Effects of endogenous H2S production inhibition on the homeostatic responses induced by acute high-salt diet consumption

Interaction of glucocorticoids and interleukins in the control of hypothalamic neurohypophysial system output in salt loaded male rats

The present study investigated the effects of a 4-day salt load (0.3 M NaCl, SL) and dexamethasone treatment (DEXA, 1 mg/Kg, subcutaneous) on the mechanisms possibly underlying glucocorticoid-mediated effects on hypothalamic neurohypophyseal system (HNS) activity. As expected, SL animals developed hyperosmolality, reflecting the progressive increase in plasma sodium concentrations. SL also triggered increased hypothalamic expression of vasopressin (AVP) and oxytocin (OT) messenger RNAs (mRNAs), increased magnocellular neuronal activation, and enhanced plasma hormone concentrations. Plasma corticosterone, interleukin (IL) 1β and tumor necrosis factor alfa, but not IL-6 levels, were also elevated in response to SL. Increased salt consumption also significantly decreased hypothalamic mRNA expression for the p65 subunit of the nuclear factor kappa B (NFkB), and increased mRNA expression for type β NFkB inhibitory protein (IκBβ). The protein expression ratio between phosphorylated and total NFκB was also elevated in SL rats. DEXA administration, in turn, prevented SL-induced AVP and OT release, as well as decreased corticosterone/IL plasma levels. Therefore, the present results suggest that increased salt consumption may originate a systemic-driven pro-inflammatory response, which can contribute to the increased secretion of corticosterone observed in SL animals. We therefore hypothesize that elevated systemic IL levels, in parallel with corticosterone secretion, may constitute, besides hyperosmolality, important redundant stimuli triggering SL-induced neuropeptide release. Conversely, high levels of corticosterone would produce, in the long term, inhibition of HNS activity and the termination of the neurosecretory response.

NLRP3 inflammasome activation in gestational diabetes mellitus placentas is associated with hydrogen sulfide synthetase deficiency

The placenta may play a key role in the activation of inflammation and initiation of insulin resistance (IR) during gestational diabetes mellitus (GDM) pathogenesis. Interleukin (IL)-1β and IL-18, regulated by NLR family pyrin domain containing-3 (NLRP3) inflammasome, are important inflammatory cytokines in the initiation of maternal IR during GDM. However, the mechanism responsible for the regulatory of NLRP3 inflammasome in placenta remains unknown. Hydrogen sulfide (H₂S) exerts anti-inflammatory function partially via suppressing the activation of the NLPR3 inflammasome. The present study aimed to investigate the role of NLRP3 inflammasome, H₂S synthetase cystathionine-γ-lyase (CSE) and cystathionine-β-synthetase (CBS) in placenta in the pathogenesis of GDM. Clinical placenta samples were collected from pregnant women with GDM (n=16) and healthy pregnant women at term (n=16). Western blot analysis was performed to detect the protein expression levels of NLRP3, cleaved caspase-1, CBS and CSE in the placenta samples. Pearson's correlation analysis was performed to assess the correlation between NLRP3 inflammasome and H₂S synthetase. Human placental cells were cultured and treated with different concentrations of NaHS (0, 10, 25 and 50 nmol/l) or L-cysteine (0, 0.25, 0.50 and 1.00 mmol/l). In addition, western blot analysis was performed to detect the protein expression levels of NLRP3 and cleaved caspase-1, while ELISA was performed to measure the production of IL-1β and IL-18 in the culture media. The results demonstrated that the expression levels of NLRP3 and cleaved caspase-1 increased, while the expression levels of CBS and CSE decreased in the placenta samples. In addition, the expression levels of NLRP3 and cleaved caspase-1 were inversely correlated with the expression levels of CBS and CSE. Notably, NaHS and L-cysteine significantly suppressed the expression levels of NLRP3 and cleaved caspase-1, and the production of IL-1 and IL-18 in human placental cells. Taken together, the results of the present study suggest that H₂S synthetase deficiency in placenta may contribute to excessive activation of NLRP3 inflammasome in GDM.