The damaging effect of ionizing radiation (IR) exposure results in the disturbance of the gut natural barrier, followed by the development of severe gastrointestinal injury. However, the dose and application segment are known to determine the effects of IR. In this study, we demonstrated the dose- and segment-specificity of tight junction (TJ) alteration in IR-induced gastrointestinal injury in rats. Male Wistar rats were subjected to a total-body X-ray irradiation at doses of 2 or 10 Gy. Isolated jejunum and colon segments were tested in an Ussing chamber 72 h after exposure. In the jejunum, 10-Gy IR dramatically altered transepithelial resistance, short-circuit current and permeability for sodium fluorescein. These changes were accompanied by severe disturbance of histological structure and total rearrangement of TJ content (increased content of claudin-1, -2, -3 and -4; multidirectional changes in tricellulin and occludin). In the colon of 10-Gy irradiated rats, lesions of barrier and transport functions were less pronounced, with only claudin-2 and -4 altered among TJ proteins. The 2-Gy IR did not change electrophysiological characteristics or permeability in the colon or jejunum, although slight alterations in jejunum histology were noted, emphasized with claudin-3 increase. Considering that TJ proteins are critical for maintaining epithelial barrier integrity, these findings may have implications for countermeasures in gastrointestinal acute radiation injury.

The Na,K-ATPase plays an important role in adaptation to hypoxia. Prolonged hypoxia results in loss of skeletal muscle mass, structure, and performance. However, hypoxic preconditioning is known to protect against a variety of functional impairments. In this study, we tested the possibility of mild hypoxia to modulate the Na,K-ATPase and to improve skeletal muscle electrogenesis. The rats were subjected to simulated high-altitude (3000 m above sea level) hypobaric hypoxia (HH) for 3 h using a hypobaric chamber. Isolated diaphragm and soleus muscles were tested. In the diaphragm muscle, HH increased the α2 Na,K-ATPase isozyme electrogenic activity and stably hyperpolarized the extrajunctional membrane for 24 h. These changes were accompanied by a steady increase in the production of thiobarbituric acid reactive substances as well as a decrease in the serum level of endogenous ouabain, a specific ligand of the Na,K-ATPase. HH also increased the α2 Na,K-ATPase membrane abundance without changing its total protein content; the plasma membrane lipid-ordered phase did not change. In the soleus muscle, HH protected against disuse (hindlimb suspension) induced sarcolemmal depolarization. Considering that the Na,K-ATPase is critical for maintaining skeletal muscle electrogenesis and performance, these findings may have implications for countermeasures in disuse-induced pathology and hypoxic therapy.

Ionizing radiation (IR) causes disturbances in the functions of the gastrointestinal tract. Given the therapeutic potential of ouabain, a specific ligand of the Na,K-ATPase, we tested its ability to protect against IR-induced disturbances in the barrier and transport properties of the jejunum and colon of rats. Male Wistar rats were subjected to 6-day intraperitoneal injections of vehicle or ouabain (1 µg/kg/day). On the fourth day of injections, rats were exposed to total-body X-ray irradiation (10 Gy) or a sham irradiation. Isolated tissues were examined 72 h post-irradiation. Electrophysiological characteristics and paracellular permeability for sodium fluorescein were measured in an Ussing chamber. Histological analysis and Western blotting were also performed. In the jejunum tissue, ouabain exposure did not prevent disturbances in transepithelial resistance, paracellular permeability, histological characteristics, as well as changes in the expression of claudin-1, -3, -4, tricellulin, and caspase-3 induced by IR. However, ouabain prevented overexpression of occludin and the pore-forming claudin-2. In the colon tissue, ouabain prevented electrophysiological disturbances and claudin-2 overexpression. These observations may reveal a mechanism by which circulating ouabain maintains tight junction integrity under IR-induced intestinal dysfunction.

The damaging effect of ionizing radiation (IR) on skeletal muscle Na,K-ATPase is an open field of research. Considering a therapeutic potential of ouabain, a specific ligand of the Na,K-ATPase, we tested its ability to protect against the IR-induced disturbances of Na,K-ATPase function in rat diaphragm muscle that co-expresses the α1 and α2 isozymes of this protein. Male Wistar rats (n = 26) were subjected to 6-day injections of vehicle (0.9% NaCl) or ouabain (1 µg/kg/day). On the fourth day of injections, rats were exposed to one-time total-body X-ray irradiation (10 Gy), or a sham irradiation. The isolated muscles were studied 72 h post-irradiation. IR decreased the electrogenic contribution of the α2 Na,K-ATPase without affecting its protein content, thereby causing sarcolemma depolarization. IR increased serum concentrations of ouabain, IL-6, and corticosterone, decreased lipid peroxidation, and changed cellular redox status. Chronic ouabain administration prevented IR-induced depolarization and loss of the α2 Na,K-ATPase electrogenic contribution without changing its protein content. This was accompanied with an elevation of ouabain concentration in circulation and with the lack of IR-induced suppression of lipid peroxidation. Given the crucial role of Na,K-ATPase in skeletal muscle performance, these findings may have therapeutic implications as countermeasures for IR-induced muscle pathology.

Growing interest in angiogenesis, a key component in the development of different diseases, requires the use of a suitable experimental model to simulate neovascularization in a laboratory. In recent years, with the development of novel therapeutic strategies, based on angiogenesis regulation, this problem has become especially important. Current in vitro and in vivo models are characterized with a variety of disadvantages, which impede results interpretation. Thus, in vitro assays provide estimation of discrete endothelial cells characteristics, which alter from the same ones in the native microenvironment. The use of in vivo assays is accompanied with difficulties in testing agent delivery and quantitative analysis of its angiogenic activity In view of these complications, the use of a combination of assays is recommended while planning the experiment in this area. The aim of this review is to critically analyze angiogenesis assays, currently used to perform fundamental investigation as well as preclinical tests of developing therapeutic agents

Для оценки влияния ионизирующего излучения на здоровье человека, а также на состояние природных экосистем в зонах повышенного радиационного загрязнения необходимы универсальные методы биоиндикации и биодозиметрии. Цель обзора – подробное освещение известных ядерных аномалий соматических клеток различных организмов как универсальных радиоспецифических биомаркеров. Рассмотрены современные и исторические, иностранные и отечественные литературные данные, посвященные изучению ядерных аномалий, возникающих в связи с воздействием генотоксических агентов. Специфическим эффектом ионизирующего излучения, проявляющимся в соматических клетках различных организмов, являются двунитевые разрывы ДНК с последующим формированием хромосомных аберраций нестабильного типа. Эти аберрации лежат в основе появления нескольких типов ядерных аномалий в интерфазе клетки. Среди таких аномалий выделяют микроядра, «хвостатые» ядра, хроматиновые мосты, а также гантелевидные ядра. Обнаружение ядерных аномалий в соматических клетках не только человека, но и растений, и животных позволяет сделать вывод о том, что данные изменения структуры ядра являются универсальными маркерами воздействия ионизирующего излучения. Использование совокупности данных видов кариопатологии в качестве радиоспецифических биондикаторов представляется перспективным для создания универсального протокола биодозиметрического теста для комплексной оценки состояния природных экосистем и здоровья человека в условиях радиационного загрязнения.