation and depolarization in H9c2 cardiomyocytes and beneficially alters the expression of Mfn-2, OPA-1 and Drp-1 –the main regulators of mitochondrial fusion and fission—in our isoproterenol (ISO)–induced heart failure model, ultimately decreasing the severity of heart failure. In mitochondria, oxidative stress causes a shift toward fission which leads to mitochondrial fragmentation and cell death. Protecting mitochondria from oxidative stress, and the regulation of mitochondrial dynamics by drugs that shift the balance toward fusion, could be a novel therapeutic approach for heart failure. On the basis of our findings, we raise the possibility that DOX could be a novel therapeutic agent in the future treatment of heart failure.

Cardioprotective Effect of Resveratrol in a Postinfarction Heart Failure Model

Despite great advances in therapies observed during the last decades, heart failure (HF) remained a major health problem in western countries. In order to further improve symptoms and survival in patients with heart failure, novel therapeutic strategies are needed. In some animal models of HF resveratrol (RES), it was able to prevent cardiac hypertrophy, contractile dysfunction, and remodeling. Several molecular mechanisms are thought to be involved in its protective effects, such as inhibition of prohypertrophic signaling molecules, improvement of myocardial Ca2+ handling, regulation of autophagy, and the reduction of oxidative stress and inflammation. In our present study, we wished to further examine the effects of RES on prosurvival (Akt-1, GSK-3β) and stress signaling (p38-MAPK, ERK 1/2, and MKP-1) pathways, on oxidative stress (iNOS, COX-2 activity, and ROS formation), and ultimately on left ventricular function, hypertrophy and fibrosis in a murine, and isoproterenol- (ISO-) induced postinfarction heart failure model. RES treatment improved left ventricle function, decreased interstitial fibrosis, cardiac hypertrophy, and the level of plasma BNP induced by ISO treatment. ISO also increased the activation of P38-MAPK, ERK1/2Thr183-Tyr185, COX-2, iNOS, and ROS formation and decreased the phosphorylation of Akt-1, GSK-3β, and MKP-1, which were favorably influenced by RES. According to our results, regulation of these pathways may also contribute to the beneficial effects of RES in HF.

Activation of mitochondrial fusion provides a new treatment for mitochondria-related diseases

Graphical abstract Figure. No Caption available. Abstract Mitochondria fragmentation destabilizes mitochondrial membranes, promotes oxidative stress and facilitates cell death, thereby contributing to the development and the progression of several mitochondria‐related diseases. Accordingly, compounds that reverse mitochondrial fragmentation could have therapeutic potential in treating such diseases. BGP‐15, a hydroxylamine derivative, prevents insulin resistance in humans and protects against several oxidative stress‐related diseases in animal models. Here we show that BGP‐15 promotes mitochondrial fusion by activating optic atrophy 1 (OPA1), a GTPase dynamin protein that assist fusion of the inner mitochondrial membranes. Suppression of Mfn1, Mfn2 or OPA1 prevents BGP‐15‐induced mitochondrial fusion. BGP‐15 activates Akt, S6K, mTOR, ERK1/2 and AS160, and reduces JNK phosphorylation which can contribute to its protective effects. Furthermore, BGP‐15 protects lung structure, activates mitochondrial fusion, and stabilizes cristae membranes in vivo determined by electron microscopy in a model of pulmonary arterial hypertension. These data provide the first evidence that a drug promoting mitochondrial fusion in in vitro and in vivo systems can reduce or prevent the progression of mitochondria‐related disorders.

Distribution pattern of γ-amino butyric acid immunoreactive neural structures in the central and peripheral nervous system of the tubificid worm, Limnodrilus hoffmeisteri

By means of whole-mount immunohistochemistry, putative inhibitory (GABAergic) neural structures were identified in the central and peripheral nervous system of the tubificid worm, Limnodrilus hoffmeisteri. In the supraoesophageal ganglion (brain) only few strongly labelled cells were observed. However, in its commissural part a high number of stained nerve fibres, arising mainly from the ventral nerve cord and prostomium, occurred. Except for the suboesophageal ganglion the arrangement of γ-amino butyric acid-immunoreactive (GABA-IR) structures proved to be identical in each VNC ganglion. Behind the first segmental nerves three pairs of heavily stained neurones were located. Their processes (both ipsi- and contralateral) form four bundles of fine-fibred polysegmental interneuronal tracts that run close to the dorsal giant axons from the terminal ganglion to the suboesophageal one without interruption. A few small motoneurons and a pair of large ones with contralateral processes were also identified. A bipolar (presumably sensory) neuron was located at the root of each second segmental nerve. GABA-IR neurons were also found in the stomatogastric ganglia and pharyngeal wall; however, the latter structure had a well-developed fibre network, as well. Present results suggest that GABA acts as a common neurotransmitter in sensory, interneuronal and motor system of L. hoffmeisteri. The possible functional role of the identified GABA-IR neural structures in locomotion, escape and withdrawal reflexes in tubificid worms is discussed.

Integrative characterization of chronic cigarette smoke-induced cardiopulmonary comorbidities in a mouse model☆

Cigarette smoke-triggered inflammatory cascades and consequent tissue damage are the main causes of chronic obstructive pulmonary disease (COPD). There is no effective therapy and the key mediators of COPD are not identified due to the lack of translational animal models with complex characterization. This integrative chronic study investigated cardiopulmonary pathophysiological alterations and mechanisms with functional, morphological and biochemical techniques in a 6-month-long cigarette smoke exposure mouse model. Some respiratory alterations characteristic of emphysema (decreased airway resistance: Rl; end-expiratory work and pause: EEW, EEP; expiration time: Te; increased tidal mid-expiratory flow: EF50) were detected in anaesthetized C57BL/6 mice, unrestrained plethysmography did not show changes. Typical histopathological signs were peribronchial/perivascular (PB/PV) edema at month 1, neutrophil/macrophage infiltration at month 2, interstitial leukocyte accumulation at months 3-4, and emphysema/atelectasis at months 5-6 quantified by mean linear intercept measurement. Emphysema was proven by micro-CT quantification. Leukocyte number in the bronchoalveolar lavage at month 2 and lung matrix metalloproteinases-2 and 9 (MMP-2/MMP-9) activities in months 5-6 significantly increased. Smoking triggered complex cytokine profile change in the lung with one characteristic inflammatory peak of C5a, interleukin-1α and its receptor antagonist (IL-1α, IL-1ra), monokine induced by gamma interferon (MIG), macrophage colony-stimulating factor (M-CSF), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) at months 2-3, and another peak of interferon-γ (IFN-γ), IL-4, 7, 13, 17, 27 related to tissue destruction. Transient systolic and diastolic ventricular dysfunction developed after 1-2 months shown by significantly decreased ejection fraction (EF%) and deceleration time, respectively. These parameters together with the tricuspid annular plane systolic excursion (TAPSE) decreased again after 5-6 months. Soluble intercellular adhesion molecule-1 (sICAM-1) significantly increased in the heart homogenates at month 6, while other inflammatory cytokines were undetectable. This is the first study demonstrating smoking duration-dependent, complex cardiopulmonary alterations characteristic to COPD, in which inflammatory cytokine cascades and MMP-2/9 might be responsible for pulmonary destruction and sICAM-1 for heart dysfunction.

The Neurokinin-1 receptor contributes to the early phase of lipopolysaccharide-induced fever via stimulation of peripheral cyclooxygenase-2 protein expression in mice

Neurokinin (NK) signaling is involved in various inflammatory processes. A common manifestation of systemic inflammation is fever, which is usually induced in animal models with the administration of bacterial lipopolysaccharide (LPS). A role for the NK1 receptor was shown in LPS-induced fever, but the underlying mechanisms of how the NK1 receptor contributes to febrile response, especially in the early phase, have remained unknown. We administered LPS (120 µg/kg, intraperitoneally) to mice with the Tacr1 gene, i.e., the gene encoding the NK1 receptor, either present (Tacr1+/+) or absent (Tacr1−/−) and measured their thermoregulatory responses, serum cytokine levels, tissue cyclooxygenase-2 (COX-2) expression, and prostaglandin (PG) E2 concentration. We found that the LPS-induced febrile response was attenuated in Tacr1−/− compared to their Tacr1+/+ littermates starting from 40 min postinfusion. The febrigenic effect of intracerebroventricularly administered PGE2 was not suppressed in the Tacr1−/− mice. Serum concentration of pyrogenic cytokines did not differ between Tacr1−/− and Tacr1+/+ at 40 min post-LPS infusion. Administration of LPS resulted in amplification of COX-2 mRNA expression in the lungs, liver, and brain of the mice, which was statistically indistinguishable between the genotypes. In contrast, the LPS-induced augmentation of COX-2 protein expression was attenuated in the lungs and tended to be suppressed in the liver of Tacr1−/− mice compared with Tacr1+/+ mice. The Tacr1+/+ mice responded to LPS with a significant surge of PGE2 production in the lungs, whereas Tacr1−/− mice did not. In conclusion, the NK1 receptor is necessary for normal fever genesis. Our results suggest that the NK1 receptor contributes to the early phase of LPS-induced fever by enhancing COX-2 protein expression in the periphery. These findings advance the understanding of the crosstalk between NK signaling and the “cytokine-COX-2-prostaglandin E2” axis in systemic inflammation, thereby open up the possibilities for new therapeutic approaches.

Chronic PARP-1 inhibition reduces carotid vessel remodeling and oxidative damage of the dorsal hippocampus in spontaneously hypertensive rats

Vascular remodeling during chronic hypertension may impair the supply of tissues with oxygen, glucose and other compounds, potentially unleashing deleterious effects. In this study, we used Spontaneously Hypertensive Rats and normotensive Wistar-Kyoto rats with or without pharmacological inhibition of poly(ADP-ribose)polymerase-1 by an experimental compound L-2286, to evaluate carotid artery remodeling and consequent damage of neuronal tissue during hypertension. We observed elevated oxidative stress and profound thickening of the vascular wall with fibrotic tissue accumulation induced by elevated blood pressure. 32 weeks of L-2286 treatment attenuated these processes by modulating mitogen activated protein kinase phosphatase-1 cellular levels in carotid arteries. In hypertensive animals, vascular inflammation and endothelial dysfunction was observed by NF-κB nuclear accumulation and impaired vasodilation to acetylcholine, respectively. Pharmacological poly(ADP-ribose)polymerase-1 inhibition interfered in these processes and mitigated Apoptosis Inducing Factor dependent cell death events, thus improved structural and functional alterations of carotid arteries, without affecting blood pressure. Chronic poly(ADP-ribose)polymerase-1 inhibition protected neuronal tissue against oxidative damage, assessed by nitrotyrosine, 4-hydroxinonenal and 8-oxoguanosine immunohistochemistry in the area of Cornu ammonis 1 of the dorsal hippocampus in hypertensive rats. In this area, extensive pyramidal cell loss was also attenuated by treatment with lowered poly(ADP-ribose)polymer formation. It also preserved the structure of fissural arteries and attenuated perivascular white matter lesions and reactive astrogliosis in hypertensive rats. These data support the premise in which chronic poly(ADP-ribose)polymerase-1 inhibition has beneficial effects on hypertension related tissue damage both in vascular tissue and in the hippocampus by altering signaling events, reducing oxidative/nitrosative stress and inflammatory status, without lowering blood pressure.