Calcium/calmodulin-dependent protein kinase inhibition potentiates thapsigargin-mediated cell death in SH-SY5Y human neuroblastoma cells

We previously demonstrated a loss in Ca(2+)/Calmodulin-dependent protein kinase (CaM kinase) activity in SH-SY5Y undergoing thapsigargin-mediated apoptosis. To extend that finding we report that CaM kinase inhibition potentiates thapsigargin-mediated cell death. CaM kinase inhibitor KN93 on its own exhibits little toxicity up to 10 mM, as measured by release of lactate dehydrogenase (LDH) into the culture medium. In SH-SY5Y cells pretreated with KN93 and the non-selective protein kinase inhibitor k252a and then treated with 2 mM thapsigargin, loss of viability is significantly greater than in cells treated with thapsigargin alone. Pretreatment with the pan-caspase inhibitor Z-D-DCB prevented the thapsigargin-mediated increase in LDH release. Furthermore, thapsigargin-induced caspase-3-like activation, demonstrated by poly(ADP)ribose polymerase cleavage and pro-caspase-3 processing, was elevated in the presence of KN93.

Contribution of intraoperative enteroscopy in the management of obscure gastrointestinal bleeding

Obscure gastrointestinal bleeding remains a significant diagnostic challenge. Our aims were (1) to determine the efficacy of intraoperative enteroscopy (IOE) in identifying lesions responsible for obscure gastrointestinal bleeding and (2) to determine the outcome of patients after treatment of these lesions. We retrospectively reviewed all patients who underwent IOE for obscure gastrointestinal bleeding from 1992 to 1998. Patients were divided into those with overt and those with occult gastrointestinal bleeding. Follow-up was complete in 67 patients (96%), with a median of 32 months (range 1 to 91 months). Seventy patients (52 overt and 18 occult) underwent IOE after extensive preoperative evaluation. Median duration of bleeding was 12 months, requiring a median of 14 blood transfusions. Risk factors for bleeding were identified in 46 patients (61%). A lesion was identified and treated in 52 patients (74%)-39 in the overt group and 13 in the occult group. Lesions identified were vascular (54%), ulcerations (31%), tumors (11%), and small bowel diverticula (4%). Overall, 35 patients (52%) were found to have one or more lesions at IOE that were treated surgically and had no further bleeding. IOE, through a mid-small bowel enterotomy, has low morbidity and is effective in that it identified a treatable lesion in 74% of patients, which led to cure of bleeding in 52%.

Evaluation of HIV-1 Tat induced neurotoxicity in rat cortical cell culture

In a substantial number of cases, Human Immunodeficiency Virus type 1 (HIV-1) infection causes neuronal cell loss and leads to the development of AIDS associated dementia. Several studies have suggested that both host and viral factors contribute to neuronal loss. Here we studied the effect of HIV-1 Tat in primary rat neuronal cells as a model to understand mechanism of neuronal cell death. At nano molar concentration, recombinant Tat induced cell death in primary rat mixed cortical neurons. Tat could also induce uptake of calcium in primary rat cultures. When cells were incubated with NMDA receptor antagonists, MK-801 and D-CPP, cell death and 45Ca uptake were inhibited. Under similar conditions non-NMDA antagonists, NBQX, DNQX and CNQX, and sodium channel antagonist, TTX, did not inhibit Tat induced neuronal cell death. In a similar way HIV associated products from in vitro HIV-1 infected cells induced neuronal cell death which was inhibited by NMDA receptor antagonist. Results presented in this paper suggest that activation of NMDA receptors by HIV-1 Tat is responsible for neuronal cell death in primary rat cortical neurons.

Synthesis of 6H-indolo[2,3-b][1,6]naphthyridines and related compounds as the 5-Aza analogues of ellipticine alkaloids

Treatment of 2-(1-alkynyl)phenyl isocyanates 6 with the iminophosphorane 14 produced in situ the benzoenynyl carbodiimides 15. Thermolysis of 15 under refluxing p-xylene furnished the 6H-indolo[2,3-b][1,6]naphthyridines 5, which could be regarded as the 5-aza analogues of ellipticine alkaloids. Similarly, condensation of 6 with the iminophosphorane 20 led to the formation of the 6H-indolo[2,3-b][1,5]naphthyridines 25 as the major isomer and the 10H- indolo[2,3-b][1,7]naphthyridines 26 as the minor isomer. The indolonaphthyridines 32, 33, and 34 having a methoxyl substituent were likewise synthesized. Treatment of the diisocyanate 43 with 2 equiv of the iminophosphorane 7 furnished 45 having two indoloquinoline units incorporated in a seven-fused-ring system.

The "aspirin" of the new millennium: cyclooxygenase-2 inhibitors

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis via the cyclooxygenase (COX) enzyme, the key to both therapeutic benefits and toxicity. COX enzyme exists in 2 isoforms, COX-1 and COX-2. COX-1 enzyme is thought to mediate "housekeeping" or homeostatic functions, and COX-2 is considered an inducible enzyme in response to injury or inflammation. COX-2 inhibitors are the "next-generation" NSAIDs that may selectively block the COX-2 isoenzyme without affecting COX-1 function. This may result in control of pain and inflammation with a lower rate of adverse effects compared with older nonselective NSAIDs. Rapidly evolving evidence suggests that COX-2 enzyme has a diverse physiologic and pathologic role. This article addresses the role of COX-2 enzyme in health and disease as well as the potential therapeutic value and safety issues related to COX-2 inhibition.

Persistent genetic abnormalities in Barrett's esophagus after photodynamic therapy

BACKGROUND & AIMS

Photodynamic therapy (PDT) is a technique for nonsurgical treatment of patients with dysplasia in Barrett's esophagus. The primary endpoint for PDT has been resolution of dysplasia. We studied the effect of PDT at the genetic level.

METHODS

Archival material from 3 patients who had initial improvement in dysplasia after PDT but occurrence of high-grade dysplasia during follow-up was used. Biopsy specimens were analyzed for increased proliferation, aneuploidy, p53 protein overexpression, p53 mutations, and p16 promoter hypermethylation.

RESULTS

Patients developed high-grade dysplasia 16, 28, and 37 months after PDT. In all cases, one or more genetic markers were positive after PDT treatment, whereas histology was downstaged consistently after therapy. Increasing genetic abnormalities were noted by the end of follow-up.

CONCLUSIONS

Genetic abnormalities may persist after PDT despite phenotypical improvement of dysplasia. These patients may progress to high-grade dysplasia or develop adenocarcinoma. Histologic improvement in dysplasia is an inadequate endpoint for PDT in patients with Barrett's esophagus.

Endoscopic mucosal resection for lesions with endoscopic features suggestive of malignancy and high-grade dysplasia within Barrett's esophagus

BACKGROUND

Endoscopic mucosal resection has been used in the treatment of superficial squamous cell cancers and gastric malignancies. Our aim was to determine whether endoscopic mucosal resection can be used in the diagnosis of lesions within Barrett's esophagus whose endoscopic appearances raise suspicion of carcinoma or high-grade dysplasia.

METHODS

Twenty-five patients with such lesions within Barrett's esophagus underwent endoscopic mucosal resection for diagnostic and therapeutic purposes. All patients underwent endoscopic ultrasound to determine the feasibility of endoscopic resection. Only lesions found to be uT0 or uT1 underwent EMR. The lift and cut technique was used in 23 patients and a variceal ligating device was used on 2 patients.

RESULTS

Endoscopic mucosal resection was performed because of a nodule or polyp within Barrett's esophagus in 11 patients (44%) and suspected superficial cancer or high-grade dysplasia in 14 patients (56%). Endoscopic mucosal resection diagnosed superficial adenocarcinoma in 13 patients (52%) and high-grade dysplasia in 4 (16%); it confirmed lesions in 8 patients (40%) to be of lower neoplastic risk. No complications occurred due to the procedure itself.

CONCLUSIONS

Endoscopic mucosal resection is a technique with low morbidity and mortality. It has led to a change in diagnosis in patients with Barrett's esophagus and lesions with endoscopic features that suggest neoplasia. Its major advantages include simplicity and retrieval of the specimen en bloc.

Processing of cdk5 activator p35 to its truncated form (p25) by calpain in acutely injured neuronal cells

Recently, it was shown that conversion of cdk5 activator protein p35 to a C-terminal fragment p25 promotes a deregulation of cdk5 activity, which may contribute to neurodegeneration in Alzheimer's disease. In this study, we present evidence that calpain is a protease involved in the conversion of p35 to p25. To activate calpain, rat cerebellar granule neurons were treated with maitotoxin (MTX). A C-terminus-directed anti-p35 antibody detected that p35 conversion to p25 paralleled the formation of calpain-generated alpha-spectrin (alpha-fodrin) breakdown products (SBDP's) in a maitotoxin-dose-dependent manner. Two calpain inhibitors (MDl28170 and SJA6017) reduced p35 processing but were unchanged when exposed to the caspase inhibitor carbobenzoxy-Asp-CH(2)OC(=O)-2, 6-dichlorobenzene or the proteasome inhibitors (lactacystin and Z-Ile-Glu(OtBu)Ala-Leu-CHO). p35 protein was also degraded to p25 when rat brain lysate was subjected to in vitro digestion with purified mu- and m-calpains. Additionally, in a rat temporary middle cerebral artery occlusion model, p35 processing to p25 again paralleled SBDP formation in the ischemic core. Lastly, in malonate-injured rat brains, the ipsilateral side showed a striking correlation of SBDP formation with p35 to p25 conversion and tau phosphorylation (at Ser202 and Thr205) increase. These data suggest that calpain is a major neuronal protease capable of converting p35 to p25 and might play a pathological role of activating cdk5 and its phosphorylation of tau in Alzheimer's disease.

Caspase-mediated proteolytic activation of calcineurin in thapsigargin-mediated apoptosis in SH-SY5Y neuroblastoma cells

We previously demonstrated a loss in calmodulin (CaM)-dependent protein kinase activity in SH-SY5Y cells undergoing thapsigargin-mediated apoptosis, (K. M. McGinnis et al., 1998, J. Biol. Chem. 273, 19993-20000). Here we demonstrate that the large subunit of the CaM-dependent protein phosphatase 2B (calcineurin) is fragmented during SH-SY5Y cell apoptosis to a major fragment of 45 kDa in a caspase inhibitor-sensitive manner. A 45-kDa fragment was also produced when purified calcineurin was digested with recombinant caspase-3. The major cleavage site was identified to be DFGD* G(386)ATAA, which removes the C-terminal CaM-binding and autoinhibitory regions from the catalytic domain. Phosphatase activity increased progressively with caspase-3 digestion, coupled with the eventual loss of CaM-dependency. Calcineurin-mediated dephosphorylation of NFATc was also detected in thapsigargin-treated cells. Last, calcineurin inhibitors FK506 and cypermethrin provided partial protection against thapsigargin-mediated apoptosis, suggesting that calcineurin overactivation contributes to thapsigargin-induced apoptosis.

The calpain small subunit gene is essential: its inactivation results in embryonic lethality

Creation of transgenic (knockout) mice deficient in calpain small (30 kDa) subunit gene was undertaken to clarify the proposed role of the small subunit for calpain proteolytic activity and to gain insight into the importance of the gene in the whole animal. The gene was targeted and disrupted in embryonic stem cells by homologous recombination, and chimeric mice were generated. Heterozygous F1 generation mice were crossed to obtain F2 generation. Among F2 generation mice, we found only wild-type and heterozygous animals in the 80 pups genotyped to date; no homozygous mice have been found, although 20 were expected. The heterozygotes had no apparent phenotypic abnormalities. Analysis of their tissues revealed no significant difference in mRNA expression, protein content, or proteolytic activity in comparison with their wild-type littermates. Genotyping of fetuses at different stages of development also revealed only wild-type and normal heterozygous fetuses. No moribund embryos or resorption sites were observed in the uterine cavity. The results indicate that at least one normal allele is essential for postnatal survival. Disruption of both alleles appears to be lethal in very early fetal development.

Complications of photodynamic therapy in gastrointestinal disease

The primary complications of photodynamic therapy of the esophagus include cutaneous photosensitivity and esophageal strictures. Atrial fibrillation and pleural effusion have been reported but appear to be rare or not clinically significant. Cutaneous photosensitivity can be minimized if the adequate precautions are taken to protect patients from sunlight exposure. Stricture formation may be decreased by proper dosimetry and avoiding multiple overlapping light applications.

Photodynamic therapy of Barrett's esophagus

Photodynamic therapy seems to be able to control high-grade dysplasia within Barrett's esophagus about 80% of the time. Long-term results are not available, but the treatment is promising. Given the success with surgical intervention, however, use of photodynamic therapy should be reserved for nonsurgical candidates at the current time. The complications that occur with photodynamic therapy are not trivial and must be weighed against the potential benefits.

Hyaluronic acid enhances peripheral nerve regeneration in vivo

Hyaluronic acid has been shown to enhance peripheral nerve regeneration in vitro. It has been proposed that, during the fibrin matrix phase of regeneration, hyaluronic acid organizes the extracellular matrix into a hydrated open lattice, thereby facilitating migration of the regenerating axons. Hyaluronic acid solutions and saline control solutions were injected into a nerve guide spanning a transected gap in the sciatic nerve of Sprague-Dawley rats (five in each group). Nerve conduction velocities were measured at 4 weeks by electromyography (EMG) before sacrifice of the animals. These studies demonstrated increased conduction velocities in the hyaluronic acid group compared with control animals (P = 0.006). After the animals were sacrificed, regenerated axon cables were quantified histologically, and axon branching was delineated by retrograde tracer analysis. In addition, the hyaluronic acid group showed an increase in myelinated axon counts at 4 weeks (P= 0.03). An increase in retrograde flow was demonstrated in the hyaluronic acid groups compared with animals receiving saline solution.

Cytochrome c release and caspase activation in traumatic axonal injury

Axonal injury is a feature of traumatic brain injury (TBI) contributing to both morbidity and mortality. The traumatic axon injury (TAI) results from focal perturbations of the axolemma, allowing for calcium influx triggering local intraaxonal cytoskeletal and mitochondrial damage. This mitochondrial damage has been posited to cause local bioenergetic failure, leading to axonal failure and disconnection; however, this mitochondrial damage may also lead to the release of cytochrome c (cyto-c), which then activates caspases with significant adverse intraaxonal consequences. In the current communication, we examine this possibility. Rats were subjected to TBI, perfused with aldehydes at 15-360 min after injury, and processed for light microscopic (LM) and electron microscopic (EM) single-labeling immunohistochemistry to detect extramitochondrially localized cytochrome c (cyto-c) and the signature protein of caspase-3 activation (120 kDa breakdown product of alpha-spectrin) in TAI. Combinations of double-labeling fluorescent immunohistochemistry (D-FIHC) were also used to demonstrate colocalization of calpain activation with cyto-c release and caspase-3-induction. In foci of TAI qualitative-quantitative LM demonstrated a parallel, significant increase in cyto-c release and caspase-3 activation over time after injury. EM analysis demonstrated that cyto-c and caspase-3 immunoreactivity were associated with mitochondrial swelling-disruption in sites of TAI. Furthermore, D-IFHC revealed a colocalization of calpain activation, cyto-c release, and caspase-3 induction in these foci, which also revealed progressive TAI. The results demonstrate that cyto-c and caspase-3 participate in the terminal processes of TAI. This suggests that those factors that play a role in the apoptosis in the neuronal soma are also major contributors to the demise of the axonal appendage.

Influence of glial growth factor and Schwann cells in a bioresorbable guidance channel on peripheral nerve regeneration

Using an established rat peripheral nerve regeneration model, we investigated the role of glial growth factor (GGF) in nerve regeneration in combination with a novel bioresorbable poly(lactic-co-glycolic) acid (PLGA) guide in vivo. Schwann cells, established from a 1-cm segment of excised rat sciatic nerve, were isolated and seeded onto nerve guides with or without GGF (n = 24/group). Living nerve guides were re-established in these animals, and nerve regeneration was assessed over a period of 12 weeks. Histological studies revealed a reduction in the total axon count and the number of myelinated axons in the presence of exogenously added Schwann cells compared to saline controls. In contrast, the addition of GGF alone enhanced the total number of axons and significantly increased the number of blood vessels. Although combining GGF with Schwann cells negated the enhanced numbers of axons and blood vessels seen with GGF alone, this combination resulted in the highest myelination index and the fastest conduction velocities recorded. The PLGA guide material did not trigger any histologically detectable host response and was permissive for nerve regeneration in this animal model. The results from this study demonstrate the potential utility of this guide in vivo and establish a promotional role for GGF in nerve regeneration.

Novel characteristics of glutamate-induced cell death in primary septohippocampal cultures: relationship to calpain and caspase-3 protease activation

Studies examined the phenotypic characteristics of glutamate-induced cell death and their relationship to calpain and caspase-3 activation. Cell viability was assessed by fluorescein diacetate and propidium iodide staining and lactate dehydrogenase release. Calpain and caspase-3 activity was inferred from signature proteolytic fragmentation of alpha-spectrin. Characterization of cell death phenotypes was assessed by Hoechst 33258 and DNA fragmentation assays. Exposure of septohippocampal cultures to 1.0, 2.0, and 4.0 mmol/L glutamate induced a dose-dependent cell death with an LD50 of 2.0 mmol/L glutamate after 24 hours of incubation. Glutamate treatment induced cell death in neurons and astroglia and produced morphological alterations that differed from necrotic or apoptotic changes observed after maitotoxin or staurosporine exposure, respectively. After glutamate treatment, cell nuclei were enlarged and eccentrically shaped, and aggregated chromatin appeared in a diffusely speckled pattern. Furthermore, no dose of glutamate produced evidence of internucleosomal DNA fragmentation. Incubation with varying doses of glutamate produced calpain and caspase-3 activation. Calpain inhibitor II (N-acetyl-Leu-Leu-methionyl) provided protection only with a narrow dose range, whereas carbobenzoxy-Asp-CH2-OC(O)-2,6-dichlorobenzene (Z-D-DCB; pan-caspase inhibitor) and MK-801 (N-methyl-D-aspartate receptor antagonist) were potently effective across a wider dose range. Cycloheximide did not reduce cell death or protease activation.

Activation of apoptosis-linked caspase(s) in NMDA-injured brains in neonatal rats

Unilateral injection of 50 nmol of N-methyl-D-aspartate (NMDA) into the left posterior striatum of 7 day-old rat pups induces massive neuronal loss in the ipsilateral hemisphere in 5 days. In this model of excitotoxicity, the form of neuronal death (necrosis vs apoptosis) has not been clearly addressed. Here we report evidence of DNA laddering in the ipsilateral hemisphere 24 h after the NMDA injection. Activation of apoptosis-linked caspase(s) was also identified, as evidenced by (i) the formation of caspase-produced 120 kDa alpha-spectrin breakdown product (SBDP120) and (ii) increase in hydrolysis of caspase-3 substrate acetyl-DEVD-7-amido-4-methylcoumarin in the homogenate from the ipsilateral hemisphere. Lastly, we note that i.p. injection (100 mg/kg) of a pan caspase inhibitor Z-D-DCB attenuates the levels of SBDP120. Our results suggest the presence of caspase-activation in this rat pup model of NMDA toxicity.

Calpain and caspase: can you tell the difference?

Both necrotic and apoptotic neuronal death are observed in various neurological and neurodegenerative disorders. Calpain is activated in various necrotic and apoptotic conditions, while caspase 3 is only activated in neuronal apoptosis. Despite the difference in cleavage-site specificity, an increasing number of cellular proteins are found to be dually susceptible to these cysteine proteases. These include alpha- and beta-fodrin, calmodulin-dependent protein kinases, ADP-ribosyltransferase (ADPRT/PARP) and tau. Intriguingly, calpastatin is susceptible to caspase-mediated fragmentation. Neurotoxic challenges such as hypoxia-hypoglycemia, excitotoxin treatment or metabolic inhibition of cultured neurons result in activation of both proteases. Calpain inhibitors can protect against necrotic neuronal death and, to a lesser extent, apoptotic death. Caspase inhibitors strongly suppress apoptotic neuronal death. Thus, both protease families might contribute to structural derangement and functional loss in neurons under degenerative conditions.