Interesting and actual study for CCR5 Antagonist D

Interesting and actual study for CCR5 Antagonist Dec. 2019/Febr. 2020
Metabolomics as an Approach to Characterise the Contrasting Roles of CCR5 in the Presence and Absence of Disease
https://www.mdpi.com/1422-0067/21/4/1472/htm



3. Conclusion:
In this article, the main focus was to review the role of CCR5 particularly in disease since genotype influences the expression and/or the amount of CCR5 present on the cell surface, susceptibility to infection and disease pathogenesis. Taken together, CCR5 is crucial for mediating signal transduction and activating immune responses which ultimately impact the cell’s metabolism. Upon reviewing the role of CCR5, frequency of the receptor, genotype and/or levels of CCR5 were frequent terminologies encountered in the literature. While the CCR5∆32 genotype is synonymous with CCR5 levels, this relationship does not hold for allelic frequency. While the role of CCR5 in some diseases such as HIV-1/AIDS is clearer, it is contradictory in others. The different findings may be attributed to various factors such as differences in study design (experimental vs. meta-analysis) as well as sample size. Most often, meta-analysis yielded no association between CCR5∆32 and disease. Given that the information from varied studies are “pooled” as part of a meta-analysis, some of the associations that may exist in individual experiments are possibly overshadowed when reported in this way.
In the case of cardiovascular diseases, central nervous system diseases and cancer for example, the sample matrix and/or model depicts different roles for CCR5. Blood is often the choice of sample since it is acquired easily using minimally invasive techniques. Furthermore, genomic DNA can easily be extracted for genetic analysis. However, while blood was the more common matrix analysed (Table 1), it mostly showed no association to CCR5 while a localised sample such as brain tissue often defined CCR5’s protective vs. non-protective roles better. Similarly, protective and non-protective roles were often better characterised in animal (mice) models. Contrasting roles for the receptor were also evident when the samples of different ethnic groups and/or from different geographical regions as well as different genders or age were compared. The type of immune response, number of cells, type of immune cells and biological processes such as internalization all have an impact on CCR5 levels and function and may ultimately influence disease pathogenesis and outcome. Depending on whether an adult or paediatric model was used, the role of CCR5 in the disease was different. With respect to cancer, CCR5 is associated with different outcomes depending on the type of cancer and/or tumour investigated and its associated microenvironment.
From Table 1 it is also evident that most of the assays used to measure CCR5 status and/or its effects comprised of molecular-type assays. The PCR and RFLP methods were the most common methods used. Both methods are easy to do, time-efficient and require low sample volumes relative to sequencing. Immune analysis was limited as was the recording of metabolic parameters. Where immune and metabolic data were recorded, investigators mostly reported on select molecules using older conventional assays.
Variable phenotypic presentation is common in most diseased states (i.e., patients with the same disease often present with different symptoms). This review and the research of others [40,53] highlights the role of CCR5 in various diseases. The increased biological characterisation of CCR5 may however clarify the contrasting roles of this molecule. Gaining knowledge regarding the altered immune and metabolic profiles due to differential CCR5 status of uninfected and infected models will ultimately improve our understanding of the receptor.
Metabolomics is defined as the study of metabolites [193] and offers the ability to link CCR5 homozygous WT, homozygous mutated and/or heterozygous genotypes with phenotype (e.g., CCR5 levels, frequency, etc.). In living organisms, small molecules known as metabolites are continuously chemically transformed in various metabolic pathways. Measuring metabolite concentrations can thus inform on the biochemical activity of cells and its associated phenotype(s) [194]. Using a metabolomics approach, metabolites can be detected in samples displaying differential CCR5 status. These metabolites can be identified and quantified in an unbiased manner in several different biofluids. Indeed, CCR5 has been shown in a CCR5-deficient mouse model during Toxoplasma gondii infection to modulate host metabolism (i.e., an increase in serum triglycerides and liver metabolic dysfunction was measured) [23]. In cancer cells, the interaction between CCL5 and CCR5 increased the expression of glucose transporters, glucose uptake, glycolysis and subsequent ATP production [21]. In diabetic mice, blocking of the CCR5 receptor increased LDL and blood triglyceride levels [24]. These CCR5-influenced metabolic changes justify a metabolomics-based investigation of the chemokine receptor.
One of the requirements of metabolomics-based analysis is that a homogenous sample set be analysed so as to make conclusive remarks about the test variable. As part of future work, a metabolomics approach can therefore be used to study those parameters identified in this review to skew CCR5-based findings. By including or excluding these parameters in a metabolomics investigation, CCR5-specific conclusions can be made. Metabolomics makes use of highly sensitive and selective techniques [195]. To date, several different analytical platforms exist, yet there is no one analytical platform which can detect and measure all of the metabolites present within a sample. This is thought to be due to the diversity of the molecules as well as the different concentrations in which they are present. Nonetheless, several metabolomics approaches exist. Untargeted metabolomics approaches investigate the metabolic profile of samples in a global, unbiased manner and the data obtained can give a comprehensive overview of the metabolism. This approach is followed when there is no prior knowledge regarding the metabolites present in the sample and the method is therefore not focused on a specific molecule or class of molecules [196,197]. In contrast, a targeted approach focuses on a specific class of compounds to inform on biochemical pathways of interest. Using any of the aforementioned metabolomics approaches, new insights can be discovered regarding the altered metabolism, as effected through CCR5-induced immune changes.
From the articles reviewed here which report on metabolic parameters [21,22,23,24,61,62,63,64,66,72,73,103,173], a general trend regarding CCR5 in disease is that it impacts mainly lipid levels, cholesterol and the glycolysis pathway. Future work should therefore analyse samples displaying differential CCR5 status, using untargeted and targeted metabolomics approaches. Untargeted analysis will uncover metabolic changes not previously associated with CCR5 whilst targeted approaches will expand on the affected pathways already known to be impacted by CCR5 and further uncover mechanisms regarding the functioning of the molecule.
The metabolomics approach followed will be guided by the aim of the study which will in turn influence the choice of the biological sample and analytical platform. Sample choice is generally made based on ease of access. Biofluids that can be obtained non-invasively are typically the first choice to use and often includes urine. Furthermore, the use of blood is also a popular choice since its collection is minimally invasive. Muscle or tissue biopsies are generally hard to come by, which makes them less popular for research purposes. In addition to clinical samples which may be scarce, primary cell cultures or established cell lines can also be used for analysis. Cell lines are more homogenous in make-up and response and their environment is more controlled, hence less variation will be built into models used to better characterise CCR5. More conclusive remarks can thus be made regarding the role of CCR5 in the absence and/or presence of disease.
Preparation of the sample will ensure that it is compatible with a specific analytical platform. This may include but is not limited to: adding an internal standard; performing metabolite extraction and derivatization; or adding a buffer and after which the sample is subjected to the analytical platform for metabolomics analysis.
To conclude, chemokines and chemokine receptors such as CCR5 play a pivotal role in health and disease. Mutations present in genes encoding for these protein molecules can impact on immune and metabolic profiles and therefore influence disease susceptibility and progression rates. The metabolic changes can be particularly measured through metabolomics. This cascading impact of CCR5 on various biosystems is summarised in Figure 1. While the role of CCR5 in the context of HIV-1 infection is more defined, its role in other diseases remains contradictory. In an article published by Klein [53], the author also highlights the contrasting role(s) of CCR5 in diseases. However, our knowledge of CCR5 has increased in the last ten years. In addition, technological advancements make it possible to investigate CCR5 in more depth. This review therefore provides a more in-depth explanation for the role(s) of CCR5 in disease, and highlights metabolomics as a tool with which to clarify the contrasting role(s) of CCR5. Metabolic and immune profiling of samples presenting differential CCR5 status stand to further improve our understanding of this molecule.