Lis1 relieves cytoplasmic dynein-1 autoinhibition by acting as a molecular wedge.

Cytoplasmic dynein-1 transports intracellular cargo towards microtubule minus ends. Dynein is autoinhibited and undergoes conformational changes to form an active complex that consists of one or two dynein dimers, the dynactin complex, and activating adapter(s). The Lissencephaly 1 gene, LIS1, is genetically linked to the dynein pathway from fungi to mammals and is mutated in people with the neurodevelopmental disease lissencephaly. Lis1 is required for active dynein complexes to form, but how it enables this is unclear. Here, we present a structure of two yeast dynein motor domains with two Lis1 dimers wedged in-between. The contact sites between dynein and Lis1 in this structure, termed 'Chi,' are required for Lis1's regulation of dynein in Saccharomyces cerevisiae in vivo and the formation of active human dynein-dynactin-activating adapter complexes in vitro. We propose that this structure represents an intermediate in dynein's activation pathway, revealing how Lis1 relieves dynein's autoinhibited state.

Study of hydrogen sulfide biosynthesis in synovial tissue from diabetes-associated osteoarthritis and its influence on macrophage phenotype and abundance.

Type 2 diabetes (DB) is an independent risk factor for osteoarthritis (OA). However, the mechanisms underlying the connection between both diseases remain unclear. Synovial macrophages from OA patients with DB present a marked pro-inflammatory phenotype. Since hydrogen sulphide (H2S) has been previously described to be involved in macrophage polarization, in this study we examined H2S biosynthesis in synovial tissue from OA patients with DB, observing a reduction of H2S-synthetizing enzymes in this subset of individuals. To elucidate these findings, we detected that differentiated TPH-1 cells to macrophages exposed to high levels of glucose presented a lower expression of H2S-synthetizing enzymes and an increased inflammatory response to LPS, showing upregulated expression of markers associated with M1 phenotype (i.e., CD11c, CD86, iNOS, and IL-6) and reduced levels of those related to M2 fate (CD206 and CD163). The co-treatment of the cells with a slow-releasing H2S donor, GYY-4137, attenuated the expression of M1 markers, but failed to modulate the levels of M2 indicators. GYY-4137 also reduced HIF-1α expression and upregulated the protein levels of HO-1, suggesting their involvement in the anti-inflammatory effects of H2S induction. In addition, we observed that intraarticular administration of H2S donor attenuated synovial abundance of CD68+ cells, mainly macrophages, in an in vivo model of OA. Taken together, the findings of this study seem to reinforce the key role of H2S in the M1-like polarization of synovial macrophages associated to OA and specifically its metabolic phenotype, opening new therapeutic perspectives in the management of this pathology.

Autophagy Activation by Resveratrol Reduces Severity of Experimental Rheumatoid Arthritis.

SCOPE: Previous work reported that dietary supplementation with resveratrol lowers synovial hyperplasia, inflammatory and oxidative damage in an antigen-induced arthritis (AIA) model. Here, it is investigated whether resveratrol can regulate the abnormal synovial proliferation by inducing autophagy and controlling the associated inflammatory response. METHODS AND RESULTS: Animals treated with resveratrol 8 weeks before AIA induction show the highest significant signal for microtubule-associated protein 1 light chain 3 by confocal microscopy. Besides, resveratrol significantly reduces p62 expression, but it does not increase the signal of beclin-1. Also, active caspase-3 expression, as well as poly(ADP-ribose) polymerase, is upregulated in the AIA group, and is significantly reduced in resveratrol-treated AIA group. Resveratrol also mitigates angiopoietin-1 and vascular endothelial growth factor signals. Finally, resveratrol significantly reduces the serum levels of IL-1ß, C reactive protein, and prostaglandin E2, as well as nuclear factor κB synovial tissue expression, which shows a significant correlation with p62 expression. CONCLUSION: Dietary supplementation with resveratrol induces the noncanonical autophagy pathway and limits the cross-talk with inflammation, which in consequence modulates the synovial hyperplasia. Preventive strategies that incorporate dietary intervention with resveratrol may offer a potential therapeutic alternative to drugs to influence the risk of rheumatoid arthritis and influence its course.

Intraarticular Administration Effect of Hydrogen Sulfide on an In Vivo Rat Model of Osteoarthritis.

Osteoarthritis (OA) is the most common articular chronic disease. However, its current treatment is limited and mostly symptomatic. Hydrogen sulfide (H2S) is an endogenous gas with recognized physiological activities. The purpose here was to evaluate the effects of the intraarticular administration of a slow-releasing H2S compound (GYY-4137) on an OA experimental model. OA was induced in Wistar rats by the transection of medial collateral ligament and the removal of the medial meniscus of the left joint. The animals were randomized into three groups: non-treated and intraarticularly injected with saline or GYY-4137. Joint destabilization induced articular thickening (≈5% increment), the loss of joint mobility and flexion (≈12-degree angle), and increased levels of pain (≈1.5 points on a scale of 0 to 3). Animals treated with GYY-4137 presented improved motor function of the joint, as well as lower pain levels (≈75% recovery). We also observed that cartilage deterioration was attenuated in the GYY-4137 group (≈30% compared with the saline group). Likewise, these animals showed a reduced presence of pro-inflammatory mediators (cyclooxygenase-2, inducible nitric oxide synthase, and metalloproteinase-13) and lower oxidative damage in the cartilage. The increment of the nuclear factor-erythroid 2-related factor 2 (Nrf-2) levels and Nrf-2-regulated gene expression (≈30%) in the GYY-4137 group seem to be underlying its chondroprotective effects. Our results suggest the beneficial impact of the intraarticular administration of H2S on experimental OA, showing a reduced cartilage destruction and oxidative damage, and supporting the use of slow H2S-producing molecules as a complementary treatment in OA.