Lactylated Histone H3K18 as a Potential Biomarker for the Diagnosis and Predicting the Severity of Septic Shock

Abstract

ObjectiveTo date, there are no studies regarding the lactylation profile and its role in critically ill patients. Thus, we aimed to examine expression of histone H3 lysine 18 (H3K18) lactylation and its role in patients with septic shock.MethodsThirteen healthy volunteers and 35 critically ill patients from the Department of Surgical Intensive Care Medicine, Beijing Hospital were enrolled in our study. Baseline information and clinical outcomes were obtained prospectively. Lactylation levels of all proteins and H3K18 from peripheral blood mononuclear (PBMC) were determined by western blotting and serum levels of inflammatory cytokines by flow cytometry. Arginase-1 (Arg1) and Krüppel-like factor-4 (Klf4) mRNA expression was evaluated by quantitative real-time PCR (qRT-PCR).ResultsLactylation was found to be an all-protein post-translational modification and was detected in PBMCs from both healthy volunteers and critically ill patients, with a significantly higher relative density in shock patients (t=2.172, P=0.045). H3K18la was expressed in all subjects, including healthy volunteers, with the highest level in septic shock patients (compared with non-septic shock patients, critically ill without shock patients and healthy volunteers P=0.033, 0.000 and 0.000, respectively). Furthermore, H3K18la protein expression correlated positively with APACHE II scores, SOFA scores on day 1, ICU stay, mechanical ventilation time and serum lactate (ρ=0.42, 0.63, 0.39, 0.51 and 0.48, respectively, ρ=0.012, 0.000, 0.019, 0.003 and 0.003, respectively). When we matched patients with septic shock and with non-septic shock according to severity, we found higher H3K18la levels in the former group (t=-2.208, P =0.040). Moreover, H3K18la exhibited a close correlation with procalcitonin levels (ρ=0.71, P=0.010). Patients with high H3K18la expression showed higher IL-2, IL-5, IL-6, IL-8, IL-10, IL-17, IFN-α levels (ρ=0.33, 0.37, 0.62, 0.55, 0.65, 0.49 and 0.374 respectively, P=0.024, 0.011, 0.000, 0.000, 0.000 and 0.000 respectively). H3K18la expression also displayed a positive correlation with the level of Arg1 mRNA (ρ=0.561, P=0.005).ConclusionsLactylation is an all-protein post-translational modification occurring in both healthy subjects and critically ill patients. H3K18la may reflect the severity of critical illness and the presence of infection. H3K18la might mediate inflammatory cytokine expression and Arg1 overexpression and stimulate the anti-inflammatory function of macrophages in sepsis.

Lactate-induced lactylation in skeletal muscle is associated with insulin resistance in humans

“…Utilizing clinical samples from lean and obese individuals, we observed a strong, positive relationship between fasting plasma lactate levels and skeletal muscle lactylation ( Figure 1C ). Chu et al ( Chu et al, 2021 ) previously reported that circulating lactate was associated with histone lactylation in the peripheral blood mononuclear cell (PBMC) of healthy and septic individuals ( Chu et al, 2021 ). Despite in vivo results providing critical physiological relevance, they unfortunately do not prove insight into causation.…”

“…The goal of the current study was to determine if lactylation was present in human skeletal muscle utilizing a pan anti-Kla antibody commonly used to identify lactylation in other cell types ( Zhang et al, 2019 ; Chu et al, 2021 ; Cui et al, 2021 ; Hagiharai et al, 2021 ; Jiang et al, 2021 ; Meng et al, 2021 ). The confirmation of lactate-induced lactylation in human skeletal muscle advocates for future research to identify the specific proteins that undergo lactylation.…”

“…The confirmation of lactate-induced lactylation in human skeletal muscle advocates for future research to identify the specific proteins that undergo lactylation. Lactate-induced lactylation was first discovered on the histones of M1 macrophages ( Zhang et al, 2019 ) with subsequent studies continuing to focus on these nuclear proteins ( Chu et al, 2021 ; Cui et al, 2021 ; Jiang et al, 2021 ; Pan et al, 2022 ). Histones consist of a central histone fold and lysine-rich tails that undergo various post-translational modifications that affect chromatin structure and transcription ( Li and Delaney 2019 ).…”

The role and mechanism of histone lactylation in health and diseases

“…Clinical trials have shown similar findings. In a study of 13 healthy volunteers and 35 critically ill patients with septic shock, Chu, X et al found that H3K18la may reflect the severity of critical illness and presence of infection, suggesting that H3K18la may have a significant impact on the balance of inflammation in sepsis ( Chu et al, 2021 ). In addition, Irizarry-C et al showed that when lacking B-cell adapter for PI3K (BCAP), macrophages show impaired lactate production and also exhibit reduced histone lactylation and lower tissue repair gene expression, which results in blunting their reparative transition ( Irizarry-Caro et al, 2020 ).…”

A bioorthogonal chemical reporter for the detection and identification of protein lactylation

“…7 Later studies have shown that histone lactylation plays key regulatory roles under a variety of biological conditions, such as cell state transition, 9 cell reprogramming, 10 neuronal excitation, 11 tumorigenesis, 12,13 glucose metabolism, 14 and so on. [15][16][17][18] The discovery of lactylation greatly extends our understanding of the functions of lactate and implies broad involvement of this modication in diverse biological processes, 19,20 given the widespread existence and high concentrations of L-lactate in mammals.…”