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Evidence indicates that nitrosative stress and mitochondrial dysfunction participate in the pathogenesis of Alzheimer's disease (AD). Amyloid beta (Aβ) and peroxynitrite induce mitochondrial fragmentation and neuronal cell death by abnormal activation of dynamin-related protein 1 (DRP1), a large GTPase that regulates mitochondrial fission. The exact mechanisms of mitochondrial fragmentation and DRP1 overactivation in AD remain unknown; however, DRP1 serine 616 (S616) phosphorylation is likely involved. Although it is clear that nitrosative stress caused by peroxynitrite has a role in AD, effective antioxidant therapies are lacking. Cerium oxide nanoparticles, or nanoceria, switch between their Ce(3+) and Ce(4+) states and are able to scavenge superoxide anions, hydrogen peroxide and peroxynitrite. Therefore, nanoceria might protect against neurodegeneration. Here we report that nanoceria are internalized by neurons and accumulate at the mitochondrial outer membrane and plasma membrane. Furthermore, nanoceria reduce levels of reactive nitrogen species and protein tyrosine nitration in neurons exposed to peroxynitrite. Importantly, nanoceria reduce endogenous peroxynitrite and Aβ-induced mitochondrial fragmentation, DRP1 S616 hyperphosphorylation and neuronal cell death.

Although the identification of specific genes that regulate apoptosis has been a topic of intense study, little is known of the role that background genetic variance plays in modulating cell death. Using germ cells from inbred mouse strains, we found that apoptosis in mature (metaphase II) oocytes is affected by genetic background through at least two different mechanisms. The first, manifested in AKR/J mice, results in genomic instability. This is reflected by numerous DNA double-strand breaks in freshly isolated oocytes, causing a high apoptosis susceptibility and impaired embryonic development following fertilization. Microinjection of Rad51 reduces DNA damage, suppresses apoptosis and improves embryonic development. The second, manifested in FVB mice, results in dramatic dimorphisms in mitochondrial ultrastructure. This is correlated with cytochrome c release and a high apoptosis susceptibility, the latter of which is suppressed by pyruvate treatment, Smac/DIABLO deficiency, or microinjection of 'normal' mitochondria. Therefore, background genetic variance can profoundly affect apoptosis in female germ cells by disrupting both genomic DNA and mitochondrial integrity.

The IkappaB kinase (IKK) complex is composed of three subunits, IKKalpha, IKKbeta, and IKKgamma (NEMO). While IKKalpha and IKKbeta are highly similar catalytic subunits, both capable of IkappaB phosphorylation in vitro, IKKgamma is a regulatory subunit. Previous biochemical and genetic analyses have indicated that despite their similar structures and in vitro kinase activities, IKKalpha and IKKbeta have distinct functions. Surprisingly, disruption of the Ikkalpha locus did not abolish activation of IKK by proinflammatory stimuli and resulted in only a small decrease in nuclear factor (NF)-kappaB activation. Now we describe the pathophysiological consequence of disruption of the Ikkbeta locus. IKKbeta-deficient mice die at mid-gestation from uncontrolled liver apoptosis, a phenotype that is remarkably similar to that of mice deficient in both the RelA (p65) and NF-kappaB1 (p50/p105) subunits of NF-kappaB. Accordingly, IKKbeta-deficient cells are defective in activation of IKK and NF-kappaB in response to either tumor necrosis factor alpha or interleukin 1. Thus IKKbeta, but not IKKalpha, plays the major role in IKK activation and induction of NF-kappaB activity. In the absence of IKKbeta, IKKalpha is unresponsive to IKK activators.

In apoptosis, Bcl-2-family proteins regulate the barrier function of the mitochondrial outer membrane (MOM), controlling the release of proapoptotic proteins from the intermembrane space into the cytoplasm. This process can be studied in vitro with freshly isolated mouse liver mitochondria. Unfortunately, mitochondria frozen/thawed in standard sucrose–mannitol buffers become leaky and useless for apoptosis research. However, here we show that mitochondria frozen in buffer containing the sugar, trehalose, maintained MOM integrity and responsiveness to Bcl-2-family proteins, much like fresh mitochondria. Trehalose also preserved ultrastructure, as well as biological functions such as ATP synthesis, calcium-induced swelling, transmembrane potential, and the import and processing of protein precursors. However, bioenergetic function was somewhat reduced. Thus, trehalose-frozen mitochondria retained most of the biological features of mitochondria including MOM integrity. Although not ideal for studies involving bioenergetics, this method will facilitate research on apoptosis and other mitochondrial functions that rely on an intact MOM.Cell Death and Differentiation (2007) 14, 616–624. doi:10.1038/sj.cdd.4402035; published online 15 September 2006 [ABSTRACT FROM AUTHOR]