Abstract:

BACKGROUND: Vibrio vulnificus inside the body could activate the NF-κB signaling pathway and initiate the inflammatory cascade. The lung is one of the earliest organs affected by sepsis associated with acute lung injury. High mobility group protein B1 (HMGB1) is an important late-acting pro-inflammatory cytokine involving in the pathophysiology of sepsis. It is also involved in the injury process in the lung, liver and intestine. There has been no report on the involvement of HMGB1 in Vibrio vulnificus sepsis-induced lung injury.
METHODS: Sixty rats were randomly divided into a normal control group (group A, n=10) and a Vibrio vulnificus sepsis group (group B, n=50). Sepsis was induced in the rats by subcutaneous injection of Vibrio vulnificus (concentration 6×10⁸ cfu/mL, volume 0.1 mL/100g)) into the left lower limbs. The rats in group B were sacrificed separately 1, 6, 12, 24, and 48 hours after the infection. Their lungs were stored as specimens, lung water content was measured, and lung pathology was observed under a light microscope. The expressions of the HMGB1 gene and protein in the lungs were detected by RT-PCR and Western blot. Data were analyzed with one-way analysis of variance (ANOVA) and the LSD method for pair-wise comparison between the two groups. P<0.05 was considered statistically significant.
RESULTS: Compared to group A (0.652±0.177), HMGB1 mRNA expression in the lungs of group B was significantly higher at 0 hour (1.161±0.358, P=0.013), 24 hours (1.679±0.235, P=0.000), and 48 hours (1.258±0.274, P=0.004) (P<0.05), and peaked at 24 hours. Compared to group A (0.594±0.190), HMGB1 protein expression at 6 hours (1.408±0.567, P=0.026) after infection was significantly increased (P<0. 05), and peaked at 24 hours (2.415±1.064, P=0.000) after infection. Compared to group A (0.699±0.054), lung water content was significantly increased at 6 hours (0.759±0.030, P=0.001),12 hours (0.767±0.023, P=0.000), 24 hours (0.771±0.043, P=0.000) and 48 hours (0.789±0.137, P=0.000) after infection (P<0.05). Compared to group A, pathological changes at 12 hours in group B indicate marked pulmonary vascular congestion, interstitial edema and inflammatory infiltration. Alveolar cavity collapse and boundaries of the alveolar septum could not be clearly identified.
CONCLUSION: Vibrio vulnificus sepsis can lead to injury in rat lungs, and increased HMGB1 expression in lung tissue may be one of the mechanisms for injury from Vibrio vulnificus sepsis.

Key words: Vibrio vulnificus, Sepsis, Lung injury, High mobility group protein B1, Reverse transcription polymerase chain reaction, Western blot, Lung water content, Histopathology