Oxyhemoglobin induces caspase-mediated cell death in cerebral endothelial cells

Damaged endothelium is one of the pathological changes of the cerebral vasospastic vessels following subarachnoid hemorrhage. Our recent study shows that oxyhemoglobin (OxyHb) induces apoptosis in vascular endothelial cells. Apoptosis generally requires the action of various classes of proteases, including a family of cysteine proteases, known collectively as the caspases. This study was undertaken to investigate the activation of caspases and the efficacy of caspase inhibitors, z-IETD-fmk and z-LEHD-fmk, for oxyhemoglobin-induced apoptosis in vascular endothelial cells. Cultured bovine brain microvascular endothelial cells (passages 5-9) were used for this study. OxyHb (10 micromol/L) was added during the 24-72 h incubation with and without caspase-8 or - 9 inhibitors (z-IETD-fmk and z-LEHD-fmk). Counting surviving cells, DNA laddering, western blotting of poly(ADP-ribose) polymerase, and measurement of caspase activities were employed to confirm the cytotoxic effects of OxyHb and the protective effects of the caspase inhibitors. OxyHb produced cell detachment in a time-dependent manner and increased caspase-8 and -9 activities in the cells. z-IETD-fmk and z-LEHD-fmk (100 micromol/L) attenuated OxyHb-induced cell loss, DNA laddering, and proteolytic cleavage of PARP, although a lower concentration (10 micromol/L) of caspase inhibitors showed partial effects. OxyHb activates caspase-8 and -9 in cultured vascular endothelial cells, and blocking the action of the caspases with the inhibitors efficiently prevents loss of vascular endothelial cells from OxyHb-induced apoptosis in vitro. These results suggest that the caspase cascade participates in OxyHb-induced apoptosis.

[Influence of adjustment of balance of Th1/Th2 type cytokines on proliferation of glioma cells]

OBJECTIVE

To study the influence of adjustment of balance of Th1/Th2 by external cytokines on proliferation of glioma cells.

METHODS

The gene expressions of Th1/Th2 type cytokines in C6, 9L, U251 and SHG44 glioma cells were detected by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). After the cells were induced with IFN-gamma + IL-4 McAb and IL-4 + IFN-gamma McAb respectively, we isolated the total RNA to proceed RT-PCR again. The evaluation of cell proliferation was proceeded by MTT assay method.

RESULTS

There was obviously predominant expression of Th2 type cytokines in glioma cell lines (P < 0.01). The expression intensity of IFN-gamma was improved in IFN-gamma + IL-4 McAb groups and Th2 type cytokines were enhanced in IL-4 + IFN-gamma McAb groups. IFN-gamma and IL-4 McAb could cause the switch from Th2 to Th1, and could remarkably inhibit the proliferation of glioma cells in a dose-dependent way (P < 0.01). On the other hand, IL-4 and IFN-gamma McAb could strengthen the switch of Th2, and might stimulate the glioma cell growth, also in a dose-dependent way (P < 0.01).

CONCLUSIONS

There is a Th2 preponderance in glioma cells. IFN-gamma and IL-4 McAb could regulate the switch from Th2 to Th0 or Th1, and inhibit the proliferation of glioma cells.

Age-related changes in P2 receptor mRNA of rat cerebral arteries

Aging alters the vascular response to extracellular nucleotides. However, the molecular mechanisms that underlie the effect of aging remain unclear. We investigated the mRNA expression of P2X(1), P2Y(1), P2Y(2) subtypes of the nucleotide receptors (P2) in the basilar artery, aorta and carotid artery from male Sprague-Dawley rats, 2-months and 19-months old. In the basilar arteries of 19-month old rats, as compared to the 2-month old rats, the P2X(1) receptor transcripts were reduced and the P2Y(1) and P2Y(2) receptor mRNA was increased. In the aorta and carotid arteries, P2Y(1) receptor mRNA was decreased in the 19-month old rats when compared to the 2-month old rats. There were no marked changes of P2X(1) and P2Y(2) receptor mRNA between the two age groups in the aorta or carotid artery. In endothelial cells, P2Y(1) and P2Y(2) receptor mRNA was reduced with age. We concluded that, down-regulation of P2X(1) and up-regulation of P2Y(1), P2Y(2) receptor mRNA in smooth muscle cells and down-regulation of P2Y(1) and P2Y(2) receptor mRNA on vascular endothelial cells might underlie the changes of cerebral vascular tone in aging.

Intrathecal application with liposome-entrapped Fasudil for cerebral vasospasm following subarachnoid hemorrhage in rats

To date, the pharmacological approach to cerebral vasospasm following subarachnoid hemorrhage has been hampered in part by an inability to attain sufficiently high concentrations of vasodilator drugs in the cerebrospinal fluid (CSF). To overcome this limitation of current drug therapy, we have developed a sustained-release preparation of protein kinase inhibitor Fasudil. Cerebral vasospasm in rats was induced by double-injection method. Treated rats received 0.417 mg liposome-entrapped Fasudil via the cisterna magna and control rats received drug-free liposomes in the same manner. The diameter of the basilar artery was assessed at 7 days after the initial blood injection. Vasoconstriction of the rat basilar artery was significantly reduced in group treated with liposomal Fasudil compared to the control group (treated group: 87.7 +/- 6.18%, n= 10; control group: 66.3 +/- 9.82%, n = 10; ***P< 0.001). This new approach for cerebral vasospasm may have significant potential for use in the clinical setting.

Role of Cl- current in endothelin-1-induced contraction in rabbit basilar artery

Cl- efflux induces depolarization and contraction of smooth muscle cells. This study was undertaken to explore the role of Cl- channels in endothelin-1 (ET-1)-induced contraction in rabbit basilar artery. Male New Zealand White rabbits (n = 26), weighing 1.8-2.5 kg, were euthanized by an overdose of pentobarbital. The basilar arteries were removed for isometric tension recording. ET-1 produced a concentration-dependent contraction of the rabbit basilar artery in the normal Cl- Krebs-Henseleit bicarbonate buffer (123 mM Cl-). The ET-1-induced contraction was reduced by the following manipulations: 1) inhibition of Na+-K+-2Cl- cotransporter with bumetanide (3 x 10(-5) and 10(-4) M), 2) bicarbonate-free solution to disable Cl-/HCO exchanger, and 3) preincubation of rings with the Cl- channel blockers niflumic acid, 5-nitro-2-(3-phenylpropylamino)benzoic acid, and indanyloxyacetic acid 94. The ET-1-induced contraction was enhanced by substitution of extracellular Cl- (10 mM) with methanesulfonic acid (113 mM). Cl- channels are involved in ET-1-induced contraction in the rabbit basilar artery.

Effect of hyperbaric oxygen on striatal metabolites: a microdialysis study in awake freely moving rats after MCA occlusion

We have shown that hyperbaric oxygen (HBO) reduced cerebral infarction in rat middle cerebral artery occlusion model (MCAO). The present study was undertaken to evaluate the effect of HBO on ischemic striatal metabolites at different times after MCAO and reperfusion. A rat MCAO model was produced via the intraluminal filament method. After 2 h of occlusion the suture was removed and reperfusion was allowed. The rats were sacrificed at 24 h after reperfusion. HBO treatment was administered by putting rats in the HBO chamber at 3 atmospheres absolute (ATA) HBO for 1 h. Glucose, lactate, pyruvate, and glutamate in striatal extracellular fluid were collected and measured by a microdialysis system at 7, 10, and 24 h after reperfusion. Glucose, pyruvate and glutamate concentrations were increased after reperfusion. HBO treatment decreased glucose, pyruvate, and glutamate almost to the control level (preocclusion level). The lactate concentration remained unchanged after ischemic/reperfusion and after HBO treatment. This study suggested that altered brain energy metabolites and excitatory amino acids occurred during cerebral ischemia and and HBO regulated these striatal metabolites, which might contribute to the protective effect of HBO in cerebral ischemia.

Age-related RhoA expression in blood vessels of rats

Aging is a major risk factor for the development of vascular diseases that lead to stroke and heart failure. Several cellular factors such as cell adhesion, motility, contractile response, and cytokinesis are involved in the aging process. RhoA, a member of the Rho family, plays a primary role in the regulation of these cellular factors. This study aims to investigate whether RhoA is involved in these age-related responses to vascular change. We found that in older rats (19 months ole), RhoA mRNA increased 1.9-fold in the aortic arteries and 2.4-fold in the basilar arteries compared to the younger rats (2 months old). Membrane binding, but not cytosol RhoA, levels were found to significantly increase in the aortic and basilar arteries with age, which suggests that RhoA activity increases in older rats. Staining of RhoA increased markedly with age in both the medial and endothelial layers of the collected aortic and basilar arteries. These results show that RhoA expression and activity in the aortic and basilar arteries increased as a function of age, thereby suggesting that RhoA might be altered in the vascular response change of aged rats.

Simulating canopy stomatal conductance of winter wheat and its distribution using remote sensing information

The canopy stomatal movement, a plant physiological process, generally occurs within leaves but its influence on exchange of CO2, water vapor, and sensible heat fluxes between atmosphere and terrestrial ecosystem. Many studies have documented that the interaction between leaf photosynthesis and canopy stomatal conductance is obvious. Thus, information on stomatal conductance is valuable in climate and ecosystem models. In current study, a newly developed model was adopted to calculate canopy stomatal conductance of winter wheat in Huang-Huai-Hai (H-H-H) Plain of China (31.5-42.7 degrees N, 110.0-123.0 degrees E). The remote sensing information from NOAA-AVHRR and meteorological observed data were used to estimate regional scale stomatal conductance distribution. Canopy stomatal conductance distribution pattern of winter wheat on March 18, 1997 was also presented. The developed canopy stomatal conductance model might be used to estimate canopy stomatal conductance in land surface schemes and seems can be acted as a boundary condition in regional climatic model runs.

Improved rat model for cerebral vasospasm studies

While the rat has been used extensively in subarachnoid hemorrhage (SAH)-cerebral vasospasm studies, concerns exist whether this animal represents a usable model because its time course and pattern of cerebral vasospasm following SAH is not comparable to that observed in man. At present, our knowledge of the rat model is based almost exclusively on studies using a 'single hemorrhage' method. Since there is a positive correlation between severity of cerebral vasospasm, and volume of subarachnoid blood, an obvious question is whether the rat will show modifications in vascular responses when insulted by a second SAH. Here, an SAH was produced in rats using a 'double hemorrhage' method. Following SAH, cerebral arteries showed pathological alterations, significant decreases in luminal perimeter, and increases in arterial wall thickness, over a 7-day post-SAH period. The above vascular features are considered to be indicative of cerebral vasospasm and their presence over a 7-day post-SAH period represents a significant time extension when compared to a single hemorrhage. These modified vascular responses made the double hemorrhaged rat a much-improved animal model.

Ceramide blocks PDGF-induced DNA synthesis in mesangial cells via inhibition of Akt kinase in the absence of apoptosis

The mechanism of action of ceramide in glomerular mesangial cells has not been studied. We investigated the effect of C2 ceramide on the mitogenic signal transduction pathways induced by PDGF in mesangial cells. Increasing concentrations of C2 ceramide inhibited PDGF-induced DNA synthesis in a dose-dependent manner with maximum inhibition at 15 microM. This inhibition of DNA synthesis was associated with attenuation of PDGF-induced early response gene c-fos transcription. PDGF receptor beta immunecomplex kinase assay showed no inhibitory effect of C2 ceramide on PDGF receptor tyrosine kinase activity. We have recently shown that the mitogenic effect of PDGF is mediated by the enzyme phosphatidylinositol (PI) 3 kinase in mesangial cells. C2 ceramide had no effect on PDGF-induced PDGFR-associated PI 3 kinase activity. These data indicate that inhibitory effect of C2 on PDGF-induced DNA synthesis is likely due to post-receptor and post-PI 3 kinase events. To address the mechanism of C2-mediated inhibition of DNA synthesis, we investigated the downstream target of PI 3 kinase, Akt. PDGF time-dependently increased Akt kinase activity in a PI 3 kinase-dependent manner. Incubation of mesangial cells with C2 ceramide inhibited PDGF-induced Akt activity. Akt kinase inhibits apoptosis of cells via phosphorylation of multiple proapoptotic proteins. However, inhibition of Akt activity by C2 ceramide did not induce apoptosis in mesangial cells. These data provide the first evidence that in mesangial cells, ceramide cross-talks with PI 3 kinase-dependent Akt kinase to inhibit PDGF-induced DNA synthesis without inducing apoptosis.

Oxyhemoglobin produces necrosis in cultured smooth muscle cells

OBJECT

Myonecrosis in the tunica media, which is defined morphologically, is one of the most striking alterations in the cerebral arterial wall following subarachnoid hemorrhage (SAH). In this study, oxyhemoglobin (OxyHb) was added to cultured rat aortic smooth muscle cells to determine the pattern of cell death by morphological and biochemical techniques.

METHODS

Confluent rat aortic smooth muscle cells were treated with OxyHb in a concentration- and time-dependent manner. Cell density was assayed by counting the number of cells that attached to the culture dishes after exposed to OxyHb. To identify cell death pattern, DNA analysis, electron microscopy, and Western blotting using poly (ADP-ribose) polymerase (PARP) antibody were performed.

CONCLUSIONS

OxyHb decreased cell density in a concentration- and time-dependent manner. DNA analysis showed a smear pattern characteristic of cell necrosis. Transmission electron microscopy demonstrated disintegration of cell membrane and destruction of cell organelles. No apoptotic changes, such as condensation of chromatin or apoptotic bodies were observed. Western blotting using PARP antibody revealed that 116 kDa PARP was not cleaved to 85 kDa, an apoptosis-related fragment. These results demonstrated morphologically and biochemically that OxyHb induced necrosis, not apoptosis, in cultured smooth muscle cells.

Role of tyrosine kinase in fibroblast compaction and cerebral vasospasm

Hemolysate, a proposed causative agent for cerebral vasospasm following subarachnoid hemorrhage, produces contraction of cerebral arteries by activation of tyrosine kinases. In addition, hemolysate accelerates fibroblast collagen compaction that could play a role in cerebral vasospasm. We studied the effect of hemolysate on tyrosine phosphorylation and fibroblast collagen compaction in cultured dog cerebral and human dermal fibroblasts using tyrosine kinase inhibitors and tyrosine antibodies (Western blot). 1) Hemolysate was found to enhance tyrosine phosphorylation of two proteins approximately 64 and 120 kDa. The effect of hemolysate was time- and concentration-dependent. 2) Two main components in hemolysate, oxyhemoglobin and adenosine triphosphate (ATP), produced similar results to that of hemolysate. 3) Tyrosine kinase inhibitor genistein and tyrphostin A51 (30 microM) markedly reduced the effect of hemolysate on tyrosine phosphorylation. 4) In another study, hemolysate increased fibroblast collagen compaction and the effect of hemolysate was reduced by genistein and tyrphostin A51. We conclude that hemolysate activates tyrosine kinase that may lead to acceleration of fibroblast compaction. This effect of hemolysate may contribute to cerebral vasospasm.

[Regulation of the transcription of oxidized low-density-lipoprotein receptor by angiotensin II]

AIM

To observe the effects of different concentrations Angiotensin II on the transcription of LOX1 in culture human umbilical vein endothelial cells and to explore its mechanism.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

(1) Angiotensin II cause a concentration-dependent increase of the level of LOX1 mRNA. (2) Losartan, the inhibitor of AT1 receptor subtypes, inhibited this effects.

CONCLUSION

Angiotensin II stimulated the gene expression of LOX1 by activating AT1 receptor subtype in culture human endothelial cells.

Protein kinase C and cerebral vasospasm

Twenty-five years after the discovery of protein kinase C (PKC), the physiologic function of PKC, and especially its role in pathologic conditions, remains a subject of great interest with 30,000 studies published on these aspects. In the cerebral circulation, PKC plays a role in the regulation of myogenic tone by sensitization of myofilaments to calcium. Protein kinase C phosphorylates various ion channels including augmenting voltage-dependent Ca2+ channels and inhibiting K+ channels, which both lead to vessel contraction. These actions of PKC amplify vascular reactivity to different agonists and may be critical in the regulation of cerebral artery tone during vasospasm. Evidence accumulated during at least the last decade suggest that activation of PKC in cerebral vasospasm results in a delayed but prolonged contraction of major arteries after subarachnoid hemorrhage. Most of the experimental results in vitro or in animal models support the view that PKC is involved in cerebral vasospasm. Implication of PKC in cerebral vasospasm helps explain increased arterial narrowing at the signal transduction level and alters current perceptions that the pathophysiology is caused by a combination of multiple receptor activation, hemoglobin toxicity, and damaged neurogenic control. Activation of protein kinase C also interacts with other signaling pathways such as myosin light chain kinase, nitric oxide, intracellular Ca2+, protein tyrosine kinase, and its substrates such as mitogen-activated protein kinase. Even though identifying PKC revolutionized the understanding of cerebral vasospasm, clinical advances are hampered by the lack of clinical trials using selective PKC inhibitors.

Effect of prolonged hypoxia on Na+ channel mRNA subtypes in the developing rat cortex

Voltage-gated Na+ channels are regulated in response to oxygen deprivation in the mammalian cortex. Past investigations have demonstrated that Na+ channel protein expression is up-regulated in the immature brain exposed to prolonged hypoxia. Since it is unknown as to which Na+ channel subtype(s) is involved in this regulation, we used RT-PCR to assess the effect of hypoxia on Na+ channel I, II and III alpha-subunit mRNA expression in the developing rat cortex. Na+ channel II mRNA tended to increase during early development, whereas Na+ channel I and III did not change or slightly decreased with age. Hypoxic exposure for 1-day had no effect on Na+ channel expression, while 5-day hypoxia significantly increased Na+ channel III density, with a slight increase in Na+ channel I and no appreciable change in Na+ channel II. These results suggest that Na+ channel subtype expression in the developing cortex is differentially regulated in response to prolonged hypoxic exposure.

Pharmacokinetics and bioavailability of sustained release and conventional formulation of acyclovir

The pharmacokinetics and relative bioavailability of a new sustained release formulation (200mg) of acyclovir (ACV) in comparison with a 100mg reference was investigated. The studies were conducted in two-way crossover design, as single and multiple oral administration in twelve healthy volunteers. Serum samples were assayed for ACV using a high-performance liquid chromatography (HPLC) method with UV detection. The bioavailability of sustained release tablets relative to conventional tablets following single and multiple dosing was 105.9 +/- 12.0% and 95.2 +/- 8.4%, respectively. ANOVA and the two-sided t-test procedures showed significant difference in Cmax and tmax but no difference was found in AUC both in single and multiple dose studies. The results of this study indicated that the new sustained release tablets and the reference are bioequivalent.

Role of MAPK in cerebral vasospasm

Cerebral vasospasm is the major cause of mortality and morbidity in patients of subarachnoid hemorrhage. Despite intensive studies during the past five decades, the signaling pathways in cerebral arteries that lead to the pathological contraction remain elusive. The complex nature of cerebral vasospasm requires a complex signaling pathway or a group of pathways that may need to interact to initiate and maintain vasospasm. This review explores the possibility that mitogen-activated protein kinase is the elusive signaling pathway responsible for cerebral vasospasm.

Mechanism of hemolysate-induced [Ca2+]i elevation in cultured fibroblasts

Erythrocyte lysate (hemolysate) released from blood clot after subarachnoid hemorrhage is the causative agent for chronic cerebral vasospasm, a prolonged contraction of cerebral arteries. Fibroblasts, the outer layer cells of vessel wall that in contact with blood clot directly, may contribute to cerebral vasospasm. However, the effect of hemolysate on intracellular Ca2+ ([Ca2+]i) mobilization in fibroblasts has not been studied. We investigated hemolysate-induced [Ca2+]i mobilization in cultured neonatal human dermal and canine middle cerebral arterial fibroblasts by using fura-2 microfluorimetry. Hemolysate increased [Ca2+]i by releasing internal Ca2+ stores and promoting Ca2+ entry. Tyrosine kinase inhibitors partially but significantly reduced the effect of hemolysate. The major components of hemolysate, oxyhemoglobin (OxyHb) and adenosine triphosphate (ATP) failed to mimic the effect of hemolysate. In cultured canine middle cerebral arterial fibroblasts, hemolysate produced similar Ca2+ mobilization to that of dermal cells. OxyHb and ATP failed again to reproduce the effect of hemolysate. We conclude that hemolysate increases [Ca2+]i in fibroblasts and this effect of hemolysate is not mediated by OxyHb or ATP but by some unknown factors.

[Studies on the chemical components of Clematis chinensis]

AIM

To study the chemical components of the root of Clematis chinensis.

METHODS

Various chromatographic techniques were used to separate and purify the components. Their structures were determined on the basis of spectral and chemical evidence.

RESULTS

Two compounds were isolated and elucidated as: clemaphenol A (I) and dihydro-4-hydroxy-5-hyroxymethy-2(3H)- furanone (II).

CONCLUSION

Compound I and II are new compounds.

Efficacy of intrathecal liposomal fasudil for experimental cerebral vasospasm after subarachnoid hemorrhage

OBJECTIVE

To investigate the safety and efficacy of liposomal fasudil in a sustained-release form for the prevention of cerebral vasospasm after subarachnoid hemorrhage (SAH).

METHODS

Eighteen rats were divided into three groups, each of which received 2.5 mg/kg of liposomal fasudil, 5 mg/kg of liposomal fasudil, or drug-free liposomes after SAH. Next, experimental SAH was induced in 15 dogs by injection of autologous arterial blood into the cisterna magna twice after baseline vertebral angiography. In six dogs, 0.94 mg/kg of liposomal fasudil was injected into the cisterna magna (treatment group). In four dogs, drug-free liposomes were similarly injected (placebo group), and the remaining five dogs were not treated with liposomal injection after SAH (control group). Angiography was repeated on Day 7, and cerebrospinal fluid was collected before the dogs were killed.

RESULTS

A high dose of liposomal fasudil caused no significant changes in mean arterial blood pressure and did not induce seizures during the observation period. Gross and microscopic examination of the brains revealed no abnormalities, but severe vasospasm was noted in the rat basilar artery, mainly in the group treated with drug-free liposomes. Likewise, in the canine placebo and control groups, significant vasospasm occurred in the basilar artery on Day 7. In the treatment group, vasospasm in the basilar artery was significantly ameliorated (P < 0.01). In vivo, 90% of fasudil was released from liposomes in the cerebrospinal fluid.

CONCLUSION

A single injection of intrathecal liposomal fasudil is safe and effective for the prevention of vasospasm in experimental SAH.