Oxidative stress.

Oxidative stress causes neural damage and inhibits essential cellular
processes, such as synaptic transmission. Despite this knowledge, currently
available pharmaceutical agents cannot effectively protect neural cells from acute
oxidative stress elicited by strokes, heart attacks, and traumatic brain injuries in a
real life clinical setting. Our lab has developed an electrophysiology protocol to
identify novel drugs that protect an essential cellular process (neurotransmission)
from acute oxidative stress-induced damage. Through this doctoral dissertation,
we have identified three new drugs, including a Big K+ (BK) K+ channel blocker
(iberiotoxin), resveratrol, and a custom made resveratrol-like compound (fly2) that
protect synaptic function from oxidative stress-induced insults. Further developing
these drugs as neuroprotective agents may prove transformative in protecting the
human brain from acute oxidative stress elicited by strokes, heart attacks, and
traumatic brain injuries. Inhibiting the protein kinase G (PKG) pathway protects neurotransmission
from acute oxidative stress. This dissertation has expanded upon these findings
by determining that the PKG pathway and BK K+ channels function through
independent biochemical pathways to protect neurotransmission from acute
oxidative stress. Taken together, this dissertation has identified two classes of
compounds that protect neurotransmission from acute oxidative stress, including
resveratrol-like compounds (resveratrol, fly2) and a BK K+ channel inhibitor
(iberiotoxin). Further developing these drugs in clinical trials may finally lead to the
development of an effective neuroprotective agent.

The inevitable aging process can be partially attributed to the accumulation of
oxidative damage that results from the action of free radicals. Methionine sulfoxide
reductases (Msr) are a class of enzymes that repair oxidized methionine residues. The
two known forms of Msr are MsrA and MsrB which reduce the R- and S- enantiomers of
methionine sulfoxide, respectively. Our lab has created the first genetic animal model
that is fully deficient for any Msr activity. Previously our lab showed that these animals
exhibit a 20 hour delay in development of the third instar larvae (unpublished data). My
studies have further shown that the prolonged third-instar stage is due to a reduced
growth rate associated with slower food intake and a markedly slower motility. These
Msr-deficient animals also exhibit decreased egg-laying that can be attributed to a lack of
female receptivity to mating.

Oxidative stress (OS) is strongly implicated in age-related neurodegeneration and
other diseases. Under OS, the production of excessive oxidants leads to increased
damages to cellular components. Recently, RNA has been discovered as a major target of
oxidative damage, including the creation of abasic sites. In this work, we developed a
method for quantifying abasic RNA in cell. Using this method, we have examined the
potential role of the RNA-processing cellular foci, stress granule (SG) and processing
bodies (PB) in eliminating abasic RNA in situ. We demonstrated that RNA is a major
target of oxidative damage, constituting the majority of OS-induced abasic nucleic acids
in HeLa cell. Importantly, the level of abasic RNA is strongly correlated with SG
abundance. Furthermore, inhibition of SG/PB formation causes accumulation of abasic
RNA, suggesting that SG/PB participates in removing oxidized RNA and protects cells
under OS, which offers novel targets for therapeutic intervention in age-related diseases.