Supplementary Material for: Euflammation Attenuates Central and Peripheral Inflammation and Cognitive Consequences of an Immune Challenge after Tumor Development

Objective: Repeated subthreshold bacterial exposures in rodents cause novel euflammation that attenuates neuroinflammation and sickness behaviors upon subsequent infectious challenges to the host without eliciting illness behavior. The investigation of bacterial exposure effects on brain and behavior is clinically relevant because bacterial-based antitumor treatments are used successfully, but are suboptimal due to their illness side effects. In addition, behavioral consequences (depression, cognitive impairments) to homeostatic challenges that are associated with inflammation are prevalent and reduce the quality of life in cancer patients and survivors. Therefore, this study tested the potential for euflammation to attenuate behavioral consequences of an immune challenge in tumor-bearing mice. Methods: Mice with and without oral tumors in their flank underwent the established peripheral euflammatory protocol or vehicle treatment, followed by an acute peripheral immune challenge (lipopolysaccharide [LPS] injection) or PBS. Cognitive function and sickness behavior were assessed after the challenge, and peripheral and central inflammatory responses were measured. Results: Euflammation reduced LPS-induced peripheral and central inflammation in all mice; however, neuroinflammation was less attenuated in tumor-bearing mice compared with tumor-free controls. LPS-induced lethargy and cognitive impairments were more pronounced among tumor-bearing mice and were effectively attenuated with euflammation. Cognitive changes were independent of brain-derived growth factor gene expression in the hippocampus. Conclusion: These results suggest that induction of euflammation may be useful in alleviating the negative side effects of bacterial-based tumor treatments and in potentially attenuating common behavioral comorbidities associated with cancer or other chronic diseases.

研究目标：啮齿类动物反复接受阈下细菌暴露会引发新型良性炎症（euflammation），该炎症可在宿主后续遭遇感染攻击时减轻神经炎症与疾病行为，且不会诱发疾病行为。探究细菌暴露对大脑与行为的影响具有临床相关性，因为基于细菌的抗肿瘤治疗已取得成功，但因会引发疾病相关副作用而未达最优效果。此外，与炎症相关的稳态挑战所引发的行为后果（抑郁、认知功能障碍）在癌症患者及幸存者中普遍存在，会降低其生活质量。因此，本研究旨在探究良性炎症（euflammation）能否减轻荷瘤小鼠在免疫攻击后的行为后果。研究方法：侧翼带有口腔瘤的小鼠与无瘤小鼠，分别接受已建立的外周良性炎症（euflammation）造模方案或赋形剂处理，随后予以急性外周免疫刺激（脂多糖[LPS]注射）或磷酸盐缓冲液[PBS]。免疫刺激完成后，对小鼠的认知功能与疾病行为进行评估，并检测外周与中枢的炎症反应。研究结果：良性炎症（euflammation）可减轻所有小鼠中LPS诱导的外周与中枢炎症；但与无瘤对照组相比，荷瘤小鼠的神经炎症减轻程度较弱。LPS诱导的嗜睡与认知功能障碍在荷瘤小鼠中更为显著，而良性炎症可有效缓解此类症状。认知功能变化与海马体内的脑源性生长因子基因表达无关。研究结论：本研究结果表明，诱导良性炎症（euflammation）或可用于减轻基于细菌的肿瘤治疗的负面副作用，并有望缓解癌症或其他慢性疾病相关的常见行为共病。