Chronic Periodontitis and Alzheimer Disease: A Putative Link of Serum Proteins Identification by 2D-DIGE Proteomics

Intraoperative plasma proteomic changes in cardiac surgery: In search of biomarkers of post-operative delirium

PURPOSE

Delirium presents a significant healthcare burden. It complicates post-operative care in up to 50% of cardiac surgical patients with worse outcomes, longer hospital stays and higher cost of care. Moreover, the nature of delirium following cardiac surgery with cardiopulmonary bypass (CPB) remains unclear, the underlying pathobiology is poorly understood, status quo diagnostic methods are subjective, and diagnostic biomarkers are currently lacking.

OBJECTIVE

To identify diagnostic biomarkers of delirium and for insights into possible neuronal pathomechanisms.

EXPERIMENTAL DESIGN

Comparative proteomic analyses were performed on plasma samples from a nested matched cohort of patients who underwent cardiac surgery. Validation by targeted proteomics was performed in an independent set of samples. Biomarkers were assessed for biological functions and diagnostic accuracy.

RESULTS

Forty-seven percent of subjects demonstrated delirium. Of 3803 proteins identified from patient samples by multiplexed quantitative proteomics, 16 were identified as signatures of exposure to CPB, and 11 biomarkers distinguished delirium cases from non-cases (AuROC = 93%). Notable among these biomarkers are C-reactive protein, serum amyloid A-1 and cathepsin-B.

CONCLUSIONS AND CLINICAL RELEVANCE

The interplay of systemic and central inflammatory markers sheds new light on delirium pathogenesis. This work suggests that accurate identification of cases may be achievable using panels of biomarkers.

Lipidomics and proteomics: An integrative approach for early diagnosis of dementia and Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder and considered to be responsible for majority of worldwide prevalent dementia cases. The number of patients suffering from dementia are estimated to increase up to 115.4 million cases worldwide in 2050. Hence, AD is contemplated to be one of the major healthcare challenge in current era. This disorder is characterized by impairment in various signaling molecules at cellular and nuclear level including aggregation of Aβ protein, tau hyper phosphorylation altered lipid metabolism, metabolites dysregulation, protein intensity alteration etc. Being heterogeneous and multifactorial in nature, the disease do not has any cure or any confirmed diagnosis before the onset of clinical manifestations. Hence, there is a requisite for early diagnosis of AD in order to downturn the progression/risk of the disorder and utilization of newer technologies developed in this field are aimed to provide an extraordinary assistance towards the same. The lipidomics and proteomics constitute large scale study of cellular lipids and proteomes in biological matrices at normal stage or any stage of a disease. The study involves high throughput quantification and detection techniques such as mass spectrometry, liquid chromatography, nuclear mass resonance spectroscopy, fluorescence spectroscopy etc. The early detection of altered levels of lipids and proteins in blood or any other biological matrices could aid in preventing the progression of AD and dementia. Therefore, the present review is designed to focus on the recent techniques and early diagnostic criteria for AD, revealing the role of lipids and proteins in this disease and their assessment through different techniques.

Colorimetric Sensor Array for Identification of Proteins and Classification of Metabolic Profiles under Various Osmolyte Conditions

Rapid and efficient detection and identification of proteins hold great promise in medical diagnostics, treatment of different diseases, and proteomics. Here, we present a simple colorimetric sensor array for the differentiation of proteins in various osmolyte solutions. Osmolytes have different influences on the conformation of proteins, which have differential binding to silver nanoparticles, resulting in color changes. The sensor array shows unique color change patterns for each of the 19 proteins, allowing unambiguous identification. Very interestingly, the differentiation of 19 proteins is related to their molecular weight. Moreover, the sensor array can be used to identify protein mixtures, thermal denaturized proteins, and unknown protein samples. Finally, the sensor array can also analyze the plasma or liver samples of the four groups of salt-sensitive rats fed with different diets, indicating that it has the potential for the classification of metabolic profiles.

DIGE Analysis of Immunodepleted Plasma

This chapter focuses on upstream immunodepletion of high-abundance proteins from plasma samples and subsequent analysis by fluorescence two-dimensional difference gel electrophoresis (2D-DIGE). The abundances of proteins in biofluid proteomes, such as serum, plasma, saliva, and bronchoalveolar lavage fluid (BALF), can exceed ten orders of magnitude. This substantial dynamic range is problematic for the detection of medium and low-abundance proteins by 2D-DIGE analysis. To increase the detection, quantification, and identification of medium-low-abundance proteins, the targeted depletion of known abundant proteins with antibody columns has been successfully employed. From the literature, it is clear that the performance of abundant protein depletion with immunodepletion columns has been successful in broadening the coverage of the biofluid proteome and facilitating the identification of disease-specific biomarkers. The task for a successful biomarker strategy involves the combination of a reproducible and robust fractionation method, coupled with a highly accurate quantitative method, a task that is exemplified by combining both immunodepletion and 2D-DIGE together to discover significant proteins associated with the disease phenotype.

Cathepsin B Deficiency Improves Memory Deficits and Reduces Amyloid-β in hAβPP Mouse Models Representing the Major Sporadic Alzheimer's Disease Condition

The lysosomal cysteine protease cathepsin B (CTSB) has been suggested as a biomarker for Alzheimer's disease (AD) because elevated serum CTSB in AD patients has been found to correlate with cognitive dysfunction. Furthermore, CTSB gene knockout (KO) in non-transgenic and transgenic AD animal models showed that elimination of CTSB improved memory deficits. However, conflicting CTSB KO results on amyloid-β (Aβ) pathology in transgenic AD models have been reported. The conflict is resolved here as likely being due to the different hAβPP transgenes used in the different AD mouse models. CTSB gene KO reduced wild-type (Wt) β-secretase activity, brain Aβ, pyroglutamate-Aβ, amyloid plaque, and memory deficits in models that used cDNA transgenes expressing hAβPP isoform 695. But in models that used mutated mini transgenes expressing hAβPP isoforms 751 and 770, CTSB KO had no effect on Wt β-secretase activity and slightly increased brain Aβ. All models expressed the AβPP transgenes in neurons. These conflicting results in Wt β-secretase activity models can be explained by hAβPP isoform specific cellular expression, proteolysis, and subcellular processing. CTSB KO had no effect on Swedish mutant (Swe) β-secretase activity in hAβPP695 and hAβPP751/770 models. Different proteolytic sensitivities for hAβPP with Wt versus Swe β-secretase site sequences may explain the different CTSB β-secretase effects in hAβPP695 models. But since the vast majority of sporadic AD patients have Wt β-secretase activity, the CTSB effects on Swe β-secretase activity are of little importance to the general AD population. As neurons naturally produce and process hAβPP isoform 695 and not the 751 and 770 isoforms, only the hAβPP695 Wt models mimic the natural neuronal hAβPP processing and Aβ production occurring in most AD patients. Significantly, these CTSB KO findings in the hAβPP695 Wt models demonstrate that CTSB participates in memory deficits and production of pyroglutamate-Aβ (pyroglu-Aβ), which provide rationale for future investigation of CTSB inhibitors in AD therapeutics development.

Uncloaking cell-impermeant gold nanorods via tumor microenvironmental cathepsin B facilitates cancer cell penetration and potent radiosensitization

Major impediments to conveyance of intravenously administered drugs to tumors are biofouling, opsonization, and rapid clearance from the circulation by macrophages and reticuloendothelial phagocytes. Cloaking nanoparticles with stealth epilayers partly overcomes these hurdles but it also foils interactions with tumor cells. Here, we describe the synthesis, characterization, and validation of smart gold nanorods (GNRs) that spontaneously transform from inert passengers in the blood stream to active cell-penetrating nanoparticles within tumors to potently sensitize tumors to radiation therapy. Intrinsically cationic and cell-penetrating GNRs were shielded from phagocytosis with a cloaking polyethylene glycol epilayer containing an intervening cleavable peptide. In the absence of an external trigger, this epilayer is clipped off by the tumor microenvironmental protease, cathepsin B, in colorectal cancers to uncloak and expose the free-circulating native unPEGylated GNR that is readily internalized by cancer cells and turn into immovable small clusters of GNRs. Selective uncloaking of GNRs in the tumor reduced off-target toxicity confirmed by hematologic, biochemical, and histopathological analysis of blood, serum, and normal organs, respectively. Subsequent irradiation led to significant tumor growth delay and improved survival of mice. By addressing multiple barriers to efficient transport and cellular internalization of nanoparticles, our results demonstrate that clinically meaningful radiosensitization can be achieved with rationally designed GNRs.

Cathepsin B Gene Knockout Improves Behavioral Deficits and Reduces Pathology in Models of Neurologic Disorders

Cathepsin B (CTSB) is a powerful lysosomal protease. This review evaluated CTSB gene knockout (KO) outcomes for amelioration of brain dysfunctions in neurologic diseases and aging animal models. Deletion of the CTSB gene resulted in significant improvements in behavioral deficits, neuropathology, and/or biomarkers in traumatic brain injury, ischemia, inflammatory pain, opiate tolerance, epilepsy, aging, transgenic Alzheimer's disease (AD), and periodontitis AD models as shown in 12 studies. One study found beneficial effects for double CTSB and cathepsin S KO mice in a multiple sclerosis model. Transgenic AD models using amyloid precursor protein (APP) mimicking common sporadic AD in three studies showed that CTSB KO improved memory, neuropathology, and biomarkers; two studies used APP representing rare familial AD and found no CTSB KO effect, and two studies used highly engineered APP constructs and reported slight increases in a biomarker. In clinical studies, all reports found that CTSB enzyme was upregulated in diverse neurologic disorders, including AD in which elevated CTSB was positively correlated with cognitive dysfunction. In a wide range of neurologic animal models, CTSB was also upregulated and not downregulated. Further, human genetic mutation data provided precedence for CTSB upregulation causing disease. Thus, the consilience of data is that CTSB gene KO results in improved brain dysfunction and reduced pathology through blockade of CTSB enzyme upregulation that causes human neurologic disease phenotypes. The overall findings provide strong support for CTSB as a rational drug target and for CTSB inhibitors as therapeutic candidates for a wide range of neurologic disorders. SIGNIFICANCE STATEMENT: This review provides a comprehensive compilation of the extensive data on the effects of deleting the cathepsin B (CTSB) gene in neurological and aging mouse models of brain disorders. Mice lacking the CTSB gene display improved neurobehavioral deficits, reduced neuropathology, and amelioration of neuronal cell death and inflammatory biomarkers. The significance of the compelling CTSB evidence is that the data consilience validates CTSB as a drug target for discovery of CTSB inhibitors as potential therapeutics for treating numerous neurological diseases.

Systems Biology in Periodontitis

Systems biology is a promising scientific discipline that allows an integrated investigation of host factors, microbial composition, biomarkers, immune response and inflammatory mediators in many conditions such as chronic diseases, cancer, neurological disorders, and periodontitis. This concept utilizes genetic decoding, bioinformatic, flux-balance analysis in a comprehensive approach. The aim of this review is to better understand the current literature on systems biology and identify a clear applicability of it to periodontitis. We will mostly focus on the association between this condition and topics such as genomics, transcriptomics, proteomics, metabolomics, as well as contextualize delivery systems for periodontitis treatment, biomarker detection in oral fluids and associated systemic conditions.

Cofilin 2 Acts as an Inflammatory Linker Between Chronic Periodontitis and Alzheimer's Disease in Amyloid Precursor Protein/Presenilin 1 Mice

Increasing evidence has shown a correlation between chronic periodontitis (CP) and Alzheimer’s disease (AD). Nevertheless, there is still a lack of direct evidence, and especially key molecules to connect the two diseases. This study aims to investigate potential protein links between CP and AD within the inflammatory aspect. The hippocampus of CP model mice and controls were collected, and changes in protein expression were evaluated using two-dimensional differential in-gel electrophoresis (2D-DIGE) analysis combined with liquid chromatography tandem mass spectrometry. A total of 15 differentially expressed proteins were identified in CP model mice, as compared with the controls. Among them, S100-A9, transthyretin, Cofilin 2, peroxiredoxin 2, and lipocalin-2 were validated by Western blot according to their dual function both in inflammation and AD. Based on 2D-DIGE analysis, CP animal model had higher levels of S100-A9, Cofilin 2, peroxiredoxin 2, and lipocalin-2 compared to controls. The level of Cofilin 2, one of the well-established proteins in the pathology of AD, was strongly correlated with the time course of CP pathology, indicating a specific molecular correlation between CP and AD. Moreover, the in vivo results showed the level of Cofilin 2 increased significantly along with a prominent increase of the phosphorylation of protein phosphatase 2 (PP2A) and tau protein in the cell lysates of Porphyromonas gingivalis (P.g-LPS)-treated SK-N-SH APPwt cells. Cofilin 2 inhibition resulted in a sharp decrease in PP2A dependent of tau phosphorylation. Furthermore, tumor growth factor (TGF)-β1 was one of the most important inflammatory cytokines for the Pg-LPS-induced Cofilin 2 upregulation in SK-N-SH APPwt cells. These results showed inflammation served as the bond between CP and AD, whereas inflammatory related proteins could be the key linkers between the two diseases. Determining the association between CP and AD at the molecular mechanism will not only hold the direct evidence of the association between the two diseases but also provide a new way of preventing and treating AD: the effective prevention and treatment of CP could serve as a useful method to alleviate the development of AD.

Can Porphyromonas gingivalis Contribute to Alzheimer's Disease Already at the Stage of Gingivitis?

Alzheimer's disease (AD) has been associated with periodontitis, which starts as gingivitis. Similar to periodontitis, gingivitis bacteria, bacterial products, and inflammatory mediators can travel to the brain via the blood stream and promote brain inflammation. Periodontal pathogens such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, both associated with AD, have been found in dental plaque of children already at the age of 3. It is suggested that these bacteria during long-term exposure may drive microglia (brain resident macrophage cells) into a pro-inflammatory M1 phase where they contribute to AD rather than protect against it. This notion comes from studies in mice showing that microglia actually can "remember" previous inflammatory challenge and become "trained" or "tolerant" to toxins like lipopolysaccharide. If gingivitis has an impact on AD, which should be verified, AD prophylaxis should start already at this pre-periodontitis stage with removal of supragingival plaque.