非Toll样受体信号通路在脓毒症致肺损伤中的研究进展

背景 急性肺损伤(acute lung injury,ALI)是由直接或间接因素引起的弥漫性肺间质和肺泡水肿,进一步发展将演变为急性呼吸窘迫综合征(acute respiratory distress syndrome,ARDS).脓毒症是ALI/ARDS的主要诱因.国内外在脓毒症致ALI/ARDS的机制研究方面开展了大量工作,Toll样受体信号通路介导脓毒症致肺损伤已被广泛阐述,近期非Toll样受体信号通路在其中的作用及机制研究备受关注.目的 总结非Toll样受体在脓毒症致ALI/ARDS发病和防治中的作用,进一步完善脓毒症致肺损伤的发病机制及其发生发展的病理生理过程,为其预警和诊治提供分子靶向.内容 系统阐述非Toll样受体信号通路在脓毒症致肺损伤发生发展中作用机制的研究进展.趋向 非Toll样受体在脓毒症致LAI/ARDS发病中扮演重要角色,将是该领域研究重视的方向.     

脓毒症大鼠生物喋呤的组织分布特点和意义

目的　探讨腹腔感染致脓毒症时重要器官生物喋呤及其合成限速酶基因表达的改变和病理生理意义。方法　腹腔感染致脓毒症模型采用盲肠结扎穿孔法(CLP),用反相高效液相分析法和逆转录-聚合酶链反应方法测定24只大鼠肝、肺、肾等组织生物喋呤含量及三磷酸鸟苷环水解酶I(GTP-CHI)mRNA的表达。结果　脓毒症大鼠2h时肝、肺、肾组织生物喋呤含量显著增多［分别为(4.18±0.16)、(2.71±0.32)、(2.45±0.27)ng/g蛋白］,同时不同组织GTP-CHImRNA表达亦明显增强,各脏器功能均表现不同程度地损害(P＜0.05)。相关分析显示,肝、肺组织生物喋呤与反映相应脏器功能的指标呈高度正相关(分别为r=0.7916,P＜0.001和r=0.8004,P＜0.001)。结论　生物喋呤参与了腹腔感染所致脓毒症的发生、发展过程。     

罗格列酮对大鼠急性胰腺炎肺损伤黏附分子表达的作用

目的 探讨过氧化物酶体增殖物激活受体-γ(PPAR-γ)激动剂罗格列酮(ROSI)对大鼠急性胰腺炎肺损伤(APALI)黏附分子的作用及其机制.方法 雄性Wistar大鼠54只,随机分为假手术组(SO组)、急性胰腺炎组(SAP组)和罗格列酮预处理组(ROSI组).胆胰管逆行注射5%牛磺胆酸钠制备急性胰腺炎模型.ROSI组造模前30 min经股静脉注射10%二甲基亚砜(DMSO)溶解的罗格列酮(6 mg/kg);SO组、SAP组则注射等量10%DMSO.术后3 h、6 h、12 h分批剖杀大鼠,每个时间点6只.检测血清淀粉酶(AMY)、肺组织髓过氧化物酶(MPO)、肺湿干比(W/D),取肺组织行病理学检查;逆转录聚合酶链反应(RT-PCR)检测肺组织细胞间黏附分子-1(ICAM-1)、P-选择素和E_选择素mRNA表达水平.结果 SAP组各时间点AMY、MPO、W/D和肺组织病理评分均较S0组升高(P<0.05);ROSI组上述指标较SAP组下降,AMY、MPO、W/D和病理评分在6 h、12 h差异有统计学意义(P<0.05).SAP组ICAM-1、P-选择素和E-选择素mRNA表达在12 h达高峰,均较SO组12 h升高(P<0.05),ROSI组上述指标mRNA表达在12 h点均较SAP组下降(P<0.05).结论 罗格列酮通过抑制肺组织IcAM-1、P-选择素和E-选择素的表达,减轻急性胰腺炎肺损伤程度.     

Heparin protects against septic mortality via apoE-antagonism

Background

Apolipoprotein E (apoE), a component of plasma lipoproteins, increases septic mortality in a rodent model of sepsis, presumably by enhancing lipid antigen presentation to antigen-presenting cells via the low-density lipoprotein receptor (LDLR). Downstream, this culminates in natural killer T (NKT) cell activation and cytokine secretion. To determine whether apoE antagonism would protect against septic mortality in mice, apoE-LDLR binding was antagonized using heparin, which can inhibit apoE's LDLR-binding site.

Methods

C57BL/6 mice underwent cecal ligation and puncture (CLP) and heparin infusion. Serum partial thromboplastin time and alanine aminotransferase were measured at 24 hours, and survival was monitored for 7 days after CLP. LDLR+/+ and LDLR−/− fibroblasts were incubated with apoE and heparin to measure apoE internalization. Hepatic NKT cells and cytokine levels were quantified via fluorescence-activated cell sorting.

Results

Heparin decreased CLP–induced mortality by 50% versus saline-treated controls, independent of anticoagulation. LDLR+/+ fibroblasts displayed decreased uptake of apoE when treated concurrently with heparin for 12 hours. In septic mice, hepatic alanine aminotransferase levels, hepatic NKT cells, and plasma cytokine levels decreased after heparin treatment.

Conclusions

This study demonstrates that heparin protects against septic mortality independent of its anticoagulant effect. This protective effect is associated with the inhibition of apoE-LDLR binding, diminished NKT proliferation and cytokine production, and hepatic dysfunction. These findings indicate a potential clinical role for apoE antagonism in the treatment of sepsis.     

(Pro)renin receptor blocker improves survival of rats with sepsis

Background

The renin-angiotensin system (RAS) affects inflammatory responses during sepsis. Nonproteolytic activation of prorenin by the (pro)renin receptor has recently been shown to stimulate the tissue RAS. In the present study, the effect of (pro)renin receptor blocker (PRRB) pretreatment on sepsis in a rat cecal ligation and puncture (CLP) model was investigated.

Materials and methods

Male Sprague-Dawley rats underwent CLP and were randomly divided into two groups: PRRB-treated group and control peptide–treated group. Survival was analyzed for 7 d after CLP. The serum concentrations of cytokines and high-mobility group box chromosomal protein 1 (HMGB1) were measured at three time points (0, 3, and 6 h after CLP). Hematoxylin-eosin staining and immunohistochemical staining for nonproteolytically activated prorenin and HMGB1 were performed on the cecum to assess pathologic changes found 6 h after CLP.

Results

Treatment with PRRB improved the survival rate of the post-CLP septic rats (P = 0.023). PRRB also significantly reduced serum tumor necrosis factor-α, interleukin-1β, and HMGB1 levels 6 h after CLP. In CLP rats that were treated with control peptide, the expression of activated prorenin was elevated in peritoneal foam cells. Moreover, expression of HMGB1 was increased in peritoneal inflammatory cells. In contrast, both were markedly suppressed in CLP rats that were treated with PRRB.

Conclusions

PRRB significantly improved the survival rate of rats with clinically relevant sepsis, possibly by attenuating a sepsis-induced systemic inflammatory response. We propose that overactivation of the RAS by activation of prorenin in foam cells may be a significant contributor to sepsis.     

AMPK attenuates inflammation to reduce fibrosis induced by acute ischemia reperfusion injury in mice

Objective To observe the effect of adenosine monophosphate activated protein kinase (AMPK) on attenuating inflammation in fibrosis induced by acute ischemia reperfusion injury (IRI) in mice. Methods Forty eight male C57BL/6 mice were randomly divided into four groups: sham operation group (sham group), IRI group, AMPK inhibitor+IRI group (AMPK/IRI group) and normal saline+IRI group (NS/IRI group), 12 mice each group. The mice with renal IRI were occluded for 30 min through clipping bilateral renal pedicle, then released renal perfusion. Mice in sham group were performed the separation of renal pedicle without clipping. Mice in AMPK/IRI group and NS/IRI group were respectively intraperitoneal injected AMPK inhibitor and normal saline before IRI. At the 2 d after operation, 6 randomly-selected mice from each group were blooded by extraction eyeball to detect BUN and Scr. The renal histopathological changes were observed through HE staining. The mRNA expression of IL-1β, IL-6 and TNF-α was detected by real time PCR, and the level of AMPK phosphorylation was detected by Western blotting. At the 14 d after operation, Collagen 1 (COL1), α-SMA and fibronectin (FN) were detected by immunofluorescence and Western blotting in 6 remained mice from each group. The degree of kidney fibrosis was observed through sirus red staining. Results Compared with those in sham group, tubular interstitial damage was aggravated (P＜0.05), BUN and Scr were increased (P＜0.05), the mRNA expression of IL-1β, IL-6 and TNF-α was increased at the 2 d after operation (all P＜0.05), and the level of AMPK phosphorylation was activated in IRI group and NS/IRI group (all P＜0.05); the degree of kidney fibrosis and the expression of COL1, α-SMA and FN were increased obviously at the 14 d (all P＜0.05). Compared with those in IRI group, in AMPK/IRI group tubular interstitial damage was aggravated (P＜0.05), BUN and Scr were increased (all P＜0.05), the mRNA expression of IL-1β, IL-6 and TNF-α was increased at the 2 d (all P＜0.05), and the level of AMPK phosphorylation was decreased (P＜0.05). Moreover, the degree of kidney fibrosis and the expression of COL1, α-SMA and FN were increased obviously at the 14 d in AMPK/IRI group (all P＜0.05). Conclusions AMPK can ameliorate the acute renal ischemia reperfusion injury induce fibrosis in mice, and the mechanism may be related to the decrease of inflammatory reaction.     

Angiotensin-(1-7) attenuates lung fibrosis by way of Mas receptor in acute lung injury

Background

Pulmonary fibrosis occurs in approximately 60% of patients with acute respiratory distress syndrome and has been significantly correlated with a poor outcome. The overexpression of angiotensin (Ang) II can induce lung inflammation and fibrosis. This observation, coupled with the knowledge that Ang-(1-7) is considered to be an endogenous antagonist of Ang II, led us to hypothesize that Ang-(1-7) would prevent lung remodeling in patients with acute respiratory distress syndrome.

Materials and methods

The protocol involved five groups: (1) control, (2) lipopolysaccharide (LPS), (3) losartan as a positive control group, (4) Ang-(1-7), and (5) [D-Ala7]-Ang-(1-7) (A779), an antagonist of the Ang-(1-7) receptor. Acute lung injury was induced by an intratracheal injection of LPS 5 mg/kg in C57BL/6 mice. Losartan (10 mg/kg) was administered by gavage daily, starting from 1 d before LPS stimulation. Ang-(1-7) or A779 in saline (100 ng/kg/min) was infused subcutaneously 1 h before acute lung injury induction for 3 or 7 d. The lung tissues were harvested for analysis at day 3 or 7 after injection of LPS.

Results

LPS stimulation resulted in significantly increased inflammation, edema, and lung collagen production. With Ang-(1-7) treatment, the lung fibrosis score and hydroxyproline level were significantly reduced, and the expression of transforming growth factor-β and Smad2/3 were decreased on days 3 and 7. Losartan attenuated lung fibrosis similarly to Ang-(1-7) after LPS exposure. In the A779 group, a tendency was seen to aggravate collagen deposition and lung remodeling.

Conclusions

These findings indicate an antiremodeling role for Ang-(1-7) in acute lung injury, similar to the blocker of Ang II receptor, that might be at least partially mediated through an Ang-(1-7) receptor.     

Influence of motor complete spinal cord injury on visceral and subcutaneous adipose tissue measured by multi-axial magnetic resonance imaging

Objective

Abdominal obesity conveys substantial health risks, in association with high levels of visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) and an increased proportion of VAT to SAT. The purposes were to determine the influence of spinal cord injury (SCI) on the associations between single axial cross-sectional area (CSA) slices and the average CSA or volumes of VAT and SAT across multi-axial slices of magnetic resonance imaging (MRI); and the relationships relative to the whole body composition and anthropometrics.

Methods

Thirteen healthy male participants with traumatic motor complete SCI underwent fast spin-echo MRI to measure VAT and SAT across multi-axial slices, followed by dual-energy X-ray absorptiometry to measure whole body fat-free mass (FFM) and fat mass (FM). Waist circumference (WC) was also measured in the seated position.

Results

The trunk CSAs of VAT and SAT were 99 ± 51 and 164 ± 69 cm², respectively, and the ratio of VAT to SAT was 0.68 ± 0.33. The CSAs of VAT and SAT at a single slice strongly predicted the average CSA and modestly predicted the volumes across multi-axial slices. VAT and SAT represented 5.7 ± 1.8% and 9.7 ± 3.2% of the total body FM, respectively. Percent body FFM was negatively related to VAT and SAT volumes, but not to a single axial CSA.

Conclusion

A single slice CSA can modestly predict the volume of multi-axial slices in individuals with SCI, yet it is not related to any of the body composition variables. Increased percent FFM is associated with a reduction in VAT and SAT volumes measured across multi-axial slices. The ratio of VAT to SAT is greater than 0.4, suggesting that individuals with SCI are at high risk of developing metabolic sequelae.