Red light-green light: T-cell trafficking in cardiac and vascular inflammation

Sensational site: the sodium pump ouabain-binding site and its ligands

Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.

Clinical significance of elevated soluble T-cell immunoglobulin and mucin domain 1 and soluble P-selectin in individuals with obstructive sleep apnea-hypopnea syndrome

OBJECTIVES

To assess the serum concentrations of soluble T-cell immunoglobulin and mucin domain 1 (sTIM-1) and soluble P-selectin (sP-selectin) in individuals who had obstructive sleep apnea-hypopnea syndrome (OSAHS).

METHODS

Between December 2020 and November 2022, 134 participants from the Sleep Monitoring Center of the Branch Hospital of Huai'an First People's Hospital, Jiangsu, China, engaged in this cross-sectional study. Participants were categorized as mild OSAHS (n=19), moderate OSAHS (n=22), severe OSAHS (n=57), and non-OSAHS (n=36) groups. Serum levels of sTIM-1, sP-selectin, and interleukin (IL)-6, as well as baseline clinical characteristics and polysomnography outcomes were assessed in each participant.

RESULTS

Compared to the non-OSAHS group, sTIM-1 and sP-selectin levels were considerably elevated in people who had moderate or severe OSAHS (all p<0.05), but there were no notable changes between those who had mild OSAHS and non-OSAHS participants (p>0.05). The sTIM-1 and sP-selectin levels showed positive associations with the apnea-hypopnea index, body mass index (BMI), and IL-6 levels (all p<0.001). While elevated sTIM-1 was independently related to OSAHS (odds ratio [OR]=1.134, p=0.001), sP-selectin was not associated with OSAHS after adjusting for BMI (OR=1.013, p=0.467).

CONCLUSION

People with moderate or severe OSAHS had higher serum sTIM-1 and sP-selectin levels, and elevated sTIM-1 is an independently related factor for OSAHS.