Overexpression of GRK2 in Alzheimer disease and in a chronic hypoperfusion rat model is an early marker of brain mitochondrial lesions

A common molecular and cellular pathway in developing Alzheimer and cancer

Globally cancer and Alzheimer's disease (AD) are two major diseases and still, there is no clearly defined molecular mechanism. There is an opposite relation between cancer and AD which are the proportion of emerging cancer was importantly slower in AD patients, whereas slow emerging AD in patients with cancer. In cancer, regulation of cell mechanisms is interrupted by an increase in cell survival and proliferation, while on the contrary, AD is related to augmented neuronal death, that may be either produced by or associated with amyloid-β (Aβ) and tau deposition. Stated that the probability that disruption of mechanisms takes part in the regulation of cell survival/death and might be implicated in both diseases. The mechanism of actions such as DNA-methylation, genetic polymorphisms, or another mechanism of actions that induce alteration in the action of drugs with significant roles in resolving the finding to repair and live or die might take part in the pathogenesis of these two ailments. The functions of miRNA, p53, Pin1, the Wnt signaling pathway, PI3 KINASE/Akt/mTOR signaling pathway GRK2 signaling pathway, and the pathophysiological role of oxidative stress are presented in this review as potential candidates which hypothetically describe inverse relations between cancer and AD. Innovative materials almost mutual mechanisms in the aetiology of cancer and AD advocates novel treatment approaches. Among these treatment strategies, the most promising use treatment such as tyrosine kinase inhibitor, nilotinib, protein kinase C, and bexarotene.

GPCR kinases differentially modulate biased signaling downstream of CXCR3 depending on their subcellular localization

Some G protein-coupled receptors (GPCRs) demonstrate biased signaling such that ligands of the same receptor exclusively or preferentially activate certain downstream signaling pathways over others. This phenomenon may result from ligand-specific receptor phosphorylation by GPCR kinases (GRKs). GPCR signaling can also exhibit location bias because GPCRs traffic to and signal from subcellular compartments in addition to the plasma membrane. Here, we investigated whether GRKs contributed to location bias in GPCR signaling. GRKs translocated to endosomes after stimulation of the chemokine receptor CXCR3 or other GPCRs in cultured cells. GRK2, GRK3, GRK5, and GRK6 showed distinct patterns of recruitment to the plasma membrane and to endosomes depending on the identity of the biased ligand used to activate CXCR3. Analysis of engineered forms of GRKs that localized to either the plasma membrane or endosomes demonstrated that biased CXCR3 ligands elicited different signaling profiles that depended on the subcellular location of the GRK. Each GRK exerted a distinct effect on the regulation of CXCR3 engagement of β-arrestin, internalization, and activation of the downstream effector kinase ERK. Our work highlights a role for GRKs in location-biased GPCR signaling and demonstrates the complex interactions between ligands, GRKs, and cellular location that contribute to biased signaling.

Functions of Astrocytes under Normal Conditions and after a Brain Disease

In the central nervous system (CNS) there are a greater number of glial cells than neurons (between five and ten times more). Furthermore, they have a greater number of functions (more than eight functions). Glia comprises different types of cells, those of neural origin (astrocytes, radial glia, and oligodendroglia) and differentiated blood monocytes (microglia). During ontogeny, neurons develop earlier (at fetal day 15 in the rat) and astrocytes develop later (at fetal day 21 in the rat), which could indicate their important and crucial role in the CNS. Analysis of the phylogeny reveals that reptiles have a lower number of astrocytes compared to neurons and in humans this is reversed, as there have a greater number of astrocytes compared to neurons. These data perhaps imply that astrocytes are important and special cells, involved in many vital functions, including memory, and learning processes. In addition, astrocytes are involved in different mechanisms that protect the CNS through the production of antioxidant and anti-inflammatory proteins and they clean the extracellular environment and help neurons to communicate correctly with each other. The production of inflammatory mediators is important to prevent changes in brain homeostasis. On the contrary, excessive, or continued production appears as a characteristic element in many diseases, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and in neurodevelopmental diseases, such as bipolar disorder, schizophrenia, and autism. Furthermore, different drugs and techniques have been developed to reverse oxidative stress and/or excess of inflammation that occurs in many CNS diseases, but much remains to be investigated. This review attempts to highlight the functional relevance of astrocytes in normal and neuropathological conditions by showing the molecular and cellular mechanisms of their role in the CNS.

Gender differences in GRK2 in cardiovascular diseases and its interactions with estrogen

G protein-coupled receptor kinase 2 (GRK2) is a multifunctional protein involved in regulating G protein-coupled receptor (GPCR) and non-GPCR signaling in the body. In the cardiovascular system, increased expression of GRK2 has been implicated in the occurrence and development of several cardiovascular diseases (CVDs). Recent studies have found gender differences in GRK2 in the cardiovascular system under physiological and pathological conditions, where GRK2's expression and activity are increased in males than in females. The incidence of CVDs in premenopausal women is lower than in men of the same age, which is related to estrogen levels. Given the shared location of GRK2 and estrogen receptors, estrogen may interact with GRK2 by modulating vital molecules such as calmodulin (CaM), caveolin, RhoA, nitrate oxide (NO), and mouse double minute 2 homolog (Mdm2), via signaling pathways mediated by estrogen's genomic (ERα and ERβ), and non-genomic (GPER) receptors, conferring cardiovascular protection in females. Highlighting the gender differences in GRK2 and understanding its interaction with estrogen in the cardiovascular system is pertinent in treating gender-related CVDs. As a result, this article explores the gender differences of GRK2 in the cardiovascular system and its relationship with estrogen during disease conditions. Estrogen's protective and therapeutic effects and its mechanism on GRK2-related cardiovascular diseases have also been discussed.

Natural Product Co-Metabolism and the Microbiota-Gut-Brain Axis in Age-Related Diseases

Complementary alternative medicine approaches are growing treatments of diseases to standard medicine practice. Many of these concepts are being adopted into standard practice and orthomolecular medicine. Age-related diseases, in particular neurodegenerative disorders, are particularly difficult to treat and a cure is likely a distant expectation for many of them. Shifting attention from pharmaceuticals to phytoceuticals and "bugs as drugs" represents a paradigm shift and novel approaches to intervention and management of age-related diseases and downstream effects of aging. Although they have their own unique pathologies, a growing body of evidence suggests Alzheimer's disease (AD) and vascular dementia (VaD) share common pathology and features. Moreover, normal metabolic processes contribute to detrimental aging and age-related diseases such as AD. Recognizing the role that the cerebral and cardiovascular pathways play in AD and age-related diseases represents a common denominator in their pathobiology. Understanding how prosaic foods and medications are co-metabolized with the gut microbiota (GMB) would advance personalized medicine and represents a paradigm shift in our view of human physiology and biochemistry. Extending that advance to include a new physiology for the advanced age-related diseases would provide new treatment targets for mild cognitive impairment, dementia, and neurodegeneration and may speed up medical advancements for these particularly devastating and debilitating diseases. Here, we explore selected foods and their derivatives and suggest new dementia treatment approaches for age-related diseases that focus on reexamining the role of the GMB.

Glial Fibrillary Acidic Protein: A Biomarker and Drug Target for Alzheimer’s Disease

Glial fibrillary acidic protein (GFAP) is an intermediate filament structural protein involved in cytoskeleton assembly and integrity, expressed in high abundance in activated glial cells. GFAP is neuroprotective, as knockout mice are hypersensitive to traumatic brain injury. GFAP in cerebrospinal fluid is a biomarker of Alzheimer’s disease (AD), dementia with Lewy bodies, and frontotemporal dementia (FTD). Here, we present novel evidence that GFAP is markedly overexpressed and differentially phosphorylated in AD hippocampus, especially in AD with the apolipoprotein E [ε4, ε4] genotype, relative to age-matched controls (AMCs). Kinases that phosphorylate GFAP are upregulated in AD relative to AMC. A knockdown of these kinases in SH-SY5Y-APP_Sw human neuroblastoma cells reduced amyloid accrual and lowered protein aggregation and associated behavioral traits in C. elegans models of polyglutamine aggregation (as observed in Huntington’s disease) and of Alzheimer’s-like amyloid formation. In silico screening of the ChemBridge structural library identified a small molecule, MSR1, with stable and specific binding to GFAP. Both MSR1 exposure and GF AP-specific RNAi knockdown reduce aggregation with remarkably high concordance of aggregate proteins depleted. These data imply that GFAP and its phosphorylation play key roles in neuropathic aggregate accrual and provide valuable new biomarkers, as well as novel therapeutic targets to alleviate, delay, or prevent AD.

Double life: How GRK2 and β-arrestin signaling participate in diseases

G-protein coupled receptor (GPCR) kinases (GRKs) and β-arrestins play key roles in GPCR and non-GPCR cellular responses. In fact, GRKs and arrestins are involved in a plethora of pathways vital for physiological maintenance of inter- and intracellular communication. Here we review decades of research literature spanning from the discovery, identification of key structural elements, and findings supporting the diverse roles of these proteins in GPCR-mediated pathways. We then describe how GRK2 and β-arrestins partake in non-GPCR signaling and briefly summarize their involvement in various pathologies. We conclude by presenting gaps in knowledge and our prospective on the promising pharmacological potential in targeting these proteins and/or downstream signaling. Future research is warranted and paramount for untangling these novel and promising roles for GRK2 and arrestins in metabolism and disease progression.

Myocardial GRK2 Reduces Fatty Acid Metabolism and β-Adrenergic Receptor-Mediated Mitochondrial Responses

G-protein coupled receptor (GPCR) kinase 2 (GRK2) is upregulated in heart failure (HF) patients and mouse models of cardiac disease. GRK2 is a regulator of β-adrenergic receptors (βARs), a GPCR involved in ionotropic and chronotropic responses. We and others have recently reported GRK2 to be localized in the mitochondria, although its function in the mitochondria and/or metabolism remain not clearly defined. We hypothesized that upregulation of GRK2 reduced mitochondrial respiratory function and responses to βAR activation. Utilizing isolated mouse primary adult cardiomyocytes (ACMs), we investigated the role of glucose, palmitate, ketone bodies, and BCAAs in mediating cell survival. Our results showed that myocyte upregulation of GRK2 promotes palmitate-induced cell death. Isotopologue labeling and mass spectrometry showed that the upregulation of GRK2 reduces β-hydroxybutyryl CoA generation. Next, using isoproterenol (ISO), a non-selective βAR-agonist, we determined mitochondrial function in mouse and human primary ACMs. Upregulation of GRK2 impaired ISO-mediated mitochondrial functional responses, which we propose is important for metabolic adaptations in pathological conditions. Increased cardiac levels of GRK2 reduced fatty acid-specific catabolic pathways and impaired ISO-stimulated mitochondrial function. Our data support the notion that GRK2 participates in bioenergetic remodeling and may be an important avenue for the development of novel pharmacological strategies in HF.

G protein-coupled receptor kinases are associated with Alzheimer's disease pathology

AIM

Alzheimer's disease (AD) is characterised by extracellular deposition of amyloid-β (Aβ) in amyloid plaques and intracellular aggregation and accumulation of hyperphosphorylated tau in neurofibrillary tangles (NFTs). Although several kinases have been identified to contribute to the pathological phosphorylation of tau, kinase-targeted therapies for AD have not been successful in clinical trials. Critically, the kinases responsible for numerous identified tau phosphorylation sites remain unknown. G protein-coupled receptor (GPCR) kinases (GRKs) have recently been implicated in phosphorylation of non-GPCR substrates, for example, tubulin and α-synuclein, and in neurological disorders, including schizophrenia and Parkinson's disease. Accordingly, we investigated the involvement of GRKs in the pathophysiology of AD.

METHODS

We performed a comprehensive immunohistochemical and biochemical analysis of the ubiquitously expressed GRKs, namely, GRK2, 3, 5 and 6, in postmortem human brain tissue of control subjects and AD patients.

RESULTS

GRKs display unique cell-type-specific expression patterns in neurons, astrocytes and microglia. Levels of GRKs 2, 5 and 6 are specifically decreased in the CA1 region of the AD hippocampus. Biochemical evidence indicates that the GRKs differentially associate with total, soluble and insoluble pools of tau in the AD brain. Complementary immunohistochemical studies indicate that the GRKs differentially colocalise with total tau, phosphorylated tau and NFTs. Notably, GRKs 3 and 5 also colocalise with amyloid plaques.

CONCLUSION

These studies establish a link between GRKs and the pathological phosphorylation and accumulation of tau and amyloid pathology in AD brains and suggest a novel role for these kinases in regulation of the pathological hallmarks of AD.

A peptide of the amino-terminus of GRK2 induces hypertrophy and yet elicits cardioprotection after pressure overload

G protein-coupled receptor (GPCR) kinase 2 (GRK2) expression and activity are elevated early on in response to several forms of cardiovascular stress and are a hallmark of heart failure. Interestingly, though, in addition to its well-characterized role in regulating GPCRs, mounting evidence suggests a GRK2 "interactome" that underlies a great diversity in its functional roles. Several such GRK2 interacting partners are important for adaptive and maladaptive myocyte growth; therefore, an understanding of domain-specific interactions with signaling and regulatory molecules could lead to novel targets for heart failure therapy. Herein, we subjected transgenic mice with cardiac restricted expression of a short, amino terminal fragment of GRK2 (βARKnt) to pressure overload and found that unlike their littermate controls or previous GRK2 fragments, they exhibited an increased left ventricular wall thickness and mass prior to cardiac stress that underwent proportional hypertrophic growth to controls after acute pressure overload. Importantly, despite this enlarged heart, βARKnt mice did not undergo the expected transition to heart failure observed in controls. Further, βARKnt expression limited adverse left ventricular remodeling and increased cell survival signaling. Proteomic analysis to identify βARKnt binding partners that may underlie the improved cardiovascular phenotype uncovered a selective functional interaction of both endogenous GRK2 and βARKnt with AKT substrate of 160 kDa (AS160). AS160 has emerged as a key downstream regulator of insulin signaling, integrating physiological and metabolic cues to couple energy demand to membrane recruitment of Glut4. Our preliminary data indicate that in βARKnt mice, cardiomyocyte insulin signaling is improved during stress, with a coordinate increase in spare respiratory activity and ATP production without metabolite switching. Surprisingly, these studies also revealed a significant decrease in gonadal fat weight, equivalent to human abdominal fat, in male βARKnt mice at baseline and following cardiac stress. These data suggest that the enhanced AS160-mediated signaling in the βARKnt mice may ameliorate pathological cardiac remodeling through direct modulation of insulin signaling within cardiomyocytes, and translate these to beneficial effects on systemic metabolism.

Unravelling the role of gut microbiota in Parkinson's disease progression: Pathogenic and therapeutic implications

In recent years, researchers have shown interest in bi-directional interaction between the brain and gut, called "gut-brain axis". Emerging pieces of evidence indicate that disturbances in this axis is found to be associated with the Parkinson's disease (PD). Several clinical investigations revealed the crucial role of gut microbiota in the pathogenesis of PD. It has been suggested that aggregation of misfolded protein α-syn, the neuropathological hallmark of PD, might begin in gut and propagates to the CNS via vagus nerve and olfactory bulb. Emerging evidences also suggest that initiation and progression of PD may be due to inflammation originating from gut. It has been shown that microbial gut dysbiosis causes the production of various pathogenic microbial metabolites which elevates pro-inflammatory environment in the gut that promotes neuroinflammation in the CNS. These observations raise the intriguing question - how gut microbial dysbiosis could contribute to PD progression. In this context, various microbiota-targeted therapies are under consideration that can re-establish the intestinal homeostasis which may have greater promise in the prevention and treatment of PD. This review focuses on the role of the gut microbiota in the initiation, progression of PD and current therapeutic intervention to deplete the severity of the disease.

G protein-coupled receptor kinase 2 modifies the ability of Caenorhabditis elegans to survive oxidative stress

Survival and adaptation to oxidative stress is important for many organisms, and these occur through the activation of many different signaling pathways. In this report, we showed that Caenorhabditis (C.) elegans G protein-coupled receptor kinases modified the ability of the organism to resist oxidative stress. In acute oxidative stress studies using juglone, loss-of-function grk-2 mutants were more resistant to oxidative stress compared with loss-of-function grk-1 mutants and the wild-type N2 animals. This effect was Ce-AKT-1 dependent, suggesting that Ce-GRK2 adjusted C. elegans oxidative stress resistance through the IGF/insulin-like signaling (IIS) pathway. Treating C. elegans with a GRK2 inhibitor, the selective serotonin reuptake inhibitor paroxetine, resulted in increased acute oxidative stress resistance compared with another selective serotonin reuptake inhibitor, fluoxetine. In chronic oxidative stress studies with paraquat, both grk-1 and grk-2 mutants had longer lifespan compared with the wild-type N2 animals in stress. In summary, this research showed the importance of both GRKs, especially GRK2, in modifying oxidative stress resistance.

Aging-related modifications to G protein-coupled receptor signaling diversity

Aging is a highly complex molecular process, affecting nearly all tissue systems in humans and is the highest risk factor in developing neurodegenerative disorders such as Alzheimer's and Parkinson's disease, cardiovascular disease and Type 2 diabetes mellitus. The intense complexity of the aging process creates an incentive to develop more specific drugs that attenuate or even reverse some of the features of premature aging. As our current pharmacopeia is dominated by therapeutics that target members of the G protein-coupled receptor (GPCR) superfamily it may be prudent to search for effective anti-aging therapeutics in this fertile domain. Since the first demonstration of GPCR-based β-arrestin signaling, it has become clear that an enhanced appreciation of GPCR signaling diversity may facilitate the creation of therapeutics with selective signaling activities. Such 'biased' ligand signaling profiles can be effectively investigated using both standard molecular biological techniques as well as high-dimensionality data analyses. Through a more nuanced appreciation of the quantitative nature across the multiple dimensions of signaling bias that drugs possess, researchers may be able to further refine the efficacy of GPCR modulators to impact the complex aberrations that constitute the aging process. Identifying novel effector profiles could expand the effective pharmacopeia and assist in the design of precision medicines. This review discusses potential non-G protein effectors, and specifically their potential therapeutic suitability in aging and age-related disorders.

The Role of the Microbiota-Gut-Brain Axis and Antibiotics in ALS and Neurodegenerative Diseases

: The human gut hosts a wide and diverse ecosystem of microorganisms termed the microbiota, which line the walls of the digestive tract and colon where they co-metabolize digestible and indigestible food to contribute a plethora of biochemical compounds with diverse biological functions. The influence gut microbes have on neurological processes is largely yet unexplored. However, recent data regarding the so-called leaky gut, leaky brain syndrome suggests a potential link between the gut microbiota, inflammation and host co-metabolism that may affect neuropathology both locally and distally from sites where microorganisms are found. The focus of this manuscript is to draw connection between the microbiota-gut-brain (MGB) axis, antibiotics and the use of "BUGS AS DRUGS" for neurodegenerative diseases, their treatment, diagnoses and management and to compare the effect of current and past pharmaceuticals and antibiotics for alternative mechanisms of action for brain and neuronal disorders, such as Alzheimer disease (AD), Amyotrophic Lateral Sclerosis (ALS), mood disorders, schizophrenia, autism spectrum disorders and others. It is a paradigm shift to suggest these diseases can be largely affected by unknown aspects of the microbiota. Therefore, a future exists for applying microbial, chemobiotic and chemotherapeutic approaches to enhance translational and personalized medical outcomes. Microbial modifying applications, such as CRISPR technology and recombinant DNA technology, among others, echo a theme in shifting paradigms, which involve the gut microbiota (GM) and mycobiota and will lead to potential gut-driven treatments for refractory neurologic diseases.

Paeoniflorin-6'-O-benzene sulfonate down-regulates CXCR4-Gβγ-PI3K/AKT mediated migration in fibroblast-like synoviocytes of rheumatoid arthritis by inhibiting GRK2 translocation

OBJECTIVE

This study aims to explore the effect of paeoniflorin-6'-O-benzene sulfonate (CP-25) on the migration of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) and the mechanism focused on CXCR4-Gβγ-PI3K/AKT signaling.

METHODS

Human synovial tissues were collected from RA and osteoarthritis (OA) patients. Immunohistochemistry (IHC) and Western blot were used to detect the protein expression of CXCR4, GRK2, Gβγ, PI3K, p-PI3K, AKT and p-AKT. Transwell was adopted to analyse the migration of fibroblast-like synoviocytes (FLS). Co-immunoprecipitation (Co-IP) and laser scanning confocal microscopy (LSCM) were used to detect the combination of GRK2 and Gβγ, the combination of PI3K and Gβγ.

RESULTS

The expression level of CXCR4, GRK2, Gβγ, p-p85 and p-AKT were increased in RA synovial tissue according to the results of IHC and Western blot. In vitro, the migration of FLS was increased after stimulation of CXCL12, inhibition of Gβγ suppressed the migration and phosphorylation of p85 and AKT induced by CXCL12 in FLS, and CP-25 had the same effect as inhibition of Gβγ. The membrane expression of GRK2, Gβγ, PI3K and the combination of GRK2 and Gβγ, the combination of PI3K and Gβγ in FLS were increased after the stimulation of CXCL12, and CP-25 had an ability in reducing the membrane expression and the combination of these proteins.

CONCLUSION

Excessive migration of FLS in RA was associated with over-activation of PI3K/AKT signaling, and the activity of Gβγ was involved in the over-activation of PI3K/AKT. CP-25 down-regulated CXCR4-Gβγ-PI3K/AKT signals by inhibiting GRK2-Gβγ complex membrane translocation.

The Microbiota-Gut-Brain Axis-Heart Shunt Part II: Prosaic Foods and the Brain-Heart Connection in Alzheimer Disease

There is a strong cerebrovascular component to brain aging, Alzheimer disease, and vascular dementia. Foods, common drugs, and the polyphenolic compounds contained in wine modulate health both directly and through the gut microbiota. This observation and novel findings centered on nutrition, biochemistry, and metabolism, as well as the newer insights we gain into the microbiota-gut-brain axis, now lead us to propose a shunt to this classic triad, which involves the heart and cerebrovascular systems. The French paradox and prosaic foods, as they relate to the microbiota-gut-brain axis and neurodegenerative diseases, are discussed in this manuscript, which is the second part of a two-part series of concept papers addressing the notion that the microbiota and host liver metabolism all play roles in brain and heart health.

The Microbiota-Gut-Brain Axis Heart Shunt Part I: The French Paradox, Heart Disease and the Microbiota

It has been well established that a vegetarian and polyphenol-rich diet, including fruits, vegetables, teas, juices, wine, indigestible fiber and whole grains, provide health-promoting phytochemicals and phytonutrients that are beneficial for the heart and brain. What is not well-characterized is the affect these foods have when co-metabolized within our dynamic gut and its colonizing flora. The concept of a heart shunt within the microbiota-gut-brain axis underscores the close association between brain and heart health and the so-called “French paradox” offers clues for understanding neurodegenerative and cerebrovascular diseases. Moreover, oxidation-redox reactions and redox properties of so-called brain and heart-protective foods are underappreciated as to their enhanced or deleterious mechanisms of action. Focusing on prodromal stages, and common mechanisms underlying heart, cerebrovascular and neurodegenerative diseases, we may unmask and understanding the means to better treat these related diseases.

Loss of dynamic regulation of G protein-coupled receptor kinase 2 by nitric oxide leads to cardiovascular dysfunction with aging

Nitric oxide (NO) and S-nitrosothiol (SNO) are considered cardio- and vasoprotective substances. We now understand that one mechanism in which NO/SNOs provide cardiovascular protection is through their direct inhibition of cardiac G protein-coupled receptor (GPCR) kinase 2 (GRK2) activity via S-nitrosylation of GRK2 at cysteine 340 (C340). This maintains GPCR homeostasis, including β-adrenergic receptors, through curbing receptor GRK2-mediated desensitization. Previously, we have developed a knockin mouse (GRK2-C340S) where endogenous GRK2 is resistant to dynamic S-nitrosylation, which led to increased GRK2 desensitizing activity. This unchecked regulation of cardiac GRK2 activity resulted in significantly more myocardial damage after ischemic injury that was resistant to NO-mediated cardioprotection. Although young adult GRK2-C340S mice show no overt phenotype, we now report that as these mice age, they develop significant cardiovascular dysfunction due to the loss of SNO-mediated GRK2 regulation. This pathological phenotype is apparent as early as 12 mo of age and includes reduced cardiac function, increased cardiac perivascular fibrosis, and maladaptive cardiac hypertrophy, which are common maladies found in patients with cardiovascular disease (CVD). There are also vascular reactivity and aortic abnormalities present in these mice. Therefore, our data demonstrate that a chronic and global increase in GRK2 activity is sufficient to cause cardiovascular remodeling and dysfunction, likely due to GRK2’s desensitizing effects in several tissues. Because GRK2 levels have been reported to be elevated in elderly CVD patients, GRK2-C340 mice can give insight into the aged-molecular landscape leading to CVD.

NEW & NOTEWORTHY Research on G protein-coupled receptor kinase 2 (GRK2) in the setting of cardiovascular aging is largely unknown despite its strong established functions in cardiovascular physiology and pathophysiology. This study uses a mouse model of chronic GRK2 overactivity to further investigate the consequences of long-term GRK2 on cardiac function and structure. We report for the first time that chronic GRK2 overactivity was able to cause cardiac dysfunction and remodeling independent of surgical intervention, highlighting the importance of GRK activity in aged-related heart disease.

Annona atemoya leaf extract ameliorates cognitive impairment in amyloid-β injected Alzheimer's disease-like mouse model

Annona atemoya is a hybrid of Annona squamosa and Annona cherimola that grow in several subtropical or tropical areas such as Florida in the US, Philippines, Cuba, Jamaica, Taiwan, and Jeju in South Korea. We report that the A. atemoya leaves (AAL) have inhibitory effects on the pathogenesis and regulatory mechanisms of Alzheimer’s disease (AD). Ethanol extract of AAL prevented amyloid-β (Aβ) aggregation and increased free radical scavenging activity. In addition, AAL extract exerted protective effects against neuronal cell death in HT22 hippocampal cells. Moreover, oral administration of AAL extract significantly improved memory loss in the passive avoidance task and Y-maze test, as well as downregulated the expression of neuronal markers neuronal nuclei and brain-derived neurotrophic factor in Aβ-injected AD mice. To verify the molecular mechanisms responsible for anti-AD actions of AAL, we conducted the antibody microarray analysis and found that epidermal growth factor receptor/G protein-coupled receptor kinase 2 signaling was activated in neuronal cells and AD-like mouse models. Additionally, quantitative analyses of the six standard compounds using high-performance liquid chromatography revealed that rutin is the most abundant compound of AAL. Furthermore, efficacy analyses of six standard compounds showed that rutin and isoquercitrin had significant inhibitory activity on Aβ aggregation. Taken together with biological activity and the content of compounds, rutin maybe a bioactive compound of AAL in the AD pathogenesis. Overall, our findings provide the first scientific support for the therapeutic effects of AAL in AD and AD-related disorders.

Impact statement

Our study was aimed to find a novel candidate drug for Alzheimer’s disease (AD) using natural products. We assessed the effects of Annona atemoya extracts on crucial events in the pathogenesis of AD. A. atemoya leaf (AAL) extract significantly inhibited amyloid-β aggregation, oxidative stress, neuronal cell death, and memory impairment through the epidermal growth factor receptor/G protein-coupled receptor kinase 2 pathway. Simultaneous analysis using HPLC determined six standard compounds of AAL extract, and rutin was identified as a bioactive compound. Of note, the anti-AD activity of AAL extract was more significant compared to other extracts from medicinal plants of which efficacy was previously reported. The potential of AAL extract as an anti-AD agent may provide insight into the new drug development for AD treatment.

The Transformative Possibilities of the Microbiota and Mycobiota for Health, Disease, Aging, and Technological Innovation

The gut microbiota is extremely important for the health of the host across its lifespan.Recent studies have elucidated connections between the gut microbiota and neurological diseaseand disorders such as depression, anxiety, Alzheimer's disease (AD), autism, and a host of otherbrain illnesses. Dysbiosis of the normal gut flora can have negative consequences for humans,especially throughout key periods during our lifespan as the gut microbes change with age in bothphenotype and number of bacterial species. Neurologic diseases, mental disorders, and euthymicstates are influenced by alterations in the metabolites produced by gut microbial milieu. Weintroduce a new concept, namely, the mycobiota and microbiota-gut-brain neuroendocrine axis anddiscuss co-metabolism with emphasis on means to influence or correct disruptions to normal gutflora throughout the lifespan from early development to old age. These changes involveinflammation and involve the permeability of barriers, such as the intestine blood barrier, the blood⁻brain barrier, and others. The mycobiota and microbiota⁻gut⁻brain axis offer new research horizonsand represents a great potential target for new therapeutics, including approaches based aroundinflammatory disruptive process, genetically engineered drug delivery systems, diseased cellculling "kill switches", phage-like therapies, medicinal chemistry, or microbial parabiosis to namea few.

Antidiabetic and Cardioprotective Effects of Pharmacological Inhibition of GRK2 in db/db Mice

Despite the availability of several therapies for the management of blood glucose in diabetic patients, most of the treatments do not show benefits on diabetic cardiomyopathy, while others even favor the progression of the disease. New pharmacological targets are needed that might help the management of diabetes and its cardiovascular complications at the same time. GRK2 appears a promising target, given its established role in insulin resistance and in systolic heart failure. Using a custom peptide inhibitor of GRK2, we assessed in vitro in L6 myoblasts the effects of GRK2 inhibition on glucose extraction and insulin signaling. Afterwards, we treated diabetic male mice (db/db) for 2 weeks. Glucose tolerance (IGTT) and insulin sensitivity (ITT) were ameliorated, as was skeletal muscle glucose uptake and insulin signaling. In the heart, at the same time, the GRK2 inhibitor ameliorated inflammatory and cytokine responses, reduced oxidative stress, and corrected patterns of fetal gene expression, typical of diabetic cardiomyopathy. GRK2 inhibition represents a promising therapeutic target for diabetes and its cardiovascular complications.

GRKs and β-Arrestins: "Gatekeepers" of Mitochondrial Function in the Failing Heart

Mitochondrial regulation of energy production, calcium homeostasis, and cell death are critical for cardiac function. Accordingly, the structural and functional abnormalities of these organelles (mitochondrial dysfunction) contribute to developing cardiovascular diseases and heart failure. Therefore the preservation of mitochondrial integrity is essential for cardiac cell survival. Mitochondrial function is regulated by several proteins, including GRK2 and β-arrestins which act in a GPCR independent manner to orchestrate intracellular signaling associated with key mitochondrial processes. It is now ascertained that GRK2 is able to recover mitochondrial function in response to insults. β-arrestins affect several intracellular signaling pathways within the cell which in turn are involved in the regulation of mitochondrial function, but a direct regulation of mitochondria needs further investigations. In this review, we discuss the recent acquisitions on the role of GRK2 and β-arrestins in the regulation of mitochondrial function.

Restricting mitochondrial GRK2 post-ischemia confers cardioprotection by reducing myocyte death and maintaining glucose oxidation

Increased abundance of GRK2 [G protein-coupled receptor (GPCR) kinase 2] is associated with poor cardiac function in heart failure patients. In animal models, GRK2 contributes to the pathogenesis of heart failure after ischemia-reperfusion (IR) injury. In addition to its role in down-regulating activated GPCRs, GRK2 also localizes to mitochondria both basally and post-IR injury, where it regulates cellular metabolism. We previously showed that phosphorylation of GRK2 at Ser⁶⁷⁰ is essential for the translocation of GRK2 to the mitochondria of cardiomyocytes post-IR injury in vitro and that this localization promotes cell death. Here, we showed that mice with a S670A knock-in mutation in endogenous GRK2 showed reduced cardiomyocyte death and better cardiac function post-IR injury. Cultured GRK2-S670A knock-in cardiomyocytes subjected to IR in vitro showed enhanced glucose-mediated mitochondrial respiratory function that was partially due to maintenance of pyruvate dehydrogenase activity and improved glucose oxidation. Thus, we propose that mitochondrial GRK2 plays a detrimental role in cardiac glucose oxidation post-injury.

Blood-Based Kinase Assessments in Alzheimer's Disease

Alzheimer’s disease (AD) is marked by memory disturbances followed by aphasia, apraxia and agnosia. Brain lesions include the accumulation of the amyloid peptide in extracellular plaques, neurofibrillary tangles with abnormally phosphorylated tau protein and synaptic and neuronal loss. New findings have suggested that brain lesions could occur one or two decades before the first clinical signs. This asymptomatic preclinical phase could be an opportunity to put in place a secondary prevention but the detection of these brain lesions can only be achieved so far by cerebrospinal fluid (CSF) evaluation or molecular amyloid and tau PET imaging. There is an urgent need to find out simple and easily accessible new biomarkers to set up an efficient screening in adult and aging population. Neuropathological and biochemical studies have revealed that abnormal accumulations of potentially toxic kinases are present in the brains of AD patients. Kinase activation leads to abnormal tau phosphorylation, amyloid production, apoptosis and neuroinflammation. Increased levels of these kinases are present in the CSF of mild cognitive impairment (MCI) and AD patients. Over the last years the search for abnormal kinase levels was performed in the blood of patients. Glycogen synthase kinase 3 (GSK 3), protein kinase R (PKR), mamalian target of rapamycin (mTOR), dual specificity tyrosine-phosphorylation-regulated kinase 1A (DIRK1A), c-Jun N-terminal kinase (JNK), protein 70 kD ribosomal protein S6 kinase (P70S6K), ERK2 and other kinase concentrations were evaluated and abnormal levels were found in many studies. For example, GSK3 levels are increased in MCI and AD patients. PKR levels are also augmented in peripheral blood mononuclear cells (PBMC) of AD patients. In the future, the assessment of several blood kinase levels in large cohorts of patients will be needed to confirm the usefulness of this test at an early phase of the disease.

Amyloid-β1-42 dynamically regulates the migration of neural stem/progenitor cells via MAPK-ERK pathway

Neural stem/progenitor cell (NSPC) based therapy represents an attractive treatment for Alzheimer's disease (AD), the most common neurodegenerative disorder with no effective treatment to date. This can be achieved by stimulating endogenous NSPCs and/or administrating exogenously produced NSPCs. Successful repair requires the migration of NSPCs to the loci where neuronal loss occurs, differentiation and integration into neural networks. However, the progressive loss of neurons in the brain of AD patients suggests that the repair by endogenous NSPCs in the setting of AD may be defective. The production and deposition of amyloid-β_1-42 (Aβ_1-42) peptides is thought to be a central event in the pathogenesis of AD. Here we report that Aβ_1-42 peptides inhibit the migration of in vitro cultured NSPCs by disturbing the ERK-MAPK signal pathway. We found that the migratory capacity of NSPCs was compromised upon treatment with oligomeric Aβ_1-42; the inhibitory effect occurred in a dose-dependent manner. Our previous studies have shown that Aβ_1-42 triggers the expression of GRK2 by unknown mechanism. Herein we found that the Aβ_1-42 evoked upregulation of GRK2 expression was attenuated upon treatment with the ERK inhibitor SCH772984 at 2.5 μM, but not with inhibitors for p38 or JNK. We detected a dose-dependent increase in levels of phosphorylated ERK1/2 after incubation of cells with oligomeric Aβ_1-42 peptides for 3 days. We observed that an increase in the phosphorylation of p38 and JNK coincided with reduced phosphorylation of ERK1/2 upon treatment with Aβ_1-42 for 6 and/or 9 days. We hypothesize that the divergence of the activation of the MAPK family of pathways may contribute to the inhibition of NSPCs migration after the long-term incubation with Aβ_1-42. Pretreatment with 1  μM MEK inhibitor U0126 reversed the effects of Aβ_1-42 on GRK2 expression of and NSPC migration. Together, our results suggest that Aβ_1-42 oligomers compromise the migratory capacity of NSPCs through the MEK-ERK pathway.

Treating cognitive impairment with transcranial low level laser therapy

This report examines the potential of low level laser therapy (LLLT) to alter brain cell function and neurometabolic pathways using red or near infrared (NIR) wavelengths transcranially for the prevention and treatment of cognitive impairment. Although laser therapy on human tissue has been used for a number of medical conditions since the late 1960s, it is only recently that several clinical studies have shown its value in raising neurometabolic energy levels that can improve cerebral hemodynamics and cognitive abilities in humans. The rationale for this approach, as indicated in this report, is supported by growing evidence that neurodegenerative damage and cognitive impairment during advanced aging is accelerated or triggered by a neuronal energy crisis generated by brain hypoperfusion. We have previously proposed that chronic brain hypoperfusion in the elderly can worsen in the presence of one or more vascular risk factors, including hypertension, cardiac disease, atherosclerosis and diabetes type 2. Although many unanswered questions remain, boosting neurometabolic activity through non-invasive transcranial laser biostimulation of neuronal mitochondria may be a valuable tool in preventing or delaying age-related cognitive decline that can lead to dementia, including its two major subtypes, Alzheimer's and vascular dementia. The technology to achieve significant improvement of cognitive dysfunction using LLLT or variations of this technique is moving fast and may signal a new chapter in the treatment and prevention of neurocognitive disorders.

G-Protein-Coupled Receptor Kinase 2 (GRK2) Inhibitors: Current Trends and Future Perspectives

G-protein-coupled receptor kinase 2 (GRK2) is a G-protein-coupled receptor kinase that is ubiquitously expressed in many tissues and regulates various intracellular mechanisms. The up- or down-regulation of GRK2 correlates with several pathological disorders. GRK2 plays an important role in the maintenance of heart structure and function; thus, this kinase is involved in many cardiovascular diseases. GRK2 up-regulation can worsen cardiac ischemia; furthermore, increased kinase levels occur during the early stages of heart failure and in hypertensive subjects. GRK2 up-regulation can lead to changes in the insulin signaling cascade, which can translate to insulin resistance. Increased GRK2 levels also correlate with the degree of cognitive impairment that is typically observed in Alzheimer's disease. This article reviews the most potent and selective GRK2 inhibitors that have been developed. We focus on their mechanism of action, inhibition profile, and structure-activity relationships to provide insight into the further development of GRK2 inhibitors as drug candidates.

G protein-coupled receptor kinase 2: a link between myocardial contractile function and cardiac metabolism

Heart failure (HF) causes a tremendous burden on the worldwide healthcare system, affecting >23 million people. There are many cardiovascular disorders that contribute to the development of HF and multiple risk factors that accelerate its occurrence, but regardless of its underlying cause, HF is characterized by a marked decrease in myocardial contractility and loss of pump function. One biomarker molecule consistently shown to be upregulated in human HF and several animal models is G protein-coupled receptor kinase-2 (GRK2), a kinase originally discovered to be involved in G protein-coupled receptor desensitization, especially β-adrenergic receptors. Higher levels of GRK2 can impair β-adrenergic receptor-mediated inotropic reserve and its inhibition, or molecular reduction has shown to improve pump function in several animal models including a preclinical pig model of HF. Recently, nonclassical roles for GRK2 in cardiovascular disease have been described, including negative regulation of insulin signaling, a role in myocyte cell survival and apoptotic signaling, and it has been shown to be localized in/on mitochondria. These new roles of GRK2 suggest that GRK2 may be a nodal link in the myocyte, influencing both cardiac contractile function and cell metabolism and survival and contributing to HF independent of its canonical role in G protein-coupled receptor desensitization. In this review, classical and nonclassical roles for GRK2 will be discussed, focusing on recently discovered roles for GRK2 in cardiomyocyte metabolism and the effects that these roles may have on myocardial contractile function and HF development.

Implication of the nutritional and nonnutritional factors in the context of preservation of cognitive performance in patients with dementia/depression and Alzheimer disease

It has been postulated that Alzheimer disease (AD) is a systemic process, which involves multiple pathophysiological factors. A combination of pharmacotherapy and nonpharmacological interventions has been proposed to treat AD and other dementia. The nonpharmacological interventions include but are not limited to increasing sensory input through physical and mental activities, in order to modify cerebral blood flow and implementing nutritional interventions such as diet modification and vitamins and nutraceuticals therapy to vitalize brain functioning. This article highlights the recent research findings regarding novel treatment strategies aimed at modifying natural course of the disease and delaying cognitive decline through simultaneous implementation of pharmacological and nonpharmacological modulators as standardized treatment protocols.

Nodes and biological processes identified on the basis of network analysis in the brain of the senescence accelerated mice as an Alzheimer's disease animal model

Harboring the behavioral and histopathological signatures of Alzheimer's disease (AD), senescence accelerated mouse-prone 8 (SAMP8) mice are currently considered a robust model for studying AD. However, the underlying mechanisms, prioritized pathways and genes in SAMP8 mice linked to AD remain unclear. In this study, we provide a biological interpretation of the molecular underpinnings of SAMP8 mice. Our results were derived from differentially expressed genes in the hippocampus and cerebral cortex of SAMP8 mice compared to age-matched SAMR1 mice at 2, 6, and 12 months of age using cDNA microarray analysis. On the basis of PPI, MetaCore and the co-expression network, we constructed a distinct genetic sub-network in the brains of SAMP8 mice. Next, we determined that the regulation of synaptic transmission and apoptosis were disrupted in the brains of SAMP8 mice. We found abnormal gene expression of RAF1, MAPT, PTGS2, CDKN2A, CAMK2A, NTRK2, AGER, ADRBK1, MCM3AP, and STUB1, which may have initiated the dysfunction of biological processes in the brains of SAMP8 mice. Specifically, we found microRNAs, including miR-20a, miR-17, miR-34a, miR-155, miR-18a, miR-22, miR-26a, miR-101, miR-106b, and miR-125b, that might regulate the expression of nodes in the sub-network. Taken together, these results provide new insights into the biological and genetic mechanisms of SAMP8 mice and add an important dimension to our understanding of the neuro-pathogenesis in SAMP8 mice from a systems perspective.

Protective effect of curcuminoids on age-related mitochondrial impairment in female Wistar rat brain

The present study demonstrated the neuroprotective effect of curcuminoids, the active polyphenols of Curcuma longa (L.) rhizomes on mitochondrial dysfunctioning in middle aged and aged female Wistar rat brain. Rats were orally treated with curcuminoids (100 mg/kg) for 3 months and their brain was collected for evaluation of mitochondrial enzymes and complexes activity, ultra structural changes in mitochondria, neuronal nitric oxide synthase (nNOS) protein expression, adenosine triphosphate (ATP) and lipofuscin content. Significant alterations were observed in all the tested parameters in highly aged rat brain when compared with young control. Long term curcuminoids administration prevented this age associated loss of mitochondrial enzymes and complexes activity in middle aged rat brain except for malate dehydrogenase, Complex II and IV activity when compared with young control. Among aged rats, curcuminoids treatment specifically elevated isocitrate and NADH dehydrogenase, cytochrome c oxidase, Complex I and total ATP content. A significant down-regulation of nNOS protein expression along with reduced lipofuscin content was also observed in curucminoids treated middle aged and aged rats. Thus, it was suggested that curcuminoids may act as a putative drug candidate for the prevention of deleterious effects of ageing and age associated neurodegenerative disorders through amelioration of aberrant mitochondrial functioning.

Targeting G protein coupled receptor-related pathways as emerging molecular therapies

G protein coupled receptors (GPCRs) represent the most important targets in modern pharmacology because of the different functions they mediate, especially within brain and peripheral nervous system, and also because of their functional and stereochemical properties. In this paper, we illustrate, via a variety of examples, novel advances about the GPCR-related molecules that have been shown to play diverse roles in GPCR pathways and in pathophysiological phenomena. We have exemplified how those GPCRs’ pathways are, or might constitute, potential targets for different drugs either to stimulate, modify, regulate or inhibit the cellular mechanisms that are hypothesized to govern some pathologic, physiologic, biologic and cellular or molecular aspects both in vivo and in vitro. Therefore, influencing such pathways will, undoubtedly, lead to different therapeutical applications based on the related pharmacological implications. Furthermore, such new properties can be applied in different fields. In addition to offering fruitful directions for future researches, we hope the reviewed data, together with the elements found within the cited references, will inspire clinicians and researchers devoted to the studies on GPCR’s properties.

Link between cancer and Alzheimer disease via oxidative stress induced by nitric oxide-dependent mitochondrial DNA overproliferation and deletion

Nitric oxide- (NO-) dependent oxidative stress results in mitochondrial ultrastructural alterations and DNA damage in cases of Alzheimer disease (AD). However, little is known about these pathways in human cancers, especially during the development as well as the progression of primary brain tumors and metastatic colorectal cancer. One of the key features of tumors is the deficiency in tissue energy that accompanies mitochondrial lesions and formation of the hypoxic smaller sized mitochondria with ultrastructural abnormalities. We speculate that mitochondrial involvement may play a significant role in the etiopathogenesis of cancer. Recent studies also demonstrate a potential link between AD and cancer, and anticancer drugs are being explored for the inhibition of AD-like pathology in transgenic mice. Severity of the cancer growth, metastasis, and brain pathology in AD (in animal models that mimic human AD) correlate with the degree of mitochondrial ultrastructural abnormalities. Recent advances in the cell-cycle reentry of the terminally differentiated neuronal cells indicate that NO-dependent mitochondrial abnormal activities and mitotic cell division are not the only important pathogenic factors in pathogenesis of cancer and AD, but open a new window for the development of novel treatment strategies for these devastating diseases.

β-amyloid42 induces desensitization of CXC chemokine receptor-4 via formyl peptide receptor in neural stem/progenitor cells

The deposition of β-amyloid (Aβ) plaques and progressive loss of neurons are two main characteristics of Alzheimer's disease (AD). Supplement of neural stem/progenitor cells (NSPCs) is a promising strategy for repair of the neurodegenerative diseases. However, hostile microenvironment of neurodegenerative brain is harmful for the neuroregeneration. Aβ(42) promoted the proliferation of NSPCs. Moreover, Aβ(42) (10-1000 nM) promoted the migration of NSPCs in a dose-dependent manner. The attraction of NSPCs toward Aβ(42) was significantly offset by 10 μM cyclosporin H, a potent and selective formyl peptide receptor antagonist. After incubation with Aβ(42) for 9 d, the migration ability of NSPCs was significantly decreased (p<0.05). The expression of formyl peptide receptor (FPR) and CXC chemokine receptor-4 (CXCR4) were significantly decreased in NSPCs. The expression of G protein-coupled receptor kinase 2 (GRK2) was up-regulated on the membrane of NSPCs correspondingly. Our results suggested that Aβ(42) decreases the migratory capacity of NSPCs by FPR heterologous desensitization after long time incubation, and GRK2 in NSPCs may be responsible for the damaged migratory capacity.

Alzheimer's disease: biological aspects, therapeutic perspectives and diagnostic tools

Alzheimer's disease (AD) is the most common form of dementia among older people. Dementia is an irreversible brain disorder that seriously affects a person's ability to carry out daily activities. It is characterized by loss of cognitive functioning and behavioral abilities, to such an extent that it interferes with the daily life and activities of the affected patients. Although it is still unknown how the disease process begins, it seems that brain damage starts a decade or more before problems become evident. Scientific data seem to indicate that changes in the generation or the degradation of the amyloid-b peptide (Aβ) lead to the formation of aggregated structures that are the triggering molecular events in the pathogenic cascade of AD. This review summarizes some characteristic features of Aβ misfolding and aggregation and how cell damage and death mechanisms are induced by these supramolecular and toxic structures. Further, some interventions for the early diagnosis of AD are described and in the last part the potential therapeutic strategies adoptable to slow down, or better block, the progression of the pathology are reported.

G protein-coupled receptor kinases: more than just kinases and not only for GPCRs

G protein-coupled receptor (GPCR) kinases (GRKs) are best known for their role in homologous desensitization of GPCRs. GRKs phosphorylate activated receptors and promote high affinity binding of arrestins, which precludes G protein coupling. GRKs have a multidomain structure, with the kinase domain inserted into a loop of a regulator of G protein signaling homology domain. Unlike many other kinases, GRKs do not need to be phosphorylated in their activation loop to achieve an activated state. Instead, they are directly activated by docking with active GPCRs. In this manner they are able to selectively phosphorylate Ser/Thr residues on only the activated form of the receptor, unlike related kinases such as protein kinase A. GRKs also phosphorylate a variety of non-GPCR substrates and regulate several signaling pathways via direct interactions with other proteins in a phosphorylation-independent manner. Multiple GRK subtypes are present in virtually every animal cell, with the highest expression levels found in neurons, with their extensive and complex signal regulation. Insufficient or excessive GRK activity was implicated in a variety of human disorders, ranging from heart failure to depression to Parkinson's disease. As key regulators of GPCR-dependent and -independent signaling pathways, GRKs are emerging drug targets and promising molecular tools for therapy. Targeted modulation of expression and/or of activity of several GRK isoforms for therapeutic purposes was recently validated in cardiac disorders and Parkinson's disease.

A role for GRK2 in myocardial ischemic injury: indicators of a potential future therapy and diagnostic

Morbidity and mortality of myocardial infarction remains significant with resulting left ventricular function presenting as a major determinant of clinical outcome. Protecting the myocardium against ischemia reperfusion injury has become a major therapeutic goal and the identification of key signaling pathways has paved the way for various interventions, but until now with disappointing results. This article describes the recently discovered new role of G-protein-coupled receptor kinase-2 (GRK2), which is known to critically influence the development and progression of heart failure, in acute myocardial injury. This article focuses on potential applications of the GRK2 peptide inhibitor βARKct in ischemic myocardial injury, the use of GRK2 as a biomarker in acute myocardial infarction and discusses the challenges of translating GRK2 inhibition as a cardioprotective strategy to a possible future clinical application.

The role of polyphenolic antioxidants in health, disease, and aging

Polyphenolic antioxidants from dietary sources are frequently a topic of interest due to widespread scientific agreement that they may help lower the incidence of certain cancers, cardiovascular and neurodegenerative diseases, and DNA damage and even may have antiaging properties. On the other hand, questions still remain as to whether some antioxidants could be potentially harmful to health, because an increase in glycation-mediated protein damage (carbonyl stress) has been reported in some cases. Nevertheless, the quest for healthy aging has led to the extensive use of phytochemically derived antioxidants to disrupt age-associated deterioration in physiological function and to prevent many age-related diseases. Although a diet rich in the polyphenolic forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders, it is still too early to define their exact clinical benefit for treating age-related disease. This review critically examines polyphenolic antioxidants, such as flavonoids, curcumene, and resveratrol in health, disease, and aging with the hope that a better understanding of the many mechanisms involved with these diverse compounds may lead to better health and novel treatment approaches for age-related diseases.

The GRK2 Overexpression Is a Primary Hallmark of Mitochondrial Lesions during Early Alzheimer Disease

Increasing evidence points to vascular damage as an early contributor to the development of two leading causes of age-associated dementia, namely Alzheimer disease (AD) and AD-like pathology such as stroke. This review focuses on the role of G protein-coupled receptor kinases (GRKs) as they relate to dementia and how the cardio and cerebrovasculature is involved in AD pathogenesis. The exploration of GRKs in AD pathogenesis may help bridge gaps in our understanding of the heart-brain connection in relation to neurovisceral damage and vascular complications of AD. The a priori basis for this inquiry stems from the fact that kinases of this family regulate numerous receptor functions in the brain, myocardium and elsewhere. The aim of this review is to discuss the finding of GRK2 overexpression in the context of early AD pathogenesis. Also, we consider the consequences for this overexpression as a loss of G-protein coupled receptor (GPCR) regulation, as well as suggest a potential role for GPCRs and GRKs in a unifying theory of AD pathogenesis through the cerebrovasculature. Finally, we synthesize this newer information in an attempt to put it into context with GRKs as regulators of cellular function, which makes these proteins potential diagnostic and therapeutic targets for future pharmacological intervention.

Interactions between the amyloid precursor protein C-terminal domain and G proteins mediate calcium dysregulation and amyloid beta toxicity in Alzheimer's disease

Alzheimer's disease is characterized by neuropathological accumulations of amyloid beta(1-42) [A beta(1-42)], a cleavage product of the amyloid precursor protein (APP). Recent studies have highlighted the role of APP in A beta-mediated toxicity and have implicated the G-protein system; however, the exact mechanisms underlying this pathway are as yet undetermined. In this context, we sought to investigate the role of calcium upregulation following APP-dependent, A beta-mediated G-protein activation. Initial studies on the interaction between APP, A beta and Go proteins demonstrated that the interaction between APP, specifically its C-terminal -YENPTY- region, and Go was reduced in the presence of A beta. Cell death and calcium influx in A beta-treated cells were shown to be APP dependent and to involve G-protein activation because these effects were blocked by use of the G-protein inhibitor, pertussis toxin. Collectively, these results highlight a role for the G-protein system in APP-dependent, A beta-induced toxicity and calcium dysregulation. Analysis of the APP:Go interaction in human brain samples from Alzheimer's disease patients at different stages of the disease revealed a decrease in the interaction, correlating with disease progression. Moreover, the reduced interaction between APP and Go was shown to correlate with an increase in membrane A beta levels and G-protein activity, showing for first time that the APP:Go interaction is present in humans and is responsive to A beta load. The results presented support a role for APP in A beta-induced G-protein activation and suggest a mechanism by which basal APP binding to Go is reduced under pathological loads of A beta, liberating Go and activating the G-protein system, which may in turn result in downstream effects including calcium dysregulation. These results also suggest that specific antagonists of G-protein activity may have a therapeutic relevance in Alzheimer's disease.

The effect of acetyl-L-carnitine and R-alpha-lipoic acid treatment in ApoE4 mouse as a model of human Alzheimer's disease

We measured age-dependent effects of human ApoE4 on cerebral blood flow (CBF) using ApoE4 transgenic mice compared to age-matched wild-type (WT) mice by use of [(14)C] iodoantipyrene autoradiography. ApoE4 associated factors reduce CBF gradually to create brain hypoperfusion when compared to WT, and the differences in CBF are greatest as animals age from 6-weeks to 12-months. Transmission electron microscopy with colloidal gold immunocytochemistry showed structural damage in young and aged microvessel endothelium of ApoE4 animals extended to the cytoplasm of perivascular cells, perivascular nerve terminals and hippocampal neurons and glial cells. These abnormalities coexist with mitochondrial structural alteration and mitochondrial DNA overproliferation and/or deletion in all brain cellular compartments. Spatial memory and temporal memory tests showed a trend in improving cognitive function in ApoE4 mice fed selective mitochondrial antioxidants acetyl-l-carnitine and R-alpha-lipoic acid. Our findings indicate that ApoE4 genotype-induced mitochondrial changes and associated structural damage may explain age-dependent pathology seen in AD, indicating potential for novel treatment strategies in the near future.

Insights into cerebrovascular complications and Alzheimer disease through the selective loss of GRK2 regulation

Alzheimer disease (AD) and stroke are two leading causes of age-associated dementia. Increasing evidence points to vascular damage as an early contributor to the development of AD and AD-like pathology. In this review, we discuss the role of G protein-coupled receptor kinase 2 (GRK2) as it relates to individuals affected by AD and how the cardiovasculature plays a role in AD pathogenesis. The possible involvement of GRKs in AD pathogenesis is an interesting notion, which may help bridge the gap in our understanding of the heart–brain connection in relation to neurovisceral damage and vascular complications in AD, since kinases of this family are known to regulate numerous receptor functions both in the brain, myocardium, and elsewhere. The aim of this review is to discuss our findings of overexpression of GRK2 in the context of the early pathogenesis of AD, because increased levels of GRK2 immunoreactivity were found in vulnerable neurons of AD patients as well as in a two-vessel occlusion (2-VO) mammalian model of ischaemia. Also, we consider the consequences for this overexpression as a loss of G-protein coupled receptor (GPCR) regulation, as well as suggest a potential role for GPCRs and GRKs in a unifying theory of AD pathogenesis, particularly in the context of cerebrovascular disease. We synthesize this newer information and attempt to put it into context with GRKs as regulators of diverse physiological cellular functions that could be appropriate targets for future pharmacological intervention.

Neuronal mitochondrial amelioration by feeding acetyl-L-carnitine and lipoic acid to aged rats

Brain function declines with age and is associated with diminishing mitochondrial integrity. The neuronal mitochondrial ultrastructural changes of young (4 months) and old (21 months) F344 rats supplemented with two mitochondrial metabolites, acetyl-L-carnitine (ALCAR, 0.2%[wt/vol] in the drinking water) and R-α-lipoic acid (LA, 0.1%[wt/wt] in the chow), were analysed using qualitative and quantitative electron microscopy techniques. Two independent morphologists blinded to sample identity examined and scored all electron micrographs. Mitochondria were examined in each micrograph, and each structure was scored according to the degree of injury. Controls displayed an age-associated significant decrease in the number of intact mitochondria (P = 0.026) as well as an increase in mitochondria with broken cristae (P < 0.001) in the hippocampus as demonstrated by electron microscopic observations. Neuronal mitochondrial damage was associated with damage in vessel wall cells, especially vascular endothelial cells. Dietary supplementation of young and aged animals increased the proliferation of intact mitochondria and reduced the density of mitochondria associated with vacuoles and lipofuscin. Feeding old rats ALCAR and LA significantly reduced the number of severely damaged mitochondria (P = 0.02) and increased the number of intact mitochondria (P < 0.001) in the hippocampus. These results suggest that feeding ALCAR with LA may ameliorate age-associated mitochondrial ultrastructural decay and are consistent with previous studies showing improved brain function.