One potential factor contributing to the susceptibility of these cells to premature death arises from the cytotoxic effects of amyloid-␤ (A␤) peptide deposition at or near sites of neuronal degeneration. Cultured human Franc ¸ois G.

Neuronal death, which follows ischemic injury or is triggered by excitotoxins, can occur by both apoptosis and necrosis. Caspases, which are not directly required for necrotic cell death, are central mediators of the apoptotic program. Here we demonstrate that caspases cleave and inactivate the plasma membrane Ca 2+ pump (PMCA) in neurons and non-neuronal cells undergoing apoptosis. PMCA cleavage impairs intracellular Ca 2+ handling, which results in Ca 2+ overload. Expression of non-cleavable PMCA mutants prevents the disturbance in Ca 2+ handling, slows down the kinetics of apoptosis, and markedly delays secondary cell lysis (necrosis). These findings suggest that caspase-mediated cleavage and inactivation of PMCAs can lead to necrosis, an event that is reduced by caspase inhibitors in brain ischemia.

Microsomal prostaglandin E synthase-1 (mPGES-1) is a terminal prostaglandin E 2 (PGE 2 ) synthase in the cyclooxygenase pathway. Inhibitors of mPGES-1 may block PGE 2 production and relieve inflammatory symptoms. To test the hypothesis, we evaluated the antipyretic and analgesic properties of a novel and selective mPGES-1 inhibitor, MF63 [2-(6-chloro-1H-phenanthro-[9,10-d]imidazol-2-yl)isophthalonitrile], in animal models of inflammation. MF63 potently inhibited the human mPGES-1 enzyme (IC 50 ϭ 1.3 nM), with a high degree (Ͼ1000-fold) of selectivity over other prostanoid synthases. In rodent species, MF63 strongly inhibited guinea pig mPGES-1 (IC 50 ϭ 0.9 nM) but not the mouse or rat enzyme. When tested in the guinea pig and a knock-in (KI) mouse expressing human mPGES-1, the compound selectively suppressed the synthesis of PGE 2 , but not other prostaglandins inhibitable by nonsteroidal anti-inflammatory drugs (NSAIDs), yet retained NSAID-like efficacy at inhibiting lipopolysaccharide-induced pyresis, hyperalgesia, and iodoacetate-induced osteoarthritic pain. In addition, MF63 did not cause NSAID-like gastrointestinal toxic effects, such as mucosal erosions or leakage in the KI mice or nonhuman primates, although it markedly inhibited PGE 2 synthesis in the KI mouse stomach. Our data demonstrate that mPGES-1 inhibition leads to effective relief of both pyresis and inflammatory pain in preclinical models of inflammation and may be a useful approach for treating inflammatory diseases.

Hypoxia-ischemia (H-I) in the developing brain results in brain injury with prominent features of both apoptosis and necrosis. A peptide-based pan-caspase inhibitor is neuroprotective against neonatal H-I brain injury, suggesting a central role of caspases in brain injury. Because previously studied peptide-based caspase inhibitors are not potent and are only partially selective, the exact contribution of specific caspases and other proteases to injury after H-I is not clear. In this study, we explored the neuroprotective effects of a small, reversible caspase-3 inhibitor M826. M826 selectively and potently inhibited both caspase-3 enzymatic activity and apoptosis in cultured cells in vitro. In a rat model of neonatal H-I, M826 blocked caspase-3 activation and cleavage of its substrates, which begins 6 h and peaks 24 h after H-I. Although M826 significantly reduced DNA fragmentation and brain tissue loss, it did not prevent calpain activation in the cortex. This activation, which is associated with excitotoxic/necrotic cell injury, occurred within 30 min to 2 h after H-I even in the presence of M826. Similar to calpain activation, we found evidence of caspase-2 processing within 30 min to 2 h after H-I that was not affected by M826. Caspase-2 processing appeared to be secondary to calpain-mediated cleavage and was not associated with caspase-2 activation. These data suggest that caspase-3 specifically contributes to delayed cell death and brain injury after neonatal H-I and that calpain activation is associated with and likely a marker for the early component of excitotoxic/necrotic brain injury previously demonstrated in this model. Hypoxic-ischemic (H-I)1 encephalopathy in the prenatal and perinatal period is a major cause of morbidity and mortality and often results in cognitive impairment, seizures, and motor impairment leading to cerebral palsy (1, 2). Many studies of neonatal H-I brain injury have utilized the well characterized Levine model in which unilateral carotid ligation is followed by exposure to hypoxia in postnatal day (P) 7 rats (3-5). This model of H-I results in a reproducible pattern of hemispheric injury ipsilateral, but not contralateral, to the carotid ligation (5-7). There are prominent features of both apoptosis and necrosis when this model is performed in neonatal rats and mice (1, 8 -11). Inhibition of caspases utilizing a pan-caspase inhibitor partially protects against brain injury after neonatal H-I injury in this model (12), and similar inhibitors have been shown to partially protect against ischemic injury in adult models (13-16). Previously utilized peptide-based caspase inhibitors (e.g. Boc-D-fmk, z-VAD-fmk, z-DEVD-fmk) required relatively large doses in vivo for their protective effects, and at high concentrations, their effects are more likely to be less selective. Thus, although these studies suggest a role for caspases, the specific caspases and other proteases, which contribute to brain injury after neonatal H-I, have not been clarified.Caspases are a family of cysteine asp...

We show here that transient forebrain ischemia selectively elevates levels of neuronal apoptosis inhibitory protein (NAIP) in rat neurons that are resistant to the injurious effects of this treatment. This observation suggests that increasing NAIP levels may confer protection against ischemic cell death. Consistent with this proposal, we demonstrate that two other treatments that increase neuronal NAIP levels, systemic administration of the bacterial alkaloid K252a and intracerebral injection of an adenovirus vector capable of overexpressing NAIP in vivo, reduce ischemic damage in the rat hippocampus. Taken together, these findings suggest that NAIP may play a key role in conferring resistance to ischemic damage and that treatments that elevate neuronal levels of this antiapoptotic protein may have utility in the treatment of stroke.

Elevated levels of prostaglandin E 2 (PGE 2 ) are often found in colorectal cancers. Thus, nonsteroidal anti-inflammatory drugs, including selective cyclooxygenase-2 (COX-2) inhibitors, are among the most promising chemopreventive agents for colorectal cancer. However, their long-term use is restricted by the occurrence of adverse events believed to be associated with a global reduction in prostaglandin production. In the present study, we evaluated the chemopreventive efficacy of targeting the terminal synthase microsomal PGE 2 synthase 1 (mPGES-1), which is responsible for generating PGE 2 , in two murine models of intestinal cancer. We report for the first time that genetic deletion of mPGES-1 in Apc-mutant mice results in marked and persistent suppression of intestinal cancer growth by 66%, whereas suppression of large adenomas (>3 mm) was almost 95%. This effect occurred despite loss of Apc heterozygosity and B-catenin activation. However, we found that mPGES-1 deficiency was associated with a disorganized vascular pattern within primary adenomas as determined by CD31 immunostaining. We also examined the effect of mPGES-1 deletion on carcinogen-induced colon cancer. The absence of mPGES-1 reduced the size and number of preneoplastic aberrant crypt foci (ACF). Importantly, mPGES-1 deletion also blocked the nuclear accumulation of B-catenin in ACF, confirming that B-catenin is a critical target of PGE 2 procarcinogenic signaling in the colon. Our data show the feasibility of targeting mPGES-1 for cancer chemoprevention with the potential for improved tolerability over traditional nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors. [Cancer Res 2008;68(9):3251-9]

Genetic mutation and pharmacological inhibition of Bruton's tyrosine kinase (Btk) both have been shown to prevent the development of collagen-induced arthritis (CIA) in mice, providing a rationale for the development of Btk inhibitors for treating rheumatoid arthritis (RA). In the present study, we characterized a novel Btk inhibitor, 6-cyclopro-, in vitro and in rodent models of immune hypersensitivity and arthritis. We demonstrated that RN486 not only potently and selectively inhibited the Btk enzyme, but also displayed functional activities in human cell-based assays in multiple cell types, blocking Fc receptor cross-linking-induced degranulation in mast cells (IC 50 ϭ 2.9 nM), Fc␥ receptor engagement-mediated tumor necrosis factor ␣ production in monocytes (IC 50 ϭ 7.0 nM), and B cell antigen receptor-induced expression of an activation marker, CD69, in B cells in whole blood (IC 50 ϭ 21.0 nM). RN486 displayed similar functional activities in rodent models, effectively preventing type I and type III hypersensitivity responses. More importantly, RN486 produced robust anti-inflammatory and boneprotective effects in mouse CIA and rat adjuvant-induced arthritis (AIA) models. In the AIA model, RN486 inhibited both joint and systemic inflammation either alone or in combination with methotrexate, reducing both paw swelling and inflammatory markers in the blood. Together, our findings not only demonstrate that Btk plays an essential and conserved role in regulating immunoreceptor-mediated immune responses in both humans and rodents, but also provide evidence and mechanistic insights to support the development of selective Btk inhibitors as small-molecule disease-modifying drugs for RA and potentially other autoimmune diseases.

Transient forebrain ischemia produced by four-vessel occlusion (4-VO) triggers the delayed death of CA1 neurons in the hippocampus, resulting in behavioral deficits of spatial learning performance. We demonstrate that CA1 neuronal loss induced by 4-VO (12 min) is preceded by a selective and marked elevation of catalytically active caspase-3 in these neurons, indicative of apoptosis. Virally mediated overexpression of the anti-apoptotic gene X chromosome-linked inhibitor of apoptosis protein (XIAP) prevented both the production of catalytically active caspase-3 and degeneration of CA1 neurons after transient forebrain ischemia. CA1 neurons protected in this manner appeared to function normally, as assessed by immunohistochemical detection of the neuronal activity marker nerve growth factor inducible-A and by spatial learning performance in the Morris water maze. These findings indicate that caspase-3 activation is a key event in ischemic neuronal death and that blockade of this event by XIAP overexpression permits CA1 neurons to survive and operate properly after an ischemic insult.