Natural killer (NK) cells play key roles in eliminating pathogen-infected cells. Verbena officinalis (V. officinalis) has been used as a medical plant in traditional and modern medicine for its anti-tumor and anti-inflammatory activities, but its effects on immune responses remain largely elusive. This study aimed to investigate the potential of V. officinalis extract (VO extract) to regulate inflammation and NK cell functions. We examined the effects of VO extract on lung injury in a mouse model of influenza virus infection. We also investigated the impact of five bioactive components of VO extract on NK killing functions using primary human NK cells. Our results showed that oral administration of VO extract reduced lung injury, promoted the maturation and activation of NK cells in the lung, and decreased the levels of inflammatory cytokines (IL-6, TNF-α and IL-1β) in the serum. Among five bioactive components of VO extract, Verbenalin significantly enhanced NK killing efficiency in vitro, as determined by real-time killing assays based on plate-reader or high-content live-cell imaging in 3D using primary human NK cells. Further investigation showed that treatment of Verbenalin accelerated the killing process by reducing the contact time of NK cells with their target cells without affecting NK cell proliferation, expression of cytotoxic proteins, or lytic granule degranulation. Together, our findings suggest that VO extract has a satisfactory anti-inflammatory effect against viral infection in vivo, and regulates the activation, maturation, and killing functions of NK cells. Verbenalin from V. officinalis enhances NK killing efficiency, suggesting its potential as a promising therapeutic to fight viral infection.

Mechanotransduction events in physiological environments are difficult to investigate, in part due to the lack of experimental tools to apply forces to mechanosensitive receptors remotely. Inspired by cellular mechanisms for force application (i.e. motor proteins pulling on cytoskeletal fibers), here we present a unique molecular machine that can apply forces at cell-matrix and cell-cell junctions using light as an energy source. The key actuator is a light-driven rotatory molecular motor linked to polymer chains, which is intercalated between a membrane receptor and an engineered biointerface. The light-driven actuation of the molecular motor is converted in mechanical twisting of the polymer chains, which will in turn effectively “pulls” on engaged cell membrane receptors (integrins, cadherins…) within the illuminated area. Applied forces have the adequate magnitude and occur at time scales within the relevant ranges for mechanotransduction at cell-friendly exposure conditions, as demonstrated in forcedependent focal adhesion maturation and T cell activation experiments. Our results reveal the potential of nanomotors for the manipulation of living cells at the molecular scale and demonstrate, for the first time, a functionality which at the moment cannot be achieved by any other means.

CD8⁺cytotoxic T lymphocytes (CTL) and natural killer (NK) cells are the main cytotoxic killer cells of the human body to eliminate pathogen-infected or tumorigenic cells (= target cells). To find their targets they have to navigate and migrate through a complex biological microenvironments, a key component of which is the extracellular matrix (ECM). The mechanisms underlying killer cell’s navigation are not well understood. To mimic an ECM we use a matrix formed by different collagen concentrations, and analyze migration trajectories of primary human CTLs. Different migration patterns are observed and can be grouped into three motility types: slow, fast and mixed. The dynamics are well described by a two-state persistent random walk model which allows cells to switch between slow motion with low persistence, and fast motion with high persistence. We hypothesize that the slow motility mode describes CTLs creating channels through the collagen matrix by deforming and tearing apart collagen fibers, and that the fast motility mode describes CTLs moving within these channels. Experimental evidence supporting this scenario is presented by visualizing migrating T cells following each other on exactly the same track and showing cells moving quickly in channel-like cavities within the surrounding collagen matrix. Consequently, the efficiency of the stochastic search process of CTLs in the ECM should strongly be influenced by a dynamically changing channel network produced by the killer cells themselves.

The killing efficiency of cytotoxic T lymphocytes (CTLs) is tightly regulated by intracellular Ca ²⁺ concentration. Glucose is the key energy source for CTLs, lack of which significantly impairs CTL activation, proliferation and effector functions. The impact of high glucose on Ca ²⁺ influx in CTLs remains largely elusive. In this work, we stimulated primary human CD8 ⁺ T cells in medium containing either 25 mM (high glucose, HG) or 5.6 mM glucose (normal glucose, NG). We found that store-operated calcium entry (SOCE) induced by thapsigargin (Tg) is elevated in HG-cultured CTLs compared to their counterparts in NG. Unexpectedly, the Ca ²⁺ influx elicited by recognition of target cells is reduced in HG-cultured CTLs. Under HG condition, STIM1 and STIM2 , the calcium sensors in the endoplasmic reticulum (ER), were down-regulated; ORAI1 , the main structural component of calcium-release activated channels, remained unchanged, whereas ORAI2 and ORAI3 were up-regulated. The fraction of necrosis of HG-cultured CTLs was enhanced after killing without affecting glucose uptake. Thus, our findings reveal that HG has a distinctive impact on Tg-evoked SOCE and target recognition-induced Ca ²⁺ influx in CTLs and causes more CTL death after killing, suggesting a novel regulatory role of high glucose on modulating CTL functions.