Effects of inhalation of polyhexamethylene guanidine disinfectant aerosol on immune organs and immune cells in mice

Background The respiratory toxicity of inhaled polyhexamethylene guanidine (PHMG) has been extensively studied since the humidifier disinfectant incident. However, the impacts of inhalation of PHMG on the immune system are not comprehensively studied yet.

Objective To explore the effects of inhalation of PHMG disinfectant aerosol on major immune organs and immune cells in mice.

Methods Thirty male C57BL/6J mice (6-8 weeks old) were randomly divided into three groups: control, low-dose (0.1 mg·m⁻³ PHMG), and high-dose (1.0 mg·m⁻³ PHMG), with ten mice in each group. The mice were administered by oral-nasal inhalation of PHMG aerosol for 4 h per day, 5 d per week for 4 weeks consecutively. After designed treatment, venous blood was collected from the inner canthus of the eyes of mice and peripheral hematological indicators were measured with a blood analyzer. Then the mice were sacrificed by cervical dislocation and the lung, thymus, spleen, and femur were isolated. Lung, thymus, and spleen were weighed and organ coefficients were calculated, and single cell suspensions of thymus, spleen, and bone marrow were prepared to analyze lymphocytes phenotypes and proportions by flow cytometry.

Results The body weight of mice in the high-dose group was lower than that of mice in the control group (P<0.01) from the 7th day of inhalation, and decreased by 15.74% compared with that of mice in the control group at the end of inhalation (P<0.01). The lung coefficients of both the low-dose and high-dose groups were higher than that of the control group (P<0.01), the thymus coefficient of mice in the high-dose group was lower than that of the control group (P<0.05), but the spleen coefficient did not change significantly (P>0.05). Leukocyte count (1.49±0.22)×10⁹·L⁻¹, lymphocyte count (0.96±0.36)×10⁹·L⁻¹ and its proportion (63.13±14.96)% in the peripheral blood of mice in the high-dose group were lower than those in the control group (2.69±0.25)×10⁹·L⁻¹, (2.33±0.28)×10⁹·L⁻¹, and (86.23±3.40)%, respectively (P<0.01), whereas red blood cell count (12.32±0.46)×10¹²·L⁻¹, hemoglobin count (175.25±4.65) g·L⁻¹, and hematocrit (53.55±0.70)% in the peripheral blood of mice in the high-dose group were higher than those in the control group (11.11±0.37)×10¹²·L⁻¹, (160.67±4.04) g·L⁻¹, and (45.10±9.75)%, respectively (P<0.05). Compared with the control group, the proportion of CD4+ CD8+ double-positive T cells decreased (P<0.05), the proportions of CD4+ T cells and CD8+ T cells increased (P<0.05), and the amounts of CD8+, CD4+ CD8+, CD4+, and CD4- CD8- cells decreased (P<0.05) in the thymus of mice of the high-dose group, the proportion of CD4+ T cells in the spleen of the high-dose group increased (P<0.05), the proportions and amounts of T cells, CD4+ T cells, and CD8+ T cells in the bone marrow of the high-dose group increased (P<0.05).

Conclusion Inhalation of PHMG may cause thymic atrophy, disrupt T-lymphocyte development, and lead to an imbalance in the number of immune cells in the bone marrow, peripheral blood, and spleen, suggesting that inhalation of PHMG induces immune dysfunction.