Regulations of immune responses by artesunate in combination with rIL-33 in the treatment of cerebral malaria in mice

doi:10.12140/j.issn.1000-7423.2020.02.002

Abstract

Abstract:

Objective To investigate the effects of artesunate (ART) in combination with recombinant interleukin-33 (rIL-33) in the treatment of cerebral malaria in mice infected with Plasmodium berghei ANKA (PbA) and its effects on immune responses of mice.Methods Forty female C57BL/6 mice were randomly divided into 5 groups (n = 8): PbA infection without treatment (PbA group), PbA infection with treatment (PbA+rIL-33 group, PbA+ART group, and PbA+rIL-33+ART group), and normal control group. Mice in the PbA infection groups were injected intraperitoneally (i.p.) with 1 × 10 ⁶ PbA-infected red cells. Two to four days post-infection, mice in the PbA+rIL-33 group received daily i.p. injections of rIL-33 (0.2 μg/mouse) for 3 consecutive days, those in the PbA+ART group received 40 mg/kg ART (once daily for 3 days) by gavage, and those in the PbA+rIL-33+ART group received ART and rIL-33 injection for 3 consecutive days. The PbA group received no treatment. The control group received the same volume of PBS at the same time points as above. From day 3 after infection, tail vein blood was collected every other day, blood smears were made for Giemsa staining to examine the infection rate of red cells, and the death and survival time span were recorded as well. To assess the integrity of the blood-brain barrier (BBB), on day 5 after infection, evans blue solution was given to the mice intravenously, then the brain tissue eluent was examined to detect penetrated blue dye passing through the barrier by measuring absorbance at 630 nm (A₆₃₀). On day 5 after infection, four mice of each group were sacrificed to determine the percentage and absolute number of Th1/Th2, Tregs, macrophages and Toll-like receptor 4 (TLR4) cells in spleen by flow cytometry. Results In the PbA group, neurological symptoms first appeared on day 6, and deaths occurred from day 6 to day 13, while in the PbA+rIL-33 and the PbA+ART groups deaths occurred on day 8. The neurological symptoms of the PbA+rIL-33+ART group were significantly suppressed, and deaths occurred on day 12 post infection. Two of 7 mice died of anemia on day 23 post infection. The infection rate of red cells in the PbA+rIL-33+ART group increased from 0.30% to 19.67% during day 3 to 13 after infection, remaining consistently lower than those of the PbA group (0.93%-20.00%) and PbA+rIL-33 group (0.46%-19.67%) (P < 0.05). In addition, BBB integrity assessment showed that the A₆₃₀ in the PbA+rIL-33+ART group was (0.11 ± 0.01), significantly lower than those in the PbA group (0.44 ± 0.01) (P < 0.01), the PbA+rIL-33 group (0.19 ± 0.01) (P < 0.01) and the PbA+ART group (0.27 ± 0.02) (P < 0.01). Flow cytometry assay showed that the percentage of Th1 cells in the PbA+rIL-33+ART group was (7.51 ± 0.26)%, which was significantly lower than that in the PbA group [(14.27 ± 0.91)%, P < 0.01], but did not differ significantly from those in the PbA+ART group [(9.56 ± 1.75)%] and PbA+rIL-33 group [(8.67 ± 0.26)%] (P > 0.05). The percentage of Th2 cells in the PbA+rIL-33+ART group was (2.63 ± 0.27)%, which was significantly higher than those in the PbA group [(0.80 ± 0.13)%, P < 0.01] and the PbA+ART group [(0.88 ± 0.12)%, P < 0.01], but did not differ significantly from that in the PbA+rIL-33 group [(1.70 ± 0.54)%] (P > 0.05). The percentage of macrophages in the PbA+rIL-33+ART group was (3.85 ± 0.32)%, which was significantly higher than that in the PbA group [(2.89 ± 0.89)%] (P < 0.05), but did not differ significantly from those in the PbA+ART group [(3.15 ± 0.46)%] and the PbA+rIL-33 group [(4.11 ± 0.68)%] (P > 0.05). The percentage of Treg cells in the PbA+rIL-33+ART group was (11.05 ± 1.50)%, which was significantly higher than those in the PbA group [(6.44 ± 0.09)%, P < 0.05] and the PbA+ART group [(6.27 ± 0.39)%, P < 0.01], but did not differ significantly from that in the PbA+rIL-33 group [(9.34 ± 0.61)%] (P > 0.05). The percentage of TLR4 cells in the PbA+rIL-33+ART group [(1.43 ± 0.21)%] was significantly higher than that in the PbA group [(3.76 ± 0.41)%] (P < 0.01), but did not differ significantly from those in the PbA+ART group [(1.69 ± 0.26)%] and the PbA+rIL-33 group [(1.61 ± 0.15)%](P > 0.05).Conclusion rIL-33 combined with ART can protect the mouse brain from experimental cerebral malaria damage, and improve the therapeutic outcome through balancing Th1/Th2 immune responses.

Key words: Plasmodium berghei ANKA, Interleukin-33, Artesunate, Cerebral malaria

CLC Number:

R531.33

Yun-ting DU, Wei ZHAO, Ya-ming CAO, Lan XU. Regulations of immune responses by artesunate in combination with rIL-33 in the treatment of cerebral malaria in mice[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2020, 38(2): 139-145.

Figures/Tables 3

References 23

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