Detection of hypochlorous acid fluctuation via a selective fluorescent probe in acute lung injury cells and mouse models

Imaging peroxynitrite in endoplasmic reticulum stress and acute lung injury with a near-infrared fluorescent probe

BACKGROUND

The cellular endoplasmic reticulum (ER) is responsible for various functions, including protein synthesis, folding, distribution, and calcium ion storage. Studies have linked ER stress with acute lung injury (ALI), which can result in oxidative stress and even cell death. Peroxynitrite (ONOO-) is a well-known reactive oxygen species (ROS) that contributes to various physiological and pathological processes in oxidative stress diseases. To understand the role of ER ONOO- in ALI, it is crucial to accurately measure its level in the ER. Unfortunately, there is currently no probe available to detect ER ONOO- in an ALI model.

RESULTS

To address this, we developed three near-infrared (NIR) fluorescent probes (DCM-F-ONOO, DCM-Cl-ONOO, and DCM-Br-ONOO) for the detection of ONOO- using pentafluorobenzenesulfonate (PFBS) moieties as fluorescence quenchers. Through comprehensive testing, we selected DCM-Br-ONOO as the best NIR fluorescent probe due to its rapid response (within 3 min), high selectivity, good sensitivity (LOD = 2.3 nM), and approximately 66-fold enhanced response to ONOO- in fluorescence intensity. The probe was successfully applied to detect changes in ONOO- levels induced by different drugs in the ER of living cells. Importantly, a significant increase in the level of ONOO- was observed in the ER of an ALI cell model (4.5-fold) and an ALI mouse model (2.5-fold) using the probe, which is essential for understanding the role of ONOO- in ER-associated diseases.

SIGNIFICANCE

Using DCM-Br-ONOO as a probe, present work further validated that the elevated levels of ONOO- secretion were accompanied by the ALI progressed. These findings may provide valuable results for figuring out the biological roles that ONOO- played in ALI.

Bis-cyanostilbene based fluorescent materials: A rational design of AIE active probe for hypochlorite sensing

In the present investigation cyanostilbene based molecular probes, PCS and PCO, bearing N,N-dimethylthiocarbamate and N,N-dimethylcarbamoyal groups, respectively, have been synthesised. These probes exhibit AIEE activity in their aggregated state in the mixed solvent system of THF: H2O by way of turning on their emission, which has also been observed in powder, neat thin films and hybrid polymer films. While the probe PCO is silent to ClO-, PCS exhibits a significant response towards ClO- rationalised on the basis of HOCl specific oxidation of thiocarbamate, which is also extended to detect ClO- in water samples. Additionally, applicability of the test strips of PCS for rapid on-site detection of ClO- has been demonstrated. The experimental results are supplemented by the theoretical calculations wherever possible.

Highly sensitive and rapid detection of hypochlorous acid in aqueous media and its bioimaging in live cells and zebrafish using an ESIPT-driven mycophenolic acid-based fluorescent probe

Excessive production of potent biological oxidants such as HOCl has been implicated in numerous diseases. Thus, it is crucial to develop highly specific and precise methods to detect HOCl in living systems, preferably with molecules that can show a distinct therapeutic effect. Our study introduces the synthesis and application of a highly sensitive fluorescence "turn-on" probe, Myco-OCl, based on the mycophenolic acid scaffold with exceptional water solubility. The ESIPT-driven mechanism enables Myco-OCl to specifically and rapidly detect (<5 s) HOCl with an impressive Stokes shift of 105 nm (λex = 417 nm, λem = 522 nm) and a sub-nanomolar (97.3 nM) detection limit with the detection range of 0 to 50 μM. The potential of Myco-OCl as an excellent biosensor is evident from its successful application for live cell imaging of exogenous and endogenous HOCl. In addition, Myco-OCl enabled us to detect HOCl in a zebrafish inflammatory animal model. These underscore the great potential of Myco-OCl for detecting HOCl in diverse physiological systems. Our findings thus offer a highly promising tool for detecting HOCl in living organisms.

Mitochondrial targeted fluorescent nitrite peroxide probe for dynamic monitoring of cellular lung injury

Herein, a mitochondrial targeted fluorescent nitrite peroxide probe CHP for dynamic monitoring of cellular lung injury was developed. For the practical delivery and selectivity, the structural features including pyridine head and borate recognition group were selected. CHP could respond to ONOO^- with the 585 nm fluorescence signal. The detecting system indicated advantages such as wide linear range (0.0-30 μM), high sensitivity (LOD = 0.18 μM), high selectivity and steadiness under different environmental conditions including pH (3.0-10.0), time (48 h) and medium. In living A549 cells, the response of CHP towards ONOO^- showed dose-dependent and time-dependent tendencies. The co-localization suggested that CHP could achieve mitochondrial targeting. Moreover, CHP could monitor the variation of endogenous ONOO^- level and the cellular lung injury induced by LPS.

De Novo Design of Activatable Photoacoustic/Fluorescent Probes for Imaging Acute Lung Injury In Vivo

Effective monitoring of the physiological progression of acute lung injury (ALI) in real time is crucial for early theranostics to reduce its high mortality. In particular, activatable fluorescence and photoacoustic molecule probes have attracted attention to assess ALI by detecting related indicators. However, the existing fluorophores often encounter issues of low retention in the lungs and slow clearance from the body, which compromise the probe's actual capability for in situ imaging by intravenous injection in vivo. Herein, a novel near-infrared hemicyanines fluorophore (FJH) bearing a quaternary ammonium group was first developed by combining with the rational design and screening strategy. The properties of good hydrophilicity and blood circulation effectively enable FJH accumulation for lung imaging. Inspired by the high retention efficiency, the probe FJH-C that turns on fluorescence and photoacoustic signals in response to the ALI indicator (esterase) was subsequently synthesized. Notably, the probe FJH-C successfully achieved the selectivity and sensitivity toward esterase in vitro and in living cells. More importantly, FJH-C can be further used to assess lipopolysaccharides and silica-induced ALI through the desired fluo-photoacoustic signal. Therefore, this study not only shows the first activatable probe for real-time imaging of lung function but also highlights the fluorophore structure with high lung retention. It is believed that FJH and FJH-C can serve as an efficient platform to reveal the pathological progression of other lung diseases for early diagnosis and medical intervention.

Simultaneous Monitoring of HOCl and Viscosity with Drug-Induced Pyroptosis in Live Cells and Acute Lung Injury

Pyroptosis is a newly identified form of cell death that is closely correlated with many diseases. Recent studies have indicated that the inflammation in pyroptosis would accelerate the generation of reactive oxygen species (ROS). In addition, intracellular viscosity is another key microenvironmental parameter that reflects many physiological and pathological states in the early stage, hypochlorous acid (HOCl), as an important ROS, also plays significant roles in a variety of pathologies. However, the fluctuation of viscosity and HOCl in the process of pyroptosis is still unknown. Herein, we present a dual-responsive fluorescent probe (Lyso-VH) for simultaneously detecting viscosity and HOCl. Lyso-VH was successfully used to image the fluctuation of HOCl and viscosity in the lysosome of three kinds of cells with dependent and independent channels. Moreover, Lyso-VH can be employed to investigate the changes of HOCl and viscosity during the process of pyroptosis in living cells and acute lung injury (ALI). Thus, this work can not only serve as a powerful tool to simultaneously visualize the fluctuation of HOCl and viscosity in lysosomes, but also provide a new insight into drug-induced pyroptosis in living cells and acute lung injury.

The Development of a 4-aminonaphthalimide-based Highly Selective Fluorescent Probe for Rapid Detection of HOCl

Recently, more and more evidence indicated that intracellular HOCl plays a crucial role in the regulation of inflammation and apoptosis, while excessive HOCl has an impact on human health problems. So, the development of methods for sensitive detection of HOCl is very vital to reveal its various physiological and pathological functions. In this paper, we have described a simple fluorescent probe for selective detection of HOCl, whereas for higher concentrations of other biological important substances, the probe almost does not respond. The experimental results show that the probe can quantitatively determine the range of 0-1 μM HOCl, the detection limit is 0.05 μM. In addition, the probe reacts quickly with HOCl (< 3 s), which is helpful to monitor HOCl in biological system because HOCl is highly reactive and short-lived. The ability of the probe to HOCl enables it to be used to track the HOCl levels in living systems.

A deep-red lysosome-targetable fluorescent probe for detection of hypochlorous acid in pure water and its imaging application in living cells and zebrafish

Hypochlorite plays a significant role in physiological processes, particularly regulation of lysosomal functions, and is involved in various diseases. Thus, it is crucial to develop highly sensitive and selective molecule tools to detect HClO in lysosomes. Herein, a novel 2H-benzo[h]chromene-pyridine derivative (1) was synthesized through condensation reaction, which exhibited a notable deep-red emission at 640 nm in pure water. This deep-red emission was specifically quenched by adding ClO^-. The response of probe 1 toward ClO^- was rapid (within 10 s), sensitive (detection limit of 0.012 μM), and effective over a wide range of pH (1.0-12.0). Due to the existence of morpholine as the lysosome-targeting unit, the probe was successfully utilized to monitor lysosomal ClO^-. Moreover, the probe 1 was also applied to detecting ClO^- in zebrafish.

A benzocoumarin-based fluorescent probe for ultra-sensitive and fast detection of endogenous/exogenous hypochlorous acid and its applications

Hypochlorous acid (HOCl) is widely used in daily production and life because of its green and strongly oxidizing properties.

Two-photon ratiometric fluorescent probe for imaging of hypochlorous acid in acute lung injury and its remediation effect

Acute lung injury (ALI) is a pulmonary inflammatory disease with high morbidity and mortality rates. However, owing to the unknown etiology and rapid progression of the disease, the diagnosis of ALI is full of challenges with no effective treatment. Since the inflammatory response and oxidative stress played vital roles in the development of ALI, we herein developed the largest emission cross-shift (△λ = 145 nm) two-photon ratiometric fluorescent probe of TPRS-HOCl with high selectivity and short response time toward hypochlorous acid (HOCl) for exploring the relevance between the degree of ALI and HOCl concentration in the development process of the disease. In addition, the inhibition effect of HOCl during different treatment periods was also evaluated. Moreover, the tendency of imaging results was basically in accordance with that of hematoxylin and eosin (H&E) staining and the treatment effect became better in the early stage when using N-acetylcysteine (NAC), demonstrating the sensitivity of TPRS-HOCl toward ALI response. Thus, TPRS-HOCl has great potential to diagnose ALI in the early stage and guide for effective treatment.

Small-molecule fluorescence-based probes for interrogating major organ diseases

Chemical tools that allow the real-time monitoring of organ function and the visualisation of organ-related processes at the cellular level are of great importance in biological research. The upregulation/downregulation of specific biomarkers is often associated with the development of organ related diseases. Small-molecule fluorescent probes have the potential to create advances in our understanding of these disorders. Viable probes should be endowed with a number of key features that include high biomarker sensitivity, low limit of detection, fast response times and appropriate in vitro and in vivo biocompatibility. In this tutorial review, we discuss the development of probes that allow the targeting of organ related processes in vitro and in vivo. We highlight the design strategy that underlies the preparation of various promising probes, their optical response to key biomarkers, and proof-of-concept biological studies. The inherent drawbacks and limitations are discussed as are the current challenges and opportunities in the field. The hope is that this tutorial review will inspire the further development of small-molecule fluorescent probes that could aid the study of pathogenic conditions that contribute to organ-related diseases.

The α2AR/Caveolin-1/p38MAPK/NF-κB axis explains dexmedetomidine protection against lung injury following intestinal ischaemia-reperfusion

Intestinal ischaemia-reperfusion (I/R) injury can result in acute lung injury due to ischaemia and hypoxia. Dexmedetomidine (Dex), a highly selective alpha2-noradrenergic receptor (α2AR) agonist used in anaesthesia, is reported to regulate inflammation in organs. This study aimed to investigate the role and mechanism of Dex in lung injury caused by intestinal I/R. After establishing a rat model of intestinal I/R, we measured the wet-to-dry specific gravity of rat lungs upon treatments with Dex, SB239063 and the α2AR antagonist Atipamezole. Moreover, injury scoring and histopathological studies of lung tissues were performed, followed by ELISA detection on tumour necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 expression. Correlation of Caveolin-1 (Cav-1) protein expression with p38, p-p38, p-p65 and p65 in rat lung tissues was analysed, and the degree of cell apoptosis in lung tissues after intestinal I/R injury was detected by TUNEL assay. The lung injury induced by intestinal I/R was a dynamic process. Moreover, Dex had protective effects against lung injury by mediating the expression of Cal-1 and α2A -AR. Specifically, Dex promoted Cav-1 expression via α2A -AR activation and mitigated intestinal I/R-induced lung injury, even in the presence of Atipamezole. The protective effect of Dex on intestinal I/R-induced lung injury was also closely related to α2A -AR/p38 mitogen-activated protein kinases/nuclear factor-kappaB (MAPK/NF-κB) pathway. Dex can alleviate pulmonary inflammation after in intestinal I/R by promoting Cav-1 to inhibit the activation of p38 and NF-κB. In conclusion, Dex can reduce pulmonary inflammatory response even after receiving threats from both intestinal I/R injury and Atipamezole.

The development of a highly selective fluorescent probe for the rapid detection of HClO in living cells and zebrafish

A new turn-on fluorescent probe, BM-HA, for the rapid detection of HClO in living cells and zebrafish is proposed, and DFT/TDDFT calculations provide insights into the optical properties of the BM-HA probe.