Timely and Appropriate Administration of Inhaled Argon Provides Better Outcomes for tMCAO Mice: A Controlled, Randomized, and Double-Blind Animal Study

Abstract

Background: Inhaled argon (iAr) has shown promising therapeutic e cacy for acute ischemic stroke (AIS) and exhibited impressive advantages over other inert gases as a neuroprotective agent. However, the optimal dose, duration and time point of iAr for AIS are unknown. Here, we explored variable iAr schedules and evaluated the neuroprotective effects of acute iAr administration on lesion volume, brain edema, and neurological function in a mouse model of cerebral ischemic/reperfusion (I/R) injury.Methods: Adult ICR mice were randomly subjected to sham, moderate (1.5 h) or severe (3 h) transient middle cerebral artery occlusion (tMCAO). One hour after tMCAO, the mice were randomized to variable iAr protocols or air (iCtr). General and focal de cit scores were assessed during double-blind treatment.Infarct volume, overall recovery and brain edema were analyzed 24 h after cerebral I/R injury.Results: Compared with those in the tMCAO only group, lesion volume (p<0.001) and neurologic outcome (general, p<0.001; focal, p<0.001) were signi cantly improved in the iAr group, which was assigned to argon inhalation 1 h after ischemia (before the onset of reperfusion). Short-term argon treatment (1 h or 3 h) showed signi cantly better outcomes with regard to infarct volume (p<0.01) compared to argon inhalation for 24 h. The concentration of argon inhalation was con rmed to be a key factor in improving the focal neurological outcome relative to that in the tMCAO group, and higher concentrations showed better effects. In addition, even though ischemia research has shown an increase in cerebral damage proportional to ischemia time, argon administration showed signi cant neuroprotective e cacy on infarct volume (p<0.001), neurological de cits (general, p<0.001; focal, p<0.001), weight recovery (p<0.001), and edema (p<0.001) in general, particularly in moderate stroke.Conclusions: Timely argon inhalation before the onset of reperfusion showed optimal neurological outcomes and minimal infarct volumes. Moreover, an appropriate duration of argon administration was important for better neuroprotective e cacy. These ndings may provide vital guidance for using argon as a neuroprotective agent and moving to clinical trials in acute ischemic stroke.

Treatment with inhaled Argon: a systematic review of pre-clinical and clinical studies with meta-analysis on neuroprotective effect

“…There were 16 in vitro studies, seven ex vivo studies, and 37 in vivo studies (six of which also included in vitro experiments). 1 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 Details of these studies are presented in the Supplemental materials ( Supplemental Tables S7 and S8 ). The sex of humans, animals, cells, and tissues involved are documented in Supplemental Table S7 (under the column labelled “cell tissue”) and…”

“…3 , panel a). 18 , 19 , 20 , 22 , 23 , 24 , 25 , 26 , 27 , 29 , 30 , 31 , 32 , 40 , 41 , 43 , 44 , 45 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 60 , 62 , 63 , 64 , 67 , 68 , 69 , 71 , 73 , 74 , 75 , 76…”

“…A total of thirty-seven in vivo studies investigating Ar as potential protective agent for different organs (brain, heart, kidney, and liver) were found ( Supplemental Table S8 ). 1 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76…”

“…The majority of the studies (33/37) was conducted on rodent’s models (rats, rabbits, and mice), 1 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 50 , 51 , 53 , 54 , 55 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 while others used swine models (4/37). 48 , 49 , 56 , 67 A comprehensive collection of all different treatment protocols (dose, onset timing, duration of administration, outcome) related to a specific clinical condition and animal model is reported in Fig.…”

Argon mitigates post-stroke neuroinflammation by regulating M1/M2 polarization and inhibiting NF-κB/NLRP3 inflammasome signaling

“…Our previous study demonstrated that timely argon administration during ischemia improves neurological outcomes and decreases infarct volumes in the tMCAO mouse model ( He et al., 2022 ), but the underlying mechanism is not clear. In this study, we tested the hypothesis that argon plays a neuroprotective role through mitigating neuroinflammation by regulating microglia/macrophage M1/M2 polarization and inhitibing NLRP3 inflammasome signaling pathway in microglia in the tMCAO mouse model and primary cultured microglia.…”