SIRT1 Inhibits High Shear Stress-Induced Apoptosis in Rat Cortical Neurons

Urtica pilulifera L. seed extract promotes folliculogenesis and alleviates the diminished ovarian reserve in the Balb/c mice model: An experimental study

Background

Urtica pilulifera L. seed (UPS) is a Persian traditional medicine prescription that positively affects female infertility.

Objective

This study aimed to evaluate the beneficial effects of UPS on a diminished ovarian reserve (DOR) model induced by cyclophosphamide in Balb/c mice.

Materials and Methods

A single intraperitoneal (75 mg/kg) of cyclophosphamide was administered to establish a DOR model. 25 female Balb/c mice (6-8 wk, 25 ± 2 gr) were randomly divided into 5 groups (n = 5/each), including control (normal saline), model (DOR), DOR+50, DOR+100, and DOR+200 (mg/kg UPS, gavage) groups for 14 days. The levels of follicle-stimulating hormone, luteinizing hormone, estradiol, malondialdehyde, superoxide dismutases, apoptosis, and histopathological alterations were analyzed. Gas chromatography-mass spectrometry analysis was performed to identify the phytochemicals of the UPS.

Results

It was observed that the UPS extract reduced malondialdehyde concentration and apoptosis in the DOR model as well as enhanced superoxide dismutases activity in the ovaries in a dose-dependent manner. Moreover, it exerted a modulatory effect on steroidal hormones such as follicle-stimulating hormone, luteinizing hormone, and estradiol. The histopathological analysis revealed the therapeutic potential of the UPS extract. The main chemical components of UPS were linoleic acid (59.25%), n-hexadecanoic acid (10.36%), and oleic acid (8.29%).

Conclusion

The results indicated that the UPS extract has therapeutic potential in the DOR model. This potential is attributed to the reduction of oxidative stress, modulation of apoptosis, and regulation of steroidal hormones that may be associated with the observed beneficial effects of fatty acids on fertility improvement.

P‑hydroxybenzyl alcohol ameliorates neuronal cerebral ischemia‑reperfusion injury by activating mitochondrial autophagy through SIRT1

Mitochondrial autophagy serves a key role in clearing damaged mitochondria. P‑hydroxybenzyl alcohol (pHBA) can improve neuronal injury induced by cerebral ischemia‑reperfusion (I/R). However, the mechanism of pHBA improving I/R damage through the mitochondrial pathway remains unclear. A rat model of middle cerebral artery occlusion and reperfusion (MCAO/R) was used in the present study. The rats were treated with sirtuin 1 (SIRT1) inhibitor EX527 and pHBA for 7 days, followed by reperfusion. At 24 h after reperfusion, the infarct size was calculated and the severity of nerve damage was evaluated. Hematoxylin and eosin and Nissl staining revealed cellular changes in the ischemic penumbra. Changes in mitochondrial structure were observed using electron microscopy. Mitochondrial function was evaluated by detecting mitochondrial membrane potential (MMP), mitochondrial permeability transition pore (mPTP) and ATP levels using commercially available kits. In addition, the ischemic penumbra tissues were used for immunofluorescence staining for p62 and LC3 proteins. The expression of SIRT1 and mitochondrial autophagy‑related proteins, PTEN‑induced kinase 1 (PINK1) and Parkin, were detected by western blotting. Finally, apoptosis was analyzed by TUNEL staining and the expression of apoptosis‑related proteins (Bax, Bcl‑2 and Caspase‑3) by western blotting. The results suggested that postoperative pHBA treatment may reduce the size of cerebral infarction and damage to the nervous system, and may improve cell damage in the ischemic penumbra of MCAO/R rats. Compared with rats in the untreated MCAO/R group, the mitochondrial structure of the pHBA‑treated group was improved, the levels of MMP and ATP were increased, and the degree of opening of mPTP was decreased. Simultaneously, immunofluorescence and western blotting results showed that compared with the MCAO/R group, the number of LC3‑ and TUNEL‑positive cells increased, the number of p62‑positive cells decreased, SIRT1 and autophagy protein (PINK1, Parkin and LC3 II/I) expression levels increased and p62 expression decreased in the pHBA group. However, these improvements were blocked by treatment with EX527. In summary, results from the present study suggested that pHBA may improve neuronal injury in the ischemic penumbra of MCAO/R rats through SIRT1‑activated mitochondrial autophagy and mitochondrial‑mediated neuronal apoptosis.

Mechanical Stretch Promotes Neurite Outgrowth of Primary Cultured Dorsal Root Ganglion Neurons via Suppression of Semaphorin 3A-Neuropilin-1/Plexin-A1 Signaling

Significant attempts have been made to promote neuronal extension and migration in nerve development and regeneration. Although mechanical stretch induces persistent elongation of the axon, the underlying molecular mechanisms are not yet clear. Some axonal guidance cues secreted in the growth cone that affect the axonal growth could attract or repel axons in neurite connection. As semaphorin 3A (Sema3A) is an important repulsion guidance molecule, inhibition of Sema3A has been postulated to promote neuronal development. In this study, the effects of mechanical stretch on dorsal root ganglion neuronal growth and the underlying mechanisms were investigated by assessing the extension direction, neurite length, cell body size, mitochondrial membrane potential, and the expression of Sema3A and its receptors. Our results showed that cell viability significantly increased at tensile strains of 2.5, 5, and 10% for 4 h, with the most prominent effect at 5% tensile strain. Moreover, neurons migrated closer to the stretching direction at 5% tensile strain (0-12 h), while the neurons of the control group moved in a disorderly manner. Furthermore, Sema3A-Neuropilin-1/Plexin-A1 signaling pathway was found to be suppressed after mechanical stretch at 5% tensile strain for 4 h by immunofluorescence staining, immunoprecipitation, and western blot assay. Finally, a Sema3A-SiRNA (SiRNA = small interfering RNA) treatment led to remarkable guidance growth in the stretch-grown neurons. Importantly, there was significant decrease of repulsive cue Sema3A expression and remarkable increase of attractive molecule Netrin-1 expression after mechanical stretching treatment, which jointly promoted neurite outgrowth. This study provides a promising new approach for the development of mechanical stretching therapy or guidance factor-related drugs in injured neuronal regeneration.

Role of sirtuin 1 in the brain development in congenital hypothyroidism rats via the regulation of p53 signaling pathway

The present study aimed to investigate the expression, role, and underlying mechanism of action of sirtuin 1 (SIRT1) in congenital hypothyroidism (CH). A CH model was established in rats, and neuronal cells were isolated from the hippocampal tissues of normal rats. Free thyroxine (fT4) and thyroid-Stimulating hormone (TSH) concentrations were determined to confirm CH model conduction. The cognitive behavior of rats with CH was examined using open field and forced swimming tests. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression levels of SIRT1, p53, B-cell lymphoma-extra-large (Bcl-xl), Bcl-2-associated X (Bax), and cytochrome c in the hippocampal tissues and neuronal cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and flow cytometry were performed to evaluate cell viability and apoptosis, respectively. The results revealed that SIRT1 was expressed at low levels in the hippocampal tissues of rats with CH. Moreover, overexpression of SIRT1 in the hippocampal tissues of rats with CH and improved rat behavior, while reducing the CH-induced nerve cell apoptosis. In addition, this overexpression increased the viability, inhibited apoptosis, and reduced the expression of p53, Bax, and cytochrome c, while increasing the expression of Bcl-xl in cultured neurons. In contrast, SIRT1-small interfering RNA exhibited the opposite effects in cultured neurons. In conclusion, SIRT1 plays a role in the occurrence and development of CH by regulating nerve cell apoptosis.

MICU3 regulates mitochondrial Ca2+-dependent antioxidant response in skeletal muscle aging

Age-related loss of skeletal muscle mass and function, termed sarcopenia, could impair the quality of life in the elderly. The mechanisms involved in skeletal muscle aging are intricate and largely unknown. However, more and more evidence demonstrated that mitochondrial dysfunction and apoptosis also play an important role in skeletal muscle aging. Recent studies have shown that mitochondrial calcium uniporter (MCU)-mediated mitochondrial calcium affects skeletal muscle mass and function by affecting mitochondrial function. During aging, we observed downregulated expression of mitochondrial calcium uptake family member3 (MICU3) in skeletal muscle, a regulator of MCU, which resulted in a significant reduction in mitochondrial calcium uptake. However, the role of MICU3 in skeletal muscle aging remains poorly understood. Therefore, we investigated the effect of MICU3 on the skeletal muscle of aged mice and senescent C2C12 cells induced by d-gal. Downregulation of MICU3 was associated with decreased myogenesis but increased oxidative stress and apoptosis. Reconstitution of MICU3 enhanced antioxidants, prevented the accumulation of mitochondrial ROS, decreased apoptosis, and increased myogenesis. These findings indicate that MICU3 might promote mitochondrial Ca²⁺ homeostasis and function, attenuate oxidative stress and apoptosis, and restore skeletal muscle mass and function. Therefore, MICU3 may be a potential therapeutic target in skeletal muscle aging.

Gongjin-Dan Enhances Neurite Outgrowth of Cortical Neuron by Ameliorating H2O2-Induced Oxidative Damage via Sirtuin1 Signaling Pathway

Gongjin-dan (GJD) is a multiherbal formula produced from 10 medicinal herbs and has been traditonally used as an oriental medicine to treat cardiovascular diseases, alcoholic hepatitis, mild dementia, and anemia. Additionally, increasing evidence suggests that GJD exerts neuroprotective effects by suppressing inflammation and oxidative stress-induced events to prevent neurological diseases. However, the mechanism by which GJD prevents oxidative stress-induced neuronal injury in a mature neuron remains unknown. Here, we examined the preventive effect and mechanism of GJD on primary cortical neurons exposed to hydrogen peroxide (H2O2). In the neuroprotection signaling pathway, Sirtuin1 is involved in neuroprotective action as a therapeutic target for neurological diseases. After pre-treatment with GJD at three concentrations (10, 25, and 50 µg/mL) and stimulation by H2O2 (30 µM) for 24 h, the influence of GJD on Sirtuin1 activation was assessed using immunocytochemistry, real-time PCR, western blotting, and flow cytometry. GJD effectively ameliorated H2O2-induced neuronal death against oxidative damage through Sirtuin1 activation. In addition, GJD-induced Sirtuin1 activation accelerated elongation of new axons and formation of synapses via increased expression of nerve growth factor and brain-derived neurotrophic factor, as well as regeneration-related genes. Thus, GJD shows potential for preventing neurological diseases via Sirtuin1 activation.