Przemysław Rzodkiewicz

Sirtuins, epigenetics and longevity

Aging of organisms begins from a single cell at the molecular level. It includes changes related to telomere shortening, cell senescence and epigenetic modifications. These processes accumulate over the lifespan. Research studies show that epigenetic signaling contributes to human disease, tumorigenesis and aging. Epigenetic DNA modifications involve changes in the gene activity but not in the DNA sequence. An epigenome consists of chemical modifications to the DNA and histone proteins without the changes in the DNA sequence. These modifications strongly depend on the environment, could be reversible and are potentially transmittable to daughter cells. Epigenetics includes DNA methylation, noncoding RNA interference, and modifications of histone proteins. Sirtuins, a family of nicotine adenine dinucleotide (NAD+)-dependent enzymes, are involved in the cell metabolism and can regulate many cellular functions including DNA repair, inflammatory response, cell cycle or apoptosis. Literature shows the strong interconnection between sirtuin expression and aging processes. However, the direct relationship is still unknown. Here, we would like to summarize the existing knowledge about epigenetic processes in aging, especially those related to sirtuin expression. Another objective is to explain why some negative correlations between sirtuin activity and the rate of aging can be assumed.

Antinociceptive properties of esculetin in non-inflammatory and inflammatory models of pain in rats

Some studies suggest that 5‐lipoxygenase (5‐LOX) inhibition or leukotriene receptor antagonism may effectively attenuate different kinds of pain. In the present study, we investigated whether esculetin (which, among other actions, potently inhibits 5‐LOX) possesses analgesic activity in acute non‐inflammatory pain and acute inflammatory pain models in rats. We also examined the effects of zileuton, a selective 5‐LOX inhibitor, on esculetin activity. Plasma concentrations of leukotriene B4 (LTB4) after administration of esculetin were also determined. Esculetin (1.25–20 mg/kg, i.p.) dose‐dependently alleviated hyperalgesia and exhibited antinociceptive effects in both experimental models. The greatest effect of esculetin was observed with a dose of 20 mg/kg. In carrageenan‐induced inflammatory pain in rats, 20 mg/kg esculetin reversed or mitigated hyperalgesia, increasing the threshold to mechanical stimuli from a control value of −23.8 ± 1.8% to 15.2 ± 2.2% (P < 0.01) and that to thermal stimuli from −52.5 ± 6.1% to −9.5 ± 3.9% (P < 0.01). In non‐inflammatory pain, after esculetin (20 mg/kg) administration the threshold values to mechanical and thermal stimuli increased to 75.9 ± 4.2% and 59.2 ± 4.3%, respectively (P < 0.01 for both). Zileuton (30 mg/kg, p.o.) alone slightly but significantly increased the pain threshold in the non‐inflammatory and inflammatory acute pain models. Pretreatment with 30 mg/kg, p.o., zileuton significantly enhanced the analgesic activity of 5 mg/kg, i.p., esculetin in both pain models. Moreover, esculetin (10 mg/kg, i.p.) decreased LTB4 concentrations in the blood from 244 ± 29 pg/mL in the control group to 185 ± 11 pg/mL (P < 0.005). The results of the present study suggest the involvement of the 5‐LOX pathway in esculetin analgesia.

Esculetin reduces leukotriene B4 level in plasma of rats with adjuvant-induced arthritis

Objectives Esculetin (6,7-dihydroxycoumarin) is a natural coumarin with anti-oxidant, anti-inflammatory and anti-nociceptive activity. It acts as a potent inhibitor of lipoxygenases (5-LOX and 12-LOX) and decreases the production of matrix metalloproteinases (MMP-1, MMP-3 and MMP-9). Because both inhibition of lipoxygenases and inhibition of matrix metalloproteinases are effective strategies in the treatment of rheumatoid arthritis, we investigated whether esculetin may be effective in adjuvant-induced arthritis in rats. Material and methods The study was performed on male Lewis rats, in the adjuvant-induced arthritis model. Rats were divided into two groups: control (treated with 1% methylcellulose) and experimental (treated with esculetin – 10 mg/kg ip.). The tested compound was administered for 5 consecutive days starting on the 21st day after induction of arthritis. Each group consisted of 7 animals. After 5 days of treatment, rats were anesthetized. The concentration of leukotriene B4 (LTB4) in plasma was determined by a competitive enzyme immunoassay. Results The LTB4 level in plasma of rats with adjuvant-induced arthritis is increased in comparison to rats without inflammation (362 ±34 vs. 274 ±15 pg/ml, p < 0.01, respectively). Five-day treatment with esculetin in adjuvant-induced arthritis rats decreases the LTB4 level to a level comparable with rats without inflammation (284 ±23 pg/ml, p < 0.01). Conclusions LTB4 is the most potent chemotactic agent influencing neutrophil migration into the joint. It is known that its level in serum of patients with active rheumatoid arthritis is increased and correlates with disease severity. Some other lipoxygenase inhibitors have already been tested as potential drug candidates in clinical and preclinical trials for rheumatoid arthritis (Zileuton, PF-4191834). Because esculetin decreases the LTB4 level in plasma of rats in adjuvant-induced arthritis, it may also be considered as an attractive drug candidate for patients with rheumatoid arthritis.

The human body as an energetic hybrid? New perspectives for chronic disease treatment?

Inflammatory response is accompanied by changes in cellular energy metabolism. Proinflammatory mediators like plasma C-reactive protein, IL-6, plasminogen activator inhibitor-1, TNF-α or monocyte chemoattractant protein-1 released in the site of inflammation activates immune cells and increase energy consumption. Increased demand for energy creates local hypoxia and lead in consequence to mitochondrial dysfunction. Metabolism of cells is switched to anaerobic glycolysis. Mitochondria continuously generate free radicals that what result in imbalance that causes oxidative stress, which results in oxidative damage. Chronic energy imbalance promotes oxidative stress, aging, and neurodegeneration and is associated with numerous disorders like Alzheimer’s disease, multiple sclerosis, Parkinson’s disease or Huntington’s disease. It is also believed that oxidative stress and the formation of free radicals play an important role in the pathogenesis of rheumatoid diseases including especially rheumatoid arthritis. Pharmacological control of energy metabolism disturbances may be valuable therapeutic strategy of treatment of this disorders. In recent review we sum up knowledge related to energy disturbances and discuss phenomena such as zombies or hibernation which may indicate the potential targets for regulation of energy metabolism.

Influence of exogenous leptin on redox homeostasis in neutrophils and lymphocytes cultured in synovial fluid isolated from patients with rheumatoid arthritis

Objectives Leptin is an adipose cells derived hormone that regulates energy homeostasis within the body. Energy metabolism of immune cells influences their activity within numerous pathological states, but the effect of leptin on these cells in unclear. On the one hand, it was observed that leptin induces neutrophils chemotaxis and modulates phagocytosis. On the other hand, neutrophils exposed to leptin did not display detectable Ca2+ ions mobilization or β2-integrin upregulation. In this study, we investigated the effect of leptin on the redox homeostasis in lymphocytes and neutrophils. Material and methods Neutrophils and lymphocytes were isolated by density-gradient centrifugation of blood from healthy volunteers. Cells were cultured with or without leptin (100 ng/ml for lymphocytes and 500 ng/ml for neutrophils) or with or without synovial fluid (85%) for 0–72 h. Culture media were not changed during incubation. Cells were homogenized and homogenate was frozen until laboratory measurements. Redox homeostasis was assessed by the reduced glutathione (GSH) vs. oxidized glutathione (GSSG) ratio and membrane lipid peroxidation evaluation. Results Lymphocytes cultured with leptin and synovial fluid showed a significant increase of the GSSG level. The GSSG/GSH ratio increased by 184 ±37%. In neutrophils incubated in a similar environment, the GSSG/GSH ratio increased by just 21 ±7%, and the effect was observed irrespectively of whether they were exposed to leptin or synovial fluid or both together. Neither leptin nor synovial fluid influenced lipid peroxidation in neutrophils, but in lymphocytes leptin intensified lipid peroxidation. Conclusions Leptin altered the lymphocytes, but not neutrophils redox state. Because firstly neutrophils are anaerobic cells and have just a few mitochondria and secondly lymphocytes have typical aerobic metabolism, the divergence of our data supports the hypothesis that leptin induces oxidative stress by modulation of mitochondria.

The role of physiological elements in future therapies of rheumatoid arthritis. III. The role of the electromagnetic field in regulation of redox potential and life cycle of inflammatory cells

Each material consisting of charged particles can be influenced by a magnetic field. Polarized particles play an essential role in almost all physiological processes. Locally generated electromagnetic fields several physiological processes within the human body, for example: stimulation of nerves, muscles, and cardiac electrical activity. This phenomenon is used today in many medical applications. In this article, we discuss ways in which electromagnetic field affects the physiological and pathological processes in cells and tissues. This knowledge will help to better understand the electrophysiological phenomenon in connective tissue diseases and can bring new therapeutic strategies (in the form of “invisible drugs”) for the treatment of rheumatic diseases?

The Role of Neutrophils in Rheumatoid Arthritis – Experiments In Vitro: A Change of Conception?

Essential cells of innate immunity, neutrophils are often considered to be a homogenous population of terminally differentiated cells (Chakravarti et al., 2009). These cells represent the body’s primary line of defence against invading pathogens such as bacteria, and constitute 40-60% of the white blood cell population. Neutrophils are short-lived polymorphonuclear phagocytes. They are known as first-responding inflammatory cells migrating towards the site of inflammation (Chakravarti et al., 2009; Edwards et al., 1997). In the circulation of healthy adults, neutrophils exist in a resting state, which ensures that their toxic intracellular contents are not accidentally released to damage host tissues. Neutrophils become activated by agents that include bacterial products and cytokines or chemokines, such as TNF-┙, IL-8 or IFN-┛. The primed neutrophils are then mobilized to the site of infection or inflammation and encounter activating signals to trigger bacterial killing. (Wright et al., 2010; Cascao et al., 2009) It must be noted, that the functions of resting blood neutrophils and primed neutrophils may be very different. Thus, many of the regulatory functions of macrophages are shared by primed (but not resting) neutrophils (Wright et al., 2010). For this reason, in vitro experiments using freshly isolated blood neutrophils often fail to recognize the full functional repertoire and capacity of neutrophils.

The effect of leptin on the respiratory burst of human neutrophils cultured in synovial fluid.

Objectives Leptin is a hormone responsible for nutritional status and immune competence coordination. In rheumatoid arthritis (RA) increased leptin levels were observed in both serum and synovial fluid. Its influence on development of the disease still remains unclear. So far, research on leptins influence on the emission of reactive oxygen intermediates (ROI) measured with chemiluminescence (CL) has provided unclear and contradictory results. In this study, we evaluated the influence of leptin on oxidative activity of neutrophils isolated from blood of healthy volunteers and cultured in different amounts of synovial fluid (SF) from patients with RA. Material and methods Neutrophils’ oxidative metabolism was measured by two types of CL. The first one, luminol-dependent CL (CL-lum), allows one to determine phagocytic activity and the level of ROI generated in a myeloperoxidase-dependent manner. The second method used was lucigenin-dependent CL (CL-luc), which monitors ROI production dependent on the NADPH oxidase enzyme complex located in the cell membranes of neutrophils and enables one to determine the scope of extracellular ROI emission. Results Neutrophils stimulated by opsonized zymosan show a decrease in the level of CL-lum, proportional to the increasing concentration of both SF and serum collected from healthy donors. The observed effect of decreased CL-lum may, therefore, be dependent on the physical conditions (viscosity of fluids used). None of these experiments showed any effect of leptin on the level of CL-lum. Conclusions The present study showed that leptin does not affect the level of any of the CL types in inactive neutrophils incubated in normal serum, and it does not affect the level of oxidative activity in resting neutrophils incubated with SF. However, leptin influences extracellular ROI emission (measured by CL-luc). Leptin reduces extracellular emission of ROI, and this effect is dependent on concentration and duration of exposure to leptin.