Biology subjects

Paquet-Durand, F.

Publications and source records attributed to Paquet-Durand, F..

24 records · Page 2Linked to original sources

bioRxiv2021

Kinase activity profiling identifies putative downstream targets of cGMP/PKG signaling in inherited retinal neurodegeneration

Inherited retinal diseases (IRDs) are a group of neurodegenerative disorders that lead to photoreceptor cell death and eventually blindness. IRDs are characterised by a high genetic heterogeneity, making it imperative to design mutation-independent therapies. Mutations in a number of IRD disease genes have been associated with a rise of cyclic 3,5-guanosine monophosphate (cGMP) levels in photoreceptors. Accordingly, the cGMP-dependent protein kinase (PKG) has emerged as a new potential target for the mutation-independent treatment of IRDs. However, the substrates of PKG and the downstream degenerative pathways triggered by its activity have yet to be determined. Here, we performed kinome activity profiling of different murine organotypic retinal explant cultures (diseased rd1 and wild-type controls) using multiplex peptide microarrays to identify proteins whose phosphorylation was significantly altered by PKG activity. In addition, we tested the downstream effect of a known PKG inhibitor CN03 in these organotypic retina cultures. Among the PKG substrates were potassium channels belonging to the Kv1 family (KCNA3, KCNA6), Cyclic AMP-responsive element-binding protein 1 (CREB1), DNA topoisomerase 2- (TOP2A), 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (F263), and the glutamate ionotropic receptor kainate 2 (GRIK2). The retinal expression of these PKG targets was further confirmed by immunofluorescence and could be assigned to various neuronal cell types, including photoreceptors, horizontal cells, and ganglion cells. Taken together, this study confirmed the key role of PKG in photoreceptor cell death and identified new downstream targets of cGMP/PKG signalling that will improve the understanding of the degenerative mechanisms underlying IRDs.

neuroscience↗

bioRxiv2021

Retinal degeneration: Multilevel protection of photoreceptor and ganglion cell viability and function with the novel PKG inhibitor CN238.

Hereditary retinal degeneration (RD) is often associated with excessive cGMP-signaling in photoreceptors. Previous research has shown that inhibition of cGMP-dependent protein kinase G (PKG) can slow down the loss of photoreceptors in different RD animal models. In this study, we identified a novel PKG inhibitor, the cGMP analogue CN238, with strong protective effects on photoreceptors in retinal degeneration rd1 and rd10 mutant mice. In long-term organotypic retinal explants, CN238 preserved rd1 and rd10 photoreceptor viability and function. Surprisingly, in explanted retinae CN238 also protected retinal ganglion cells from axotomy induced retrograde degeneration and preserved their functionality. Together, these results confirm the strong neuroprotective capacity of PKG inhibitors for both photoreceptors and retinal ganglion cells, thereby significantly broadening their potential applications for the treatment of retinal diseases and possibly neurodegenerative diseases in general.

neuroscience↗

bioRxiv2021

Composite solid lipid nanoparticles with hydrogel core for delivering small hydrophilic molecules to the retina: an in vitro study using ARPE-19 and 661W cells

In this study, we developed a novel solid lipid nanoparticle (SLN) formulation for drug delivery of small hydrophilic cargo to the retina. The new formulation, based on a gel core and composite shell, allowed up to two times increase in the encapsulation efficiency. The type of hydrophobic polyester used in the composite shell mixture affects the particle surface charge, colloidal stability, and cell internalization profile. We validated the SLN capability as a drug delivery system by performing encapsulation of a hydrophilic neuroprotective cyclic guanosine monophosphate analogue, previously demonstrated to hold retinoprotective properties, and the best formulation resulted in particles with size of {+/-} 250nm, anionic charge > -20 mV, and an encapsulation efficiency value of {+/-}60%, criteria that are suitable for retinal delivery. In vitro studies using ARPE-19 and 661W retinal cell lines revealed a relatively low SLN toxicity, even when high particle concentration was used. More importantly, SLN could be uptaken by the cells and the release of the hydrophilic cargo in the cytoplasm was visually demonstrated. These findings suggest that the newly developed SLN with a gel core and composite polymer/lipid shell holds all characteristics suitable for drug delivery of small hydrophilic active molecules into retinal cell.

neuroscience↗

bioRxiv2020

Redefining the role of Ca2+-permeable channels in hereditary photoreceptor degeneration using the D- and L-cis enantiomers of diltiazem

Hereditary degeneration of photoreceptors has been linked to over-activation of Ca2+-permeable channels, excessive Ca2+-influx, and downstream activation of Ca2+-dependent calpain-type proteases. Unfortunately, after more than 20 years of pertinent research, unequivocal evidence proving significant and reproducible photoreceptor protection with Ca2+-channel blockers is still lacking. Here, we show that both D- and L-cis enantiomers of the anti-hypertensive drug diltiazem were very effective at blocking photoreceptor Ca2+-influx, most probably by blocking the pore of Ca2+-permeable channels. Yet, unexpectedly, this block neither reduced the activity of calpain-type proteases, nor did it result in photoreceptor protection. Remarkably, application of the L-cis enantiomer of diltiazem even led to a strong increase in photoreceptor cell death. These findings shed doubt on the previously proposed links between Ca2+ and retinal degeneration and are highly relevant for future therapy development as they may serve to refocus research efforts towards alternative, Ca2+-independent degenerative mechanisms.

neuroscience↗

bioRxiv2019

HDAC inhibition ameliorates cone survival in retinitis pigmentosa mice

Cone photoreceptor cell death in inherited retinal diseases, such as Retinitis Pigmentosa (RP), leads to the loss of high acuity and color vision and ultimately to blindness. In RP, a vast number of mutations perturb the structure and function of rod photoreceptors while cones remain initially unaffected. Cone death follows rod death secondarily due to increased oxidative stress, inflammation, and loss of structural and nutritional support provided by rods. Here, we show that secondary cone cell death in animal models for RP was associated with an increased activity of histone deacetylates (HDACs). A single intravitreal injection of an HDAC inhibitor at a late stage of the disease, when majority of rods have already degenerated, was sufficient to delay cone death and support long-term cone survival. Moreover, the surviving cones remained light sensitive and initiated light-driven ganglion cell responses. RNA-seq analysis of protected cones demonstrated that HDAC inhibition led to multi-level protection via regulation of different pro-survival pathways, including MAPK, PI3K-Akt, and autophagy. This study suggests a unique possibility for a targeted pharmacological protection of both primary degenerating rods and secondary dying cones by HDAC inhibition and creates hope to maintain vision in RP patients independent of the disease stage.

neuroscience↗

bioRxiv2019

Systematic spatio-temporal mapping reveals divergent cell death pathways in three mouse models of hereditary retinal degeneration

Calcium (Ca2+) dysregulation has been linked to neuronal cell death, including in hereditary retinal degeneration. Ca2+ dysregulation is thought to cause rod and cone photoreceptor cell death. Spatial and temporal heterogeneities in retinal disease models have hampered validation of this hypothesis. We examined the role of Ca2+ in photoreceptor degeneration, assessing the activation pattern of Ca2+-dependent calpain proteases, generating spatio-temporal maps of the entire retina in the cpfl1 mouse model for primary cone degeneration, and in the rd1 and rd10 models for primary rod degeneration. We used Gaussian process models to distinguish the temporal sequences of degenerative molecular processes from other variability sources. In the rd1 and rd10 models, spatio-temporal pattern of increased calpain activity matched the progression of primary rod degeneration. High calpain activity coincided with activation of the calpain-2 isoform but not with calpain-1, suggesting differential roles for both calpain isoforms. Primary rod loss was linked to upregulation of apoptosis-inducing factor (AIF), although only a minute fraction of cells showed activity of the apoptotic marker caspase-3. After primary rod degeneration concluded, caspase-3 activation appeared in cones, suggesting apoptosis as the dominant mechanism for secondary cone loss. Gaussian process models highlighted calpain activity as a key event during primary rod photoreceptor cell death. Our data suggests a causal link between Ca2+ dysregulation and primary, non-apoptotic degeneration of photoreceptors and a role for apoptosis in secondary degeneration of cones, highlighting the importance of the spatial and temporal location of key molecular events, which may guide the evaluation of new therapies.

neuroscience↗