Biology subjects

Shirshin, E. A.

Publications and source records attributed to Shirshin, E. A..

4 recordsLinked to original sources

bioRxiv2024

Metabolic heterogeneity of colorectal cancer as a prognostic factor: insights gained from fluorescence lifetime imaging

Heterogeneity of tumor metabolism is an important, but still poorly understood aspect of tumor biology. Present work is focused on the visualization and quantification of cellular metabolic heterogeneity of colorectal cancer using fluorescence lifetime imaging (FLIM) of redox cofactor NAD(P)H. FLIM-microscopy of NAD(P)H was performed in vitro in four cancer cell lines, in vivo in the four types of tumors in mice and ex vivo in patients tumor samples. The dispersion and bimodality of the decay parameters were evaluated to quantify the intercellular metabolic heterogeneity. Our results demonstrate that patients tumors have significantly higher heterogeneity of energy metabolism compared with cultured cells and tumor xenografts, which was displayed as a wider and frequently bimodal distribution of a contribution of a free (glycolytic) fraction of NAD(P)H within a sample. Among patients tumors, the dispersion was larger in the high-grade and early stage ones, without, however, any association with bimodality. These results indicate that cell-level metabolic heterogeneity assessed from NAD(P)H FLIM has a potential to become a clinical prognostic factor.

cancer biology↗

bioRxiv2022

Label-free sensing of cells with fluorescence lifetime imaging: the quest for metabolic heterogeneity

Molecular, morphological and physiological heterogeneity is the inherent property of cells, which governs differences in their response to external influence. The tumor cells metabolic heterogeneity is of a special interest due to its clinical relevance to the tumor progression and therapeutic outcomes. Rapid, sensitive and non-invasive assessment of metabolic heterogeneity of cells is of a great demand for biomedical sciences. Fluorescence lifetime imaging (FLIM), which is an all-optical technique is an emerging tool for sensing and quantifying cellular metabolism by measuring fluorescence decay parameters (FDPs) of endogenous fluorophores, such as NAD(P)H. To achieve the accurate discrimination between metabolically diverse cellular subpopulations, appropriate approaches to FLIM data collection and analysis are needed. In this report, the unique capability of FLIM to attain the overarching goal of discriminating metabolic heterogeneity has been demonstrated. This has been achieved using a novel approach to data analysis based on the non-parametric analysis, which revealed a much better sensitivity to the presence of metabolically distinct subpopulations as compare more traditional approaches of FLIM measurements and analysis. The new approach was further validated for imaging cultured cancer cells treated with chemotherapy. Those results pave the way for an accurate detection and quantification of cellular metabolic heterogeneity using FLIM, which will be valuable for assessing therapeutic vulnerabilities and predicting clinical outcomes.

cancer biology↗

bioRxiv2021

Label-free imaging of macrophage phenotypes and phagocytic activity in the human dermis in vivo using two-photon excited FLIM

Macrophages (M{Phi}s) are important immune effector cells that promote (M1 M{Phi}s) or inhibit (M2 M{Phi}s) inflammation and are involved in numerous physiological and pathogenic immune responses. Their precise role and relevance, however, is not fully understood because of the lack of non-invasive quantification methods. Here, we show that two-photon excited fluorescence lifetime imaging (TPE-FLIM), a label-free non-invasive method, can visualize M{Phi}s in human dermis in vivo. We demonstrate in vitro that human dermal M{Phi}s exhibit specific TPE-FLIM properties that distinguish them from the main components of the extracellular matrix and other dermal cells. We visualized M{Phi}s, their phenotypes and phagocytosis in the skin of healthy individuals in vivo using TPE-FLIM. Additionally, machine learning identified M1 and M2 M{Phi}s with a sensitivity of 0.88{+/-}0.04 and 0.82{+/-}0.03 and a specificity of 0.89{+/-}0.03 and 0.90{+/-}0.03, respectively. In clinical research, TPE-FLIM can advance the understanding of the role of M{Phi}s in health and disease.

biophysics↗

bioRxiv2017

The photocycle of orange carotenoid protein conceals distinct intermediates and asynchronous changes in the carotenoid and protein components

The 35 kDa water-soluble Orange Carotenoid Protein (OCP) is responsible for photoprotection in cyanobacteria. It acts as a light intensity sensor that simultaneously serves as efficient quencher of phycobilisome excitation energy as well as of reactive oxygen species. Photoactivation triggers large-scale conformational rearrangements to convert OCP from the orange OCPO state to the red active signaling state OCPR, as demonstrated by various structural methods. Eventually, such rearrangements imply complete yet reversible separation of structural domains (C- and N-terminal domain) and significant translocation of the carotenoid cofactor. Very recently, dynamic crystallography of OCPO crystals suggested the existence of photocycle intermediates with small-scale rearrangements that may trigger further transitions in the protein. However, the currently existing gap between the ultra-fast picosecond and 100 millisecond time scale of spectroscopic and structural data precludes knowledge about distinct intermediate states. In this study, we took advantage of single 7 ns laser pulses to study carotenoid absorption transients in OCP on the time-scale from 100 ns to 10 s, which allowed us to detect a red intermediate state preceding the red signaling state OCPR. In addition, time-resolved fluorescence spectroscopy and following assignment of carotenoid-induced quenching of different tryptophan residues revealed a novel orange intermediate state, which appears during back-relaxation of photoactivated OCPR to OCPO. Our results show asynchronous changes in the carotenoid and protein components and provide refined mechanistic information about the OCP photocycle as well as introduce new kinetic signatures for future studies of OCP photoactivity and photoprotection.\n\nSignificance statementCyanobacteria utilize the Orange Carotenoid Protein (OCP) to protect their photosynthetic apparatus from the harmful effects of intense sunlight. OCP is a blue light-triggered photoswitch, which undergoes photoconversion from its dark adapted orange to the active red state, the latter being able to interact with the phycobilisome antennae and quench their fluorescence, thus avoiding excessive energy flow to the photosystems. With the help of the fluorescence recovery protein (FRP), OCP detaches from phycobilisomes and can return faster into the orange state. Until now, only the thermodynamically stable orange state and the metastable red state are established in a primitive photocycle. In this work, we apply transient absorption and fluorescence spectroscopy and identify two novel photocycle intermediates of physiological relevance.

biophysics↗