The pathogenesis of sepsis is complex. Mitochondrial dysfunction, which is responsible for energy metabolism, intrinsic apoptotic pathway, oxidative stress, and systemic inflammatory responses, is closely related with severe sepsis induced death. Mitochondria DNA (mtDNA) contain un-methylated cytosine phosphate guanine (CpG) motifs, which exhibit immune stimulatory capacities. The aim of this study was to investigate the role and mechanism of mtDNA release on lipopolysaccharide (LPS) induced acute lung injury (ALI) and systemic inflammation. Following LPS injection, plasma mtDNA copies peak at 8 h. Compared with wild-type (WT) mice, mtDNA in toll like receptor 4 knockout (TLR4 KO) mice were significantly decreased. MtDNA intra-peritoneal administration causes apparent ALI as demonstrated by increased lung injury score, bronchoalveolar lavage fluid (BALF) total protein and wet/dry (W/D) ratio; mtDNA injection also directly provokes systemic inflammation, as demonstrated by increased IL-1β, IL-6, high-mobility group protein B1 (HMGB1) level; while nuclear DNA (nDNA) could not induce apparent ALI and systemic inflammation. However, compared with WT mice, TLR4 KO could not protect from mtDNA induced ALI and systemic inflammation. Specific TLR9 inhibitor, ODN 2088 pretreatment can significantly attenuate mtDNA induced ALI and systemic inflammation, as demonstrated by improved lung injury score, decreased lung wet/dry ratio, BALF total protein concentration, and decreased systemic level of IL-1β, IL-6 and HMGB1. MtDNA administration activates the expression of p-P38 mitogen-activated protein kinases (MAPK) in lung tissue and specific TLR9 inhibitor pretreatment can attenuate this activation. Thus, LPS-induced mtDNA release occurs in a TLR4-dependent manner, and mtDNA causes acute lung injury and systemic inflammation in a TLR9-dependent and TLR4-independent manner.

Recent studies have indicated that autophagy contributes to tumorigenesis and participates in acquired chemotherapeutic resistance. The present study aimed to determine the function and underlying mechanism of cisplatin‑induced autophagy in A549 human lung cancer cells. Autophagy was measured by LC3B‑I/II conversion, LC3B puncta and autophagosomes formation. Apoptotic cell death was measured by caspase‑3 activity, caspase‑3 cleavage and LDH release. The transcriptional and expressional level of autophagy related proteins were measured by reverse transcription-quantitative polymerase chain reaction and western blot analysis. Beclin 1 and Atg 5 siRNA transfection was used to explore the function of cisplatin‑induced autophagy. The results demonstrated that cisplatin induces apoptotic cell death in A549 cells and triggers an autophagic response, as indicated by increased microtubule‑associated protein 1 light chain 3β (LC3B)‑I/II conversion, increased LC3B puncta and autophagosome formation. Mechanisms underlying cisplatin‑induced autophagic responses were also investigated. Cisplatin induced autophagy by upregulating the mRNA and protein expression levels of autophagy protein (Atg)5 and Beclin 1, whereas the mRNA and protein expression levels of serine/threonine‑protein kinase ULK1, Atg3, Atg7, Atg12, and sequestosome‑1 were not markedly upregulated. In addition, knockdown of Atg5 and Beclin 1 by small interfering RNA transfection impaired cisplatin‑induced activation of autophagic responses, increased caspase‑3 cleavage and inhibited cell viability. These findings suggested that disruption of autophagy via the inhibition of Atg5 and Beclin 1 may promote cisplatin‑induced apoptotic cell death in A549 human lung cancer cells. In conclusion, the present study demonstrated that targeting autophagy may be used in the future for the treatment of lung cancer.