Single-cell RNA sequencing deciphers the mechanism of sepsis-induced liver injury and the therapeutic effects of artesunate.

Liver, as an immune and detoxification organ, represents an important line of defense against bacteria and infection and a vulnerable organ that is easily injured during sepsis. Artesunate (ART) is an anti-malaria agent, that also exhibits broad pharmacological activities including anti-inflammatory, immune-regulation and liver protection. In this study, we investigated the cellular responses in liver to sepsis infection and ART hepatic-protective mechanisms against sepsis. Cecal ligation and puncture (CLP)-induced sepsis model was established in mice. The mice were administered ART (10 mg/kg, i.p.) at 4 h, and sacrificed at 12 h after the surgery. Liver samples were collected for preparing single-cell RNA transcriptome sequencing (scRNA-seq). The scRNA-seq analysis revealed that sepsis-induced a dramatic reduction of hepatic endothelial cells, especially the subtypes characterized with proliferation and differentiation. Macrophages were recruited during sepsis and released inflammatory cytokines (Tnf, Il1b, Il6), chemokines (Ccl6, Cd14), and transcription factor (Nfkb1), resulting in liver inflammatory responses. Massive apoptosis of lymphocytes and abnormal recruitment of neutrophils caused immune dysfunction. ART treatment significantly improved the survival of CLP mice within 96 h, and partially relieved or reversed the above-mentioned pathological features, mitigating the impact of sepsis on liver injury, inflammation, and dysfunction. This study provides comprehensive fundamental proof for the liver protective efficacy of ART against sepsis infection, which would potentially contribute to its clinical translation for sepsis therapy. Single cell transcriptome reveals the changes of various hepatocyte subtypes of CLP-induced liver injury and the potential pharmacological effects of artesunate on sepsis.

Single-cell transcriptomic dissection of the cellular and molecular events underlying the triclosan-induced liver fibrosis in mice.

BACKGROUND: Triclosan [5-chloro-2-(2,4-dichlorophenoxy) phenol, TCS], a common antimicrobial additive in many personal care and health care products, is frequently detected in human blood and urine. Therefore, it has been considered an emerging and potentially toxic pollutant in recent years. Long-term exposure to TCS has been suggested to exert endocrine disruption effects, and promote liver fibrogenesis and tumorigenesis. This study was aimed at clarifying the underlying cellular and molecular mechanisms of hepatotoxicity effect of TCS at the initiation stage. METHODS: C57BL/6 mice were exposed to different dosages of TCS for 2 weeks and the organ toxicity was evaluated by various measurements including complete blood count, histological analysis and TCS quantification. Single cell RNA sequencing (scRNA-seq) was then carried out on TCS- or mock-treated mouse livers to delineate the TCS-induced hepatotoxicity. The acquired single-cell transcriptomic data were analyzed from different aspects including differential gene expression, transcription factor (TF) regulatory network, pseudotime trajectory, and cellular communication, to systematically dissect the molecular and cellular events after TCS exposure. To verify the TCS-induced liver fibrosis, the expression levels of key fibrogenic proteins were examined by Western blotting, immunofluorescence, Masson's trichrome and Sirius red staining. In addition, normal hepatocyte cell MIHA and hepatic stellate cell LX-2 were used as in vitro cell models to experimentally validate the effects of TCS by immunological, proteomic and metabolomic technologies. RESULTS: We established a relatively short term TCS exposure murine model and found the TCS mainly accumulated in the liver. The scRNA-seq performed on the livers of the TCS-treated and control group profiled the gene expressions of > 76,000 cells belonging to 13 major cell types. Among these types, hepatocytes and hepatic stellate cells (HSCs) were significantly increased in TCS-treated group. We found that TCS promoted fibrosis-associated proliferation of hepatocytes, in which Gata2 and Mef2c are the key driving TFs. Our data also suggested that TCS induced the proliferation and activation of HSCs, which was experimentally verified in both liver tissue and cell model. In addition, other changes including the dysfunction and capillarization of endothelial cells, an increase of fibrotic characteristics in B plasma cells, and M2 phenotype-skewing of macrophage cells, were also deduced from the scRNA-seq analysis, and these changes are likely to contribute to the progression of liver fibrosis. Lastly, the key differential ligand-receptor pairs involved in cellular communications were identified and we confirmed the role of GAS6_AXL interaction-mediated cellular communication in promoting liver fibrosis. CONCLUSIONS: TCS modulates the cellular activities and fates of several specific cell types (including hepatocytes, HSCs, endothelial cells, B cells, Kupffer cells and liver capsular macrophages) in the liver, and regulates the ligand-receptor interactions between these cells, thereby promoting the proliferation and activation of HSCs, leading to liver fibrosis. Overall, we provide the first comprehensive single-cell atlas of mouse livers in response to TCS and delineate the key cellular and molecular processes involved in TCS-induced hepatotoxicity and fibrosis.

[Start-up Performance and Sludge Characteristics of Single-stage Autotrophic Nitrogen Removal System with Granular Sludge at Low Ammonia Nitrogen Concentration at Room Temperature].

The start-up and stable operation of single-stage autotrophic nitrogen removal process under low ammonia nitrogen substrate at room temperature appears as the premise and basis for the application in municipal wastewater treatment. In this study, the PN/A (partial nitritation and ANAMMOX) granular sludge for long-term storage was inoculated into an air-lift bioreactor to investigate the nitrogen removal performance during the start-up of single-stage partial nitritation and ANAMMOX process under the following conditions:temperature at (23±2)℃, pH at 7.7-8.0. Synthetic wastewater with ammonia nitrogen concentration of 70 mg·L-1 was used as influent. By stepwise shortening hydraulic retention time (HRT) (1.1 h→0.9 h→0.7 h→0.5 h) and increasing ammonia nitrogen loading rate[1.53 kg·(m3·d)-1→1.87 kg·(m3·d)-1→2.40 kg·(m3·d)-1→3.36 kg·(m3·d)-1], the bioactivity as the synergy between the ammonia oxidizing bacteria (AOB) and anaerobic oxidizing bacteria (AMX) were gradually restored. After 95 d operation and regulation, the process was successfully established and the removal rate of NH4+-N and TN were 85% and 69%, respectively. According to the performance of sludge at each stage, the nitrite oxidizing bacteria (NOB) were selectively inhibited by controlling dissolved oxygen strictly. The average particle size gradually increased and finally was reached to 1.30 mm after the sludge was adapted to the environment. The profile of the mature autotrophic granular sludge was smooth and clear, SEM showed that the center of granular sludge formed a cavity with porous structure on the surface, the sludge morphology consisted mainly of cocci, with a small amount of bacilli and short bacilli. The major component of EPS in granular sludge was protein (81.48%) indicating that it had a good settling performance.