Blockage of mechanosensitive Piezo1 channel alleviates the severity of experimental malaria-associated acute lung injury.

BACKGROUND: Malaria-associated acute lung injury (MA-ALI) is a well-recognized clinical complication of severe, complicated malaria that is partly driven by sequestrations of infected red blood cells (iRBCs) on lung postcapillary induced impaired blood flow. In earlier studies the mechanosensitive Piezo1 channel emerged as a regulator of mechanical stimuli, but the function and underlying mechanism of Piezo1 impacting MA-ALI severity via sensing the impaired pulmonary blood flow are still not fully elucidated. Thus, the present study aimed to explore the role of Piezo1 in the severity of murine MA-ALI. METHODS: Here, we utilized a widely accepted murine model of MA-ALI using C57BL/6 mice with Plasmodium berghei ANKA infection and then added a Piezo1 inhibitor (GsMTx4) to the model. The iRBC-stimulated Raw264.7 macrophages in vitro were also targeted with GsMTx4 to further explore the potential mechanism. RESULTS: Our data showed an elevation in the expression of Piezo1 and number of Piezo1+-CD68+ macrophages in lung tissues of the experimental MA-ALI mice. Compared to the infected control mice, the blockage of Piezo1 with GsMTx4 dramatically improved the survival rate but decreased body weight loss, peripheral blood parasitemia/lung parasite burden, experimental cerebral malaria incidence, total protein concentrations in bronchoalveolar lavage fluid, lung wet/dry weight ratio, vascular leakage, pathological damage, apoptosis and number of CD68+ and CD86+ macrophages in lung tissues. This was accompanied by a dramatic increase in the number of CD206+ macrophages (M2-like subtype), upregulation of anti-inflammatory cytokines (e.g. IL-4 and IL-10) and downregulation of pro-inflammatory cytokines (e.g. TNF-α and IL-1ß). In addition, GsMTx4 treatment remarkably decreased pulmonary intracellular iron accumulation, protein level of 4-HNE (an activator of ferroptosis) and the number of CD68+-Piezo1+ and CD68+-4-HNE+ macrophages but significantly increased protein levels of GPX4 (an inhibitor of ferroptosis) in experimental MA-ALI mice. Similarly, in vitro study showed that the administration of GsMTx4 led to a remarkable elevation in the mRNA levels of CD206, IL-4, IL-10 and GPX-4 but to a substantial decline in CD86, TNF-α, IL-1ß and 4-HNE in the iRBC-stimulated Raw264.7 cells. CONCLUSIONS: Our findings indicated that blockage of Piezo1 with GsMTx4 alleviated the severity of experimental MA-ALI in mice partly by triggering pulmonary macrophage M2 polarization and subsequent anti-inflammatory responses but inhibited apoptosis and ferroptosis in lung tissue. Our data suggested that targeting Piezo1 in macrophages could be a promising therapeutic strategy for treating MA-ALI.

Malaria-derived exosomes exacerbate liver injury during blood stage of Plasmodium berghei infection.

Liver injury is a common clinical feature of Plasmodium spp. infection and contributes to multi-organ failure of severe malaria. Malaria-derived exosomes (MD-Exos) have recently engaged as key mediators in parasite-host interactions, modulating the subsequent pathogenic process. However, the role of MD-Exos in malaria-related liver injury and the underlying mechanisms remain unclear. Herein, exosomes from C57BL/6 mice infected with or without P. berghei ANKA serum (namely inf-Exos or un-Exos) were isolated and characterized by transmission electron microscopy, western blotting, and nanoparticle tracking analysis. The miRNAs profiling between inf-Exos and un-Exos were generated using RNA-seq and qPCR. The functions of inf-Exos on liver injury were investigated after two types of exosomes injected into mice intravenously (i.v.), by examining histopathological and apoptotic changes, macrophage polarization, and pro-inflammatory response. The infected red blood cells-stimulated mouse Raw264.7 macrophage cells targeted by inf-Exos or un-Exos were cultured for further study and verification the potential mechanisms. We found that both inf-Exos and un-Exos displayed a typical cup-shaped structure with a diameter of 60-200 nm, and had a positive expression of exosomal markers (e.g., CD9, CD63, and CD81). Compared with infected control mice, the treatment of inf-Exos but not un-Exos dramatically enhanced peripheral blood parasitemia and ECM incidence, exacerbated liver histopathological damage, elevated numbers of liver apoptotic cells, CD68+and CD86+ macrophages. The CD68+-TREM-1+ macrophages in liver tissues and the mRNA levels of pro-inflammatory cytokines (e.g., iNOS, TNF-α, IL-1ß, and IL-6) were increased by inf-Exos treatment in vivo. Meanwhile, the treatment of inf-Exos resulted in a substantial increase of the mRNA levels of CD86, iNOS, TNF-α, IL-1ß, and IL-6, but led to a remarkable decrease of Bcl-6 and SOCS-1 in Raw264.7 cells stimulated with iRBC in vitro. Notably, compared to un-Exos, five types of miRNAs (including miR-10a-5p, miR-10b-5p, miR-155-5p, miR-205-5p, and miR-21a-5p), that were previously reported to target Bcl-6 or SOCS-1, present higher abundance on inf-Exos, as demonstrated by RNA-seq and qPCR. Collectively, our data suggest that inf-Exos exacerbate malaria-induced liver pathology via triggering excessive pro-inflammatory response and promoting macrophage M1 polarization. Our findings will provide new insights into the roles of inf-Exos in malaria parasite-host interaction and pathogenesis of liver injury.