The study revealed that a controlled mandibular injury (incomplete fracture) in rats chronically exposed to alcohol resulted in a significant upregulation of bone resorption markers on the 14th day post-trauma. Specifically, serum levels of acid phosphatase and its bone (tartrate-resistant) isoform increased by 58.9% (P<0.001) and 35.1% (P<0.01), respectively. In contrast, neither trauma nor ethanol exposure alone had a significant impact on these enzyme activities. Furthermore, no significant changes were observed in alkaline phosphatase activity (a marker of bone formation) and total plasma calcium levels in any of the groups. Reproduction of chronic alcohol intoxication significantly increases the total and inducible NO synthase activity in the homogenate of the rat mandible (by 80.6%, P<0.01, and 98.8%, P<0.001, respectively) that is accompanied by a rise in the concentration of the key marker of nitrosative stress, peroxynitrite, by 39.2% (P<0.01). This study demonstrated for the first time that on day 14 after the reproduction of dosed injury to the mandible (model of its incomplete fracture) during chronic alcohol intoxication, NO synthase activity and the content of peroxynitrites of alkaline and alkaline-earth metals in the bone homogenate exceed the results in groups exposed to trauma or alcohol along. Under these conditions, the activity of ornithine decarboxylase, a key enzyme of polyamine biosynthesis that competes with NO synthase for substrate, significantly decreases in the mandibular homogenate. On the 14th day after controlled injury to the mandible (model of its incomplete fracture) during chronic alcohol intoxication, depolymerization of bone biopolymers (collagen, glycoproteins and proteoglycans) significantly increases that does not occur under conditions of separate exposure to trauma and ethanol. Reproduction of chronic alcohol intoxication with subsequent sham trauma to the mandible disrupts the biomechanical properties of the bone, in particular, tensile elasticity, as indicated by a significant decrease in Young's modulus. On the 14th day after the reproduction of a controlled injury to the mandible (model of its incomplete fracture), including the latter during chronic alcohol intoxication, the elasticity of the bone in the affected area during tension and its strength remain reduced, as indicated by a decrease in Young's modulus and tensile strength. Chronic alcohol intoxication was found to delay reparative regeneration of bone tissue after controlled injury to the mandible (model of its incomplete fracture), accompanied by a decrease in the relative amount of reticulofibrous bone tissue and ellular elements of the fibroblastic series, especially mature fibroblasts, as well as a delay in the maturation of granulation tissue in the lesion area. The activity of bone resorption markers in blood serum, the balance of the nitric oxide system, and the depolymerization processes of collagen, proteoglycans, and sialoglycoproteins in the extracellular organic matrix of mandibular bones following controlled injury under chronic alcohol intoxication are dependent on the functional activity of the transcription factors NF-κB and Nrf2. This study is the first to have found that the administration of specific modulators of NF-κB and Nrf2 transcription factors (ammonium pyrrolidinium dithiocarbamate and dimethyl fumarate) after dosed injury to the mandible against the background of chronic alcohol intoxication leads to a significant increase in the activity of the enzyme-marker of bone resorption, acid phosphatase (by 29, 7%, P<0.01, and 25.0%, P<0.01, respectively) in blood serum, a significant decrease in the activity of the inducible isoform of NO synthase (by 41.8%, P<0.001, and 43.1%, P<0.001, respectively) and the concentration of peroxynitrite (by 42, 5%, P<0.001, and 44.8%, P<0.01, respectively) in the mandibular bone homogenate, as well as to a decrease in the depolymerization of collagen, proteoglycans, and sialoglycoproteins.
Key words: bone fracture, alcohol intoxication, transcription factors NF-κB and Nrf2, bone metabolism, reactive oxygen and nitrogen species, oxidative and nitrosative stress, lipid peroxidation, prooxidant-antioxidant balance, connective tissue, extracellular matrix, collagen, oxyproline, glycosaminoglycans, sialic acids.
