Potential Therapeutic Effects of Isopropyltoluene (P-Cymene) Against Toxoplasma gondii Infection in Dexamethasone-Immunosuppressed Mice.

Background: Toxoplasmosis is a potentially life-threatening opportunistic infection that primarily affects individuals with weakened immune systems. Given the pharmacological characteristics of p-Cymene (p-isopropyltoluene, CM), the present experimental study was undertaken to evaluate the therapeutic effects and possible mechanisms of action of CM against Toxoplasma gondii infection in immunocompromised mice.

Methods: BALB/c mice, rendered immunocompromised through dexamethasone treatment and subsequently infected with the T. gondii ME49 strain. Then, mice received CM at doses of 5 and 10 mg/kg, either as a monotherapy or in conjunction with pyrimethamine (PYM, 10 mg/kg), over a two-week period. The investigation involved the assessment of various parasitological parameters such as the number and dimensions of T. gondii cysts and tissue levels of oxidant and antioxidant markers such as malondialdehyde (MDA), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in the brain of the tested mice. In addition, the gene expression level of immune responses related cytokines (IFN-γ, IL-4, and IL-12) as well as apoptosis (Caspase-3, Bcl-2, and BAX) and pathogenesis-related genes (BAG1) were analyzed using quantitative reverse transcription polymerase chain reaction (Real-time-PCR).

Results: The administration of CM, particularly in conjunction with PYM, resulted in a significant (p < 0.001) reduction in the number and size of brain Toxoplasma cysts. This treatment also significantly reduced the tissue level of MDA (p < 0.001), whereas markedly increased the activities of antioxidant enzymes of GPx and SOD (p < 0.001). CM at the dose of 10 mg/kg mainly in combination with PYM significantly (p < 0.001) upregulated the expression levels of IFN-γ (5.23-fold change), IL-12 (4.33-fold change), Caspase-3 (3.3-fold change), and BAX (4.21-fold change); whereas, obviously (p < 0.001) downregulated the expression of IL-4 (1.10-fold change), Bcl-2 (1.09-fold change), and BAG1 (1.28-fold change). Following treatment with CM, particularly the combinations of PYM at 10 mg/kg over a 14-day period, there was a marked modulation of serum levels of AST, ALT, BUN, and Cr in the IC-infected mice. Post hoc analysis indicated no significant differences in the serum levels of liver and kidney function biomarkers between healthy mice treated with CM at doses of 5 and 10 mg/kg and the control group of healthy mice that received normal saline.

Conclusion: The findings of this survey indicate that CM alone and in combination with PYM demonstrates significant efficacy in treating chronic toxoplasmosis in mice with dexamethasone-induced immunosuppression. The results suggest that potential mechanisms for managing latent toxoplasmosis may include the regulation of oxidative stress, enhancement of antioxidant enzyme activity, induction of apoptosis, and modulation of inflammatory responses, all while maintaining the functionality of vital organs without toxicity. To further substantiate the therapeutic potential of this compound, it is imperative to conduct clinical trials that evaluate both its toxicity and therapeutic efficacy.