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Bioluminescence Imaging of NADPH Oxidase Activity in Different Animal Models
Published on: October 22, 2012
NADPH oxidase 2 as a potential therapeutic target for protection against cognitive deficits following systemic
Wan-Yu Huang1, Ko-Hung Liu2, Shankung Lin2
1Institute of Basic Medicine, College of Medicine, National Cheng-Kung University, Tainan, Taiwan; Pediatrics of Kung-Ten General Hospital, Taichung City, Taiwan.
Background:
Research indicates that sepsis increases the risk of developing cognitive impairment. After systemic inflammation, a corresponding activation of microglia is rapidly induced in the brain, and multiple neurotoxic factors, including inflammatory mediators (e.g., cytokines) and reactive oxygen species (e.g., superoxide), are also released that contribute to neuronal injury. NADPH oxidase (NOX) enzymes play a vital role in microglial activation through the generation of superoxide anions. We hypothesized that NOX isoforms, particularly NOX2, could exhibit remarkable abilities in developing cognitive deficits induced by systemic inflammation.
Methods:
Mice with deficits of NOX2 organizer p47phox (p47phox-/-) and wild-type (WT) mice treated with the NOX inhibitor diphenyleneiodonium (DPI) were used in this study. Intraperitoneal lipopolysaccharide (LPS) injection was used to induce systemic inflammation. Spatial learning and memory were compared among treatment groups using the radial arm maze task. Brain tissues were collected for evaluating the transcript levels of proinflammatory cytokines, whereas immunofluorescence staining and immunoblotting were conducted to determine the percentage of activated glia (microglia and astroglia) and damaged neurons and the expression of synaptic proteins and BDNF.
Results:
Cognitive impairment induced by systemic inflammation was significantly attenuated in the p47phox-/- mice compared to that in the WT mice. The p47phox-/- mice exhibited reduced microglial and astroglial activation and neuronal damage and attenuated the induction of multiple proinflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and CCL2. Similar to that observed in the p47phox-/- mice, the administration of DPI significantly attenuated the cognitive impairment, reduced the glial activation and brain cytokine concentrations, and restored the expression of postsynaptic proteins (PSD-95) and BDNF in neurons and astrocytes, compared to those in the vehicle-treated controls within 10 days after LPS injection.
Conclusions:
This study clearly demonstrates that NOX2 contributes to glial activation with subsequent reduction in the expression of BDNF, synaptic dysfunction, and cognitive deficits after systemic inflammation in an LPS-injected mouse model. Our results provide evidence that NOX2 might be a promising pharmacological target that could be used to protect against synaptic dysregulation and cognitive impairment following systemic inflammation.
Insights
Systemic inflammation causes cognitive impairment by activating microglia. Inhibiting NADPH oxidase 2 (NOX2) in mice reduced this inflammation-induced cognitive decline, suggesting NOX2 as a potential therapeutic target.
Area of Science:
- Neuroscience
- Immunology
- Pharmacology
Background:
- Sepsis and systemic inflammation are linked to increased risk of cognitive impairment.
- Microglial activation and release of neurotoxic factors, including cytokines and reactive oxygen species, contribute to neuronal injury during inflammation.
- NADPH oxidase (NOX) enzymes, particularly NOX2, are critical for superoxide generation during microglial activation.
Purpose of the Study:
- To investigate the role of NOX isoforms, specifically NOX2, in the development of cognitive deficits induced by systemic inflammation.
- To evaluate the therapeutic potential of targeting NOX2 for preventing inflammation-associated cognitive impairment.
Main Methods:
- Utilized p47phox knockout mice (lacking NOX2 organizer) and wild-type mice treated with the NOX inhibitor diphenyleneiodonium (DPI).
- Induced systemic inflammation using intraperitoneal lipopolysaccharide (LPS) injection.
- Assessed spatial learning and memory via radial arm maze; analyzed brain cytokine levels, glial activation, neuronal damage, synaptic protein expression (PSD-95), and BDNF levels.
Main Results:
- Mice deficient in p47phox showed significantly attenuated cognitive impairment, reduced glial activation, and lower levels of proinflammatory cytokines (TNF-α, IL-1β, IL-6, CCL2) post-LPS.
- DPI treatment mirrored these protective effects, reducing cognitive deficits, glial activation, and cytokine concentrations while restoring PSD-95 and BDNF expression.
- Both genetic deficiency of NOX2 and pharmacological inhibition demonstrated neuroprotective effects against LPS-induced cognitive dysfunction.
Conclusions:
- NOX2 plays a significant role in mediating glial activation, synaptic dysfunction, and cognitive deficits following systemic inflammation.
- Inhibition of NOX2 effectively protects against inflammation-induced cognitive impairment and synaptic dysregulation in a mouse model.
- NOX2 represents a promising pharmacological target for developing treatments to prevent cognitive decline associated with systemic inflammation.
