Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) are an important family of catalytic enzymes that generate reactive oxygen species (ROS), which mediate the regulation of diverse cellular functions. Although phagocyte Nox2/gp91phox is closely associated with the activation of host innate immune responses, the roles of Nox family protein during Toxoplasma gondii (T. gondii) infection have not been fully investigated. Here, we found that T. gondii-mediated ROS production was required for the upregulation of macrophage migration inhibitory factor (MIF) mRNA and protein levels via activation of mitogen-activated protein kinase and nuclear factor-κB signaling in macrophages. Interestingly, MIF knockdown led to a significant increase in the survival of intracellular T. gondii in bone marrow-derived macrophages (BMDMs). Moreover, Nox4 deficiency, but not Nox2/gp91phox and the cytosolic subunit p47phox, resulted in enhanced survival of the intracellular T. gondii RH strain and impaired expression of T. gondii-mediated MIF in BMDMs. Additionally, Nox4-deficient mice showed increased susceptibility to virulent RH strain infection and increased cyst burden in brain tissues and low levels of MIF expression following infection with the avirulent ME49 strain. Collectively, our findings indicate that Nox4-mediated ROS generation plays a central role in MIF production and resistance to T. gondii infection.

Stellaria dichotoma var. lanceolata (SdLv), a member of the Caryophyllaceae, is a traditional herbal medicine that has been used to treat fever, night sweats, and malaria in East Asia. Inflammation plays an essential role in both host defense and pathogenesis during infection by diverse intracellular pathogens. Herein, we showed that an herbal extract from SdLv effectively attenuated inflammatory responses from infection of Mycobacterium abscessus (Mab), but not Toxoplasma gondii (T. gondii). In primary murine macrophages, Mab infection resulted in the rapid activation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK), as well as in the generation of proinflammatory cytokines, such as tumor necrosis factor α and interleukin-6, which were all significantly inhibited by pretreatment with SdLv. However, herbal extracts from Bupleurum chinense DC. (Buch) or Bupleurum falcatum L. (Bufa) did not affect M. abs-induced activation of proinflammatory responses. Importantly, we demonstrated that generation of intracellular reactive oxygen species, which are important signaling intermediaries in the activation of NF-κB and the MAPK signaling pathway, was rapidly increased in Mab-infected macrophages, and this was effectively suppressed by pretreatment with SdLv, but not Buch and Bufa. We further found that the treatment of Buch and Bufa, but not SdLv, led to the activation of NF-κB and the MAPK signaling pathway and the generation of intracellular reactive oxygen species. Moreover, oral administration of SdLv significantly reduced lethality in Mab-infected mice. Collectively, these results suggest the possible use of SdLv as an effective treatment for Mab infection.