Aberrant Rho-associated kinase function could be associated with increased bone fragility. Since cigarette smoke (CS) exposure promotes the increase in bone fragility due to changes in bone tissue components, this study aimed to investigate how CS exposure could modulate the Rho kinase-associated bone structural changes. Mice were assigned to four groups: control; smoke; control with Rho kinase inhibitor administration; and smoke with a Rho kinase inhibitor. Bone samples were obtained to assess bone histomorphometry analysis, type I collagen composition, and MEPE expression in trabeculae. We observed that CS exposure induced decreased trabecular and osteoid thickness. A concomitant increase in the osteoclastic and erosion surfaces and a decrease in the mineralization surface were observed. Additionally, CS exposure decreased the type I collagen and MEPE expression. Rho kinase inhibitor administration recovered the bone mineralization and the collagen type I deposition. Conclusions: CS exposure increases Rho kinase activity in bone cells, leading to structural changes. The administration of a Rho GTPases inhibitor partially reverses these effects, likely due to the recovery in osteoblast activity.

Background: The importance of regulatory T cells (Treg) in regulating the suppression of inflammatory process in COPD have been addressed. Clinical and experimental studies have demonstrated that Treg cells immunosuppressive activity could be impaired in COPD. There are distinct Treg cells phenotypes: resting Tregs (rTregs, CD25++CD45RA+) and activated Tregs (aTregs, CD25+++CD45RA−), which, shows immunosuppressive activity, and also the cytokine-secreting T cells (FrIII, CD25++CD45RA−) with pro-inflammatory activity. Objective: To evaluate the different Treg cell phenotypes in COPD patients at different stages and non-obstructed smokers (NOS). Methods: We evaluated by flow cytometry the frequencies of Treg cell phenotypes and systemic inflammatory cytokines (IL-17, IL-10). Individuals are subset in three groups: non-obstructed smoker NOS (n=25), COPD stage I-II (n=25), and COPD stage III-IV (n=25) groups. Results: We observed an increase in the total Treg cells in the COPD III-IV group compared with NOS (p=0.03), as well as an increase in rTreg cells in both COPD groups compared with NOS (p<0.01). In contrast, aTreg cells (p=0.01) and FrIII Treg cells (p=0.01) were decreased in both COPD groups compared with NOS, whereas IL-10+CD4+ cells were increased in the COPD I-II group compared with COPD III-IV (p=0.01). The COPD I-II group showed increased RORγt+CD4+cells (p<0.01) and IL-17+RORγt+CD4+cells (p=0.02) compared with NOS. Conclusion: COPD individuals, since early stages, showed decreased proportion of Treg cells subpopulations with immunosuppressive activity whereas subpopulations with low immunosuppressive activity are observed increased.

COPD involves progressive airflow limitation driven by chronic inflammation, largely triggered by cigarette smoke. Disease progression is linked to heightened Th17/IL-17 responses, with STAT3 playing a key regulatory role. Targeting STAT3 such as with the selective inhibitor Cryptotanshinone may offer a promising strategy to reduce COPD associated inflammation. This study aimed to evaluate the effects of Cryptotanshinone administration on the Th17 immune response in a murine model of chronic cigarette smoke exposure. C57BL/6 mice were exposed to cigarette smoke for six months, while controls breathed filtered air. From the fourth month, mice received intramuscular Cryptotanshinone treatment. Lung function, airspace enlargement, and STAT3/Th17 responses were assessed through respiratory mechanics, histology, immunohistochemistry, and ELISA. Cigarette-smoke reduced tissue elastance and increased alveolar enlargement. Cryptotanshinone attenuated structural damage but did not improve lung function. Smoke exposure elevated STAT3 and IL-17 positive cells and IL-17 levels, all of which were significantly reduced by treatment, indicating suppression of the STAT3/IL-17 inflammatory axis. Pharmacological inhibition of STAT3 with Cryptotanshinone mitigated structural lung damage and reduced Th17-driven inflammation in a chronic cigarette smoke exposure model. These findings reinforce the importance of the STAT3/Th17 axis in COPD pathogenesis and progression.