E. J. Charles1, B. Miao1, R. G. Sawyer1, Z. Yang1 1University Of Virginia,Surgery,Charlottesville, VA, USA
Introduction: The spleen is the largest secondary immune organ that mediates immunological processes and inflammatory responses. Our previous study using rats with severe septic shock demonstrates that the spleen plays a pivotal role in mediating inflammatory responses and contributes to shortened survival duration. Recent studies have elucidated a role for pulsed ultrasound (pUS) to modulate spleen-mediated inflammatory responses and attenuate renal ischemia-reperfusion injury. We hypothesized that pUS treatment of the spleen improves survival in rats with severe septic shock by inhibiting inflammatory responses.
Methods: Male Sprague Dawley rats (n=3-4/group) underwent cecal ligation and incision (CLI) to induce severe sepsis or sham celiotomy. After 2 hours, rats were treated with peritoneal lavage (300 mL normal saline) and intraperitoneal cefazolin (0.1 mg/g body weight). Three experimental groups were randomized: no further treatment (Control), splenectomy (Splx), or pUS treatment during washout, and compared to sham rats. pUS was administered with 7 MHz frequency and 1.2 bursting mechanical index for 1 second, and repeated every 6 seconds for 2 minutes (total exposure = 20 seconds). Plasma was obtained in all groups 4 hours after laparotomy.
Results: Control rats had significantly higher plasma levels of TNF-α (19.5±5 vs. 0±0 pg/mL, p=0.0007) and MCP-1 (6962.6±1088.2 vs. 127.7±59 pg/mL, p=0.0001) compared with Sham. Both splenectomy and pUS treatment at 2 hours significantly reduced circulating levels of TNF-α (Splx: 1.8±0.7 pg/mL, p=0.002; pUS: 6.9±1.3 pg/mL, p=0.02) and MCP-1 (Splx: 2397.7±446.6 pg/mL, p=0.006; pUS: 3680.5±736.3 pg/mL, p=0.03) compared with Control (Figure). Circulating levels of TNF-α and MCP-1 were not significantly different between Splx and pUS rats. Phosphorylated Akt in the splenic tissue was significantly higher in pUS compared with Control (56.4±4.4 vs. 42.5±1.4 % of total Akt, p=0.048). Additionally, pUS rats had significantly lower levels of splenic tissue IL-10 (p=0.048) and decreased leukocytosis (p=0.03) compared with Control rats.
Conclusion: Both pUS treatment of the spleen and splenectomy significantly reduce circulating levels of pro-inflammatory TNF-α and MCP-1 in rats with severe septic shock. pUS is a non-pharmacologic and noninvasive treatment that may improve survival in patients with severe sepsis by modulating the spleen and inhibiting the inflammatory response.
