Modulation of Oxidative Stress, Inflammatory Cytokines, and Mucosal Immunity by Green Synthesized Zinc Nanoparticles...

Giardiasis remains one of the most important intestinal infections and common drugs such as metronidazole (MET), especially at therapeutic doses, are associated with side effects and drug resistance. The aim of this study was to investigate the efficacy of zinc nanoparticles synthesized with Astragalus ecbatanus extract in the treatment of a mouse model of giardia.

In this study, 72 male Balb/C mice were randomly divided into nine different groups, including a healthy control group, an infected control group, a group receiving MET at a dose of 15 mg/kg, three groups receiving ZN as monotherapy at doses of 2.5, 5, and 10 mg/kg, and three groups receiving combination therapy (ZN plus MET at a dose of 7.5 mg/kg). After seven days of treatment, various indicators, including the number and survival of Giardia cysts in feces, serum electrolyte concentrations, oxidative stress parameters including malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx), as well as the expression of cytokine genes (IL-1β, TNF-α, and IL-10), the level of secretory IgA in intestinal tissue, and biochemical indicators of hepatotoxicity and renal toxicity, were measured and analyzed.

The prepared nanoparticles had a size between 15 and 70 nm and a zeta stability of - 19.6 mV. Treatment with ZN significantly reduced the number of cysts; doses of 2.5, 5 and 10 mg/kg excreted 366.6, 89.9 and 39.9 cysts less than the infected control (726.6 cysts), respectively. Cyst survival also decreased by 50.2%, 64.6% and 82.7%, respectively. The combination of ZN with low dose MET completely eliminated the infection. Also, sodium increased from 56.8 to 89.6-115.9 mmol/L and to 130.3 mmol/L in the combination treatment; potassium also increased from 1.36 to 2.66-3.54 mmol/L and to 4.1 mmol/L in the combination treatment. MDA levels decreased by 1.69-1.82 U/mg and SOD increased by 51.3-56.6 U/mg. Cytokine analysis revealed strong anti-inflammatory effects: IL-1β decreased to  1.21- and  1.13- fold, TNF-α decreased to  1.31- and  1.18- fold, while IL-10 increased up to  3.91- fold in ZN + MET groups. sIgA levels markedly increased (up to 312.3 pg/mL vs. 212.3 pg/mL in full-dose MET). Liver/kidney markers showed no significant toxicity (P > 0.05).

Green-synthesized zinc nanoparticles derived from A. ecbatanus showed significant therapeutic effects against giardiasis, particularly in combination with low-dose metronidazole. Treatment reduced cyst burden, improved oxidative stress and inflammatory markers, and enhanced mucosal immunity. These findings suggest a dual antiparasitic and host-modulatory role. However, further mechanistic studies and clinical validation are required to confirm their therapeutic potential.