BackgroundThe optimal timing of initiating renal replacement therapy (RRT) in critical illness complicated by acute kidney injury (AKI) is not clearly established. Trials completed on this topic have been marked by contradictory findings as well as quality and heterogeneity issues. Our goal was to perform a synthesis of the evidence regarding the impact of “early” versus “late” RRT in critically ill patients with AKI, focusing on the highest-quality research on this topic.MethodsA literature search using the PubMed and Embase databases was completed to identify studies involving critically ill adult patients with AKI who received hemodialysis according to “early” versus “late”/“standard” criteria. The highest-quality studies were selected for meta-analysis. The primary outcome of interest was mortality at 1 month (composite of 28- and 30-day mortality). Secondary outcomes evaluated included intensive care unit (ICU) and hospital length of stay (LOS).ResultsThirty-six studies (seven randomized controlled trials, ten prospective cohorts, and nineteen retrospective cohorts) were identified for detailed evaluation. Nine studies involving 1042 patients were considered to be of high quality and were included for quantitative analysis. No survival advantage was found with “early” RRT among high-quality studies with an OR of 0.665 (95 % CI 0.384–1.153, p = 0.146). Subgroup analysis by reason for ICU admission (surgical/medical) or definition of “early” (time/biochemical) showed no evidence of survival advantage. No significant differences were observed in ICU or hospital LOS among high-quality studies.ConclusionsOur conclusion based on this evidence synthesis is that “early” initiation of RRT in critical illness complicated by AKI does not improve patient survival or confer reductions in ICU or hospital LOS.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1291-8) contains supplementary material, which is available to authorized users.

High-mobility group box 1 (HMGB1) is a nuclear protein that has been implicated in the myocardial inflammation and injury induced by ischemia-reperfusion (I/R). The purpose of the present study was to assess the role of HMGB1 in myocardial apoptosis induced by I/R. In vivo, myocardial I/R induced an increase in myocardial HMGB1 expression and apoptosis. Inhibition of HMGB1 (A-box) ameliorated the I/R-induced myocardial apoptosis. In vitro, isolated cardiac myocytes were challenged with anoxia-reoxygenation (A/R; in vitro correlate to I/R). A/R-challenged myocytes also generated HMGB1 and underwent apoptosis. Inhibition of HMGB1 attenuated the A/R-induced myocyte apoptosis. Exogenous HMGB1 had no effect on myocyte apoptosis. However, inhibition of HMGB1 attenuated myocyte TNF-α production after the A/R was challenged; surprisingly, HMGB1 itself did not induce myocyte TNF-α production. Exogenous TNF-α induced a moderate proapoptotic effect on the myocytes, an effect substantially potentiated by coadministration of HMGB1. It is generally accepted that apoptosis induced by TNF-α is regulated by the balance of activation of c-Jun NH(2)-terminal kinase (JNK) and NF-κB. Indeed, in the present study, TNF-α increased the phosphorylation status of JNK and p65, a subunit of NF-κB; HMGB1 greatly potentiated TNF-α-induced JNK phosphorylation. Furthermore, inhibition of JNK (SP-600125) prevented the myocyte apoptosis induced by a TNF-α/HMGB1 cocktail. Finally, A/R increased HMGB1 production in both wild-type and toll-like receptor 4-deficient myocytes; however, deficiency in toll-like receptor 4 diminished A/R-induced myocyte apoptosis, TNF-α, and JNK activation. Our results indicate that myocyte-derived HMGB1 and TNF-α work in concert to promote I/R-induced myocardial apoptosis through JNK activation.

Myocardial contractile dysfunction in sepsis is associated with the increased morbidity and mortality. Although the underlying mechanisms of the cardiac depression have not been fully elucidated, an exaggerated inflammatory response is believed to be responsible. Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome is an intracellular platform that is involved in the maturation and release of interleukin (IL)-1β. The aim of the present study is to evaluate whether sepsis activates NLRP3 inflammasome/caspase-1/IL-1β pathway in cardiac fibroblasts (CFs) and whether this cytokine can subsequently impact the function of cardiomyocytes (cardiac fibroblast-myocyte cross-talk). We show that treatment of CFs with lipopolysaccharide (LPS) induces upregulation of NLRP3, activation of caspase-1, as well as the maturation (activation) and release of IL-1β. In addition, the genetic (small interfering ribonucleic acid [siRNA]) and pharmacological (glyburide) inhibition of the NLRP3 inflammasome in CFs can block this signaling pathway. Furthermore, the inhibition of the NLRP3 inflammasome in cardiac fibroblasts ameliorated the ability of LPS-chalenged CFs to impact cardiomyocyte function as assessed by intracellular cyclic adenosine monophosphate (cAMP) responses in cardiomyocytes. Salient features of this the NLP3 inflammasome/ caspase-1 pathway were confirmed in in vivo models of endotoxemia/sepsis. We found that inhibition of the NLRP3 inflammasome attenuated myocardial dysfunction in mice with LPS and increased the survival rate in mice with feces-induced peritonitis. Our results indicate that the activation of the NLRP3 inflammasome in cardiac fibroblasts is pivotal in the induction of myocardial dysfunction in sepsis.