Antioxidant and Anti-Inflammatory Effects of Garlic in Ischemic Stroke: Proposal of a New Mechanism of Protection through Regulation of Neuroplasticity

Stroke represents one of the main causes of death and disability in the world; despite this, pharmacological therapies against stroke remain insufficient. Ischemic stroke is the leading etiology of stroke. Different molecular mechanisms, such as excitotoxicity, oxidative stress, and inflammation, participate in cell death and tissue damage. At a preclinical level, different garlic compounds have been evaluated against these mechanisms. Additionally, there is evidence supporting the participation of garlic compounds in other mechanisms that contribute to brain tissue recovery, such as neuroplasticity. After ischemia, neuroplasticity is activated to recover cognitive and motor function. Some garlic-derived compounds and preparations have shown the ability to promote neuroplasticity under physiological conditions and, more importantly, in cerebral damage models. This work describes damage/repair mechanisms and the importance of garlic as a source of antioxidant and anti-inflammatory agents against damage. Moreover, we examine the less-explored neurotrophic properties of garlic, culminating in proposals and observations based on our review of the available information. The aim of the present study is to propose that garlic compounds and preparations could contribute to the treatment of ischemic stroke through their neurotrophic effects.

S-allyl cysteine ameliorates heat stress-induced oxidative stress by activating Nrf2/HO-1 signaling pathway in BMECs

Heat stress-induced oxidative stress in bovine mammary epithelial cells (BMECs) threatens the normal growth and development of bovine mammary tissue, resulting in lower milk production of dairy cows. The aim of the present study is to investigate the protective effects of S-allyl cysteine (SAC), an organosulfur component extracted from aged garlic, on heat stress-induced oxidative stress and apoptosis in BMECs and to explore its underlying mechanisms. Our results showed that heat stress treatment considerably decreased cell viability, whereas SAC treatment dose-dependently restored cell viability of BMECs under heat-stress conditions. In addition, SAC protected BMECs from heat stress-induced oxidative damage by inhibiting the excessive accumulation of reactive oxygen species (ROS) and increasing the activity of antioxidant enzymes. It also inhibited heat stress-induced apoptosis by reducing the ratio of Bax/Bcl-2 and blocking proteolytic the cleavage of caspase-3 in BMECs. Interestingly, we found that the protective effect of SAC on heat stress-induced oxidative stress and apoptosis was dependent on the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. SAC promoted the Nrf2 nuclear translocation in heat stress-induced BMECs. The results were also validated by Nrf2 and Keap1 knockdown experiments further demonstrating that Nrf-2 was indeed involved in the protective effect of SAC on heat stress-induced oxidative damage and apoptosis. In summary, our results showed that SAC could protect BMECs from heat stress-induced injury by mediating the Nrf2/HO-1 signaling pathway, suggesting that SAC could be considered as a therapeutic drug for attenuating heat stress-induced mammary gland diseases.

The Enhancing Effects of S-Allylcysteine on Liver Regeneration Are Associated with Increased Expression of mRNAs Encoding IGF-1 and Its Receptor in Two-Thirds Partially Hepatectomized Rats

Two-thirds partial hepatectomy (PHx) was performed in rats, and the differences in effects between S-allylcysteine (SAC) and other sulfur-containing compounds on regeneration of the remaining liver and restoration of the injury were examined. Three days after two-thirds PHx, rats treated with 300 mg/kg/d, per os (p.o.) SAC showed a 1.2-fold increase in liver weight per 100 g body weight compared with saline-treated controls. In contrast, S-methylcysteine (SMC) (300 mg/kg/d, p.o.) or cysteine (Cys) (300 mg/kg/d, p.o.) did not have a regeneration-promoting effect. In the comparison with control rats, the regenerating liver of SAC-treated rats showed a significantly higher 5-bromo-2'-deoxyuridine labeling index on day 1. In contrast, serum alanine aminotransferase activity, which increases following PHx, was significantly inhibited by SAC and SMC (but not Cys) on day 1 after two-thirds PHx. In addition, SAC induced increases in insulin-like growth factor (IGF)-1 and its receptor mRNA expressions at 1 h after two-thirds PHx, and it increased phosphorylation of extracellular signal-regulated kinase (ERK)2 and Akt at 3 h after two-thirds PHx without affecting serum growth hormone levels. These results demonstrate that SAC is a mitogenic effector of normal remnant liver and promotes recuperation of liver function after two-thirds PHx. Moreover, SAC-induced proliferative effects are mediated via increased mRNA expressions of IGF-1 and its receptor and subsequent phosphorylation of ERK2 and Akt.

Essential oils from two Allium species exert effects on cell proliferation and neuroblast differentiation in the mouse dentate gyrus by modulating brain-derived neurotrophic factor and acetylcholinesterase

Background

In the present study, we investigated the effects of oil products from two Allium species: Allium sativum (garlic) and Allium hookeri (Chinese chives) on cell proliferation and neuroblast differentiation in the mouse dentate gyrus.

Methods

Using corn oil as a vehicle, the essential oil from garlic (10 ml/kg), or Chinese chives (10 ml/kg) was administered orally to 9-week-old mice once a day for 3 weeks. One hour following the last treatment, a novel object recognition test was conducted and the animals were killed 2 h after the test.

Results

In comparison to the vehicle-treated group, garlic essential oil (GO) treatment resulted in significantly increased exploration time and discrimination index during the novel object recognition test, while Chinese chives essential oil (CO) reduced the exploration time and discrimination index in the same test. In addition, the number of Ki67-immunoreactive proliferating cells and doublecortin-immunoreactive neuroblasts significantly increased in the dentate gyrus of GO-treated animals. However, administration of CO significantly decreased cell proliferation and neuroblast differentiation. Administration of GO significantly increased brain-derived neurotrophic factor (BDNF) levels and decreased acetylcholinesterase (AChE) activity in the hippocampal homogenates. In contrast, administration of CO decreased BDNF protein levels and had no significant effect on AChE activity, compared to that in the vehicle-treated group.

Conclusions

These results suggest that GO significantly improves novel object recognition as well as increases cell proliferation and neuroblast differentiation, by modulating hippocampal BDNF protein levels and AChE activity, while CO impairs novel object recognition and decreases cell proliferation and neuroblast differentiation, by reducing BDNF protein levels in the hippocampus.

Systemic administration of low dosage of tetanus toxin decreases cell proliferation and neuroblast differentiation in the mouse hippocampal dentate gyrus

In the present study, we investigated the effect of Tetaus toxin (TeT) on cell proliferation and neuroblast differentiation using specific markers: 5-bromo-2-deoxyuridine (BrdU) as an exogenous marker for cell proliferation, Ki-67 as an endogenous marker for cell proliferation and doublecortin (DCX) as a marker for neuroblasts in the mouse hippocampal dentate gyrus (DG) after TeT treatment. Mice were intraperitoneally administered 2.5 and 10 ng/kg TeT and sacrificed 15 days after the treatment. In both the TeT-treated groups, no neuronal death occurred in any layers of the DG using neuronal nuclei (NeuN, a neuron nuclei maker) and Fluoro-Jade B (F-J B, a high-affinity fluorescent marker for the localization of neuronal degeneration). In addition, no significant change in glial activation in both the 2.5 and 10 ng/kg TeT-treated-groups was found by GFAP (a marker for astrocytes) and Iba-1 (a marker for microglia) immunohistochemistry. However, in the 2.5 ng/kg TeT-treated-group, the mean number of BrdU, Ki-67 and DCX immunoreactive cells, respectively, were apparently decreased compared to the control group, and the mean number of each in the 10 ng/kg TeT-treated-group was much more decreased. In addition, processes of DCX-immunoreactive cells, which projected into the molecular layer, were short compared to those in the control group. In brief, our present results show that low dosage (10 ng/kg) TeT treatment apparently decreased cell proliferation and neuroblast differentiation in the mouse hippocampal DG without distinct gliosis as well as any loss of adult neurons.

Diallyl disulfide impairs hippocampal neurogenesis in the young adult brain

Garlic and garlic extracts are used as seasonings and are generally considered beneficial to human health, which include antioxidant and neuroprotective properties in neurological disorders. In the present study, we examined the effects of garlic sulfur components on the proliferation of neural progenitor cells (NPCs) and hippocampal neurogenesis. Of the sulfur compounds extracted, diallyl disulfide (DADS) significantly suppressed the proliferation of NPCs, whereas other sulfur containing components had no effect. In order to investigate the effect of DADS on adult hippocampal neurogenesis, DADS was administered orally to young (6 week-old) male C57BL/6 mice for 2 weeks. It was found that 10 mg/kg of DADS significantly decreased the proliferation of NPCs in the dentate gyrus without affecting the survival of newly generated cells. Furthermore, DADS decreased levels of hippocampal BDNF, phosphorylated CREB signaling, and phosphorylated ERKs, which are known to be related to hippocampal neurogenesis and NPCs proliferation. In addition, DADS induced significant memory defects as compared with controls. We report that DADS may have adverse effects on hippocampal neurogenesis and neurocognitive functions by modulating ERK and BDNF-CREB signaling, and suggest that the advisability of consuming large amounts of garlic products should be considered, particularly during the period of neural growth.