【Abstract】
Background: Lupus nephritis is one of the most common and severe complications of systemic lupus erythematosus, of which poor prognosis is indicated by aggravated renal hypoxia and tubulointerstitial fibrosis. Cell adhesion molecules play a key role in the progression of lupus nephritis tubulointerstitial lesion, including P-selectin, which mediates the rolling of leukocytes and subsequent adhesion and infiltration and then initiates the inflammatory immune response and ischemia and hypoxia injury. However, the effects and mechanisms of P-selectin in lupus nephritis remain to be investigated, and a noninvasive measurement of lupus nephritis tubulointerstitial hypoxia and fibrosis remains to be explored.
Methods: Thirty-four MRL/lpr mice were randomly divided into the following three groups: MRL/lpr, saline, and anti–P-selectin, which consisted of no treatment, treatment with normal saline, and treatment with anti–P-selectin monoclonal antibody (mAb) from 12 to 16 weeks of age, respectively. Ten male C57BL/6 mice of the same age served as normal controls. Twenty-four-hour urinary protein, urinary albumin–creatinine ratio, and periodic acid–Schiff were used to assess kidney damage; Western blot or immunohistochemical staining of the hypoxia probe HypoxyprobeTM-1, hypoxia-inducible factor 1α (HIF-1α), and CD31 were used to evaluate hypoxia in renal tissue; and NADPH oxidase subunit gp91phox and p22phox were used to examine renal oxidative stress. The correlation between kidney injury and blood oxygen level–dependent magnetic resonance imaging (BOLD-MRI) was calculated to assess the clinical value of BOLD-MRI.
Results: P-selectin is upregulated in lupus nephritis. Blocking P-selectin with mAb alleviated renal tubulointerstitial fibrosis, renal hypoxia, and peritubular capillary loss, without alteration of the levels of lupus activity indicators, anti-dsDNA antibody, or complement C3. BOLD-MRI showed that the reduced R2* values in the renal cortex and medulla of lupus mice were increased when treated with anti–P-selectin mAb as compared with those treated with normal saline, which were negatively correlated with HypoxyprobeTM-1 hypoxia probe and the expression of HIF-1α.
Conclusions: Early intervention of lupus nephritis with anti–P-selectin mAb can significantly improve the hypoxic state of the kidney and reduce the severity of tubulointerstitial lesions. BOLD-MRI techniques are noninvasive and can dynamically evaluate the changes in renal lesions and intrarenal oxygenation levels before and after treatment in lupus nephritis.
【中文摘要】
背景：狼瘡性腎炎是系統性紅斑狼瘡最常見、最嚴重的併發症之一，其預後不良與腎臟缺氧及腎小管間質纖維化有關。細胞粘附分子P-選擇素等在狼瘡性腎炎腎小管間質病變的進展中起著關鍵作用，可介導白細胞滾動、粘附和浸潤，並啟動炎性免疫反應以及局部缺血、缺氧損傷，但其具體作用機制尚不明確。此外，如何無創地評估狼瘡性腎炎的腎小管間質缺氧和纖維化狀態亦有待探索。
方法：將34隻MRL/lpr小鼠隨機分為以下三組：MRL/lpr未干預組、生理鹽水對照組和抗P-選擇素幹預組，10隻相同年齡的雄性C57BL/6小鼠作為正常對照。檢測24小時尿蛋白定量、尿白蛋白-肌酐比值和PAS染色評估腎臟病理損害。缺氧探針HypoxyprobeTM-1，缺氧誘導因子1α（HIF-1α）和CD31的Western印跡或免疫組化染色用於評估腎臟組織缺氧情況。用NADPH氧化酶亞基gp91phox和p22phox檢測腎臟的氧化應激。檢測腎臟損傷與血氧水平依賴性磁共振成像（BOLD-MRI）結果之間的相關性，以評估BOLD-MRI的臨床價值。
結果：狼瘡性腎炎腎組織中P-選擇素表達上調。用單克隆抗體阻斷P-選擇素可減輕腎小管間質纖維化、腎臟缺氧和腎小管周圍毛細血管丟失，而不會改變狼瘡活動指標抗dsDNA抗體或補體C3水平。BOLD-MRI檢測顯示，抗-P-選擇素單抗治療的狼瘡小鼠腎皮質和髓質中降低的R2*值較生理鹽水幹預組顯著增高，R2*值與HypoxyprobeTM-1低氧探針和HIF-1α的表達呈負相關。
結論：抗-P-選擇素單抗早期幹預狼瘡性腎炎可顯著改善腎臟的低氧狀態，並減輕腎小管間質病變的嚴重程度。BOLD-MRI技術可無創性、動態地評估狼瘡性腎炎治療前後腎臟病變和腎臟內氧合水平的變化。