To explore the effect and mechanism of alcohol withdrawal (AW) on the pain and inflammatory response of septic mice.

A total of 30 mice were randomly divided into a control group, a sepsis group [lipopolysaccharide (LPS) group], and an AW + sepsis group (AW + LPS group), with 10 mice in each group. Mice in the control group were fed normally for 14 days and injected with 0.1 mL isotonic NaCl solution via the tail vein on the 15th day. Mice in the LPS group received routine feeding for 14 days, followed by tail vein injection of 0.1 mL LPS solution on the 15th day. Mice in the AW + LPS group were given gradient alcohol feeding for 14 days, and injected with 0.1 mL LPS solution via the tail vein on the 15th day. Daily observations were made on the changes of mice' weight, water intake, food intake and behavior, and the pain assessments were conducted. Mice were euthanized to collect lung tissue for detecting the wet-to-dry weight ratio (W/D), measuring the protein and messenger RNA (mRNA) expression of inducible nitric oxide synthase (iNOS), and observing pathological slices via hematoxylin-eosin (HE) staining. Bronchoalveolar lavage fluid (BALF) was collected to detect the expression levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6).

Compared with the control group, mice in the LPS group and AW + LPS group presented decreased body weight and markedly reduced water and food intake, with moderate pain. HE staining revealed obvious pulmonary edema, congestion, and increased infiltration of inflammatory cells in the lungs of mice in both the LPS group and the AW + LPS group. There were statistically significant differences in the lung W/D ratio, iNOS mRNA and protein expression, and BALF TNF-α and IL-6 levels among the three groups (F = 215.400, 20.270, 26.900, 2 318.000, 985.500; all P < 0.001). Compared with the control group, all the above indexes were significantly increased in the LPS group and AW + LPS group, with highest levels in the AW + LPS group (all P < 0.05).

AW aggravates sepsis-induced pain, pulmonary injury and systemic inflammatory response, which may be mediated by the regulation of iNOS protein.