RIPC and RpostC improved survival and suppressed pro-inflammatory cytokines, NF-κB activation, and hepatic inflammation in the LPS-induced sepsis mice model. The present study has shown that RpostC has also protective effects on LPS-induced endotoxemia as RIPC.
The survival rate of remote ischemic conditioned mice in the LPS-induced systemic inflammation model amounted to 60-65%, while the survival rate of unconditioned LPS injected mice was 5% in this study. The pharmacologic studies with cerivastatin or imipramine in LPS (15 – 20 mg/kg, i.p.) induced sepsis mice model showed that the survival rate of those treatment groups were 60 – 70% and that survival rate of non-treatment group were 10 – 20% [20, 21]. This result suggests that RIPC and RpostC improved survival rates to an extent comparative to some pharmacologic therapies.
Clinical and experimental studies have shown that LPS-induced sepsis can lead to a rapid simultaneous secretion of two functionally heterogeneous groups of cytokines: pro-inflammatory cytokines (e.g., TNF-α, IL-1β and IL-6) and anti-inflammatory (e.g., IL-10) . The correlation between TNF-α or IL-6 level and severity of disease exhibit the importance of these cytokines in septic shock [23–25]. Cytokine levels increased in a dose dependent manner. The dosage of LPS, 20 mg/kg used in this study was chosen as indicated by our preliminary experiment and other studies . A single injection of high-dose LPS induces a very rapid, but transient, systemic cytokines with peak levels between 1.5 and 4 hours that began to decline at 8 hours . Our preliminary study showed that TNF-α peaked at 1 hour after LPS injection, while IL-6 peaked at 4 hours after LPS injection. Therefore, we measured TNF-α, IL-1β, IL-6, and IL-10 plasma at 1 and/or 4 hours after LPS or saline administration.
RIPC significantly suppressed the release of TNF-α and IL-6 and RpostC also significantly suppressed the release of TNF-α, IL-6, and IL-1β increasing the release of anti-inflammatory cytokine IL-10. This was a finding similar to a previous study in which ischemic post-conditioning had caused a significant reduction in systemic inflammatory response .
In immune and inflammatory responses, NF-κB is a critical transcription factor and plays a crucial role through the regulation of genes encoding pro-inflammatory cytokines (e.g., TNF-α, IL-1β, IL-6), adhesion molecules, chemokines (e.g., interleukin-8), and monocyte chemotactic protein-1 (MCP-1) . Therefore, NF-κB is activated early in the pathogenesis of organ injury in sepsis [4, 5]. In models of sepsis, greater levels of nuclear accumulation of NF-κB are associated with higher rates of mortality and worse clinical outcomes . Contrariwise, suppression of NF-κB activation decreases acute inflammatory responses and organ dysfunction outcome  and down-regulation of NF-κB activation could be a suitable therapeutic target in sepsis. This present study provides evidence that RIPC and RpostC decreases NF-κB DNA binding activity in the liver during endotoxemia. Also, this result may be related to in less death in RIPC and RpostC treated groups.
Some studies have reported that NF-κB activation and nuclear translocation are inhibited by HO-1 [6, 7]. HO-1 is an enzyme catalyzing the degradation of heme into carbon monoxide, biliverdin, and free iron . HO-1 and its by-products have been shown to promote cytoprotection from oxidative stress, apoptotic cell death, and cell injury during ischemia/reperfusion [30, 31]. Ischemic pre-conditioning and post-conditioning protect against I/R injury and reduce systemic pro-inflammatory cytokine release by induction of HO-1 [9–11, 30]. More importantly, HO-1 induction by chemical inducers could provide protection against LPS-induced liver injury in rats . HO-1 may diminish extravascular edema formation and endothelial cell swelling by virtue of its anti-inflammatory, anti-apoptotic and anti-proliferative actions, resulting in reduced microvascular compression and improved organ perfusion [32, 33]. Another aim of this study was to determine if RpostC are associated with the activation of HO-1 as the protective mechanism for LPS induced hepatic damage. HO-1 activation was substantially increased in the RIPC/LPS and LPS/RpostC groups when compared with that in the LPS group. However, this study did not show significant differences. A previous study showed that intestinal ischemic preconditioning significantly reduced the LPS-induced expression of inflammatory cytokine in intestine and lung, while ischemic preconditioning selectively increased HO-1 mRNA expression in only intestine and there was no expression in lungs (18). Therefore, it is possible that HO-1 activation may not be shown in liver. Further study is need for this HO-1 activation.
Hepatocyte vacuolation and nodular necrosis were observable at 12 hours post-LPS-injection (20 mg/kg, i.p.) and mice began to die within 16 hours of LPS injection in our study . Therefore, liver tissues were collected at 12 hours after LPS injection. Histological examinations of liver sections from LPS-treated mice revealed infiltrated neutrophil and necrotic hepatocytes. However, RIPC and RpostC suppressed significantly LPS-induced intrahepatic sinusoidal neutrophils infiltration. These results seem to be correlated to survival rate.
The anti-inflammatory effects of remote ischemic conditioning were observed in mice, which will most likely yield different results in humans  and the effects of RIPC or RpostC could be questionable in septic patients. Nevertheless, intermittent pneumatic compression is routinely applied to ICU patients and it might be used as an alternative method of IPC. Therefore, clinical trials would be needed to establish its potential role for treatment of sepsis in humans.
Severe sepsis and septic shock have been responsible for the high morbidity and mortality among intensive care unit (ICU) patients. Mortality rates have decreased considerably with the discovery of antimicrobial agents. However, morbidity and mortality of sepsis have steadily increased due to the emergence of antimicrobial-resistant microorganisms . Also, antimicrobial agents themselves often result in irreversible organ failure . Therefore, this study attempts to understand innate protective mechanisms and develop new therapies against sepsis. In summary, both RIPC and RpostC attenuated NF-κB activation and reduced production of pro-inflammatory cytokines and increased anti-inflammatory cytokines release and attenuated hepatic injury and improved survival rate in LPS-induced systemic inflammation model. These results suggest that RIPC and RpostC may be a useful therapeutic approach in the treatment of sepsis.