Neutrophil depletion reduces edema formation and tissue loss following traumatic brain injury in mice

Background  

Brain edema as a result of secondary injury following traumatic brain injury (TBI) is a major clinical concern. Neutrophils are known to cause increased vascular permeability leading to edema formation in peripheral tissue, but their role in the pathology following TBI remains unclear.     

水通道结合膜蛋白-4在大鼠缺血性脑水肿中的表达变化

目的：探讨脑水肿与水通道结合膜蛋白-4(AQP4)表达间的变化关系。方法：阻塞大脑中动脉(MCAO)，制作缺血性脑水肿模型，用干湿重法测定不同程度脑水肿状况下梗塞侧脑组织的含水量，用免疫组化及图像分析法观察AQP4阳性细胞数量及面积的变化。结果：MCAO 6h后，脑组织中水份开始增加，同时梗塞区部分组织深染，细胞肿大，梗塞区周围见阳性细胞开始增多。随梗塞时间延长，脑水肿加重，AQP4在整个梗塞区的表达增强，梗塞区周围阳性细胞数量递增。MCAO后在松果体血管周围及腺细胞间，以及最后区血管周围和一些阳性细胞染色增强。结论：AQP4与脑水肿的形成有关，并可能与AVP等神经内分泌活动有关。     

水通道蛋白-4在早期缺血性脑水肿中的表达

目的：探讨水通道蛋白-4(AQP-4)在早期缺血性脑水肿过程中的表达规律。方法：对大鼠进行大脑中动脉栓塞，于术后15min～24h采用免疫组化、原位杂交和图像分析技术检测AQP-4的表达量，同时用光镜和电镜行病理观察。结果：AQP-4基因和蛋白表达具有一致性。AQP-4表达丰富的部位主要集中在脉络丛、室管膜细胞、海马和梗塞区细胞并在术后15min～lh时段呈线性增加。病理显示此期主要为细胞内水肿，即缺血半暗带。随着时间的延长，AQP-4表达呈缓慢增高趋势。对应的病理改变为血管源性水肿，最后组织坏死。结论：AQP-4表达增强与早期缺血性脑水肿密切相关，它可能是形成超早期细胞内水肿一半暗带的重要因素之一。     

水通道蛋白4在大鼠轻度脑外伤后脑水肿形成中的作用

目的:通过研究大鼠脑外伤后,血脑屏障(BBB)通透性的改变和水通道蛋白4(AQP4)的表达变化,探讨其在脑外伤后脑水肿的形成、发展及转归中的作用,为临床治疗脑水肿提供依据.方法:采用伊文蓝测定法、免疫荧光双标显色、RT-PCR、干湿重法,分别检测BBB损伤程度,AQP4的表达,双侧大脑皮质、海马AQP4 mRNA的含量变化和脑含水量.结果:伤侧大脑BBB损伤于脑外伤后1～24 h明显,以1 h为甚,之后逐渐减轻;对侧则于伤后6～48 h损伤明显.免疫荧光双标和RT-PCR结果基本一致,双侧皮质AQP4及其mRNA于3 h增高,随后先降低再升高,至48～72 h达峰值;双侧海马几乎于各时段均呈显著降低.双侧皮质、海马含水量均于6 h显著增加,并达峰值,之后先略有下降后再次增加,至48～72 h达次高峰.结论:脑外伤早期,AQP参与了细胞外水肿的清除,其表达的下调和BBB的损伤,导致细胞外水肿形成.脑外伤继发损伤期,AQP4参与了细胞外水肿的清除和细胞内水肿的形成.     

Effect of astrocyte-derived factors on ischemic brain edema induced by rat MCA occlusion

To clarify whether astrocyte-derived factors may protect cerebral tissue from ischemia, we examined brain edema, demyelination and astrocyte proliferation in brains with focal ischemia and treated with astrocyte-cultured medium. We occluded the left middle cerebral artery of rats and implanted the Osmotic Minipump, which continuously infused the glial-cultured medium or control medium into the left lateral ventricle. Animals were sacrificed at 3 days or 7 days after occlusion. Brains of both groups were compared by several markers, i.e. extravasation of Evans blue, demyelination by Woelcke's staining and glial proliferation by GFAP staining. We found the astrocyte-cultured medium reduced leakage of Evans blue-plasma protein complex from ischemic lesions and reduced the size of demyelinated lesions. However, the degree of astrocyte proliferation was similar in both groups. From these data, we speculate that humoral factors derived from cultured astrocytes lessened the brain edema by modifying the blood-brain barrier. These factors might also induce proliferation of the microglia, and may protect the neurons from secondary injury by oxygen-free radicals.     

Antigen-induced formation of a lymphokine with a possible role as a mediator of the late component of dual allergic reaction

In a penicillin-allergic patient who showed a strong dual skin reaction (immediate and late components) to an intradermal injection of the antigen, we investigated the possibility that the lymphokine, histamine-releasing factor (HRF), which has been shown to release histamine from human basophils and mast cells, might play a part in the elicitation of the late phase of the 'dual reaction'. In vitro stimulation of this patient's lymphocytes, but not those of a patient with a monophasic (immediate) reaction with the antigen, caused the production of a large amount of HRF, while a moderate lymphoproliferation occurred in both patients. The purified HRF released histamine from the patient's own leucocytes and also caused immediate wheal and flare reaction on intradermal injection.     

Neuroinflammation in ischemic brain injury as an adaptive process

Cerebral ischaemia triggers various physiological processes, some of which have been considered deleterious and others beneficial. These processes have been characterized in one influential model as being part of a transition from injury to repair processes. We argue that another important distinction is between dysregulated and regulated processes. Although intervening in the course of dysregulated processes may be neuroprotective, this is unlikely to be true for regulated processes. This is because from an evolutionary perspective, regulated complex processes that are conserved across many species are likely to be adaptive and provide a survival advantage. We argue that the neuroinflammatory cascade is an adaptive process in this sense, and contrast this with a currently popular theory which we term the maladaptive immune response theory. We review the evidence from clinical and preclinical pharmacology with respect to this theory, and deduced that the evidence is inconclusive at best, and probably falsifies the theory. We argue that this is why there are no anti-inflammatory treatments for cerebral ischaemia, despite 30 years of seemingly promising preclinical results. We therefore propose an opposing theory, which we call the adaptive immune response hypothesis.     

缺血后适应减轻树鼩缺血性脑水肿及脑梗死的机制

目的 观察缺血后适应对树鼩血栓性脑缺血时大脑皮层脑水含量、局部脑血流、梗塞面积及神经元超微结构的影响,探讨其对树鼩脑缺血时神经保护的可能机制。 方法 将88只健康成年树鼩随机分为对照组、脑缺血4 h组、脑缺血24 h组、后适应4 h组及后适应24 h组（每组n=8）,另取8只动物做HE染色（n=3）及电子显微镜观察（n=5）。本实验采用光化学反应诱导树鼩血栓性脑缺血而建立脑缺血动物模型,在脑缺血模型建成后4 h夹闭缺血侧颈总动脉5 min,再灌注5 min,如此交替进行3个循环以建立缺血后适应模型。测定大脑皮层局部脑血流,脑组织含水量,脑梗死范围,并观察皮层及海马CA1区神经元超微结构改变。 结果 脑缺血时神经元固缩,线粒体肿胀,嵴溶解或形成空泡,内质网肿胀,内质网池形成。缺血后适应能使海马CA1区神经元固缩减少,线粒体和内质网的病理改变减轻,细胞水肿改善。随着缺血时间的延长,缺血24h组脑水含量明显增加86.81%±1.08%,此时脑梗塞面积明显扩大33.00%±3.03%,局部脑血流明显降低（134.27±28.75）ml/min。缺血后适应24h组脑组织含水量明显减少（81.04%±1.04%,P＜0.01）;脑梗塞面积缩小（16.79%±1.29%,P＜0.01）;而局部脑血流明显增加［（195.25±21.18）ml/min,P＜0.01］。 结论 缺血后适应可缓解树鼩缺血性脑水肿并缩小梗死范围,其机制可能与改善局部脑血流有关。     

Smad-3 as a mediator of the fibrotic response

Introduction Smad‐3, a key cytoplasmic mediator of transforming growth factor‐β (TGF‐β) signalling, mediates many of its inflammatory and fibrotic effects in vivo ( Roberts et al. 2001 ). Smad‐3 null mice are protected against cutaneous injury induced by ionizing irradiation ( Flanders et al. 2002 ). Here, we report on our continuing studies on radioprotection as well as protection against tubulointerstitial fibrosis following unilateral ureteral obstruction (UUO) in Smad‐3 null mice. Methods For radioprotection studies, the flank skin of Smad‐3^+/+ wild‐type (WT) and Smad‐3^–/– knockout (KO) mice was exposed to 30 Gy of localized γ‐irradiation and analysed for histology and gene expression at various times post irradiation. In the UUO model, the right proximal ureter of WT and KO mice was ligated, and 1–2 weeks later kidneys were analysed for inflammation, fibrosis and gene expression. Results Six weeks after exposure to irradiation, skin from KO mice shows less epidermal acanthosis and influx of mast cells, macrophages and neutrophils than skin of WT mice. Paradoxically, at 6–8 h post irradiation, KO skin shows a significantly greater number of neutrophils. Irradiated KO skin also exhibits less immunoreactive TGF‐β, fewer myofibroblasts and less scarring than does WT. Smad‐3 null dermal fibroblasts do not respond to the chemotactic effects of TGF‐β and show less induction of fibrogenic cytokines when treated with irradiation plus TGF‐β compared to WT cells. Following UUO, normal kidney architecture is preserved in KO mice, while kidneys from WT mice are enlarged with an influx of mononuclear cells and increased expression of collagen and TGF‐β1. Additionally, renal tubules in obstructed kidneys of KO mice remain positive for E‐cadherin without expression of α‐smooth muscle actin, while the opposite expression pattern is seen in obstructed kidneys of WT mice. TGF‐β treatment of primary cultures of WT renal tubular epithelial cells results in a phenotypic change from a cobblestone pattern to a spindle‐shaped fibroblastic appearance, while KO cells treated with TGF‐β maintain their original appearance. Conclusion Smad‐3 plays an important role in mediating pathogenic inflammation and fibrosis in several model systems and is also essential for TGF‐β1‐induced epithelial–mesenchymal transition in renal tubular epithelial cells. Inhibitors of the Smad‐3 pathway may have clinical applications in the treatment of a number of fibrotic conditions.     

Oxidative stress as a mediator of apoptosis

Many agents which induce apoptosis are either oxidants or stimulators of cellular oxidative metabolism. Conversely, many inhibitors of apoptosis have antioxidant activities or enhance cellular antioxidant defenses. Mammalian cells exist in a state of oxidative siege in which survival requires an appropriate balance of oxidants and antioxidants. Thomas Buttke and Paul Sandstrom suggest that eukaryotic cells may benefit from this perilous existence by invoking oxidative stress as a common mediator of apoptosis.     

VEGF as a mediator of tumor-associated immunodeficiency

Decreased immune function in cancer patients is well-characterized (I), and tumor cells have developed a variety of mechanisms, to avoid anti-tumor immune responses (2–8). One mechanism for inhibition of immune cell function by tumors in the production of soluble factors, such as IL-10, TNF, TGF-β, and Vascular Endothelial Growth Factor (VEGF). The effects of these factors appear, to be twofold: To inhibit effect or function and to impair the development of immune cells by acting on earlier stages of immunopoiesis. Immune suppression by tumors is accomplished by a variety of cellular and molecular mechanisms, and virtually all branches of the immune system can be affected. VEGF and its receptors have profound effects on the early development and differentiation of both vascular endothelial and hematopoetic progenitors (9). It induces proliferation of mature endothelial cells and is an important component in the formation of tumor neovasculature (10). VEGF is abundantly expressed by a large percentage of solid tumors and this over-expression is closely associated with a poor prognosis (11, 12). Some of the earliest hematopoetic progenitors express receptors for VEGF (13), and we have demonstrated that VEGF causes a defect in the functional maturation of dendritic cells (DC) from progenitors. This developmental defect is associated with impaired activation of NF-κB (14–17). This review describes research demonstrating that VEGF is not only important for tumor vascularization, but is also a key factor produced by solid tumors to inhibit recognition and destruction of tumor cells by the immune system.     

Vasopressin as a putative mediator in SHR hypoalgesia

The purpose of this note is to show that vasopressin might be involved in the hypoalgesia of the spontaneously hypertensive rat. This proposal rests upon published data.     

Exercise as a mediator of hepcidin activity in athletes

Iron is a trace mineral used by the body in many physiological processes that are essential for athletic performance. However, it is common that an athlete’s iron stores are compromised via several well-established exercise-related mechanisms such as hemolysis, hematuria, sweating and gastrointestinal bleeding. Recently, however, a new mechanism for athletics-induced iron deficiency has been proposed, involving the influence of physical activity on the post-exercise hepcidin response. Hepcidin is a liver-produced hormone that regulates iron metabolism in the gut and macrophages. This hormone has become the focus of recent investigations into altered iron metabolism in athletes, and may be a mitigating factor implicated in athletics-induced iron deficiency. This review attempts to summarize and disseminate the collective knowledge currently held regarding exercise and hepcidin expression, in addition to suggesting the direction for future research in this area.