The cytoskeletal protein non-erythroid alpha-spectrin is well documented as an endogenous calpain substrate, especially under pathophysiological conditions. In cell necrosis (e.g. maitotoxin-treated neuroblastoma SH-SY5Y cells), alpha-spectrin breakdown products (SBDPs) of 150 kDa and 145 kDa were produced by cellular calpains. In contrast, in neuronal cells undergoing apoptosis (cerebellar granule neurons subjected to low potassium and SH-SY5Y cells treated with staurosporine), an additional SBDP of 120 kDa was also observed. The formation of the 120 kDa SBDP was insensitive to calpain inhibitors but was completely blocked by an interleukin 1 beta-converting-enzyme (ICE)-like protease inhibitor, Z-Asp-CH2OC(O)-2,6-dichlorobenzene. Autolytic activation of both calpain and the ICE homologue CPP32 was also observed in apoptotic cells. alpha-Spectrin can also be cleaved in vitro by purified calpains to produce the SBDP doublet of 150/145 kDa and by ICE and ICE homologues [ICH-1, ICH-2 and CPP32(beta)] to produce a 150 kDa SBDP. In addition, CPP32 and ICE also produced a 120 kDa SBDP. Furthermore inhibition of either ICE-like protease(s) or calpain protects both granule neurons and SH-SY5Y cells against apoptosis. Our results suggest that both protease families participate in the expression of neuronal apoptosis.

We characterized the activation of interleukin‐1β‐converting enzyme (ICE)‐like proteases (caspases) in human neuroblastoma cells (SH‐SY5Y) following challenge with staurosporine, an established agent known to induce apoptosis. Time course analyses of lactate dehydrogenase release detected a significant increase in cell death as early as 6 h that continued at least until 24 h following staurosporine treatment. Western blot analyses using anti‐poly(ADP‐ribose) polymerase (anti‐PARP) and anti‐CPP32 antibodies revealed proteolytic processing of CPP32 (an ICE homologue) as well as fragmentation of PARP as early as 3 h following staurosporine challenge. Furthermore, the hydrolysis of the CPP32 substrate acetyl‐DEVD‐7‐amido‐4‐methylcoumarin was detected as early as 3 h and became maximal at 6 h after staurosporine challenge, suggesting a delayed and sustained period of CPP32‐like activation. In addition, we used the first immunohistochemical examination of CPP32 and PARP in cells following an apoptotic challenge. The localization of CPP32 in untreated SH‐SY5Y cells was exclusively restricted to the cytoplasm. Following staurosporine challenge there was a condensing of CPP32 immunofluorescence from the cytoplasm to a region adjacent to the plasma membrane. In contrast, PARP immunofluorescence was evenly distributed in the nucleus in untreated SH‐SY5Y cells and on staurosporine challenge was found to be associated with condensed chromatin. It is important that a pan ICE inhibitor [carbobenzoxy‐Asp‐CH2OC(O)‐2,6‐dichlorobenzene] was able to attenuate lactate dehydrogenase release and PARP and CPP32 cleavage and altered immunohistochemical staining patterns for PARP and CPP32 following staurosporine challenge.

Two isoforms of the cyclooxygenase (COX) enzyme have been identified: COX-1, which is expressed constitutively, and COX-2, which is induced in inflammation. Recently, it has been shown that selective COX-2 inhibitors have antiinflammatory activity and lack the GI side effects typically associated with NSAIDs. Initial mass screening and subsequent SAR studies have identified 6b (PD164387) as a potent, selective, and orally active COX-2 inhibitor. It had IC50 values of 0.14 and 100 microM against recombinant human COX-2 and purified ovine COX-1, respectively. It inhibited COX-2 activity in the J774A.1 cell line with an IC50 of 0.18 microM and inhibited COX-1 activity in platelets with an IC50 of 3.1 microM. The choline salt of compound 6b was also orally active in vivo with an ED40 of 7. 1 mg/kg in the carrageenan footpad edema (CFE) assay. In vivo studies in rats at a dose of 100 mg/kg showed that this compound inhibited gastric prostaglandin E2 (PGE2) production in gastric mucosa by 77% but caused minimal GI damage. SAR studies of this chemical series revealed that the potency and selectivity are very sensitive to minor structural changes.

Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to be potent antiinflammatory agents with fewer side effects than currently marketed nonsteroidal antiinflammatory drugs (NSAIDs). Initial mass screening and subsequent structure-activity relationship (SAR) studies have identified 4b (PD138387) as the most potent and selective COX-2 inhibitor within the thiazolone and oxazolone series of di-tert-butylphenols. Compound 4b has an IC50 of 1.7 microM against recombinant human COX-2 and inhibited COX-2 activity in the J774A.1 cell line with an IC50 of 0.17 microM. It was inactive against purified ovine COX-1 at 100 microM and did not inhibit COX-1 activity in platelets at 20 microM. Compound 4b was also orally active in vivo with an ED40 of 16 mg/kg in the carrageenan footpad edema (CFE) assay and caused no gastrointestinal (GI) damage in rats at the dose of 100 mg/kg but inhibited gastric prostaglandin E2 (PGE2) production in rats' gastric mucosa by 33% following a dose of 100 mg/kg. The SAR studies of this chemical series revealed that the potency and selectivity are very sensitive to minor structural changes. A simple isosteric replacement led to the reversal of selectivity.

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