Mitochondrial base excision repair pathway failed to respond to status epilepticus induced by pilocarpine

Dynamic-related protein 1 inhibitor eases epileptic seizures and can regulate equilibrative nucleoside transporter 1 expression

Background

Dynamic-related protein 1 (Drp1) is a key protein involved in the regulation of mitochondrial fission, and it could affect the dynamic balance of mitochondria and appears to be protective against neuronal injury in epileptic seizures. Equilibrative nucleoside transporter 1 (ENT1) is expressed and functional in the mitochondrial membrane that equilibrates adenosine concentration across membranes. Whether Drp1 participates in the pathogenesis of epileptic seizures via regulating function of ENT1 remains unclear.

Methods

In the present study, we used pilocarpine to induce status epilepticus (SE) in rats, and we used mitochondrial division inhibitor 1 (Mdivi-1), a selective inhibitor to Drp1, to suppress mitochondrial fission in pilocarpine-induced SE model. Mdivi-1administered by intraperitoneal injection before SE induction, and the latency to firstepileptic seizure and the number of epileptic seizures was thereafter observed. The distribution of Drp1 was detected by immunofluorescence, and the expression patterns of Drp1 and ENT1 were detected by Western blot. Furthermore, the mitochondrial ultrastructure of neurons in the hippocampal CA1 region was observed by transmission electron microscopy.

Results

We found that Drp1 was expressed mainly in neurons and Drp1 expression was significantly upregulated in the hippocampal and temporal neocortex tissues at 6 h and 24 h after induction of SE. Mitochondrial fission inhibitor 1 attenuated epileptic seizures after induction of SE, reduced mitochondrial damage and ENT1 expression.

Conclusions

These data indicate that Drp1 is upregulated in hippocampus and temporal neocortex after pilocarpine-induced SE and the inhibition of Drp1 may lead to potential therapeutic target for SE by regulating ENT1 after pilocarpine-induced SE.

Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model

Though succinate accumulation is associated with reactive oxygen species (ROS) production and neuronal injury, which play critical roles in epilepsy, it is unclear whether succinate accumulation contributes to the onset of epilepsy or seizures. We sought to investigate changes in succinate, oxidative stress, and mito-SOX levels, as well as mitophagy and neuronal change, in different status epilepticus (SE) rat models. Our results demonstrate that KA-induced SE was accompanied by increased levels of succinate, oxidative stress, and mito-SOX, as well as mitophagy and neuronal degeneration. The similarly increased levels of succinate, oxidative stress, and mito-SOX were also found in pilocarpine-induced SE. Moreover, the reduction of succinate accumulation by the inhibition of succinate dehydrogenase (SDH), malate/aspartate shuttle (MAS), or purine nucleotide cycle (PNC) served to reduce succinate, oxidative stress, and mito-SOX levels, thereby preventing oxidative stress-related neuronal damage and lessening seizure severity. Interestingly, simulating succinate accumulation with succinic acid dimethyl ester may induce succinate accumulation and increased oxidative stress and mito-SOX levels, as well as behavior and seizures in electroencephalograms similar to those observed in rats exposed to KA. Our results indicate that succinate accumulation may contribute to the increased oxidative stress/mitochondrial ROS levels, neuronal degeneration, and SE induced by KA administration. Furthermore, we found that succinate accumulation was mainly due to the inverse catalysis of SDH from fumarate, which was supplemented by the MAS and PNC pathways. These results reveal new insights into the mechanisms underlying SE and that reducing succinate accumulation may be a clinically useful therapeutic target in SE.

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KA- or pilocarpine-induced SE was accompanied by succinate accumulation.

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Succinate accumulation caused elevated ROS/mito-ROS levels and neuronal injury.

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Inverse catalysis of SDH from fumarate mainly caused succinate accumulation.

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Inhibiting succinate accumulation relieved oxidative stress level, neuronal injury, and seizure.

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Simulating succinate accumulation induced elevated oxidative stress level and seizure.

Mitophagy in Refractory Temporal Lobe Epilepsy Patients with Hippocampal Sclerosis

This study aimed to determine if there is an association between mitophagy and refractory temporal lobe epilepsy (rTLE) with hippocampal sclerosis. During epilepsy surgery, we collected tissue samples from the hippocampi and temporal lobe cortexes of rTLE patients with hippocampal sclerosis (as diagnosed by a pathologist). Transmission electron microscopy (TEM) was used to study the ultrastructural features of the tissue. To probe for mitophagy, we used fluorescent immunolabeling to determine if mitochondrial and autophagosomal markers colocalized. Fourteen samples were examined. TEM results showed that early autophagosomes were present and mitochondria were impaired to different degrees in hippocampi. Immunofluorescent labeling showed colocalization of the autophagosome marker LC3B with the mitochondrial marker TOMM20 in hippocampi and temporal lobe cortexes, indicating the presence of mitophagy. Mitochondrial and autophagosomal marker colocalization was lower in hippocampus than in temporal lobe cortex (P < 0.001). Accumulation of autophagosomes and mitophagy activation are implicated in rTLE with hippocampal sclerosis. Aberrant accumulation of damaged mitochondria, especially in the hippocampus, can be attributed to defects in mitophagy, which may participate in epileptogenesis.

Wound healing potential of naringin ointment formulation via regulating the expression of inflammatory, apoptotic and growth mediators in experimental rats

CONTEXT

Wound healing is a consequence of a complex process involving inflammatory, proliferative, and remodeling phases. Naringin, a flavanone glycoside, is associated with modulation of various oxido-inflammatory and growth factors.

AIM

The aim of this study is to evaluate the wound-healing activity of naringin ointment formulation (NOF) on experimental wound models.

MATERIALS AND METHODS

A soft paraffin-based cream containing 1, 2, and 4% (w/w) naringin was formulated and evaluated for physicochemical characters. Excision wounds and incisions wounds were used to study the topical effect of NOF for 20 d (once a day) on various biochemical, molecular, and histological parameters.

RESULTS

NOF (2 and 4%, w/w) treatment showed a significant decrease (p < 0.05) in wound area and epithelization period whereas the rate of wound contraction increased significantly (p < 0.05). The altered levels of oxido-nitrosative stress (SOD, GSH, MDA, MPO, and NO) were significantly (p < 0.05) restored by NOF. Treatment produced a significant increase (p < 0.05) in tensile strength, hydroxyproline content, and protein content. TNF-α, IL-1β, IL-6, IL-8, NF-κB, smad-7, and Bax mRNA expression were significantly down-regulated (p < 0.05) by NOF, whereas polymerase gamma (pol-γ), smad-3, VEGF and TGF-β, and collagen-1 mRNA expressions were significantly up-regulated (p < 0.05) by NOF. Histological alterations in wound skin were also restored by NOF.

CONCLUSION

NOF exerts wound healing potential via down-regulated expression of inflammatory (NF-κB, TNF-α, and ILs), apoptotic (pol-γ and Bax), and up-regulated growth factor (VEGF and TGF-β) expression, thus modulating collagen-1 expression to induce angiogenesis leading to wound healing.

Base excision repair in physiology and pathology of the central nervous system

Relatively low levels of antioxidant enzymes and high oxygen metabolism result in formation of numerous oxidized DNA lesions in the tissues of the central nervous system. Accumulation of damage in the DNA, due to continuous genotoxic stress, has been linked to both aging and the development of various neurodegenerative disorders. Different DNA repair pathways have evolved to successfully act on damaged DNA and prevent genomic instability. The predominant and essential DNA repair pathway for the removal of small DNA base lesions is base excision repair (BER). In this review we will discuss the current knowledge on the involvement of BER proteins in the maintenance of genetic stability in different brain regions and how changes in the levels of these proteins contribute to aging and the onset of neurodegenerative disorders.

Status epilepticus stimulates peroxisome proliferator-activated receptor γ coactivator 1-α/mitochondrial antioxidant system pathway by a nitric oxide-dependent mechanism

Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1-α (PGC-1α) is a transcriptional coactivator identified as an upstream regulator of lipid catabolism, mitochondrial number and function. PGC-1α protects neurons against oxidative damage by inducing several members of the mitochondrial antioxidant system such as superoxide dismutase 2 (SOD2) and uncoupling protein 2 (UCP2). Its role in seizure-induced oxidative stress has not been studied. Here we showed that pilocarpine-induced status epilepticus (SE) stimulates the PGC-1α/mitochondrial antioxidant system signaling pathway in the rat hippocampus. Because nitric oxide (NO) is the key factor of mitochondrial biogenesis through the transcriptional induction of PGC-1α, we investigated whether NO is involved in activation of the PGC-1α/mitochondrial antioxidant system after SE. Treatment with the NO synthase (NOS) inhibitor N(G)-nitro-l-argininemethyl ester (l-NAME) attenuated the increased expression of the PGC-1α/mitochondrial antioxidant system after SE and enhanced oxidative stress. These results suggest that SE can induce the PGC-1α/mitochondrial antioxidant system signaling pathway, which may represent a protective mechanism against SE-induced oxidative stress. Furthermore, NO may positively regulate the mitochondrial antioxidant system by inducing PGC-1α in pilocarpine-induced SE.