Chlorogenic Acid Decreases Glutamate Release from Rat Cortical Nerve Terminals by P/Q-Type Ca2+ Channel Suppression: A Possible Neuroprotective Mechanism

The glutamatergic neurotransmitter system has received substantial attention in research on the pathophysiology and treatment of neurological disorders. The study investigated the effect of the polyphenolic compound chlorogenic acid (CGA) on glutamate release in rat cerebrocortical nerve terminals (synaptosomes). CGA inhibited 4-aminopyridine (4-AP)-induced glutamate release from synaptosomes. This inhibition was prevented in the absence of extracellular Ca2+ and was associated with the inhibition of 4-AP-induced elevation of Ca2+ but was not attributed to changes in synaptosomal membrane potential. In line with evidence observed through molecular docking, CGA did not inhibit glutamate release in the presence of P/Q-type Ca2+ channel inhibitors; therefore, CGA-induced inhibition of glutamate release may be mediated by P/Q-type Ca2+ channels. CGA-induced inhibition of glutamate release was also diminished by the calmodulin and Ca2+/calmodilin-dependent kinase II (CaMKII) inhibitors, and CGA reduced the phosphorylation of CaMKII and its substrate, synapsin I. Furthermore, pretreatment with intraperitoneal CGA injection attenuated the glutamate increment and neuronal damage in the rat cortex that were induced by kainic acid administration. These results indicate that CGA inhibits glutamate release from cortical synaptosomes by suppressing P/Q-type Ca2+ channels and CaMKII/synapsin I pathways, thereby preventing excitotoxic damage to cortical neurons.

Novel Mechanistic Insights and Potential Therapeutic Impact of TRPC6 in Neurovascular Coupling and Ischemic Stroke

Ischemic stroke is one of the most disabling diseases and a leading cause of death globally. Despite advances in medical care, the global burden of stroke continues to grow, as no effective treatments to limit or reverse ischemic injury to the brain are available. However, recent preclinical findings have revealed the potential role of transient receptor potential cation 6 (TRPC6) channels as endogenous protectors of neuronal tissue. Activating TRPC6 in various cerebral ischemia models has been found to prevent neuronal death, whereas blocking TRPC6 enhances sensitivity to ischemia. Evidence has shown that Ca2+ influx through TRPC6 activates the cAMP (adenosine 3’,5’-cyclic monophosphate) response element-binding protein (CREB), an important transcription factor linked to neuronal survival. Additionally, TRPC6 activation may counter excitotoxic damage resulting from glutamate release by attenuating the activity of N-methyl-d-aspartate (NMDA) receptors of neurons by posttranslational means. Unresolved though, are the roles of TRPC6 channels in non-neuronal cells, such as astrocytes and endothelial cells. Moreover, TRPC6 channels may have detrimental effects on the blood–brain barrier, although their exact role in neurovascular coupling requires further investigation. This review discusses evidence-based cell-specific aspects of TRPC6 in the brain to assess the potential targets for ischemic stroke management.

Novel Mechanistic Insights and Potential Therapeutic Impact of TRPC6 in Neurovascular Coupling and Ischemic Stroke

Ischemic stroke is one of the most disabling diseases and a leading cause of death globally. Despite advances in medical care, the global burden of stroke continues to grow, as no effective treatments to limit or reverse ischemic injury to the brain are available. However, recent preclinical findings have revealed the potential role of transient receptor potential cation 6 (TRPC6) channels as endogenous protectors of neuronal tissue. Activating TRPC6 in various cerebral ischemia models has been found to prevent neuronal death, whereas blocking TRPC6 enhances sensitivity to ischemia. Evidence has shown that Ca2+ influx through TRPC6 activates cAMP response element-binding protein (CREB), an important transcription factor linked to neuronal survival. Additionally, TRPC6 activation may counter excitotoxic damage resulting from glutamate release by attenuating the activity of NMDA receptors of neurons by posttranslational means. Unresolved though, are the roles of TRPC6 channels in non-neuronal cells such as astrocytes and endothelial cells. Moreover, TRPC6 channels may have detrimental effects on the blood-brain barrier, although their exact role in neurovascular coupling requires further investigation. This review discusses evidence-based cell-specific aspects of TRPC6 in the brain to assess the potential targets for ischemic stroke management.

Positive Allosteric Modulation of CB1 and CB2 Cannabinoid Receptors Enhances the Neuroprotective Activity of a Dual CB1R/CB2R Orthosteric Agonist

Preclinical studies highlighted that compounds targeting cannabinoid receptors could be useful for developing novel therapies against neurodegenerative disorders. However, the chronic use of orthosteric agonists alone has several disadvantages, limiting their usefulness as clinically relevant drugs. Positive allosteric modulators might represent a promising approach to achieve the potential therapeutic benefits of orthosteric agonists of cannabinoid receptors through increasing their activity and limiting their adverse effects. The aim of the present study was to show the effects of positive allosteric ligands of cannabinoid receptors on the activity of a potent dual orthosteric agonist for neuroinflammation and excitotoxic damage by excessive glutamate release. The results indicate that the combination of an orthosteric agonist with positive allosteric modulators could represent a promising therapeutic approach to the treatment of neurodegenerative disorders.