長期性細菌感染以及常見性感染是糖尿病患者主要的併發症之一，這兩者皆與發炎細胞之活化具有相關聯性。然而，長期高濃度葡萄糖對於巨噬細胞活化作用，卻無太多相關性的研究。
因此，本研究以 LPS 刺激 RAW 264.7 巨噬細胞，作為一個實驗的模型，再以 15 mM 高濃度葡萄糖培養液去探討不同的培養時間，與正常 DMEM 培養下的 RAW 264.7 巨噬細胞，分別對於 LPS 刺激後的情形。實驗結果發現，RAW 264.7 巨噬細胞在15 mM 高濃度葡萄糖培養 1 天（急性）， 7 天（中慢性）和 14 天（慢性） 之後，basal NO 產生量會比正常細胞的多，而 LPS 刺激的 NO 產量卻明顯不如正常細胞。然而，在 iNOS protein 與 iNOS mRNA 的表現上，經長期慢性培養後，卻有反彈性大量增加的情形。
添加 15 mM 葡萄糖培養液培養 1 天及 14 天的 RAW 264.7 巨噬細胞，於 LPS 刺激後所產的促發炎細胞激素 TNF-a，與正常 DMEM 培養的細胞相比較是沒有明顯差異。不過，LPS 刺激的 TNF-a 產量在經過 15 mM 葡萄糖培養液培養培養 7 天後的巨噬細胞卻明顯比正常 DMEM 培養的細胞的產量少。15 mM 葡萄糖培養後的 RAW 264.7 巨噬細胞，所產生的 IL-1 b 產量在 basal 值與正常 DMEM 培養的細胞相比，均有明顯大量誘發的情形。培養 1 天及 14 天 15 mM 高濃度葡萄糖，在添加 LPS 刺激後，所產生的 IL-1 b 濃度與正常 DMEM 培養的細胞相比，有較為明顯上升的情形。然而，在 IL-6 的表現量方面，經 LPS 刺激 15 mM 高濃度葡萄糖培養 1 天後的 RAW 264.7 巨噬細胞，與正常 DMEM 培養的細胞相比，有著明顯上升的情形。有趣的是，在培養 7 天後，IL-6 的產量有被抑制的情況，而 14 天高葡萄糖培養後，卻又有一個回升的現象。
然而造成這些結果的原因，可能與細胞隨著高濃度葡萄糖長期培養後，而產生適應性和一個生理弁鄐W正向調節 ( up-regulation ) 的情形。隨著葡萄糖培養之 RAW 264.7 巨噬細胞，經由 LPS 活化細胞後，所誘發的促發炎細胞激素 ( TNF-a, IL-6, IL-1 b ) 皆與 iNOS protein 和 iNOS mRNA 的表現有著正相關性。 One of major complications of diabetes is the frequency of infection and long-term duration of bacterial infections. Both conditions have been shown to be related to activation of inflammatory cells. However, the influences of macrophage activation by long-term exposure to high glucose, a situation that mimics the hyperglycemia of diabetics, have not been fully investigated.
We used a lipopolysaccharide ( LPS ) activated macrophage RAW 264.7 model to investigate effects of acute ( 1 day ), sub-chronic ( 7 days ), and chronic ( 14 days ) 15 mM glucose treatment on activation of inflammatory cells. Basal NO production was higher in all glucose treated groups than that produced in normal cells. In contrast, LPS-induced NO production was sustained lower in the glucose treated cells than in the normal group. Interestingly, LPS-stimulated iNOS protein or iNOS mRNA expression in chronic glucose treated cells showed a more condensed bend than acute, sub-chronic or normal cells.
Treatment of RAW264.7 macrophages with 15 mM glucose for 1 and 14 days did not affect LPS-stimulated tumour necrosis factor-alpha ( TNF-a ) production. However, the same treatment for 7 days suppressed TNF-a production. Basal interleukin-1 beta (IL-1b) was increased significantly in high glucose treatment groups than that in normal control group. LPS-stimulated IL-1 productions were also increased except for 7-day treated group. Acute glucose challenge induced both basal and LPS-stimulated interleukin-6 ( IL-6 ) production. These increases were both suppressed in sub-acute groups. Interestingly, chronic glucose treatment did not affect basal IL-6 production but the production was raised the LPS-stimulated condition.
These results shown that may be due to an up-regulation or adaptation change after cells exposed to glucose chronically. Pro-inflammatory cytokines, TNF-a, IL-1b, and IL-6 that mediate the activation of macrophage via LPS stimulation, are also shown a similar adaptive pattern as iNOS protein and mRNA expression in responding to glucose treatment.
