RNase1 as a potential mediator of remote ischaemic preconditioning for cardioprotection†

OBJECTIVES

Remote ischaemic preconditioning (RIPC) is a non-invasive and virtually cost-free strategy for protecting the heart against acute ischaemia-reperfusion injury (IRI). We have recently shown that the inhibition of extracellular RNA (eRNA) using non-toxic RNase1 protected the heart against acute IRI, reduced myocardial infarct (MI) size and preserved left ventricular systolic function in rodent animal MI models. Based on this previous work in animals, the role of the eRNA/RNase1 system in cardiac RIPC in humans should be defined.

METHODS

Fourteen patients underwent cardiac surgery without RIPC; from each patient, six separate 5 ml blood specimens from radial artery and two blood specimens from coronary sinus at different time points during heart surgery were taken. Six healthy donors received RIPC (4 × 5 min upper limb ischaemia); blood parameters were quantified before and after RIPC. Twelve patients underwent cardiac surgery of which 6 received RIPC, whereas the remaining 6 were exposed to sham procedure. Circulating eRNA was quantified in plasma from arterial and coronary sinus blood obtained from patients undergoing cardiac by standard procedures. Tumour necrosis factor-α (TNF-α) production by heart tissue was assessed by enzyme-linked immuno-sorbent assay; RNase activity was quantified by an enzymatic assay.

RESULTS

Before surgery, eRNA levels were similar in both groups (14 ± 6 vs 13 ± 5 ng/ml; P = 0.9967). In patients without RIPC, arterial eRNA levels rose during surgery (87 ± 12 ng/ml) and peaked after (127 ± 11 ng/ml) aortic declamping; accordingly, eRNA levels in coronary sinus blood were significantly higher (206 ± 32 ng/ml; P = 0.0129) than that in radial artery. Moreover, significant elevation of TNF-α (36 ± 6 ng/ml; P = 0.0059) particularly in coronary sinus blood after opening of the aortic clamping was observed. Interestingly, applying a RIPC protocol significantly increased levels of plasma endogenous vascular RNase1 by >7-fold, and the levels of arterial (31 ± 7 ng/ml; P = 0.0024) and coronary sinus (37 ± 9 ng/ml; P < 0.0001) circulating eRNA, as well as circulating TNF-α (20 ± 4 ng/ml; P = 0.0050) levels were significantly reduced.

CONCLUSIONS

Upon RIPC, the level of cardioprotective RNase1 increased, while the concentration of damaging eRNA and TNF-α decreased. The present findings imply a significant contribution of the RIPC-dependent (endothelial) RNase1 for improving the outcome of cardiac surgery. However, the exact mechanism of RNase1-induced cardioprotection still remains to be explored.

Protective effect of ethyl acetate fraction of Drynaria quercifolia against CCl4 induced rat liver fibrosis via Nrf2/ARE and NFκB signalling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Drynaria quercifolia rhizome is traditionally used as hepatoprotective drug especially in chronic jaundice.

AIM OF THE STUDY

The present study was undertaken to scientifically evaluate the efficacy of D. quercifolia rhizome against liver fibrosis.

MATERIALS AND METHODS

D. quercifolia rhizome crude extract (DQ) and its fractions of hexane (HDQ), ethyl acetate (EDQ), butanol (BDQ) were evaluated in vitro using primary hepatocytes and RAW 264.7 cells. In vivo anti-liver fibrotic activity of EDQ was assessed using CCl₄ induced liver fibrosis in Wistar rats and serum biochemical parameters (AST, ALT, ALP, SB, cholesterol), MDA, PT, INR, GSH, SOD, CAT, liver glycogen, serum albumin levels were monitored. qRT-PCR analysis of TNF-α, COX-2, iNOS were performed. ELISA method was used to estimate TNF-α, COX-1 & 2. Histopathological studies like H & E, Masson's trichrome, immunohistochemistry staining for α-SMA, TIMP-1, Nrf2 were conducted. LC-Q-TOF-MS analysis of EDQ was conducted.

RESULTS

In vitro activity guided fractionation of D. quercifolia revealed EDQ as active fraction when compared to other extracts. EDQ treatment significantly inhibited the expression of α-SMA, TIMP-1, COX-2, TNF-α, iNOS and increased the levels of Nrf2 in rat liver fibrosis. LC-Q-TOF-MS analysis of EDQ confirmed the presence of naringin and naringenin.

CONCLUSION

The anti-liver fibrotic activity of EDQ is via inhibition of NFκB signalling pathway, antioxidant response through Nrf2 activation and further inhibition of HSC activation.

Notch and TNF-α signaling promote cytoplasmic accumulation of OLFM4 in intestinal epithelium cells and exhibit a cell protective role in the inflamed mucosa of IBD patients

Notch signaling is activated in the intestinal epithelial cells (IECs) of patients with inflammatory bowel disease (IBD), and contributes to mucosal regeneration. Our previous study indicated that TNF-α and Notch signaling may synergistically promote the expression of the intestinal stem cell (ISC) marker OLFM4 in human IECs. In the present study, we investigated the gene regulation and function of OLFM4 in human IEC lines. We confirmed that TNF-α and Notch synergistically upregulate the mRNA expression of OLFM4. Luciferase reporter assay showed that OLFM4 transcription is regulated by the synergy of TNF-α and Notch. At the protein level, synergy between TNF-α and Notch promoted cytoplasmic accumulation of OLFM4, which has potential anti-apoptotic properties in human IECs. Analysis of patient-derived tissues and organoids consistently showed cytoplasmic accumulation of OLFM4 in response to NF-κB and Notch activation. Cytoplasmic accumulation of OLFM4 in human IECs is tightly regulated by Notch and TNF-α in synergy. Such cytoplasmic accumulation of OLFM4 may have a cell-protective role in the inflamed mucosa of patients with IBD.

•

Notch and TNF-α signaling is important in IECs of patients with IBD.

•

Notch and TNF-α signaling promotes the cytoplasmic accumulation of OLFM4.

•

OLFM4 accumulation may have anti-apoptotic properties.

•

OLFM4 could protect against mucosal inflammation in IBD.