Age-associated effects of disodium glutamyl-cysteinyl-glycine in a complex treatment regimen for multidrug-resistant tuberculosis (experimental study)

The effect of a combination of glutamyl-cysteinyl-glycine disodium and bedaquiline on the treatment of multidrug-resistant tuberculosis in rabbits of different ages was studied. Combination therapy improved the condition of animals, reduced inflammation and the size of lesions in the lungs, especially effective in elderly individuals. The data obtained emphasize the importance of taking into account the patient's age when prescribing anti-tuberculosis therapy.

BACKGROUND. The high incidence of tuberculosis and the difficulties of its treatment in older people are an urgent problem of phthisiatry and geriatrics. The growing drug resistance of mycobacteria and an increase in immunodeficiency diseases lead to the search and development of new medicines. Disodium glutamyl-cysteinyl-glycine has shown high efficacy as a means of preventing and treating secondary immunodeficiency conditions associated with radiation, chemical and infectious factors. Being a structural analog of oxidized glutathione, disodium glutamyl-cysteinyl-glycine has high bioavailability, modulating effect on intracellular processes of thiol metabolism, promotes initiation of cytokine system, activation of phagocytosis. The drug glutamyl-cysteinyl-glycine disodium is approved for use in pulmonary tuberculosis, but age-associated effects have not been studied.

OBJECTIVE. Evaluation of age-associated effects of glutamyl-cysteinyl-glycine disodium in combination with bedaquiline in multidrug-resistant tuberculosis in rabbits

MATERIALS AND METHODS. Three groups of 25 rabbits each with standard laboratory conditions were formed.: 1st ― young animals (1 year old), body weight ― 1,000–1,200 g; 2nd ― middle-aged animals (4 years old), body weight ― 1,700–1,900 g; 3rd ― elderly animals (7 years old), body weight ― 2,000–2,300 g. Three subgroups were identified in each age group: 1st (n = 5) ― infection control (infected animals without treatment); 2nd (n = 10) ― treatment control (infected animals receiving only bedaquiline); 3rd (n = 10) ― main (infected animals receiving bedaquiline + glutamyl-cysteinyl-glycine disodium). Thus, nine subgroups were formed: 1.1 ― a subgroup for the control of infection of young animals; 2.1 ― a subgroup for the control of infection of middle-aged animals; 3.1 ― a subgroup for the control of infection of elderly animals; 1.2 ― a subgroup for the control of treatment of young animals; 2.2 ― a subgroup for the control of treatment of middle-aged animals; 3.2 ― a subgroup for the control of treatment of elderly animals; 1.3 ― the main subgroup of young animals; 2.3 ― the main subgroup of middle-aged animals; 3.3 ― the main subgroup of elderly animals. Infection was carried out intravenously with a clinical strain of M. tuberculosis with multiple drug resistance. Treatment began on the third day after infection with bedaquiline and glutamyl-cysteinyl-glycine disodium. The condition of the animals, physical activity, food and water intake, and weight dynamics were monitored. CT scans of the lungs and hypersensitivity reaction tests were used. The data was processed using a package Statistica 7.0.

RESULTS. Monitoring the condition of the animals 6 weeks after infection allowed us to obtain the following results.

Young rabbits (1 year old). Infection control ― poor condition, low activity, low consumption of food and water. Treatment control ― satisfactory condition, good activity, normal diet and drink. The main subgroup is in excellent condition, maximum activity, increased intake of food and water.

Middle-aged rabbits (4 years old). Infection control ― poor condition, decreased activity, low intake of food and water. Treatment control ― satisfactory condition, good activity, increased intake of food and water. The main subgroup is in good condition, high activity, moderate intake of food and water.

Elderly rabbits (7 years old). Infection control is a critical condition, severe loss of activity, minimal intake of food and water. Treatment control ― satisfactory condition, good activity, sufficient intake of food and water. The main subgroup is satisfactory condition, average activity, and average food and water intake. In the first 3 weeks after infection, an increase in body weight was noted in all subgroups, in the 4th and 5th weeks, against the background of a clear decrease in these indicators, an increase in the average weight of animals in the main subgroups was observed in the infection control and treatment control subgroups. In response to intradermal administration of a sample with a tuberculosis recombinant allergen (Diaskintest) 18 days after inoculation of mycobacterium tuberculosis in intact experimental animals, a negative reaction was noted, and in all model rabbits a positive test result was recorded in the form of erythema with a size of (18.50 ± 1.49) mm (p < 0.0001), which indicated the presence of sensitization and confirmed the development of the tuberculosis process.

CT scans of the chest organs of animals from the infection control subgroups (subgroups 1.1, 2.1, 3.1) in all three age groups studied showed the presence of large polycyclic infiltrates of heterogeneous density in the upper lobes of the lungs, most likely of a specific nature. At the same time, in the group of elderly animals, pathophysiological changes formed faster and were more pronounced. CT scans of the thoracic organs of animals from the treatment control subgroups (subgroups 1.2, 2.2, 3.2) in all three age groups studied showed the presence of small foci of infiltration in the lungs with areas like frosted glass around the periphery. At the same time, the observed changes in the groups of middle-aged and elderly rabbits were more pronounced and had a longer duration with a tendency to chronicle the pathological process. CT scans of the thoracic organs of animals from the main subgroups (subgroups 1.3, 2.3, 3.3) in all three age groups studied showed the presence of focal infiltrative changes in the lungs of low intensity, which are less pronounced than in animals from the treatment control subgroups of the corresponding age groups. After infection, small focal shadows in the subpleural regions of the lungs, corresponding to the primary foci of infection, were observed in young rabbits. In middle-aged and elderly rabbits, more extensive infiltrates and focal shadows were detected, occupying significant areas of the lung. In elderly rabbits, signs of active inflammation with the presence of exudate in the alveoli were observed. An increase in the size of the intrathoracic lymph nodes, especially bronchopulmonary and tracheobronchial, was observed in rabbits of all age groups studied. The rabbits' body weight was unstable throughout the experiment. The changes depended on age and treatment regimen. Computed tomography of the lungs confirmed the formation of tuberculous changes of varying severity depending on age and treatment. In general, the treated animals showed better health, activity, and appetite compared to the untreated ones.

CONCLUSION. The results obtained confirm the presence of an inflammatory process in animals in the infection control subgroups of all ages. Inflammatory changes were also observed in the main subgroups and treatment control subgroups, and they were more pronounced in the latter. Computed tomography of the lungs in the main subgroups showed less pronounced focal infiltrative changes compared with the comparison subgroups, which indicates the potentiating effect of glutamyl-cysteinyl-glycine disodium. The study demonstrates the potential of this substance in combination with bedaquiline and opens up prospects for its inclusion in tuberculosis treatment regimens, including age-related aspects.