Cross-Sectional and Longitudinal Comparison of Tau Imaging with 18F-MK6240 and 18F-Flortaucipir in Populations Matched for Age, MMSE and Brain Beta-Amyloid Burden

OBJECTIVES

Longitudinal tau quantification may provide a useful marker of drug efficacy in clinical trials. Different tau PET tracers may have different sensitivity to longitudinal changes, but without a head-to-head dataset or a carefully designed case-matching procedure, comparing results in different cohorts can be biased. In this study, we compared the tau PET tracers, 18F-MK6240 and 18F-flortaucipir (FTP), both cross-sectionally and longitudinally by case-matching subjects in the AIBL and ADNI longitudinal cohort studies.

METHODS

A subset of 113 participants from AIBL and 113 from ADNI imaged using 18F-MK6240 and 18F-FTP respectively, with baseline and follow-up, were matched based on baseline clinical diagnosis, MMSE, age and amyloid (Aβ) PET centiloid value. Subjects were grouped as 64 Aβ- cognitively unimpaired (CU), 22 Aβ+ CU, 14 Aβ+ mild cognitive impairment (MCI) and 13 Aβ+ Alzheimer's disease (AD). Tracer retention was measured in the mesial, temporoparietal, rest of the cortex, and a meta-temporal region composed of entorhinal, inferior/middle temporal, fusiform, parahippocampus and amygdala. T-tests were employed to assess group separation at baseline using SUVR Z-scores and longitudinally using SUVR%/Yr.

RESULTS

Both tracers detected statistically significant differences at baseline in most regions between all clinical groups. Only 18F-MK6240 showed statistically significant higher rate of SUVR increase in Aβ+ CU compared to Aβ- CU in the mesial, meta-temporal and temporoparietal regions.

CONCLUSION

18F-MK6240 appears to be a more sensitive tracer for change in tau level at the preclinical stage of AD.

Two-Year Prognostic Utility of Plasma p217+tau across the Alzheimer's Continuum

BACKGROUND

Plasma p217+tau has shown high concordance with cerebrospinal fluid (CSF) and positron emission tomography (PET) measures of amyloid-β (Aβ) and tau in Alzheimer's Disease (AD). However, its association with longitudinal cognition and comparative performance to PET Aβ and tau in predicting cognitive decline are unknown.

OBJECTIVES

To evaluate whether p217+tau can predict the rate of cognitive decline observed over two-year average follow-up and compare this to prediction based on Aβ (18F-NAV4694) and tau (18F-MK6240) PET. We also explored the sample size required to detect a 30% slowing in cognitive decline in a 2-year trial and selection test cost using p217+tau (pT+) as compared to PET Aβ (A+) and tau (T+) with and without p217+tau pre-screening.

DESIGN

A prospective observational cohort study.

SETTING

Participants of the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL) and Australian Dementia Network (ADNeT).

PARTICIPANTS

153 cognitively unimpaired (CU) and 50 cognitively impaired (CI) individuals.

MEASUREMENTS

Baseline p217+tau Simoa® assay, 18F-MK6240 tau-PET and 18F-NAV4694 Aβ-PET with neuropsychological follow-up (MMSE, CDR-SB, AIBL-PACC) over 2.4 ± 0.8 years.

RESULTS

In CI, p217+tau was a significant predictor of change in MMSE (β = -0.55, p < 0.001) and CDR-SB (β =0.61, p < 0.001) with an effect size similar to Aβ Centiloid (MMSE β = -0.48, p = 0.002; CDR-SB β = 0.43, p = 0.004) and meta-temporal (MetaT) tau SUVR (MMSE: β = -0.62, p < 0.001; CDR-SB: β = 0.65, p < 0.001). In CU, only MetaT tau SUVR was significantly associated with change in AIBL-PACC (β = -0.22, p = 0.008). Screening pT+ CI participants into a trial could lead to 24% reduction in sample size compared to screening with PET for A+ and 6-13% compared to screening with PET for T+ (different regions). This would translate to an 81-83% biomarker test cost-saving assuming the p217+tau test cost one-fifth of a PET scan. In a trial requiring PET A+ or T+, p217+tau pre-screening followed by PET in those who were pT+ would cost more in the CI group, compared to 26-38% biomarker test cost-saving in the CU.

CONCLUSIONS

Substantial cost reduction can be achieved using p217+tau alone to select participants with MCI or mild dementia for a clinical trial designed to slow cognitive decline over two years, compared to participant selection by PET. In pre-clinical AD trials, p217+tau provides significant cost-saving if used as a pre-screening measure for PET A+ or T+ but in MCI/mild dementia trials this may add to cost both in testing and in the increased number of participants needed for testing.

Sirtuins as therapeutic targets for improving delayed wound healing in diabetes

Sirtuins are a vast family of histone deacetylases, which are NAD⁺ dependent enzymes, consisting of seven members, namely SIRT 1, SIRT 6 and SIRT 7 located within the nucleus, SIRT 2 in the cytoplasm and SIRT 3, SIRT 4, and SIRT 5 in the mitochondria. They have vital roles in regulating various biological functions such as age-related metabolic disorders, inflammation, stress response, cardiovascular and neuronal functions. Delayed wound healing is one of the complication of diabetes, which can lead to lower limb amputation if not treated timely. SIRT 1, 3 and 6 are potent targets for diabetic wound healing. SIRT 1 deficiency reduces recruitment of fibroblasts, macrophages, mast cells, neutrophils to wound site and delays wound healing; negatively expressing MMP-9. The SIRT 1 mediated signalling pathway in diabetic wound healing is the SIRT 1-foxo-C-Myc pathway. On the contrary SIRT 3 deficiency, impairs proliferation and migration of fibroblasts and SIRT 6 deficiency impairs wound closure rate and interrupts the vascular remodelling. This review focuses on the role of sirtuins in improving delayed wound healing in diabetes and its natural modulators with their specific functions towards healing diabetic wounds.

Beta-Caryophyllene, a CB2R Selective Agonist, Protects Against Cognitive Impairment Caused by Neuro-inflammation and Not in Dementia Due to Ageing Induced by Mitochondrial Dysfunction

BACKGROUND

Dementia is a neurodegenerative disorder majorly evidenced by cognitive impairment. Although there are many types of dementia, the common underlying etiological factors in all the types are neuro-inflammation or aging induced apoptosis. β-caryophyllene, a cannabinoid type-2 receptor agonist, has been reported to have promising neuroprotective effects in cerebral ischemia and neuro-inflammation.

OBJECTIVE

In the present study, we evaluated the effects of β-caryophyllene against animal models of dementia whose etiology mimicked neuro-inflammation and aging.

METHODS

Two doses (50 and 100 mg/kg of body weight) of β-caryophyllene given orally were tested against AlCl₃-induced dementia in male Sprague Dawley (SD) rats using the Morris water maze test. Subsequently, the effect of the drug was assessed for episodic memory in female SD rats using novel object recognition task in doxorubicin-induced neuro-inflammation and chemobrain model. Moreover, its effects were evaluated in D-galactose-induced mitochondrial dysfunction leading to dementia.

RESULTS

β-caryophyllene, at both doses, showed significant improvement in memory when assessed using parameters like target quadrant entries, escape latency and path efficiency in the Morris water maze test for spatial memory. In the doxorubicin-induced chemobrain model, β-caryophyllene at 100 mg/kg significantly elevated acetylcholinesterase and catalase levels and lowered lipid peroxidation compared to the disease control. In the novel object recognition task, β-caryophyllene at 100 mg/kg significantly improved recognition index and discrimination index in the treated animals compared to the disease control, with a significant increase in catalase and a decrease in lipid peroxidation in both hippocampus and frontal cortex. However, in the D-galactose-induced mitochondrial dysfunction model, β-caryophyllene failed to show positive effects when spatial memory was assessed. It also failed to improve D-galactose-induced diminished mitochondrial complex I and II activities.

CONCLUSION

Hence, we conclude that β-caryophyllene at 100 mg/kg protects against dementia induced by neuro-inflammation with no effect on neuronal aging induced by mitochondrial dysfunction.

Sesamol-Loaded PLGA Nanosuspension for Accelerating Wound Healing in Diabetic Foot Ulcer in Rats

Background

Diabetic foot ulcer is an intractable complication of diabetes, characterized by the disturbed inflammatory and proliferative phases of wound healing. Sesamol, a phenolic compound, has been known for its powerful antioxidant, anti-inflammatory, anti-hyperglycaemic and wound healing properties. The aim of the present study was to develop a sesamol nano formulation and to study its effect on the various phases of the wound healing process in diabetic foot condition.

Methods

Sesamol-PLGA (SM-PLGA) nanosuspension was developed  using nanoprecipitation method. TEM, in vitro drug release assay and in vivo pharmacokinetic studies were performed for the optimised formulation. Diabetic foot ulcer (DFU) in high fat diet (HFD)-fed streptozotocin-induced type-II diabetic animal model was used to assess the SM-PLGA nanosuspension efficacy. SM-PLGA nanosuspension was administered by oral route. TNF-α levels were estimated using ELISA and Western blot analysis was performed to assess the effect on the expression of HSP-27, ERK, PDGF-B and VEGF in wound tissue. Wound re-epithelization, fibroblast migration, collagen deposition and inflammatory cell infiltration were assessed by H&E and Masson’s trichrome staining. Effect on angiogenesis was assessed by CD-31 IHC staining in wound sections.

Results

The optimized SM-PLGA nanosuspension had an average particle size of <300 nm, PDI<0.200 with spherical shaped particles. Approximately 80% of the drug was released over a period of 60 h in in vitro assay. Half-life of the formulation was found to be 13.947 ± 0.596 h. SM-PLGA nanosuspension treatment decreased TNF-α levels in wound tissue and accelerated the collagen deposition. Whereas, HSP-27, ERK, PDGF-B and VEGF expression increased and improved new blood vessels’ development. Rapid re-epithelization, fibroblast migration, collagen deposition and reduced inflammatory cell infiltration at the wound site were also observed.

Conclusion

Results indicate that sesamol-PLGA nanosuspension significantly promotes the acceleration of wound healing in diabetic foot ulcers by restoring the altered wound healing process in diabetic condition.

Catechin ameliorates depressive symptoms in Sprague Dawley rats subjected to chronic unpredictable mild stress by decreasing oxidative stress

Catechin is an active ingredient of green tea. It is reported to inhibit corticosteroid-induced anxiety and depression-like symptoms. Considering the complex nature of depression, effects of catechin need to be studied in a clinically relevant depression model. The present study was designed to explore the antidepressant effect of catechin in Sprague Dawley rats subjected to chronic unpredictable mild stress (CUMS). Animals were subjected to CUMS and treated with (+)-catechin (50 mg/kg) or escitalopram (10 mg/kg) orally; a CUMS control and a vehicle control that was not exposed to CUMS were also established. Various stressors were applied daily in an unpredictable manner for 8 weeks achieve CUMS. Sucrose preference test were performed after 4 and 8 weeks and forced swim tests (FSTs) were conducted at weeks 4, 6 and 8. At the end of week 8, animals were sacrificed and the brain homogenate was studied for antioxidant parameters. Compared with the vehicle control, animals of the CUMS control group showed a significant decrease in sucrose intake. Catechin and escitalopram treatment significantly improved the sucrose intake compared with the CUMS control. A similar trend was observed in the FSTs, where catechin and escitalopram treatment significantly reduced the immobility time, and antioxidant parameters, including catalase, glutathione and superoxide dismutase levels were recovered in treated animals compared with the CUMS control. Thus, it was concluded that catechin reverses CUMS-induced depression in rats by ameliorating oxidative stress, which may help to develop a novel treatment for major depressive disorder.

Targeting glucose-dependent insulinotropic polypeptide receptor for neurodegenerative disorders

INTRODUCTION

Incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) exert pleiotropic effects on endocrine pancreas and nervous system. Expression of GIP and GIP receptor (GIPR) in neurons, their roles in neurogenesis, synaptic plasticity, neurotransmission, and neuromodulation uniquely position GIPR for therapeutic applications in neurodegenerative disorders. GIP analogs acting as GIPR agonists attenuate neurobehavioral and neuropathological sequelae of neurodegenerative disorders in preclinical models, e.g. Alzheimer's disease (AD), Parkinson's disease (PD), and cerebrovascular disorders. Modulation of GIPR signaling offers an unprecedented approach for disease modification by arresting neuronal viability decline, enabling neuronal regeneration, and reducing neuroinflammation. Growth-promoting effects of GIP signaling and broad-based neuroprotection highlight the therapeutic potential of GIPR agonists. Areas covered: This review focuses on the role of GIPR-mediated signaling in the central nervous system in neurophysiological and neuropathological conditions. In context of neurodegeneration, the article summarizes potential of targeting GIPR signaling for neurodegenerative conditions such as AD, PD, traumatic brain injury, and cerebrovascular disorders. Expert opinion: GIPR represents a validated therapeutic target for neurodegenerative disorders. GIPR agonists impart symptomatic improvements, slowed neurodegeneration, and enhanced neuronal regenerative capacity in preclinical models. Modulation of GIPR signaling is potentially a viable therapeutic approach for disease modification in neurodegenerative disorders.

Long circulating PEGylated-chitosan nanoparticles of rosuvastatin calcium: Development and in vitro and in vivo evaluations

The aim of this study was to improve the pharmacokinetics and pharmacodynamics profile of rosuvastatin calcium by formulating long-circulating PEGylated chitosan nanoparticles (NPs). Chitosan was PEGylated by a carbodiimide mediated reaction, using a carboxylic acid derivative of PEG (polyethylene glycol). The NPs were optimised for particle size, polydispersity index, zeta potential and drug entrapment efficiency. In vitro drug release, pharmacokinetic and pharmacodynamics studies of the optimized nanoparticles were performed. PEGylation of chitosan was confirmed by FTIR analysis. Drug-excipient compatibility was studied by differential scanning calorimetry and FTIR analyses. Two batches of nanoparticles were optimized with particle size of <200nm and entrapment efficiency of ≈14%. In vitro drug release studies revealed cumulative release of 14.07±0.57% and 22.02±0.81% of rosuvastatin over the period of 120h, indicating appreciable sustained release of drug. TEM analysis showed the spherical structure of nanoparticles. Pharmacokinetic studies indicated that optimized NPs showed prolonged drug release over a period of 72h. Pharmacodynamics studies in hyperlipidemic rat model demonstrated greater lipid-lowering capability of rosuvastatin nanoparticles in comparison with plain rosuvastatin. The nanoparticles demonstrated substantial prolonged delivery of the drug in vivo along with better therapeutic action, which could be potential drug delivery modality for 'statins'.

Rutin protects against neuronal damage in vitro and ameliorates doxorubicin-induced memory deficits in vivo in Wistar rats

Doxorubicin (DOX) is the most widely used broad-spectrum anticancer agent, either alone or in combination, for most cancers including breast cancer. Long-term use of chemotherapeutic agents to treat breast cancer patients results in cognitive complications with a negative impact on survivors’ quality of life. The study objective was to evaluate rutin (RUT) for its neuroprotective effect against DOX in human neuroblastoma (IMR32) cells in vitro and study its potential to ameliorate DOX-induced cognitive dysfunction in Wistar rats. Cell viability assay (3-[4,5 dimethyl thiazol-2-yl]-2,5-diphenyl tetrazolium bromide), neurite growth assay, detection of apoptosis by (acridine orange/ethidium bromide) staining, intracellular reactive oxygen species (ROS) assay, and flowcytometric analysis were carried out to assess neuroprotective potential against DOX. An in vivo study was conducted for assessing protective effect of RUT against memory deficit associated with DOX-induced chemobrain using object recognition task (ORT). Locomotion was assessed using open field test. Serum biochemistry, acetylcholinesterase, oxidative stress markers in hippocampus, and frontal cortex were assessed. Histopathological analysis of major organ systems was also carried out. Prior exposure to RUT at 100 µM protected IMR32 cells from DOX (1 µM) neurotoxicity. DOX exposure resulted in increased cellular death, apoptosis, and intracellular ROS generation with inhibition of neurite growth in differentiated IMR32 cells, which was significantly ameliorated by RUT. Cognitive dysfunction was induced in Wistar rats by administering ten cycles of DOX (2.5 mg/kg, intra-peritoneal, once in 5 days), as we observed significant impairment of episodic memory in ORT. Coadministration with RUT (50 mg/kg, per os) significantly prevented memory deficits in vivo without any confounding influence on locomotor activity. RUT also offered protection against DOX-induced myelosuppression, cardiotoxicity, and nephrotoxicity. In conclusion, RUT may be a possible adjuvant therapeutic intervention to alleviate cognitive and other complications associated with DOX chemotherapy.

Impact of caffeic acid on aluminium chloride-induced dementia in rats

OBJECTIVE

Literature favours the in vitro neuroprotective role of caffeic acid, a naturally derived polyphenolic compound. This study was aimed to investigate the role of caffeic acid in experimental model of Alzheimer's disease.

METHODS

Firstly, caffeic acid was tested for in vitro anticholinesterase potential using rat brain homogenate. Later, in vivo antidementia activity of caffeic acid was assessed against aluminium chloride (AlCl3 )-induced dementia in rats. Behavioural (Morris water maze test) and brain biochemical parameters (acetylcholinesterase (AChE), catalase, glutathione-S-transferase (GST) activity, glutathione (GSH) and nitrite levels) were assessed to correlate the cognitive function with cholinergic transmission and oxidative stress.

KEY FINDINGS

Rats administered with caffeic acid showed improved cognitive function in Morris water maze test. The antidementia activity of caffeic acid was confirmed by the reduction in brain AChE activity and nitrite levels. Further, caffeic acid corrected the diminished level of antioxidant enzymes such as catalase, GSH and GST in brain.

CONCLUSION

These findings suggest the antidementia activity of caffeic acid against AlCl3 -induced dementia in rats. The outcome of present study offers a wider scope to screen caffeic acid against neurodegeneration associated disorders.

Synthesis and antihistaminic activity of 3H-benzo [4,5] thieno [2,3-d][1,2,3] triazin-4-ones

In the present study the antihistaminic activity of tricyclic benzothieno 1,2,3-triazine derivatives namely CP-3 (3-(phenyl)-5,6,7,8-tetrahydro,3H-benzo[4,5] thieno [2,3-d][1,2,3] triazin-4-one), CP-5 (3-(3-methyl phenyl)-5,6,7,8-tetrahydro,3H-benzo[4,5] thieno [2,3-d][1,2,3] triazin-4-one) and CP-8 (3-(4-chloro phenyl)-5,6,7,8-tetrahydro,3H-benzo[4,5] thieno [2,3-d][1,2,3] triazin-4-one) were evaluated using in vitro (isolated guinea pig ileum) and in vivo (bronchodilator activity in guinea pigs) models and the sedative potential of the test compounds were evaluated using actophotometer in mice. In in vitro antihistaminic study, the CP-3, CP-5, CP-8 and chlorpheniramine maleate (CPM) have shown a rightward shift in concentration response curve (CRC) of histamine with a change in EC50 values of histamine in all the four tissue preparations. The slope obtained in the schild plot indicated that CP-5, CP-8 and CPM were competitive in nature for H1-receptors. However, CP-3 has shown non-competitive antagonism. In in vivo antihistaminic study, the CP-3, CP-5, CP-8 and CPM have shown mean increase in exposition time against histamine challenge compared to control group (p < 0.001). All the test drugs (10 mg/kg) and CPM (2 mg/kg) have offered a significant (p < 0.001) protection against preconvulsive dyspnoea (PCD) compared to control. In conclusion, all the test drugs have shown very good antihistaminic activity and the test drugs have very little sedative action compared to CPM.