To address fundamental questions concerning drug-induced mitochondrial dysfunction, Caenorhabditis elegans was developed as a model organism. Several studies have shown the occurrence of mitochondrial dysfunction as a consequence of therapeutic drug use, especially the drugs used to treat HIV infected individuals. The cause of these side-effects appears to be a common mechanism: a decreased mitochondrial energy-generating capacity putatively caused by the secondary inhibition of mitochondrial DNA polymerase γ, resulting in the depletion of mitochondrial DNA (mtDNA). However, the exact mechanism behind this remains unknown. Since most of these results have been obtained in patient- or cell culture studies, it poses limitations on the experiments that can be performed. Progress in this field is highly dependent on the development of a good model system. With our model system we could show a concentration dependent decline in mtDNA copies when the worms are cultured in the presence of various anti-retroviral drugs. This decline was both absolute and relative compared to nuclear DNA. Moreover, exposure to these drugs resulted in increased ROS production and/or a morphologically discernible disruption of the mitochondrial network. The severity of the observed effects is drug-specific and concentration dependent. Interestingly, the observed biochemical and morphological effects are not necessarily provoked by the same compounds and some of the effects can be alleviated by providing supplementation with compounds active on the mitochondrial respiratory chain. Since the side-effects of the drugs in patients on anti-retroviral therapy closely resemble our observed effects in C. elegans, we conclude that C. elegans is a highly suitable model organism to study drug induced mitochondrial dysfunction and highly expedient to search for compounds to alleviate the induced toxicities. Preliminary results suggest the beneficial effect of supplementation as a way of counteracting and alleviating some of these pernicious side-effects.

It is now widely appreciated that normal tissue morphology and function rely upon cells' ability to sense and generate forces appropriate to their correct tissue context. Although the effects of forces on cells have been studied for decades, our understanding of how those forces propagate through and act on different cell substructures remains at an early stage, especially for pathologic situations. In this talk I will discuss three different topics in cell mechanics where insight is gained through the development of a variety of different micromechanical methods to probe cells' dynamic deformation in response to deformations, time-varying force and pharmacological agents. First I will discuss how the cytoskeletal properties of white blood cells can be involved in their sequestration in pulmonary capillaries, which is arguably the initiating event of lung injury in acute respiratory distress syndrome [1-2]. Specifically, I will present a microfluidic investigation of the roles of actin organization and myosin II activity during the different stages of leukocyte trafficking through narrow capillaries (entry, transit and shape relaxation) using specific drugs (latrunculin A, jasplakinolide, and blebbistatin). The second part of the talk will focus on pathophysiological mechanisms by which non-penetrating injuries damage the brain. Based on experiments using two hierarchical in vitro systems (a high velocity stretcher and a magnetic tweezer) to mimic traumatic brain injury to rat cortical neurons, I will show how an acute mechanical perturbation of neuronal integrins is sufficient to induce neuronal focal swelling, reminiscent to diffuse axonal injury in vivo [3]. In the third part, I will present ongoing work on the mechanical regulation of the nucleus in response to endothelial cell shape changes. By using a combination of micromanipulation tools, I will show that tension in central stress fibers is gradually generated by anisotropic force contraction dipoles and how cell shape changes can induce condensation of chromatin and affect cell proliferation [4]. On the basis of these findings, I will propose a simple mechanical model that quantitatively accounts for our experimental data and provides a conceptual framework for the mechanistic coordination between cell and nuclear shapes.
References: [1] S. Gabriele, A.M. Benoliel, P. Bongrand and O. Theodoly, Biophysical Journal, 96, 4308-4318 (2009) [2] S. Gabriele, M. Versaevel et al. Lab on a Chip, 10, 1459-1467 (2010) [3] M. Hemphill, B. Dabiri, S. Gabriele et al. PLoS ONE, 6, E22899 (2011) [4] M. Versaevel, T. Grevesse and S. Gabriele, Nature Communications, 3, 671 (2012)

Metal (mainly gold) nanoparticles (NPs) have attracted significant interest as a novel platform for nanobiotechnology and biomedicine because of convenient surface bioconjugation with molecular probes and remarkable optical properties related with the localized plasmon resonance (PR). Here, we give a short review of our recent work on fabrication, optical properties, fictionalization, and biomedical applications of plasmon- resonant nanoparticles. The emphasis is upon nanoparticle inducted laser cancer hyperthermia (LCH). Three types of nanostructures are considered: gold nanorods, silica/gold gold nanoshells, and silver/gold nanocages. The plasmonic properties of such nanostructures can be tuned across visible-NIR spectral bands by variation in the particle shape, structure, and composition. In particular, photothermal applications of gold nanorods are especially attractive owing to their highly efficient NIR absorption. Moreover, the strong-intensive longitudinal PR supports several nonlinear phenomena, including two-photon luminescence, which has already been used for cancer cell imaging and for tracking of nanoparticle cellular uptake. The choice of optimal nanoparticles platform for LCH, nanoparticles synthesis, functionalization, biodistribution, toxicity and efficiency of nanoparticles inducted therapy will be discussed.

Our research focuses on gaining a quantitative mechanistic understanding of mitochondrial (patho)physiology at the (sub)cellular level. To study mitochondrial (dys)function, fluorescent reporter molecules are introduced in pathological and healthy cell models. (Patho)physiology is then investigated using classical biochemical techniques, high-resolution respirometry, state-of-the-art quantitative (sub)cellular life cell microscopy, single-molecule spectroscopy and mathematical modelling. This strategy is applied to answer the following research questions: (i) What is the connection between mitochondrial (ultra)structure and metabolic (dys)function? (ii) How does mitochondrial (dys)function affect mitochondrial/cellular properties in mammalian cells? (iii) In which way do cells adapt to mitochondrial dysfunction? (iv) How can mitochondrial dysfunction be mitigated at the cellular and organismal level? To provide a better understanding of mitochondrial (patho)physiology and guide future drug-development, the obtained experimental data is being iteratively integrated into mathematical models of cellular metabolism within the recently established “Centre for Systems Biology and Bioenergetics”.