Effects of kinetin on thymic lymphocyte proliferation, mitochondrial membrane potential, and apoptosis-regulatory gene expression in D-galactose–induced aging rats

Objective: To determine whether kinetin (Kn) attenuates D-galactose-induced thymic lymphocyte dysfunction in rats and to evaluate changes in mitochondrial membrane potential and apoptosis-regulatory gene expression. Methods: 50 healthy Sprague-Dawley rats were randomly allocated to 5 groups (n = 10/group): control, D-galactose model, and D-galactose plus Kn at 5, 10, or 20 mg/kg. D-galactose (125 mg/kg) was administered once daily for 45 days, and Kn was administered IP once daily from days 11 through 45. Thymic lymphocyte proliferation was assessed by thiazolyl blue assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT] assay), mitochondrial membrane potential by JC-1 staining, and Bcl-2 and Bax mRNA expression by semiquantitative reverse transcription PCR. Results: D-galactose decreased thymic lymphocyte stimulation indices and the JC-1 red-to-green fluorescence ratio and was associated with decreased Bcl-2 and increased Bax mRNA expression. Kinetin increased mitogen-induced stimulation indices, improved the JC-1 red-to-green fluorescence ratio, increased Bcl-2 expression, and decreased Bax expression compared with the D-galactose model group. Conclusions: Kinetin partially reversed D-galactose-induced impairment of thymic lymphocyte proliferation and shifted mitochondrial apoptosis-related markers toward a less proapoptotic profile. Clinical Relevance: Kinetin may mitigate experimental thymic immune aging by preserving mitochondrial function and regulating apoptosis-related gene expression, supporting further veterinary geroscience studies of immune aging interventions.