Non-apoptotic functions of caspases in cellular proliferation and differentiation

The cysteinyl aspartate-specific proteases (caspases) have been identified as key players in the cellular process termed programmed cell death or apoptosis. During apoptosis, activated apoptotic caspases cleave selected target proteins to execute cell death. Additionally to their established function in cell death, a variety of recent publications have provided increasing evidence that apoptotic caspases also participate in several non-apoptotic cellular processes. Activated caspases exhibit functions during T-cell proliferation and cell cycle regulation, but are also involved in the differentiation of a diverse array of cell types. In some cell types, their differentiation can be morphologically viewed as a kind of incomplete apoptosis. Analysis of well-known apoptotic targets of caspases implicates that the cleavage of a limited number of selected substrates plays a major role during non-apoptotic functions of caspases. Selective substrate cleavage might be regulated by activation of anti-apoptotic factors, via a compartmentalized activation of caspases, or through limited activity of caspases during apoptosis-independent functions. The increasing evidence for caspase function in non-apoptotic cellular events suggests that caspases play a much more diverse role than previously assumed.     

Currently evaluated calpain and caspase inhibitors for neuroprotection in experimental brain ischemia

Currently available therapies for brain ischemia, with a few exceptions, provide only symptomatic relief in patients. Recent investigations in experimental models provided an understanding of the cellular and molecular mechanisms that lead to neurodegeneration in ischemic injury, and also indicate targets for prevention and amelioration of the devastating consequences of stroke. An enormous increase in intracellular free Ca(2+) levels following stroke activates Ca(2+)-dependent enzymes, contributing to neuronal death and dysfunction. Additionally, ischemic injury generates highly reactive free radicals and triggers release of cytotoxic cytokines for activation of cysteine proteases. A number of studies already indicated a prominent role for the cysteine proteases of the calpain and caspase families in the pathogenesis of brain ischemia. Proteolytic activities of these proteases degrade various cytoskeletal proteins and membrane proteins, destabilizing the structural integrity and forcing the neurons to delayed death in ischemic penumbra. Some current studies have unequivocally confirmed the neuronal apoptosis in ischemia and showed that administration of calpain and caspase inhibitors alone or in combination can provide functional neuroprotection in various animal models of cerebral ischemia. This article will discuss the molecular structures and activities of calpain and caspase inhibitors and their therapeutic efficacy in experimental brain ischemia. However, further investigations are necessary for improvements in the structural design of calpain and caspase inhibitors for their persistent therapeutic efficacy in animal models of stroke and for clinical trials in the future.     

Isoflurane preconditioning increases B-cell lymphoma-2 expression and reduces cytochrome c release from the mitochondria in the ischemic penumbra of rat brain

We and others have shown that prior exposure to the volatile anesthetic isoflurane induces ischemic tolerance in the brain. Our results also suggest that isoflurane preconditioning reduces cell apoptosis in the penumbral region of rat brain. We designed this study to determine whether isoflurane preconditioning decreased mitochondria-dependent cell apoptosis. Adult male Sprague-Dawley rats were exposed to or not exposed to 2% isoflurane for 30 min at 24 h before the permanent middle cerebral arterial occlusion. Western blotting was used to quantify protein expression in the cytosolic and mitochondrial fractions of non-ischemic brain cortex and brain cortex in the ischemic core and penumbra. Isoflurane preconditioning significantly decreased the infarct volume of cerebral cortex and improved neurological outcome. Isoflurane increased the expression of the antiapoptotic B-cell lymphoma-2 (Bcl-2) proteins in the cerebral cortex of rats without brain ischemia. Rats preconditioned with isoflurane before brain ischemia had increased Bcl-2 expression in the penumbra. Isoflurane preconditioning reduced the release of cytochrome c from the mitochondria and the activation of caspase 3 in the penumbra. However, isoflurane preconditioning did not alter the translocation of Bid and Bax from the cytosol to the mitochondria, identified mechanisms for Bcl-2 to block the release of cytochrome c from the mitochondria. Our results suggest that isoflurane preconditioning increases Bcl-2 expression to block the release of cytochrome c from the mitochondria to decrease the cell apoptosis in the penumbra.     

乐尔脉胶囊对大鼠缺血再灌注后期大脑皮层细胞凋亡的干预作用

目的:研究乐尔脉胶囊(LEM)对大鼠局灶性脑缺血2h再灌注30d后所致大脑皮层神经细胞凋亡的干预作用。方法:以线栓阻断(MCAO)法制备大鼠右侧大脑中动脉缺血再灌注模型,分为假手术、模型、盐酸氟桂利嗪及LEM高、低剂量组;应用免疫组化、凋亡细胞原位末端标记法(TUNEL)与逆转录聚合酶链反应(RT-PCR)技术检测大鼠大脑细胞凋亡和细胞凋亡相关基因产物(Fas)、凋亡促进基因(Bax)mRNA的表达,并进行图像分析。结果:模型组凋亡细胞主要位于缺血侧大脑皮层缺血边缘区(半暗带区);缺血侧大脑皮层Fas、Bax mRNA的表达在缺血再灌注30d后仍有升高;LEM组Fas、Bax mRNA的表达显著低于模型组(P<0.01),凋亡细胞数也显著低于模型组(P<0.01)。LEM组可明显降低损伤侧脑组织Fas、Bax mRNA的表达,抑制细胞凋亡,减轻缺血再灌注对大鼠大脑皮层神经细胞的损伤。结论:LEM对大鼠脑缺血再灌注30d后的细胞凋亡有一定的干预作用。     

超负荷血糖对鼠脑缺血再灌注后神经细胞凋亡及FADD、Daxx表达的影响

目的 观察超负荷血糖对大鼠脑缺血再灌注缺血半暗带侧皮质区FADD、Daxx表达的影响,进一步探讨超负荷血糖加重脑缺血再灌注损伤的分子机制.方法 SD大鼠腹腔内注射链脲佐菌素(STZ),建立糖尿病高血糖大鼠模型,之后应用栓线法建立大鼠脑缺血再灌注模型.随机分为三大组:假手术组(A)、脑缺血再灌注组(B)和糖尿病脑缺血再灌注组(C).于缺血1h再灌注12h行神经功能评分,TTC染色测梗死面积,Tunel法检测细胞凋亡数目,免疫组化及Western blot检测FADD、Daxx的表达,并进行图像分析.结果 糖尿病脑缺血再灌注组的神经功能评分为(3.50±0.55),梗死面积为(39.99±2.23),细胞凋亡数为(27.51土3.43),免疫组化检测FADD为(110.18±4.21)、Daxx为(101.26士3.27);Western blot检测FADD为(1.191±0.041),Daxx为(1.389±0.052).脑缺血再灌注组的神经功能评分为(2.67±0.81),梗死面积为(30.13±2.04),细胞凋亡数为(18.28±2.09),免疫组化检测FADD为(131.46士3.24),Daxx为(123.16士2.19);Western blot检测FADD为(1.035±0.032),Daxx为(1.146±0.083).与脑缺血再灌注组相比,糖尿病脑缺血再灌注组的神经功能评分、梗死面积、细胞凋亡数、FADD及Daxx蛋白表达均明显增加(P＜0.05).结论 FADD、Daxx可能参与了超负荷血糖加重脑缺血再灌注损伤过程,上调FADD、Daxx表达可能是超负荷血糖加重脑缺血再灌注损伤的机制之一.     

New method for evaluating the effects of neuroprotective therapy in the hemodynamic penumbra

Recently, we established a novel temporal correlation mapping (TCM) technique in combination with high-resolution functional computed tomography (CT) scanning to analyze the temporal changes in bolus transit dynamics of iodinated contrast agents in focal cerebral ischemia. Based on changes in the temporal dynamics of blood flow, we defined a new kind of penumbra and core in focal ischemia: the hemodynamic penumbra and hemodynamic core. We visualized for the first time a larger hemodynamic core and smaller hemodynamic penumbra in endothelial NOS knockout mice than in wild type mice early after focal ischemia by using the TCM analysis technique. In addition, neuroprotective effects of the water-soluble AMPA receptor antagonist YM872 were for the first time observed in the hemodynamic penumbra after focal ischemia. In conclusion, early TCM analysis could be used to directly and quantitatively evaluate the effects of neuroprotective therapy and the evolution of neuronal damage in the hemodynamic penumbra.     

丹参对大鼠持续局灶性脑缺血后神经元 cyclin G1 蛋白表达的影响

目的:观察大鼠局灶性脑缺血后神经元内细胞周期蛋白G1(cyclin G1)的蛋白表达与神经细胞凋亡的关系以及丹参对其的影响.方法:采用线栓法大鼠大脑中动脉持续栓塞模型,应用免疫组化和TUNEL染色方法观察缺血组、丹参组和对照组神经元阳性细胞染色数量和分布情况.结果:缺血组cyclin G1蛋白自缺血后1h开始表达增加,缺血后3h达高峰,72h恢复至对照组水平;凋亡细胞自缺血后12h开始表达,缺血后72h达高峰.丹参组仅在缺血12h时间点cyclin G1蛋白表达较缺血组明显增加(P＜0.01);凋亡细胞在缺血后12,24和48h均减少(P＜0.05),缺血后72h明显减少(P＜0.01).相邻切片可见cyclin G1蛋白表达和凋亡细胞染色区域基本相同.结论:cyclin G1蛋白在缺血后神经元内表达增加与缺血性神经细胞的凋亡无关,而可能与缺血神经细胞的自我保护适应性和损伤修复有关;丹参可能通过增加cyclin G1的表达,增加神经细胞的缺血损伤适应性,从另一方面发挥其神经细胞的保护作用.     

复方白花前胡液对大脑中动脉缺血再灌注大鼠 Caspase-3蛋白表达的影响

目的 :探索复方白花前胡液对大脑中动脉缺血再灌注大鼠Caspase 3蛋白表达的影响。方法 :线栓法制备大脑中动脉缺血再灌注大鼠模型 ,术后2 4、4 8、72h分别检测大鼠的神经功能缺损 ;并采用免疫组织化学法检测凋亡相关基因Caspase 3蛋白表达。结果 :MCAO R 2 4、4 8、72h后 ,所有动物都出现程度不同的运动障碍 ,且大鼠脑组织中Caspase 3蛋白表达显著升高 ,复方白花前胡液可明显改善大脑中动脉缺血再灌注大鼠的神经功能缺损症状 ,抑制大鼠Caspase 3蛋白表达水平。结论 :复方白花前胡液能有效抑制凋亡相关基因Caspase 3蛋白的表达 ,减轻或消除缺血级联反应中迟发性神经元死亡 ,复方白花前胡液是其治疗缺血性中风病的机理之一。     

ZW1-2对局灶脑缺血小鼠纹状体、皮质及海马脑区BDNF和VEGF蛋白表达的影响

目的观察化合物zome wermel 1-2(ZW1-2)对小鼠永久性局灶脑缺血后的神经功能,以及对脑源性营养因子和血管内皮生长因子的影响。方法制备小鼠永久性局灶脑缺血模型,并分别于脑缺血后2.5 h和7.5 h,灌胃给予不同剂量的化合物ZW1-2,脑缺血后24 h采用免疫组化法测定小鼠各个脑缺血易损区的脑源性神经营养因子和血管内皮生长因子表达情况。结果 ZW1-2能够显著降低小鼠局灶性脑缺血导致的行为功能评分,可以显著提高皮质、纹状体和海马脑区的脑源性神经营养因子表达,显著降低这些脑区中的血管内皮生长因子蛋白表达。结论 ZW1-2具有抗实验性脑缺血作用,其作用机制可能通过调控脑源性神经营养因子以及血管内皮生长因子而起到对脑缺血损伤的治疗作用。     

前列地尔对局灶性脑缺血大鼠脑组织p53的影响

目的:从脑组织p53的表达变化的角度来探讨前列地尔对大鼠局灶性脑缺血的防治机制及其量效关系。方法:采用大脑中动脉闭塞方法建立局灶性脑缺血动物模型,观察低、中、高剂量前列地尔对局灶性脑缺血大鼠大脑皮质p53表达的影响。结果:前列地尔各组大鼠脑组织p53表达平均灰度分别为115.75±11.38、140.13±11.38、156.21±10.05,均高于缺血对照组97.91±10.01。结论:前列地尔防治大鼠局灶性脑缺血损伤的机制可能与抑制脑组织p53表达有关,且以高剂量效果较好。     

Delayed intervention in experimental stroke with TRC051384--a small molecule HSP70 inducer

Induction of HSPs is a natural response of stressed cells that protects against many insults including acute ischemia. TRC051384, a novel compound belonging to substituted 2-propen-1-one class is a potent inducer of heat shock protein 70 (HSP70). The aim of this study was to investigate the ability of TRC051384 in reducing neuronal injury and disability upon delayed treatments (4 and 8 hours post ischemia onset) in a rat model of transient cerebral ischemia.Focal cerebral ischemia was produced in rats by occluding the MCA using the intra luminal suture technique. Rats subjected to 2 hours focal cerebral ischemia were administered by intra-peritoneal route, TRC051384 or vehicle every 2 hours for 48 hours, from 4th hour or 8th hour after onset of ischemia. Progression of infarct and edema was assessed up to 48 hours post ischemic insult using magnetic resonance imaging and the neurological disability and survival studied till 7 days.Here we show for the first time that treatment with TRC051384 significantly reduces stroke associated neuronal injury (87% reduction in area of penumbra recruited to infarct, and 25% reduction in brain edema) and disability in a rat model of transient ischemic stroke even when administered 8 hours post onset of ischemia. Significant improvement in survival (50% by day2 and 67.3% by day 7) was observed with TRC051384 treatment initiated at 4 hours after ischemia onset. Induction of HSP70 by TRC051384 involves HSF1 activation and results in elevated chaperone and anti-inflammatory activity. These results show that TRC051384 has the potential to be developed as a novel pharmacological agent for the treatment of ischemic stroke.     

WIN55,212-2 protects oligodendrocyte precursor cells in stroke penumbra following permanent focal cerebral ischemia in rats

Aim:

To explore whether the synthetic cannabinoid receptor agonist WIN55,212-2 could protect oligodendrocyte precursor cells (OPCs) in stroke penumbra, thereby providing neuroprotection following permanent focal cerebral ischemia in rats.

Methods:

Adult male SD rats were subjected to permanent middle cerebral artery occlusion (p-MCAO). The animals were administered WIN55,212-2 at 2 h, and sacrificed at 24 h after the ischemic insult. The infarct volumes and brain swelling were assessed. The expression of cannabinoid receptor type 1 (CB1) in the stroke penumbra was examined using Western blot assay. The pathological changes and proliferation of neural glial antigen 2-positive OPCs (NG2⁺ cells) in the stroke penumbra were studied using immunohistochemistry staining.

Results:

p-MCAO significantly increased the expression of CB1 within the stroke penumbra with the highest level appearing at 2 h following the ischemic insult. Administration of WIN55,212-2 (9 mg/kg, iv) significantly attenuated the brain swelling, and reduced the infarct volume as well as the number of tau-immunoreactive NG2⁺ cells (tau-1⁺/NG2⁺ cells) in the stroke penumbra. Moreover, WIN55,212-2 significantly promoted the proliferation of NG2⁺ cells in the stroke penumbra and in the ipsilateral subventricular zone at 24 h following the ischemic insult. Administration of the selective CB1 antagonist rimonabant (1 mg/kg, iv) partially blocked the effects caused by WIN55,212-2.

Conclusion:

Tau-1 is expressed in NG2⁺ cells following permanent focal cerebral ischemic injury. Treatment with WIN55,212-2 reduces the number of tau-1⁺/NG2⁺ cells and promotes NG2⁺ cell proliferation in the stroke penumbra, which are mediated partially via CB1 and may contribute to its neuroprotective effects.     

Protein transduction technology offers novel therapeutic approach for brain ischemia

Transient or permanent reduction in cerebral blood flow following ischemia can lead to severe and irreversible tissue damage to the brain. Emerging biochemical evidence suggests a role for apoptosis in neuronal death following cerebral ischemia. Despite the abundance of studies on the subject, therapeutic interventions for ischemia-related cell injury have so far proved disappointing in clinical trials. Recently, four new, exciting studies reported the use of protein transduction technology to deliver anti-apoptotic molecules to protect neuronal cells following ischemic stroke in vivo. These studies offer new avenues for the treatment and prevention of cell death following brain injuries.     

Involvement of caspase on apoptosis in ischemia-induced neuronal cell death: usefulness of caspase inhibitors for stroke therapy

This overviews recent understanding of the mechanisms of apoptosis on ischemia-induced neuronal cell death. Apoptosis is a prominent feature of the developing nervous system. Several lines of evidence suggest that apoptosis is also an important mechanism of cell death in adult brain in acute or chronic diseases such as stroke and Alzheimer's disease. In animal models of stroke, markers of apoptosis such as cytoplasmic and nuclear condensation and DNA fragmentation appear in neurons. A variety of physiological and pathological stimuli can activate signal-transduction pathways that result in the sequential proteolytic activation of caspase family members. The activation of caspases can be inhibited by several molecules, including peptide aldehydes (caspase-1 and or caspase-3 inhibitors) and crmA that target the active-site cysteine of caspase family members, Bcl-2, IAP (inhibitor of apoptosis protein) and NAIP (neuronal apoptosis inhibitory protein). Once activated, caspase-1 protease can activate the caspase family members and hydrolyze a discrete set of cellular targets. Poly (ADP-ribose)polymerase (PARP), which appears to facilitate apoptosis, was recognized as a substrate of activated caspase-3. These results suggest that caspase family, bcl-2 family, IAP family and substrates such PARP contribute to mechanisms of cell death in ischemic brain injury. Inhibition of the caspase family, particularly by non-peptide inhibitors that cross the blood-brain barrier and easily penetrate neurons and glia, could provide novel treatments for stroke and other forms of brain and spinal cord injury in humans.     

Cellular and molecular events underlying ischemia-induced neuronal apoptosis

Neurons subjected to ischemia undergo necrosis or apoptosis depending on their anatomic distribution and the severity and duration of ischemia. Recent work has shown that apoptosis can occur in some settings, primarily within the ischemic penumbra. It is recognized that both mitochondrial and death-receptor pathways are involved in the transduction of apoptotic signals in the context of cerebral ischemia. Recent data also highlight the pivotal role of caspase 3 in the execution of ischemia-induced apoptosis, although a caspase-independent pathway is gaining increasing attention. In this review, we examine some of these findings and their potential therapeutic implications for ischemic stroke.     

褪黑激素对受损伤脑神经元的保护作用与bcl-2蛋白过度表达有关(英文)

目的:研究褪黑激素对受损伤脑神经元的保护作用和对脑缺血后bcl-2,bax表达的影响,方法:用大鼠大脑中动脉梗死再灌注脑缺血模型,以脑梗死面积和存活细胞百分率作为脑损伤指标,用免疫组化的方法分析bcl-2,bax的表达,结果:缺血再灌后24 h褪黑激素呈剂量依赖性的减少脑梗死面积,减少缺血周边区细胞死亡,并显著增加该区bcl-2的表达,而对bar的表达则无明显影响,结论:褪黑激素具有明显减少缺血性神经细胞死亡的作用,该作用机制可能与神经细胞上bcl-2的表达有关。     

三七皂甙对急性脑缺血的保护作用

三七总皂甙对沙土鼠脑缺血再灌流损伤有明显保护作用;能减少脑缺血45min再灌流6h的卒中指数,并降低再灌流24h的死亡率。三七总皂甙单体Rb_1对树鼩局部脑缺血有保护作用:能减轻树鼩局部脑缺血12h后的脑水肿,并降低缺血脑组织的钙含量及缩小梗塞范国,而三七总皂甙单体Rg_1的作用不明显。     

Activation and role of caspases in chemotherapy-induced apoptosis

The importance of caspase activation during apoptosis has become eminently apparent in the last few years. The caspases participate in a proteolytic cascade activated in response to various stimuli, including anticancer drugs, that results in the systematic and orderly eradication of the cell. The core machinery of caspase activation is now emerging and involves multiple molecular complexes. We describe the two best-studied models of caspase activation, the mitochondrial pathway and the cell death receptor pathway, and discuss their involvement in caspase activation induced by various anticancer drugs used in chemotherapy. Defective apoptosis contributes to tumor growth and drug resistance. Understanding the activation and role of caspases in apoptosis may help develop new therapeutic strategies to circumvent drug resistance.