Biology subjects

Owen, B.

Publications and source records attributed to Owen, B..

9 recordsLinked to original sources

bioRxiv2024

Connexin 43 mediated mitochondrial transfer prevents cisplatin induced sensory neurodegeneration.

Platinum based chemotherapeutics including cisplatin are front-line treatments for paediatric and adult cancer. Despite advancements in medical interventions, chemotherapy-induced peripheral sensory neuropathy is a common adverse health related complication that can persist for the long-term and impacts upon an individuals quality of life. Recently, the causes of chemotherapy induced sensory neurodegeneration has been linked to sensory neuronal mitochondrial dysfunction. Here this study investigated how monocytic mitochondria donation to recipient cisplatin damaged dorsal root ganglia (DRG) sensory neurons prevented platinum-based chemotherapy-induced sensory neurotoxicity. Neuronal cell line, SH-SY5Y, or mouse DRG sensory neurons were treated with either vehicle or cisplatin, and co-cultured with mitotracker-labelled THP1 monocytes. Cisplatin induced dysmorphic mitochondria and diminished oxidative phosphorylation dependent energy production in cisplatin treated dorsal root ganglia sensory neurons. DRG sensory neurons exposed to cisplatin were recipients of monocyte mitochondria indicated by increased intracellular mitotracker fluorescent labelling. Mitochondrial transfer to sensory neurons was neuroprotective, preventing neurite loss and sensory neuronal apoptosis. Vehicle treated DRG sensory neurons did not demonstrate significant mitochondrial uptake. Furthermore, cisplatin induced mitochondrial transfer was prevented by pharmacological inhibition of gap junction protein, connexin 43. Connexin 43 inhibition led to reduced neuroprotective capacity via mitochondrial transfer. These findings demonstrate that monocytic mitochondria transfer to DRG sensory neurons damaged by cisplatin, is dependent upon gap junction intercellular communication to promote sensory neuronal survival. This novel process in sensory neuronal protection is a potential novel therapeutic intervention for alleviating neuropathic pain in individuals treated for cancer.

neuroscience↗

bioRxiv2023

Numerical analysis of flow anisotropy in rotated-square deterministic lateral displacement devices at moderate Reynolds number

Deterministic lateral displacement (DLD) is a microfluidic method for accurately separating particles by size or deformability. Recent efforts to operate DLD devices in the inertial, rather than in the Stokes, flow regime have been hindered by a loss of separation efficiency and difficulty predicting the separation behaviour. One factor contributing to these problems is the onset of inertia-induced flow anisotropy where the average flow direction does not align with the direction of the pressure gradient in the device. We use the lattice-Boltzmann method to simulate two-dimensional flow through a rotated-square DLD geometry with circular pillars at Reynolds number up to 100 for different gap sizes and rotation angles. We find that anisotropy in this geometry is a non-monotonous function of Reynolds number and can be positive or negative. This finding is in contradiction to the naive expectation that inertia would always drive flow along principal direction of the pillar array. Anisotropy tends to increase in magnitude with gap size and rotation angle. By analysing the traction distribution along the pillar surface, we explain how the change of the flow field upon increasing inertia leads to the observed trends of anisotropy. Our work contributes to a better understanding of the inertial flow behaviour in ordered cylindrical porous media, and might contribute to improved DLD designs for operation in the inertial regime.

bioengineering↗

bioRxiv2023

Numerical investigation of heterogeneous soft particle pairs in inertial microfluidics

The formation of pairs of particles or cells of different types in microfluidic channels can be desired or detrimental in healthcare applications. It is still unclear what role softness heterogeneity plays in the formation of these particle pairs. We use an in-house lattice-Boltzmann-immersed-boundary-finite-element solver to simulate a pair of particles with different softness flowing through a straight channel with a rectangular cross-section under initial conditions representative of a dilute suspension. We find that softness heterogeneity significantly affects the pair dynamics, determining whether a pair will form or not, and determining the lateral and inter-particle equilibrium behaviour in the pair. We also observe close matches between the transient deformation of particles in a linear pair and single particles in isolation. These results further our understanding of pair behaviour, providing a foundation for understanding particle train formation, and open up the potential to develop reduced-order models for particle pair formation based upon the behaviour of single particles.

bioengineering↗

bioRxiv2023

Lattice-Boltzmann Modelling for Inertial Particle Microfluidics Applications -A Tutorial Review

Inertial particle microfluidics (IPMF) is an emerging technology for the manipulation and separation of microparticles and biological cells. Since the flow physics of IPMF is complex and experimental studies are often time-consuming or costly, computer simulations can offer complementary insights. In this tutorial review, we provide a guide for researchers who are exploring the potential of the lattice-Boltzmann (LB) method for simulating IPMF applications. We first review the existing literature to establish the state of the art of LB-based IPMF modelling. After summarising the physics of IPMF, we then present related methods used in LB models for IPMF and show several case studies of LB simulations for a range of IPMF scenarios. Finally, we conclude with an outlook and several proposed research directions.

biophysics↗

bioRxiv2022

Numerical investigation of the dynamics of a rigid spherical particle in a vortical cross-slot flow at moderate inertia

The study of flow and particle dynamics in microfluidic cross-slot channels is of high relevance for lab-on-a-chip applications. In this work we investigate the dynamics of a rigid spherical particle in a cross-slot junction for a channel height-to-width ratio of 0.6 and at a Reynolds number of 120 for which a steady vortex exists in the junction area. Using an in-house immersed- boundary-lattice-Boltzmann code, we analyse the effect of the entry position of the particle in the junction and the particle size on the dynamics and trajectory shape of the particle. We find that the dynamics of the particle depends strongly on its lateral entry position in the junction and weakly on its vertical entry position; particles that enter close to the centre show trajectory oscillations. Larger particles have longer residence times in the junction and tend to oscillate less due to their confinement. Our work contributes to the understanding of the particle dynamics in intersecting flows and enables the design of optimised geometries for cytometry and particle manipulation.

biophysics↗

bioRxiv2022

Numerical study of the formation and stability of a pair of particles of different sizes in inertial microfluidics

The formation of pairs and trains of particles in inertial microfluidics is an important consideration for device design and applications, such as particle focussing and separation. We study the formation and stability of linear and staggered pairs of nearly rigid spherical particles of different sizes in a pressure-driven flow through a straight duct with rectangular cross-section under mild inertia. An in-house lattice-Boltzmann-immersed-boundary-finite-element code is used for the simulations. We find that the stability and properties of pairs of heterogeneous particles strongly depends on the particle sizes and their size ratio, while the formation of the pairs is also determined by the initial lateral position and the axial order of the particles. Our findings imply that perturbations of particle trajectories caused by other particles, as they are expected to happen even in dilute suspensions, can be important for the formation of stable pairs in inertial microfluidics.

biophysics↗

bioRxiv2022

Blockade of TGF-β signaling reactivates HIV-1/SIV reservoirs and immune responses in vivo

Elevated levels of TGF-{beta}, a potent immunosuppressive factor, are present in HIV-1 infected individuals even after years of antiretroviral therapy (ART). TGF-{beta} plays a critical role in maintaining immune cells in a resting state by inhibiting cell activation and proliferation. Resting HIV-1 target cells represent one of the main cellular reservoirs after long term ART and the low inducibility of the latent provirus constitutes one of the major obstacles to "kick and kill" cure strategies. We hypothesized that releasing cells from TGF-{beta}-driven signaling would promote latency reversal. To test our hypothesis, we compared ex vivo models of HIV-1 latency reactivation with and without TGF-{beta} and a TGF-{beta} type 1 receptor (TGFBR1) inhibitor, galunisertib. We also tested the effect of galunisertib in SIV infected, ART treated macaques by monitoring SIV envelope (env) protein expression via PET/CT using the Cu64-anti gp120 Fab (7D3) probe, along with plasma and tissue viral loads (VL). Exogenous TGF-1{beta} reduced HIV-1 reactivation in U1 and ACH2 latency models. Galunisertib increased HIV-1 latency reversal both in ex vivo models and in PBMC from HIV-1 infected, cART treated aviremic donors. In vivo, oral galunisertib promoted increased SIV env protein total standardized uptake values (SUVtot) in PET/CT images of tissues (gut and lymph nodes) of 5 out of 7 aviremic, long-term ART-treated, SIV-infected, macaques. This increase correlated with an increase in SIV RNA in gut tissue. Two out of 7 animals also exhibited increases in plasma viral load. Higher anti-SIV T cell responses and anti-SIV env antibody titers were detected after galunisertib treatment in most animals. In summary, our data suggest that blocking TGF-{beta} signaling simultaneously increases retroviral reactivation events and enhances anti-SIV immune responses.

immunology↗

bioRxiv2021

Disruption of synaptic transmission in the Bed Nucleus of the Stria Terminalis reduces seizure-induced death in DBA/1 mice and alters brainstem E/I balance

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in refractory epilepsy patients. Accumulating evidence from recent human studies and animal models suggests that seizure-related respiratory arrest may be important for initiating cardiorespiratory arrest and death. Prior evidence suggests that apnea onset can coincide with seizure spread to the amygdala and that stimulation of the amygdala can reliably induce apneas in epilepsy patients, potentially implicating amygdalar regions in seizure-related respiratory arrest and subsequent postictal hypoventilation and cardiorespiratory death. This study aimed to determine if an extended amygdalar structure, the dorsal bed nucleus of the stria terminalis (dBNST), is involved in seizure-induced respiratory arrest (S-IRA) and death using DBA/1 mice, a mouse strain which has audiogenic seizures and a high incidence of postictal respiratory arrest and death. The presence of S-IRA significantly increased c-Fos expression in the dBNST of DBA/1 mice. Furthermore, disruption of synaptic output from the dBNST via viral-induced tetanus neurotoxin significantly improved survival following S-IRA in DBA/1 mice without affecting baseline breathing or hypercapnic and hypoxic ventilatory response. This disruption in the dBNST resulted in changes to the balance of excitatory/inhibitory synaptic events in the downstream brainstem regions of the lateral parabrachial nucleus (PBN) and the periaqueductal gray (PAG). These findings suggest that the dBNST is a potential subcortical forebrain site necessary for the mediation of seizure-induced respiratory arrest, potentially through its outputs to brainstem respiratory regions. SUMMARY STATEMENTThis study used a viral expression technique to disrupt synaptic output in the bed nucleus of the stria terminalis (BNST) of DBA/1 audiogenic seizure mice. Inactivating the BNST significantly improved survival following seizures and altered brainstem excitation/inhibition balance.

neuroscience↗

bioRxiv2020

Sexually dimorphic roles for the type 2 diabetes-associated C2cd4b gene in murine glucose homeostasis

Variants close to the VPS13C/C2CD4A/C2CD4B locus are associated with altered risk of type 2 diabetes in genome-wide association studies. Whilst previous functional work has suggested roles for VPS13C and C2CD4A in disease development, none has explored the role of C2CD4B. Here, we show that systemic inactivation of C2cd4b in mice leads to marked, but highly sexually dimorphic, changes in body weight and glucose homeostasis. Female C2cd4b mice display unchanged body weight but abnormal glucose tolerance and defective in vivo, but not in vitro, insulin secretion, associated with a marked decrease in follicle stimulating hormone levels. In sharp contrast, male C2cd4b null mice displayed normal glucose tolerance but an increase in body weight and fasting glycemia after maintenance on high fat diet. No metabolic disturbances were observed after global inactivation of C2cd4a in mice, or in pancreatic {beta} cell function at larval stages in C2cd4ab null zebrafish. These studies suggest that C2cd4b may act centrally to influence sex-dependent circuits which control pancreatic {beta} cell function and glucose tolerance in rodents. However, the absence of sexual dimorphism in the impact of diabetes risk variants argues for additional roles for C2CD4A or VPS13C in the control of glucose homeostasis in man.

genetics↗