Naringin alleviates pneumonia caused by Klebsiella pneumoniae infection by suppressing NLRP3 inflammasome.

Klebsiella pneumoniae (Kpn) is an important pathogen of hospital-acquired pneumonia, which can lead to sepsis and death in severe cases. In this study, we simulated pneumonia induced by Kpn infection in mice to investigate the therapeutic effect of naringin (NAR) on bacterial-induced lung inflammation. Mice infected with Kpn exhibited increases in white blood cells (WBC) and neutrophils in the peripheral blood and pathological severe injury of the lungs. This injury was manifested by increased expression of the inflammatory cytokines interleukin (IL)- 18, IL-1ß, tumor necrosis factor-α (TNF-α) and IL-6, and elevated the expression of NLRP3 protein. NAR treatment could decrease the protein expression of NLRP3, alleviate lung inflammation, and reduce lung injury in mice caused by Kpn. Meanwhile, molecular docking results suggest NAR could bind to NLRP3 and Surface Plasmon Resonance (SPR) analyses also confirm this result. In vitro trials, we found that pretreated with NAR not only inhibited nuclear translocation of nuclear factor (NF)-κB protein P65 but also attenuated the protein interaction of NLRP3, caspase-1 and ASC and inhibited the assembly of NLRP3 inflammasome in mice AMs. Additionally, NAR could reduce intracellular potassium (K+) efflux, inhibiting NLRP3 inflammasome activation. These results indicated that NAR could protect against Kpn-induced pneumonia by inhibiting the overactivation of the NLRP3 inflammasome signaling pathway. The results of this study confirm the efficacy of NAR in treating bacterial pneumonia, refine the mechanism of action of NAR, and provide a theoretical basis for the research and development of NAR as an anti-inflammatory adjuvant.

Screening of essential oils with acaricidal activity against Haemaphysalis longicornis (Acari: Ixodidae) and analysis of active components.

Haemaphysalis longicornis (Acari: Ixodidae) is an important vector of numerous pathogens and poses a great threat to veterinary and public health. Commercially available tick repellents are extensively used and primarily comprise synthetic molecules; however, there are concerns over their safety and environmental impacts. Biologically based acaricides, particularly the plant-derived essential oils (EOs), may constitute an appealing alternative. We screened 20 different EOs by packet tests of unfed H. longicornis nymphs, and found that EOs of cinnamon, clove and chamomile were the most toxic (mortality > 80 %). Cinnamon EO had the most competitive acaricidal activity, with lethal concentration 50 (LC50) rates of 0.4530 %, 0.2316 % and 0.0342 % (v/v) for unfed adults, nymphs and larvae, respectively. Furthermore, 5.00 % (v/v) cinnamon EO showed reproductive inhibition against H. longicornis, with significantly higher rates of oviposition reduction (53.19 %) and hatching reduction (46.21 %) compared with the negative control group. Composition analysis of cinnamon EO by gas chromatography-mass spectrometry (GC-MS) revealed that the major chemical compounds were trans-cinnamaldehyde (72.21 %) and cinnamic acid (19.45 %), with the former showing similar levels of acaricidal activity and oviposition inhibition as cinnamon EO. This study has demonstrated the potential of cinnamon EO and trans-cinnamaldehyde as natural acaricides against H. longicornis, and is the first to characterize their oviposition inhibition activity.