Stroke is one of the leading causes of death worldwide. Nearly 6 million people die from stroke each year, and it is estimated that the lifetime risk for stroke is 8% to 10%. Ischemic stroke accounts for 85% of all strokes, while hemorrhagic stroke accounts for 15% [1
]. The hazards associated with ischemic stroke are mainly caused by cerebral ischemia and reperfusion injury (CI/RI), which is a pathological condition characterized by an initial restriction of blood supply to an organ followed by the subsequent restoration of perfusion and concomitant reoxygenation [2
]. Additionally, ischemia and reperfusion injury contribute to pathologies under a wide range of conditions, mainly including energy metabolism disorders, oxidative stress, inflammatory stress [4
] and cytokine damage glutamate toxicity, Ca2+
overload, excessive nitric oxide (NO) synthesis, apoptosis, and many other factors [3
]. CI/RI and the secondary damage it causes to brain tissues are closely associated with immunity and inflammation responses [4
]. In past decades, to explore better treatment options for ischemic stroke and reperfusion injury, researchers have carried out extensive and in-depth studies. More than 1000 drugs have been tested, with over 400 demonstrating efficacy in animal models of stroke; furthermore, substantial efforts have been made to explore preventive methods to reduce the morbidity and mortality of stroke [7
], resulting in the development of recombinant tissue plasminogen activator (r-TPA), aspirin and heparin [3
]. However, most of these treatments have disappointingly been found to be ineffective during the acute phase of stroke, and intravenous recombinant tissue plasminogen activator (r-tPA) is currently the only approved agent for the treatment of acute ischemia stroke [9
], and it has safety concerns associated with reperfusion injury and hemorrhage. Therefore, it is necessary to examine some potential neuroprotective agents for their ability to treat ischemic stroke.
(Burk) F. H. Chen and Panax ginseng
C. A. Mey are two commonly used Chinese medicinal herbs, the roots or stems of which have been used for the treatment of cardiovascular disease in many Asian countries for several hundred years [10
]. Pharmacological studies have shown that P. notoginseng
, P. ginseng
, and their extracts, panax notoginseng saponins (PNS) and ginseng total saponins (GTS), exert multiple pharmacological activities, such as anti-inflammatory [11
], anti-oxidative [12
], platelet aggregation-inhibiting, and neuronal apoptosis-suppressing effects [14
As shown in Figure 1
, ginsenoside Rg1 (G-Rg1) is a tetracyclic triterpenoid mainly derived from the roots or stems of P. notoginseng
and P. ginseng
that is obtained via an extraction and purification processes (Figure 1
) and chemically belongs to the PPT ginsenoside group [15
]. The G-Rg1 content was determined via simple and accurate HPLC or UPLC methods and found to account for 0.22% ± 0.02% of sun-cured ginseng
, 0.64% ± 0.004% of the stems and leaves of ginseng
], 4.41% ± 0.05% of the roots or stems of P. notoginseng
, and 3.21% ± 0.08% of the roots or stems of P. notoginseng
]. These data indicate that the G-Rg1 content is clearly higher in P. notoginseng
than in P. ginseng
and that the stems and leaves seem to have more value. Additionally, G-Rg1 is regarded as one of the main bioactive compounds responsible for the pharmaceutical actions of ginseng, which show little toxicity, and some evidence has shown that its pharmacological effects are remarkable in that they include neurotrophic and neuroprotective effects on the central nervous system [20
]. Most importantly, as a tetracyclic triterpenoid (Figure 1
E) found in natural medicinal plants, G-Rg1 could promote hippocampal neurogenesis, improve neuroplasticity, enhance learning and memory, exert anti-aging [30
] and antifatigue effects, and regulate immunity and antitumor activity [31
]. Additionally, an increasing amount of evidence indicates that G-Rg1 exerts neuroprotective effects both in vivo and in vitro [30
]. Various mechanisms have been shown to underlie G-Rg1 activity [38
], including the activation of anti-oxidant, immune stimulatory, anti-inflammatory and anti-apoptotic activities, effects on nerve growth factors, the inhibition of excitotoxicity, the induction of excessive Ca2+
influx into neurons, the preservation of the structural integrity of neurons, and the maintenance of cellular adenosine triphosphate (ATP) levels.
However, to date, no systematic review has been conducted to assess the protective effects of and mechanisms underlying how G-Rg1 combats cerebral ischemia/reperfusion injury (CI/RI). A systematic review of all evidence available from animal experiments preceding clinical trials would provide an adequate interpretation of the limitations and potential of novel treatment strategies. Moreover, while various candidate drugs have failed to treat cerebral ischemia, those studies have prompted series of suggestions that could improve the likelihood of successful translation. Among these is that if a systematic review and analysis of preclinical studies of alternative active ingredients was to be carried out, it would likely promote candidate drug development and provide more information from the previous literature that could be used as a bridge into clinical trials of stroke. Therefore, in the present study, we conducted a systematic review of all available animal studies to evaluate the preclinical evidence related to G-Rg1 in experimental CI/RI studies.
To explore and summarize the protective effects and relevant mechanisms of ginsenoside Rg1 against CI/RI, we conducted this review by searching the “PubMed” database via using “Ginsenoside Rg1” and “Ischemia” as search terms to obtain the literature concerning animal experiments in latest 10 years (https://www.ncbi.nlm.nih.gov/pubmed/?term = ((ginsenoside ± Rg1%5BTitle%2FAbstract%5D) ± AND ± ischemia)
). This allowed us to organize and analyze the literature concerning the pharmacological effects and mechanisms of ginsenoside Rg1 against CI/RI, which will be valuable for further promoting candidate drug development and providing more citation-based information that can be applied in clinical trials of stroke.
3. Conclusions and Remarks
Cerebral ischemia-reperfusion is a complicated pathological process. The damage and cascade of reactions caused by ischemia and reperfusion in brain tissues are related to decreased blood flow, ischemic-induced energy metabolism disorder, oxidative stress, inflammatory stress, cytokine damage, excitatory toxicity by glutamate, intracellular calcium overload, NO synthesis, and many other factors [2
], even including some genetic disease as a possible complication, such as Fabry disease [100
]. Moreover, the numerous abovementioned factors and mechanisms that lead to CI/RI are related to each other and can interact with and cause each other, eventually leading to apoptosis or nerve necrosis in the ischemic region [102
Ginseng Rg1, a saponin obtained as a natural active ingredient in traditional Chinese medicine (TMR), is a traditional stem extract of ginseng and Panax notoginseng
, and its pharmacological effects are remarkable in that it exerts neurotrophic and neuroprotective effects on the central nervous system. In our review, we summarize the protective effects of G-Rg1 against CI/RI in addition to the mechanisms underlying these effects. The results of our analysis show that 4 main mechanisms are involved (Figure 2
): anti-oxidant and associated apoptotic effects; anti-inflammatory and immunostimulatory-related effects on apoptosis or necrosis; neurological cell cycle, proliferation, differentiation, and regeneration; and energy metabolism and regulation of cellular ATP levels, blood-brain barrier (BBB) permeability, excitatory amino acids (EAAs), and other processes, including the activation of nerve growth factor (NGF), excitotoxicity, and excessive Ca2+
influx into neurons.
First, G-Rg1 can upregulate the anti-oxidant capacity of SOD, MPO, GSH-Px, and CAT, while simultaneously downregulating oxidative free radicals, such as ROS, RNS, and OH; it can also inhibit ischemic nerve damage and associated apoptotic effects (such as protein denaturation, enzyme inactivation, lipid membrane oxidation, mitochondrial oxidative respiratory chain damage, mitochondrial apoptosis induction, CC-3, Bal, and AIF) caused by oxidative stress and induced via the Akt, Nrf2/HO-1, PPARγ/HO-1, ERK, p38 and JNK MAPK pathways, the mitochondrial apoptosis pathway and the caspase-3/ROCK1/MLC pathway, thereby providing significant neuroprotective effects against cerebral ischemic injury.
Second, G-Rg1 can downregulate harmful inflammatory cytokines, such as IL-6, IL-1β, TNF-α, ICAM-1, and MMP-9, at both the protein and mRNA levels; upregulate anti-inflammatory factors regulated by NF-κB (p50 and p65) and IKK; inhibit the levels of PPARγ, Bax, CC-3, and CC-9 at both the protein and mRNA levels; and inhibit HMGB1 and the associated necrotic and apoptotic effects caused by oxidative stress (such as the activation of microglia and astrocytes in resident cells, the destruction of the blood-brain barrier caused by the inflammatory factors MMP-2, MMP-3, and MMP9, brain edema, loss of neuronal cells, and a large amount of ROS induced by excessive inflammatory responses) by regulating MAPK pathways, such as the JNK1/2, ERK1/2, and JAK1/STAT1 pathways, in addition to ERS, the HMGB1-induced TLR2/4/9 and RAGE pathways, and activate NF-κB, resulting in significant neuroprotective effects against cerebral ischemic injury.
Third, G-Rg1 can increase the levels of cytokines that promote cell proliferation and differentiation, such as HIF-1α, EPO, VEGF, BDNF, and NGF, at both the protein and mRNA levels; promote angiogenesis and induce neurogenesis by regulating MAPK pathways, such as the JNK1/2 and ERK1/2, PI3K-Akt/mTOR, PKB/Akt, and HIF-1α/VEGF pathways; and affect ERS, resulting in significant neuroprotective effects against cerebral ischemic injury. However, the specific regulatory mechanisms that are affected in neurons and during angiogenesis remain unclear.
Finally, G-Rg1 can upregulate the energy metabolism capacity of Na-K-ATPase in addition to iNOS activity, ATP, AMP, total adenine nucleotides (TANs), and energy charge (EC); downregulate the free radical contents of Glu and asparaginic acid (Asp), modulated (inhibited) the influx of extracellular calcium and the release of intracellular calcium as well as nNOS activity; enhance the expression of GLUT3 and the activation of AMPKα1/2; and inhibit ischemic nerve damage and its associated apoptotic effects (such as intracellular calcium overload, AAA toxicity, energy metabolism disorder and mitochondrial apoptosis) via its effects on NMDA receptors, ERS, and the AMP/AMPK-GLUT pathways.
In summary, ginseng Rg1 is a tetracyclic triterpenoid derivative derived from natural medicinal plants that has significant and representative pharmacological activities. Additionally, in this overview, we show that GR promotes anti-ischemic stroke via its links to multiple pathways and its multitarget effects, as shown in Figure 2
. On the one hand, its role and the results of relevant studies suggest potential strategies and novel methods that use multitarget and multilink combination therapy for the treatment of ischemic stroke; on the other hand, while these data provide a strong scientific basis for network pharmacology studies on natural medicinal plants, the pharmacological effects and mechanisms of active ingredients obtained from Panax notoginseng
and ginseng have been comprehensively elaborated, a situation that is more conducive to the development and utilization of Panax notoginseng
and ginseng. These findings provide ideas for research into the pharmacological actions and mechanisms of other active constituents, a reference for the rational clinical use of drugs, and scientific protection of resource utilization.
However, many of the actions and mechanisms of G-Rg1 remain unknown. These include its ability to regulate inflammation after the I/R activation of keratinocytes, and few studies have explored its effects on neurogenesis and autophagy regulation in brain nerve cells (Figure 2
). At the same time, studies of the ginsenoside Rg1 have mostly focused on the effects of Rg1 on inhibiting apoptosis, while fewer cross-topic studies of multiple pathways have been performed. Therefore, it is worth exploring whether the ginsenoside Rg1 affects autophagy and inflammation-induced necrosis and whether its effects are protective or damaging to cerebral ischemia reperfusion so that we can obtain a more comprehensive understanding of the regulatory mechanisms used by G-Rg1 in the body.