**4. First neuroprotective pharmacological and non-pharmacological treatments**

In the search to find new alternatives of neuroprotective agents, a great variety of molecules have been explored that affect one or several strategic points of the pathophysiology, and that promise good results; some are mentioned below.

During the onset of AIS, glucose and oxygen concentrations decrease, and this promotes the activation of adenosine monophosphate-activated protein kinase (AMPK). This process upregulates cellular pathways that control energy metabolism through catabolic pathways such as glycolysis and lipid oxidation to increase adenosine triphosphate (ATP) production and decrease its consumption through the inhibition of gluconeogenesis. Observations have been made regarding the fact that the activation of this enzyme for short periods increases neural survival, but its activation for extended periods will lead to cell death through apoptosis, necrosis, and autophagy [53], which is why several drugs that modulate AMPK activation have been tested recently in search for beneficial effects.

To mention some, metformin has been widely studied for cerebral ischemia since it possesses pleiotropic activity and modulates AMPK activation [54]. In 2016, Zhang et al. administered 7 mg/kg of metformin intraperitoneally to C57BL/6 mice for 7 days, before middle cerebral artery occlusion (MCAO). After MCAO, the authors observed that it induced neuroprotection by reducing infarct size, through lower AMPK, results that were not observed if administered for short periods of 1–3 days before MCAO, or after the occlusion; also, these benefits were not found in the case of reperfusion [55]. Also, the neuroprotective effect of metformin was observed in a global ischemia model in rats; after administration, apoptosis decreased, and mitochondrial biogenesis was induced [56]. Other experiments have demonstrated that metformin has the potential to improve memory and learning through the increase in brain-derived neurotrophic factor (BDNF) and p7056k protein [57]. On the other hand, it has also been implicated in the reduction of IL-6, IL-1β, TNF-α, and adhesion molecule levels, as well as a decrease in neutrophil infiltration [58]. Considering these results, it is crucial to clarify how this modulation is carried out since there is some controversy about the mechanism (**Table 1**).

**Drug Mechanism Observed effect Authors**

*Available Therapeutics after a Stroke: Current and Promising Options*

Infarct size Neurological deficit

Infarct size Neurological deficit

Memory Learning

barrier

Protection of blood-brain

Neurological deficit

CA1 neurons of the

Edema

hippocampus

Infarct size Neural survival

Infarct size Edema

Infarct size Neurological deficit

Neurological deficit

barrier

Neurogenesis Infarct size

Protection of blood-brain

Deng et al. [55]

Ashabi et al. [56]

Liu et al. [58]

Cheng et al. [60]

Shao et al. [61]

Xu et al. [68]

Chang et al. [70]

Cai et al. [71]

Belayev et al. [72]

Neural survival Bazzigaluppi et al. [69]

Ghadernezhad et al. [57]

Metformin AMPK

Apoptosis

*DOI: http://dx.doi.org/10.5772/intechopen.91282*

AMPK Apoptosis

AMPK BDNF P70S6K

AMPK NFkβ IL-6 IL-1β TNF-α ICAM Neutrophils

pJNK3 Caspase 3

AMPK pAKT

ROS Astrogliosis

TNF-α IL-6 IL-1β

Macrophages Neutrophils T lymphocytes B lymphocytes Infiltration Polarization of macrophages to M2

Microglia Leukocyte infiltration

DHA Macrophages

Ketosis HIF-α

**285**

Atorvastatin Aquaporin AQP4 Infarct size

Atorvastatin is a statin that has pleiotropic effects, since it allows angiogenesis and synaptogenesis, increases blood flow, blunts atherosclerotic plaque formation, and provides neuroprotection in cerebral ischemia model [59] by reducing aquaporin 4 expression (AQP4) [60], thus, preventing cerebral edema and the increase of infarct size. This statin has also been reported to attenuate cognitive deficit [61] through caspase 3 inhibition and avoiding neural death in the CA1 region of the hippocampus.

There is also a great variety of neuroprotective drugs or molecules that act closer by modulating inflammation, through the promotion of an anti-inflammatory microglial phenotype activation; only the most representative will be mentioned below.

DRα1 recombinant protein linked to the MOG peptide has demonstrated the ability to decrease macrophage migration and monocyte activation through its binding to CD74, which translates to a reduction in infarct size [62]. It has also been shown that it reduces proinflammatory cytokine expression, such as IL-1β, I-17, TNF-α, and INF-ϒ, as well as lowers T lymphocyte infiltration and promotes a polarization toward an M2 phenotype macrophage activation [63].

Cop-1 or glatiramer acetate is a copolymer formed by four amino acids (L-alanine, L-lysine, L-glutamic, and L-tyrosine) that has shown to exert neuroprotective effects by being able to reduce infarct size and improve neurological deficit [64]. Cop-1 increases the expression of IL-10, BDNF, Insulin-like growth factor-1 (IGF-1), and neurotrophin (NT-3) in the choroid plexus [65], and the cortex, which stimulates greater neurogenesis [66]. Mangin et al. and their study group obtained similar results; they reported that Cop-1 is capable of reducing COX-2, CD32, TNF-α, and IL-1β, as well as inducing greater neurogenesis and thus, reducing memory loss in mice with cerebral ischemia [67].

On the other hand, food strategies have also been proposed; for example, dietinduced ketosis has demonstrated its neuroprotective effects. Xu et al. observed, in 2017, that the ketogenic diet induced a reduction in infarct size through the overexpression of transcription factors HIF-1α, pAKT, and AMPK [68]; in 2018 Stefanovic, beneficial effects of administering exogenous β-hydroxybutyrate intraperitoneally were also observed in a model of cerebral ischemia induced by endothelin-1 in rats. He reported that the ischemic penumbra cells had a diminished glucose uptake, which translated into less ROS production, astrogliosis, and neuronal death [69]. Ketone bodies or ketosis is worth further exploration since clinical


*Available Therapeutics after a Stroke: Current and Promising Options DOI: http://dx.doi.org/10.5772/intechopen.91282*

To mention some, metformin has been widely studied for cerebral ischemia since it possesses pleiotropic activity and modulates AMPK activation [54]. In 2016, Zhang et al. administered 7 mg/kg of metformin intraperitoneally to C57BL/6 mice for 7 days, before middle cerebral artery occlusion (MCAO). After MCAO, the authors observed that it induced neuroprotection by reducing infarct size, through lower AMPK, results that were not observed if administered for short periods of 1–3 days before MCAO, or after the occlusion; also, these benefits were not found in the case of reperfusion [55]. Also, the neuroprotective effect of metformin was observed in a global ischemia model in rats; after administration, apoptosis

*New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*

decreased, and mitochondrial biogenesis was induced [56]. Other experiments have demonstrated that metformin has the potential to improve memory and learning through the increase in brain-derived neurotrophic factor (BDNF) and p7056k protein [57]. On the other hand, it has also been implicated in the reduction of IL-6, IL-1β, TNF-α, and adhesion molecule levels, as well as a decrease in neutrophil infiltration [58]. Considering these results, it is crucial to clarify how this modulation is carried out since there is some controversy about the mechanism (**Table 1**). Atorvastatin is a statin that has pleiotropic effects, since it allows angiogenesis and synaptogenesis, increases blood flow, blunts atherosclerotic plaque formation,

and provides neuroprotection in cerebral ischemia model [59] by reducing aquaporin 4 expression (AQP4) [60], thus, preventing cerebral edema and the increase of infarct size. This statin has also been reported to attenuate cognitive deficit [61] through caspase 3 inhibition and avoiding neural death in the CA1

There is also a great variety of neuroprotective drugs or molecules that act closer

DRα1 recombinant protein linked to the MOG peptide has demonstrated the ability to decrease macrophage migration and monocyte activation through its binding to CD74, which translates to a reduction in infarct size [62]. It has also been shown that it reduces proinflammatory cytokine expression, such as IL-1β, I-17, TNF-α, and INF-ϒ, as well as lowers T lymphocyte infiltration and promotes a

by modulating inflammation, through the promotion of an anti-inflammatory microglial phenotype activation; only the most representative will be mentioned

Cop-1 or glatiramer acetate is a copolymer formed by four amino acids (L-alanine, L-lysine, L-glutamic, and L-tyrosine) that has shown to exert

neuroprotective effects by being able to reduce infarct size and improve neurological deficit [64]. Cop-1 increases the expression of IL-10, BDNF, Insulin-like growth factor-1 (IGF-1), and neurotrophin (NT-3) in the choroid plexus [65], and the cortex, which stimulates greater neurogenesis [66]. Mangin et al. and their study group obtained similar results; they reported that Cop-1 is capable of reducing COX-2, CD32, TNF-α, and IL-1β, as well as inducing greater neurogenesis and thus,

On the other hand, food strategies have also been proposed; for example, dietinduced ketosis has demonstrated its neuroprotective effects. Xu et al. observed, in

endothelin-1 in rats. He reported that the ischemic penumbra cells had a diminished glucose uptake, which translated into less ROS production, astrogliosis, and neuronal death [69]. Ketone bodies or ketosis is worth further exploration since clinical

2017, that the ketogenic diet induced a reduction in infarct size through the overexpression of transcription factors HIF-1α, pAKT, and AMPK [68]; in 2018 Stefanovic, beneficial effects of administering exogenous β-hydroxybutyrate intra-

peritoneally were also observed in a model of cerebral ischemia induced by

polarization toward an M2 phenotype macrophage activation [63].

reducing memory loss in mice with cerebral ischemia [67].

region of the hippocampus.

below.

**284**


Neurotrophins are a group of proteins that are involved in the maintenance and survival of the central nervous system [75]; this includes BDNF, NT-3, NT-4, NT-5, nerve growth factor (NGF), and IGF-1. Neurotrophins interact with two types of receptors, Trk (tyrosine kinase receptors) and the p75 receptor that belongs to the

Among the most studied neurotrophins are BDNF and NT-3; BDNF is produced by almost all brain cells and is known to participate in processes of proliferation, survival, and neuronal differentiation. Its receptors are widely distributed [76] and activate critical signaling pathways such as PLCγ, PI3K, and ERK, which ultimately lead to phosphorylation and activation of the transcription factor CREB that mediates the expression of genes that are essential for the survival and differentiation of neurons [77]. NT-3 has also been involved in the processes of cell proliferation and differentiation through the notch pathway [78], as well as participating in processes

Experiments have shown that the increase of neurotrophic factors in the ischemia model is commonly related to a better functional or memory recovery and that it is usually associated with neurogenesis or neuroplasticity—as in the case of metformin, which showed an increase in BDNF expression and that induced a more significant recovery of memory and learning [57]. Also, Cop-1 was able to induce the increase of BDNF, IGF-1, and NT-3; which correlated with the increase in neurogenesis [65]; and the experiments of Luan et al. showed that patients with cerebral ischemia who presented higher levels of NGF obtained a better functional

Stem cell transplantation has also been linked to better neurological recovery; although clinical trials have not reported the expected results [80], basic research using stem cells has shown an increase in neurological rehabilitation and suggested mechanisms include the overexpression of BDNF and IGF-1 [81, 82], as well as immunomodulatory cytokines like IL-10, which together induce a polarization

In recent years, there has been an increase in the interest of studying how the external environment has a direct effect on the structure and neuronal function, that is, on neuroplasticity [84], and that is why researchers keep studying what kind of external characteristics (specifically physical and social activity) can increase

In 2017, Chen et al. explored whether a specific type of environment stimulated the production of BDNF in rats with cerebral ischemia, and what they observed was that physical stimulation increases the expression of neurotrophic factors more than social stimulation and obtains a higher neurological recovery [85]. Mang, on the other hand, observed that the increase in BDNF after an ischemic event is determined by the type of aerobic exercise and the val66met variant of the BDNF gene [86].

The effects on NT-3 have also been evaluated, and the results have been very similar; there is an increase in its levels with physical stimulation after the ischemic event and a more significant functional recovery [87]. Other proteins have also been associated with neuronal plasticity through axonal growth, such as the growthassociated protein 43 (GAP-43), which has been observed to increase when rats

Electrical stimulation directly into the fastigial nucleus (FNS) has proven to be beneficial in a model of MCAO [89]. The mechanism through which FNS has shown to improve walking balance and neurological scores is due to the activation of the PKA/cAMP pathway, suppressing the expression of Rho-Kinase, and through the

In this sense, experiments continue to be designed to establish the efficacy of

TNFR receptor family, implicated in apoptosis processes.

*Available Therapeutics after a Stroke: Current and Promising Options*

*DOI: http://dx.doi.org/10.5772/intechopen.91282*

of memory and learning [76].

recovery at 3 months after the ischemia [79].

toward an anti-inflammatory M2 microglial phenotype [83].

these factors and thereby obtain more significant benefits.

with cerebral ischemia undergo fastigial electrostimulation [88].

training types and times to modulate inflammation, the production of

overexpression of GAP-43 protein [89].

**287**

#### **Table 1.**

*Main neuroprotective agents in ischemia.*

trials in Alzheimer's patients with mild cognitive decline have shown improvements in verbal memory after being treated with a ketogenic diet [73].

Dietary administration with docosahexaenoic acid (DHA) has also proven to have anti-inflammatory and neuroprotective effects in cerebral ischemia through the reduction of proinflammatory cytokine expression, such as TNF-α, IL-1β and IL-6; even, a decrease in macrophage and microglial activation and a decrease in leukocyte infiltration to the lesion site [70]. Similar observations were made by Cai et al. who noted that macrophage, neutrophil, and T and B lymphocyte infiltration was significantly decreased, besides stimulating an anti-inflammatory macrophage (M2) activation [71]; DHA is also capable of inducing neurogenesis and angiogenesis [72], which makes it a promising molecule for future experimental research.

## **5. Neurorestoration**

Many of the cytokines and growth factors that result from immunomodulation processes are directly involved in neurorestoration processes, the latter understood as the set of strategies that seek to reconstruct the affected neural circuits through neuroplasticity or neurogenesis [74].

#### *Available Therapeutics after a Stroke: Current and Promising Options DOI: http://dx.doi.org/10.5772/intechopen.91282*

Neurotrophins are a group of proteins that are involved in the maintenance and survival of the central nervous system [75]; this includes BDNF, NT-3, NT-4, NT-5, nerve growth factor (NGF), and IGF-1. Neurotrophins interact with two types of receptors, Trk (tyrosine kinase receptors) and the p75 receptor that belongs to the TNFR receptor family, implicated in apoptosis processes.

Among the most studied neurotrophins are BDNF and NT-3; BDNF is produced by almost all brain cells and is known to participate in processes of proliferation, survival, and neuronal differentiation. Its receptors are widely distributed [76] and activate critical signaling pathways such as PLCγ, PI3K, and ERK, which ultimately lead to phosphorylation and activation of the transcription factor CREB that mediates the expression of genes that are essential for the survival and differentiation of neurons [77]. NT-3 has also been involved in the processes of cell proliferation and differentiation through the notch pathway [78], as well as participating in processes of memory and learning [76].

Experiments have shown that the increase of neurotrophic factors in the ischemia model is commonly related to a better functional or memory recovery and that it is usually associated with neurogenesis or neuroplasticity—as in the case of metformin, which showed an increase in BDNF expression and that induced a more significant recovery of memory and learning [57]. Also, Cop-1 was able to induce the increase of BDNF, IGF-1, and NT-3; which correlated with the increase in neurogenesis [65]; and the experiments of Luan et al. showed that patients with cerebral ischemia who presented higher levels of NGF obtained a better functional recovery at 3 months after the ischemia [79].

Stem cell transplantation has also been linked to better neurological recovery; although clinical trials have not reported the expected results [80], basic research using stem cells has shown an increase in neurological rehabilitation and suggested mechanisms include the overexpression of BDNF and IGF-1 [81, 82], as well as immunomodulatory cytokines like IL-10, which together induce a polarization toward an anti-inflammatory M2 microglial phenotype [83].

In recent years, there has been an increase in the interest of studying how the external environment has a direct effect on the structure and neuronal function, that is, on neuroplasticity [84], and that is why researchers keep studying what kind of external characteristics (specifically physical and social activity) can increase these factors and thereby obtain more significant benefits.

In 2017, Chen et al. explored whether a specific type of environment stimulated the production of BDNF in rats with cerebral ischemia, and what they observed was that physical stimulation increases the expression of neurotrophic factors more than social stimulation and obtains a higher neurological recovery [85]. Mang, on the other hand, observed that the increase in BDNF after an ischemic event is determined by the type of aerobic exercise and the val66met variant of the BDNF gene [86].

The effects on NT-3 have also been evaluated, and the results have been very similar; there is an increase in its levels with physical stimulation after the ischemic event and a more significant functional recovery [87]. Other proteins have also been associated with neuronal plasticity through axonal growth, such as the growthassociated protein 43 (GAP-43), which has been observed to increase when rats with cerebral ischemia undergo fastigial electrostimulation [88].

Electrical stimulation directly into the fastigial nucleus (FNS) has proven to be beneficial in a model of MCAO [89]. The mechanism through which FNS has shown to improve walking balance and neurological scores is due to the activation of the PKA/cAMP pathway, suppressing the expression of Rho-Kinase, and through the overexpression of GAP-43 protein [89].

In this sense, experiments continue to be designed to establish the efficacy of training types and times to modulate inflammation, the production of

trials in Alzheimer's patients with mild cognitive decline have shown improvements

Dietary administration with docosahexaenoic acid (DHA) has also proven to have anti-inflammatory and neuroprotective effects in cerebral ischemia through the reduction of proinflammatory cytokine expression, such as TNF-α, IL-1β and IL-6; even, a decrease in macrophage and microglial activation and a decrease in leukocyte infiltration to the lesion site [70]. Similar observations were made by Cai et al. who noted that macrophage, neutrophil, and T and B lymphocyte infiltration was significantly decreased, besides stimulating an anti-inflammatory macrophage (M2) activation [71]; DHA is also capable of inducing neurogenesis and angiogenesis [72], which makes it a promising molecule for future experimental research.

Many of the cytokines and growth factors that result from immunomodulation processes are directly involved in neurorestoration processes, the latter understood as the set of strategies that seek to reconstruct the affected neural circuits through

in verbal memory after being treated with a ketogenic diet [73].

**Drug Mechanism Observed effect Authors**

*New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*

Infarct size Motor functions

Neurological deficit

Infarct size Neurological deficit

Edema Memory

Infarct size Benedek et al. [62]

Neurological deficit Cruz et al. [65].

Neurological deficit Cruz et al. [66]

Wang et al. [63]

Ibarra et al. [64]

Mangin et al. [67]

Macrophages migration Monocytes

Cop-1 Immunomodulation Infarct size

TNF-α IL-17 IL-1β INF-ϒ T lymphocytes Infiltration

IL-10 BDNF IGF-1 NT-3

Neurogenesis NT-3

COX2 Cd32 TNF-α IL-1β

*, regulation ; , activation.*

*Main neuroprotective agents in ischemia.*

**Table 1.**

DRα-1MOG35-55

**5. Neurorestoration**

**286**

neuroplasticity or neurogenesis [74].

neurotrophins, and the impact on patient mobility, as in the proposal developed by Scalzo et al. [89] that gives rise to the continued development of a well-founded physical therapy for patients with cerebral ischemia.

Functional electrical therapy has been used alongside other types of electrical stimulation to induce repetitive muscular contraction to mobilize certain joints [6]. Somatosensory stimulation might enhance neurorehabilitation after stroke through the stimulation of corticomotoneuronal excitability [6]. It has been proposed that this type of therapy increases muscle strength, reduces spasticity, and facilitates

Guided self-rehabilitation (GSR) is a method in which the intensity of training can be increased inside the home environment. While combined with conventional rehabilitation, it has proven to be efficacious in engaging the patients in their recovery through a contract between the patient and the therapist, allowing for an increased sense of responsibility and motivation for the patients, who are required to register their progress in a diary [100]. Although not many physical therapists accept such an approach [100], positive changes have been observed after 1 year of GSR and conventional rehabilitation in ultrasound measuring of the soleus' and medial gastrocnemius' thickness and fascicle length, as well as clinical improvement, observed in soleus extensibility and ambulation speed [101] in chronic stroke patients.

Constraint-induced therapy requires constraining the non-affected limb for 90%

Videogame- or virtual reality-based (VRb) therapies have been under study for

In addition to continuing the search for pharmacological agents that allow the neuroprotection and neurorestoration of tissue affected by cerebral ischemia, the development of physical therapy and diet modification offers new horizons that have shown satisfactory results in the clinical setting in short times. However, it has not yet been possible to establish a protocolized treatment that can be added to the health care guidelines; so it is important to continue exploring all possible strategies to improve the quality of life of people who have suffered a cerebral infarction and

of the waking hours, forcing the patient to use the paretic limb, inducing the increase of use-dependent plasticity, although this therapy is not practical for most

upper extremity functional recovery in acute and subacute or chronic patients [91, 96, 99, 102]; the rationale for such approaches is that they promote motor learning and repetitive, intense movements, and in the specific case of virtual reality, the patient is exposed to interactive visual, auditive, and proprioceptive feedback [91, 102]. Different videogame and VRb therapies have reported improvements in fine dexterity, grip strength [96], and grasp force [99] in upper extremities, and, activities of daily living [91] and cognition [102] in young and elderly patients after several weeks of rehabilitation. Better results have been observed when combined with conventional therapy, although it is still not known

voluntary movements, among other motor benefits [6].

*Available Therapeutics after a Stroke: Current and Promising Options*

*DOI: http://dx.doi.org/10.5772/intechopen.91282*

whether it enhances or speeds up recovery [91].

**7. Final remarks and future directions**

of the population [6].

that of their caregivers.

**289**
