Protective Effects of Hydrogen Sulfide Against Cigarette Smoke Exposure-Induced Placental Oxidative Damage by Alleviating Redox Imbalance via Nrf2 Pathway in Rats

Background/Aims: Cigarette smoke exposure (CSE) during pregnancy is a well-recognized health hazard that causes placental damage. Hydrogen sulfide (H2S) has been reported to protect multiple organs from injury. However, the protective effects of H2S have not been tested in the placenta. This study aimed to explore the potential of H2S in protecting placenta against oxidative injury induced by CSE during pregnancy and the possible underlying mechanisms. Methods: Pregnant SD rats were randomly divided into 4 groups: NaCl, NaHS (a donor of H2S), CSE and CSE+NaHS. Placental oxidative damage was detected by 8-hydroxy-2-deoxyguanosine (8-OHdG) stain and malondialdehyde (MDA) assay. Placental redox status was assessed by measuring reactive oxygen species (ROS), total antioxidant capacity (T-AOC) and glutathione (GSH) levels, as well as copper/zinc SOD (SOD1), manganese SOD (SOD2), catalase (CAT) and glutathione peroxidase (GPx) activities and expressions. Meanwhile, nuclear factor erythroid 2-related factor 2 (Nrf2) was analyzed by immunohistochemistry, real-time PCR and Western blot. Results: We found that NaHS markedly reduced the elevated levels of 8-OHdG and MDA induced by CSE. Further, NaHS treatment effectively mitigated CSE-induced placental redox imbalance by inhibiting ROS production, restoring T-AOC level, increasing GSH/GSSG ratio, and augmenting SOD1 SOD2, CAT and GPx activities and expressions. More notably, NaHS administration also reversed the aberrant decrease of Nrf2 due to CSE in rat placentas. Conclusion: Our data demonstrate that H2S can protect against CSE-induced placental oxidative damage probably by alleviating redox imbalance via Nrf2 pathway

Impairment of Central Chemoreception in Neonatal Rats Induced by Maternal Cigarette Smoke Exposure during Pregnancy.

It has been postulated that prenatal cigarette smoke exposure (CSE) increases the risk for sudden infant death syndrome. The victims of infant death syndrome suffer from respiratory abnormalities, such as central apnea, diminished chemoreflex and alteration in respiratory pattern during sleep. However, no experimental evidence on CSE model exists to confirm whether prenatal CSE gives rise to reduction of neonatal central chemoreception in in vitro preparations in absence of peripheral sensory feedback. The aim of the present study was to test the hypothesis that maternal CSE during pregnancy depresses central chemoreception of the neonatal rats. The pregnant rats were divided into two groups, control (n = 8) and CSE (n = 8). Experiments were performed on neonatal (0-3days) rat pups. Fictive respiratory activity was monitored by recording the rhythmic discharge from the hypoglossal rootlets of the medullary slices obtained from the neonatal rats. The burst frequency (BF) and integrated amplitude (IA) of the discharge were analyzed. Their responses to acidified artificial cerebrospinal fluid (aCSF) were tested to indicate the change of the central chemosensitivity. Under condition of perfusing with standard aCSF (pH 7.4), no significant difference was detected between the two groups in either BF or IA (P>0.05). Under condition of perfusing with acidified aCSF (pH 7.0), BF was increased and IA was decreased in both groups (P<0.01). However, their change rates in the CSE group were obviously smaller than that in the control group, 66.98 ± 10.11% vs. 143.75 ± 15.41% for BF and -22.38 ± 2.51% vs. -44.90 ± 3.92% for IA (P<0.01). In conclusion, these observations, in a prenatal CSE model, provide important evidence that maternal smoking during pregnancy exerts adverse effects on central chemoreception of neonates

Recordings of hypoglossal rootlets discharge in medullary slices.

<p>Typical recording of the discharge from the control group (A) and the CSE group (B), respectively. In each panel, the upper line indicates the compression format of activities of the hypoglossal rootlets throughout the experiment, and the middle and lower lines indicate the raw and integrated activities of the hypoglossal rootlets before, during and after acidification, respectively.</p

Statistical comparison of basal discharge of hypoglossal rootlets in medullary slices.

<p>Comparison of the basal burst frequency (A) and integrated amplitude (B) of the hypoglossal rootlets activities of the medullary slices in neonatal rats between the control group (n = 13) and the CSE group (n = 15).</p

Changes in hypoglossal rootlets discharge in medullary slices induced by acidification.

<p>(A) and (B): Changes of burst frequency (BF) in the control (n = 13) and CSE groups (n = 15), respectively; (C) and (D): Changes of integrated amplitude (IA) in the control (n = 13) and CSE groups (n = 15), respectively. All data were normalized to the baseline value which was defined as the average BF and IA for 5min prior to acidic stimulation. *<i>P</i>< 0.05, **<i>P</i>< 0.01 vs. baseline.</p

Comparison of changes in hypoglossal rootlets discharge in medullary slices induced by acidification.

<p>(A) Comparison of burst frequency (BF) of hypoglossal rootlets between the control (n = 13) and CSE (n = 15) groups; (B) Comparison of integrated amplitude (IA) of hypoglossal rootlets between the control (n = 13) and CSE (n = 15) groups. *<i>P</i>< 0.05, **<i>P</i>< 0.01 vs. CSE.</p