**Author details**

Antonella Borreca

Address all correspondence to: antonella.borreca@gmail.com

CNR-National Research Council, Institute of Cell Biology and Neurobiology, Italy

**Chapter 2**

Provisional chapter

**Neuroprotective Strategies of Blood-Brain Barrier**

Neuroprotective Strategies of Blood-Brain Barrier

**to Ameliorate Mitochondrial Dysfunctioning in**

to Ameliorate Mitochondrial Dysfunctioning in

**Neurotoxic Experimental Model of Autism**

Neurotoxic Experimental Model of Autism

Sidharth Mehan, Himanshi Khera and Ramit Sharma

gies to ameliorate the neurodevelopmental disorder autism.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80046

Ramit Sharma

Abstract

forskolin

1. Introduction

Sidharth Mehan, Himanshi Khera and

**Penetrant "Forskolin" (AC/cAMP/PKA/CREB Activator)**

DOI: 10.5772/intechopen.80046

New developments in the study of brain are among the most exciting frontiers of contemporary neuroscientific research for the clinical practitioner. Increasing knowledge of neurocomplications and of their discrete localization in the various regions of brain permits new modes of pharmacological management of some major neurological disorders like autism. The research work reported in this scheme is undertaken with an objective to explore the potential molecular targets (AC/cAMP/PKA/CREB) for the development of newer therapeutics strategies (forskolin) for the management of neurological disorders and associated symptoms. Studies aimed at addressing these questions have fallen into two main categories: in-vivo behavioral paradigms and in-vitro differentiation biochemical, morphological and histopathological analysis. Therefore, first time, we aim to gather the propensity of mitochondrial cofactors, neuropathological mechanisms and various diagnostic methods to explore the clinical therapeutic strate-

Keywords: neurodegeneration, autism, mitochondrial dysfunction, adenylyl cyclase,

Neurological disorders are a heterogeneous group of diseases of the nervous system having different etiologies. They represent illnesses of the selective regions of the brain and nervous

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Penetrant "Forskolin" (AC/cAMP/PKA/CREB Activator)

#### **Neuroprotective Strategies of Blood-Brain Barrier Penetrant "Forskolin" (AC/cAMP/PKA/CREB Activator) to Ameliorate Mitochondrial Dysfunctioning in Neurotoxic Experimental Model of Autism** Neuroprotective Strategies of Blood-Brain Barrier Penetrant "Forskolin" (AC/cAMP/PKA/CREB Activator) to Ameliorate Mitochondrial Dysfunctioning in Neurotoxic Experimental Model of Autism

DOI: 10.5772/intechopen.80046

Sidharth Mehan, Himanshi Khera and Ramit Sharma Sidharth Mehan, Himanshi Khera and Ramit Sharma

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80046

#### Abstract

New developments in the study of brain are among the most exciting frontiers of contemporary neuroscientific research for the clinical practitioner. Increasing knowledge of neurocomplications and of their discrete localization in the various regions of brain permits new modes of pharmacological management of some major neurological disorders like autism. The research work reported in this scheme is undertaken with an objective to explore the potential molecular targets (AC/cAMP/PKA/CREB) for the development of newer therapeutics strategies (forskolin) for the management of neurological disorders and associated symptoms. Studies aimed at addressing these questions have fallen into two main categories: in-vivo behavioral paradigms and in-vitro differentiation biochemical, morphological and histopathological analysis. Therefore, first time, we aim to gather the propensity of mitochondrial cofactors, neuropathological mechanisms and various diagnostic methods to explore the clinical therapeutic strategies to ameliorate the neurodevelopmental disorder autism.

Keywords: neurodegeneration, autism, mitochondrial dysfunction, adenylyl cyclase, forskolin

### 1. Introduction

Neurological disorders are a heterogeneous group of diseases of the nervous system having different etiologies. They represent illnesses of the selective regions of the brain and nervous

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

tissues which control vital physiological functions such as learning and memory, posture and coordination of movements of nerves/muscles [1]. A variety of CNS disorders including Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis (ALS), autism spectrum disorders, brain abscess, multiple sclerosis, spinal cord injury, and cerebral stroke, traumatic brain injury are characterized primarily by neurodegeneration and neuroinflammation [2].

enhance neuronal survival [32] and memory performance [31]. In view of the above, the enhancement and prolongation of cAMP and cGMP signaling can thus be helpful in dealing with neurodegenerative disorders including ICH. This can be accomplished by activating the adenylyl cyclase enzyme, which metabolizes these cyclic nucleotides. Forskolin a major diterpenoid isolated from the roots of Coleus forskohlii directly activates the enzyme adenylyl cyclase, thereby increasing the intracellular level of cAMP and leading to various physiolog-

Neuroprotective Strategies of Blood-Brain Barrier Penetrant "Forskolin" (AC/cAMP/PKA/CREB Activator)…

http://dx.doi.org/10.5772/intechopen.80046

7

Despite substantial research into neuroprotection, treatment options are still limited to supportive care and the management of complications. Currently available drugs provide symptomatic relief but do not stop progression of disease. Thus, the development of new therapeutic strategies remains an unmet medical need. Failure of current drug therapy may be due to their action at only one of the many neurotransmitters involved [33] or their inability to up regulate signaling messengers reported to have important role in neuronal excitability [34], neurotransmitter biosynthesis and release [35], neuronal growth and differentiation [30],

Administration of PPA to rodents, results in CNS lesions that selectively target right lateral ventricle associated within striatum, cortex, cerebellum, hippocampus, amygdala recapitulating the regional and neuronal specificity of pathologic events especially in autism [37]. The mitochondrial toxin PPA interferes with the conversion of succinate to fumarate in TCA cycle, responsible for the generation of FADH2 utilized in the complex-II in mitochondrial electron transport chain (ETC) by which it direct inhibits the activity of the mitochondrial metabolic enzyme succinate dehydrogenase and reduced the definite amount of NADH where it consumed in complex-I with the help of an enzyme complex-I (NADPH oxidase) as well as involve in the dysregulation of complex-IV (cytochrome c oxidase), is the final protein complex in the ETC helping to establish a transmembrane difference of proton electrochemical potential that the complex-V (ATP synthase) then uses to synthesize ATP [38].PPA has now become an experimental tool to study neuronal susceptibility and motor phenotypes that are characteris-

In rats, PPA-induced lesions in brain region that are associated with elevated lactate levels resulted in increased NMDA-receptor binding. PPA toxicity arises from secondary excitotoxic mechanisms, whereby energy depletion within vulnerable neurons facilitates abnormal activation of NMDA receptors and subsequent Ca2+ influx [40]. Stimulating energy generation by administering creatine markedly attenuates PPA toxicity and ameliorates lesion volume, lactate production and ATP depletion in PPA-treated rats [41]. Numerous reports assert that PPA toxicity is associated with increased oxidative damage within the CNS. The involvement of impairments in intrinsic anti-oxidant protection pathways after PPA administration is further

supported by observations of reduced glutathione (GSH) levels in autistic brain [42].

ical effects.

synaptic plasticity and cognitive functioning [36].

tic of autism (Figure 1) [39].

2. Experimental animal model of PPA-induced neurotoxicity

Intracellular molecules also known as secondary messengers such as cyclic nucleotides i.e. cAMP and cGMP play a critical role in neuronal signaling and synaptic plasticity by activation of several pathways like cAMP/PKA/CREB, cGMP/PKG/CREB and factors like brain-derived neurotrophic factor (BDNF) [3], semaphorins [4], netrin-1&16 [5], nerve growth factor (NGF) [6], Neurotrophins 3,4,5-inhibitory factors associated with myelin and myelin associated glycoprotein [MAG] [7]. These pathways and factors are well known to help in neuronal survival, neurogenesis and protect neurons from injury [8].

Elevation of cAMP causes both short- and long-term increase in synaptic strength [9] and stimulates cholinergic neuronal cells to release acetylcholine [10]. But, the levels of cAMP and cGMP are reported to be decreased in neuropathological conditions including cerebral stroke and AD [11].

It has been reported that cerebral ischemia-induced energy failure also leads to reduction in the levels of key signaling molecules such as cAMP and cGMP and results in disruption of cAMP/PKA/CREB [11] and cGMP/PKG/CREB signaling pathways [12]. On the other hand it had been reported to impair hippocampal long-term potentiation (LTP), a neurophysiological correlate of memory [13], by inhibiting the activation of both cAMP/PKA/CREB [14] as well as cGMP/PKG/CREB pathways in ICH pathology [15]. The pyramidal CA1 neurons of hippocampus, involved in learning and memory become vulnerable target in cerebral stroke [16]. Further, cAMP or cGMP dependent CREB phosphorylation has too been reported to induce long term memory (LTP) [17] and inhibit apoptotic and necrotic cell death [18].

CREB is a transcriptional factor responsible for synthesis of proteins which are important for the growth and development of synaptic connections and increase in synaptic strength [19]. Thus, agents that enhance cAMP/PKA/CREB &cGMP/PKG/CREB pathways have potential for the treatment of stroke [73], AD and other neurological diseases [20]. cAMP and cGMP mediate signaling of several neurotransmitters including serotonin, acetylcholine, glutamate and dopamine, which play important role in cognitive functioning [21]. The activation of the cAMP-dependent protein kinase [PKA] significantly inhibits TNF-α [22] and inducible nitric oxide synthase [iNOS] in astrocytes and macrophages [23] which are implicated in neuroinflammation [22] and oxidative stress, respectively [24]. cAMP system is closely involved in the regulation of BDNF expression too [25] which play important role in neuronal survival [3], synaptic plasticity [26], learning and memory [27]. Further elevation of cAMP and cGMP levels is known to restore the energy levels [28], reduce excitotoxic damage [29], prevent Aβ-mediated neurotoxicity [14], enhance biosynthesis and release of neurotransmitters [22], inhibit apoptotic and necrotic cell death [30] leading to improvement in cognitive functioning [31]. Central administration of cAMP and cGMP has been reported to

enhance neuronal survival [32] and memory performance [31]. In view of the above, the enhancement and prolongation of cAMP and cGMP signaling can thus be helpful in dealing with neurodegenerative disorders including ICH. This can be accomplished by activating the adenylyl cyclase enzyme, which metabolizes these cyclic nucleotides. Forskolin a major diterpenoid isolated from the roots of Coleus forskohlii directly activates the enzyme adenylyl cyclase, thereby increasing the intracellular level of cAMP and leading to various physiological effects.

tissues which control vital physiological functions such as learning and memory, posture and coordination of movements of nerves/muscles [1]. A variety of CNS disorders including Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis (ALS), autism spectrum disorders, brain abscess, multiple sclerosis, spinal cord injury, and cerebral stroke, traumatic brain injury are characterized primarily by neurodegeneration

Intracellular molecules also known as secondary messengers such as cyclic nucleotides i.e. cAMP and cGMP play a critical role in neuronal signaling and synaptic plasticity by activation of several pathways like cAMP/PKA/CREB, cGMP/PKG/CREB and factors like brain-derived neurotrophic factor (BDNF) [3], semaphorins [4], netrin-1&16 [5], nerve growth factor (NGF) [6], Neurotrophins 3,4,5-inhibitory factors associated with myelin and myelin associated glycoprotein [MAG] [7]. These pathways and factors are well known to help in neuronal survival,

Elevation of cAMP causes both short- and long-term increase in synaptic strength [9] and stimulates cholinergic neuronal cells to release acetylcholine [10]. But, the levels of cAMP and cGMP are reported to be decreased in neuropathological conditions including cerebral stroke

It has been reported that cerebral ischemia-induced energy failure also leads to reduction in the levels of key signaling molecules such as cAMP and cGMP and results in disruption of cAMP/PKA/CREB [11] and cGMP/PKG/CREB signaling pathways [12]. On the other hand it had been reported to impair hippocampal long-term potentiation (LTP), a neurophysiological correlate of memory [13], by inhibiting the activation of both cAMP/PKA/CREB [14] as well as cGMP/PKG/CREB pathways in ICH pathology [15]. The pyramidal CA1 neurons of hippocampus, involved in learning and memory become vulnerable target in cerebral stroke [16]. Further, cAMP or cGMP dependent CREB phosphorylation has too been reported to induce

CREB is a transcriptional factor responsible for synthesis of proteins which are important for the growth and development of synaptic connections and increase in synaptic strength [19]. Thus, agents that enhance cAMP/PKA/CREB &cGMP/PKG/CREB pathways have potential for the treatment of stroke [73], AD and other neurological diseases [20]. cAMP and cGMP mediate signaling of several neurotransmitters including serotonin, acetylcholine, glutamate and dopamine, which play important role in cognitive functioning [21]. The activation of the cAMP-dependent protein kinase [PKA] significantly inhibits TNF-α [22] and inducible nitric oxide synthase [iNOS] in astrocytes and macrophages [23] which are implicated in neuroinflammation [22] and oxidative stress, respectively [24]. cAMP system is closely involved in the regulation of BDNF expression too [25] which play important role in neuronal survival [3], synaptic plasticity [26], learning and memory [27]. Further elevation of cAMP and cGMP levels is known to restore the energy levels [28], reduce excitotoxic damage [29], prevent Aβ-mediated neurotoxicity [14], enhance biosynthesis and release of neurotransmitters [22], inhibit apoptotic and necrotic cell death [30] leading to improvement in cognitive functioning [31]. Central administration of cAMP and cGMP has been reported to

long term memory (LTP) [17] and inhibit apoptotic and necrotic cell death [18].

and neuroinflammation [2].

6 Recent Advances in Neurodegeneration

and AD [11].

neurogenesis and protect neurons from injury [8].

Despite substantial research into neuroprotection, treatment options are still limited to supportive care and the management of complications. Currently available drugs provide symptomatic relief but do not stop progression of disease. Thus, the development of new therapeutic strategies remains an unmet medical need. Failure of current drug therapy may be due to their action at only one of the many neurotransmitters involved [33] or their inability to up regulate signaling messengers reported to have important role in neuronal excitability [34], neurotransmitter biosynthesis and release [35], neuronal growth and differentiation [30], synaptic plasticity and cognitive functioning [36].
