Rapid detection of dysfunctional high-density lipoproteins using isoelectric focusing-based microfluidic device to diagnose senescence-related disease

Recent Advances in Senotherapeutics Delivery

Accumulation of senescent cells (SnCs) in various tissue types has been connected to an occurrence of different age-related diseases that are indicated by its own tissue-specific hallmarks. Discovery of novel senolytic compounds that target major cellular mechanisms to inhibit the level of SnCs within the specific tissues or organs has been an emerging field in the age-related disease research. Although the positive effect of senolytics in global suppression of SnCs has been well studied in the past, effective tissue-specific delivery strategy of senotherapeutics before clinical application needs to be further investigated. In this review, we discuss the latest biological insights to currently available senotherapeutic options and explore the impactful in vitro tissue-engineered models possibly as a testbed for replicable testing of tissue-specific potency of senolytics. Impact statement Senotherapy, the inhibition of accumulated senescent cells, is recognized as a significantly impactful way to treat various human diseases. However, there is limited comprehensive reviews on this topic. This review provides in-depth discussion on diverse delivery strategies of senolytic agents and latest updates on a novel senotherapeutic research.

Structural and Functional Changes of Reconstituted High-Density Lipoprotein (HDL) by Incorporation of α-synuclein: A Potent Antioxidant and Anti-Glycation Activity of α-synuclein and apoA-I in HDL at High Molar Ratio of α-synuclein

α-synuclein (α-syn) is a major culprit of Parkinson's disease (PD), although lipoprotein metabolism is very important in the pathogenesis of PD. α-syn was expressed and purified using the pET30a expression vector from an E. coli expression system to elucidate the physiological effects of α-syn on lipoprotein metabolism. The human α-syn protein (140 amino acids) with His-tag (8 amino acids) was expressed and purified to at least 95% purity. Isoelectric focusing gel electrophoresis showed that the isoelectric point (pI) of α-syn and apoA-I were pI = 4.5 and pI = 6.4, respectively. The lipid-free α-syn showed almost no phospholipid-binding ability, while apoA-I showed rapid binding ability with a half-time (T_1/2) = 8 ± 0.7 min. The α-syn and apoA-I could be incorporated into the reconstituted HDL (rHDL, molar ratio 95:5:1:1, palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC):cholesterol:apoA-I:α-syn with the production of larger particles (92 Å) than apoA-I-rHDL (86 and 78 Å) and α-syn-rHDL (65 Å). An rHDL containing both apoA-I and α-syn showed lower α-helicity around 45% with a red shift of the Trp wavelength maximum fluorescence (WMF) from 339 nm, while apoA-I-HDL showed 76% α-helicity and 337 nm of WMF. The denaturation by urea addition showed that the incorporation of α-syn in rHDL caused a larger increase in the WMF than apoA-I-rHDL, suggesting that the destabilization of the secondary structure of apoA-I by the addition of α-syn. On the other hand, the addition of α-syn induced two-times higher resistance to rHDL glycation at apoA-I:α-syn molar ratios of 1:1 and 1:2. Interestingly, low α-syn in rHDL concentrations, molar ratio of 1:0.5 (apoA-I:α-syn), did not prevent glycation with more multimerization of apoA-I. In the lipid-free and lipid-bound state, α-syn showed more potent antioxidant activity than apoA-I against cupric ion-mediated LDL oxidation. On the other hand, microinjection of α-syn (final 2 μM) resulted in 10% less survival of zebrafish embryos than apoA-I. A subcutaneous injection of α-syn (final 34 μM) resulted in less tail fin regeneration than apoA-I. Interestingly, incorporation of α-syn at a low molar ratio (apoA-I:α-syn, 1:0.5) in rHDL resulted destabilization of the secondary structure and impairment of apoA-I functionality via more oxidation and glycation. However, at a higher molar ratio of α-syn in rHDL (apoA-I:α-syn = 1:1 or 1:2) exhibited potent antioxidant and anti-glycation activity without aggregation. In conclusion, there might be a critical concentration of α-syn and apoA-I in HDL-like complex to prevent the aggregation of apoA-I via structural and functional enhancement.

Capacitively coupled contactless conductivity detection for microfluidic capillary isoelectric focusing

We report capacitively coupled contactless conductivity detection (C4D) of proteins separated by microfluidic capillary isoelectric focusing (μCIEF). To elucidate the evolution of negative conductivity peaks during focusing and seek IEF conditions for sensitive conductivity detection, numerical simulation was performed using a model protein GFP (green fluorescence protein) and hypothetical carrier ampholytes (CAs). C4D was successfully applied to the μCIEF by optimizing assay conditions using a simple and effective pressure-mobilization approach. The conductivity and fluorescence signals of a focused GFP band were co-detected, confirming that the obtained negative C4D peak could be attributed to the actual protein, not the non-uniform background conductivity profile of the focused CAs. GFP concentrations of 10 nM-30 μM was quantified with a detection limit of 10 nM. Finally, the resolving power was analyzed by separating a mixture of R-phycoerythrin (pI 5.01), GFP-F64L (pI 5.48), and RK-GFP (pI 6.02). The conductivities of the three separated fluorescence proteins were measured with average separation resolution of 2.06. We expect the newly developed label-free μCIEF-C4D technique to be widely adopted as a portable, electronics-only protein-analysis tool.

Lab-on-a-Chip Platforms for Detection of Cardiovascular Disease and Cancer Biomarkers

Cardiovascular disease (CVD) and cancer are two leading causes of death worldwide. CVD and cancer share risk factors such as obesity and diabetes mellitus and have common diagnostic biomarkers such as interleukin-6 and C-reactive protein. Thus, timely and accurate diagnosis of these two correlated diseases is of high interest to both the research and healthcare communities. Most conventional methods for CVD and cancer biomarker detection such as microwell plate-based immunoassay and polymerase chain reaction often suffer from high costs, low test speeds, and complicated procedures. Recently, lab-on-a-chip (LoC)-based platforms have been increasingly developed for CVD and cancer biomarker sensing and analysis using various molecular and cell-based diagnostic biomarkers. These new platforms not only enable better sample preparation, chemical manipulation and reaction, high-throughput and portability, but also provide attractive features such as label-free detection and improved sensitivity due to the integration of various novel detection techniques. These features effectively improve the diagnostic test speed and simplify the detection procedure. In addition, microfluidic cell assays and organ-on-chip models offer new potential approaches for CVD and cancer diagnosis. Here we provide a mini-review focusing on recent development of LoC-based methods for CVD and cancer diagnostic biomarker measurements, and our perspectives of the challenges, opportunities and future directions.

Breast Milk from Smokers Contains Less Cholesterol and Protein and Smaller Size of Apolipoprotein A-I Resulting in Lower Zebrafish Embryo Survivability

BACKGROUND

To determine the quality of breast milk (BM), we compared the functions of BM from ex-smokers and nonsmokers.

SUBJECTS AND METHODS

We analyzed the contents of lipids, glucose, and protein in BM from ex-smokers (10 cigarettes/day for 13 ± 3 years) as well as infant formula.

RESULTS

Nonsmokers' BM showed 2.4- and 1.4-fold higher cholesterol and protein contents, respectively, than BM from smokers. Infant formula contained almost no cholesterol, but did show remarkably higher glucose and triglyceride levels than BM. Microinjection of BM (50 nL) from nonsmokers and smokers into zebrafish embryos resulted in 59% and 44% survival, respectively, whereas formula injection resulted in 31% survival. The higher cholesterol and protein contents of BM were directly correlated with higher embryo survivability, suggesting that cholesterol content is directly and critically associated with growth of neonate infants. Smokers' BM contained smaller-sized apolipoproteinA-I (apoA-I) (24.4 ± 0.2 kDa) than BM from nonsmokers (26.7 ± 0.4 kDa), suggesting that putative modification and cleavage occurred in apoA-I. BM containing higher molecular weight apoA-I resulted in higher embryo survivability.

CONCLUSIONS

Smoking before pregnancy can affect the composition and quality of BM, resulting in almost complete loss of cholesterol and protein, especially lactoferrin, lactalbumin, and apoA-I, accompanied by proteolytic degradation. These impairment effects of BM are associated with elevation of oxidative stress and lower embryo survivability.

Breast Milk from Frequent Trans Fatty Acid Consumers Shows High Triglyceride and Glucose Levels, but Low Cholesterol and Apolipoprotein A-I levels, with Resulting Impaired In Vitro Zebrafish Embryo Growth and Survival

BACKGROUND

It is well known that breast milk is the best nutritional source for infant growth. However, there has been no information about the quality of breast milk from individuals who daily consume a trans fatty acid (TFA)-enriched diet.

SUBJECTS AND METHODS

We performed compositional and functional analyses with breast milk from lactating mothers, in terms of lipid content and zebrafish embryo survivability, among individuals who daily consumed TFA-enriched food (n = 5), normal diet as control (n = 5), and powder formula (n = 5).

RESULTS

In lipid content of breast milk, the control group showed 2.5- and 4.5-fold higher cholesterol content than the TFA group and infant formula, respectively. The TFA group and infant formula showed 1.8- and 2.0-fold higher triglyceride (TG) than the control group. Moreover, the TFA group and formula showed 1.4- and 4.8-fold higher glucose levels compared with control. The TFA group also showed 25% lower protein content than control. Microinjection with breast milk (50 nL) from the TFA group showed significantly lower zebrafish embryo survivability (50% ± 4%) compared with the control (66% ± 5%), whereas microinjection with formula showed the lowest survivability (39% ± 5%) with the slowest developmental speed. Immunodetection revealed that breast milk from the TFA group showed smaller-sized apoA-I (25.5 ± 0.6 kDa) than that from the control group (27.5 ± 1.5 kDa), whereas formula did not contain apoA-I. Larger apoA-I size in breast milk was directly associated with higher embryo survivability.

CONCLUSIONS

Breast milk from the TFA group showed increased TG and loss of cholesterol, lactalbumin (14 kDa), and apoA-I proteins, resulting in functional impairment of development and growth.

Fructated apolipoprotein A-I exacerbates cellular senescence in human umbilical vein endothelial cells accompanied by impaired insulin secretion activity and embryo toxicity

Glycation of apolipoproteins is a major feature of the production of dysfunctional high-density lipoprotein (HDL), which is associated with the incidence of several metabolic diseases such as coronary artery disease and diabetes. In this report, fructated apoA-I (fA-I) induced by fructose treatment showed a covalently multimerized band without cross-linking, and lysine residues were irreversibly modified to prevent crosslinking. Using pancreatic β-cells, insulin secretion was impaired by fA-I in the lipid-free and reconstituted HDL (rHDL) states, by up to 35%, and 40%, respectively, under hyperglycemic conditions (25 mmol/L glucose). Treatment of human umbilical vein endothelial cells (HUVECs) with fA-I and HDL from elderly patients caused a 1.8-fold and 1.5-fold increased cellular senescence, respectively, along with increased lysosomal enlargement. In the lipid-free and rHDL states, fA-I increased embryo death by 1.5-fold and 2.5-fold, respectively, along with the production of oxidized species. Furthermore, rHDL containing fA-I (fA-I-rHDL) showed a higher isoelectric point (pI, approximately 8.5), whereas rHDL containing nA-I (nA-I-rHDL) showed a narrow band range with lower pI (around 8.0) as well as a much smaller particle size than that of nA-I-rHDL. In conclusion, fructose-mediated apoA-I fructation resulted in the severe loss of several beneficial functions of apoA-I and HDL, including anti-senescence and insulin secretion activities, accompanied with increased susceptibility to protein degradation and structural modification.