Dehydration affects cardiovascular nitric oxide synthases and caveolins in growing rats

Hydration for prevention of kidney injury after primary coronary intervention for acute myocardial infarction: a randomised clinical trial

OBJECTIVE

To evaluate the efficacy of aggressive hydration compared with general hydration for contrast-induced acute kidney injury (CI-AKI) prevention among patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI).

METHODS

The Aggressive hydraTion in patients with STEMI undergoing pPCI to prevenT Contrast-Induced Acute Kidney Injury study is an open-label, randomised controlled study at 15 teaching hospitals in China. A total of 560 adult patients were randomly assigned (1:1) to receive aggressive hydration or general hydration treatment. Aggressive hydration group received preprocedural loading dose of 125/250 mL normal saline within 30 min, followed by postprocedural hydration performed for 4 hours under left ventricular end-diastolic pressure guidance and additional hydration until 24 hours after pPCI. General hydration group received ≤500 mL 0.9% saline at 1 mL/kg/hour for 6 hours after randomisation. The primary end point is CI-AKI, defined as a >25% or 0.5 mg/dL increased in serum creatinine from baseline during the first 48-72 hours after primary angioplasty. The safety end point is acute heart failure.

RESULTS

From July 2014 to May 2018, 469 patients were enrolled in the final analysis. CI-AKI occurred less frequently in aggressive hydration group than in general hydration group (21.8% vs 31.1%; risk ratio (RR) 0.70, 95% CI 0.52 to 0.96). Acute heart failure did not significantly differ between the aggressive hydration group and the general hydration group (8.1% vs 6.4%, RR 1.13, 95% CI 0.66 to 2.44). Several subgroup analysis showed the better effect of aggressive hydration in CI-AKI prevention in male, renal insufficient and non-anterior myocardial infarction participants.

CONCLUSIONS

Comparing with general hydration, the peri-operative aggressive hydration seems to be safe and effective in preventing CI-AKI among patients with STEMI undergoing pPCI.

Hyperosmotic stress promotes endoplasmic reticulum stress-dependent apoptosis in adult rat cardiac myocytes

In different pathological situations, cardiac cells undergo hyperosmotic stress and cell shrinkage. This change in cellular volume has been associated with contractile dysfunction and cell death. However, the intracellular mechanisms involved in hyperosmotic stress-induced cell death have not been investigated in depth in adult cardiac myocytes. Given that osmotic stress has been shown to promote endoplasmic reticulum stress (ERS), a recognized trigger for apoptosis, we examined whether hyperosmotic stress triggers ERS in adult cardiac myocytes and if so whether this mechanism mediates hyperosmotic stress-induced cell death. Adult rat cardiomyocytes cultured overnight in a hypertonic solution (HS) containing mannitol as the osmolite, showed increased expression of ERS markers, GRP78, CHOP and cleaved-Caspase-12, compared with myocytes in isotonic solution (IS), suggesting that hyperosmotic stress induces ERS. In addition, HS significantly reduced cell viability and increased TUNEL staining and the expression of active Caspase-3, indicative of apoptosis. These effects were prevented with the addition of the ERS inhibitor, 4-PBA, indicating that hyperosmotic stress-induced apoptosis is mediated by ERS. Hyperosmotic stress-induced apoptosis was also prevented when cells were cultured in the presence of a Ca²⁺-chelating agent (EGTA) or the CaMKII inhibitor (KN93), suggesting that hyperosmotic stress-induced ERS is mediated by a Ca²⁺ and CaMKII-dependent mechanism. Similar results were observed when hyperosmotic stress was induced using glucose as the osmolite. We conclude that hyperosmotic stress promotes ERS by a CaMKII-dependent mechanism leading to apoptosis of adult cardiomyocytes. More importantly, we demonstrate that hyperosmotic stress-triggered ERS contributes to hyperglycemia-induced cell death.

AMPK-dependent nitric oxide release provides contractile support during hyperosmotic stress

In different pathological situations, cardiac cells undergo hyperosmotic stress (HS) and cell shrinkage. This change in cellular volume has been associated with contractile dysfunction and cell death. Given that nitric oxide (NO) is a well-recognized modulator of cardiac contractility and cell survival, we evaluated whether HS increases NO production and its impact on the negative inotropic effect observed during this type of stress. Superfusing cardiac myocytes with a hypertonic solution (HS: 440 mOsm) decreased cell volume and increased NO-sensitive DAF-FM fluorescence compared with myocytes superfused with an isotonic solution (IS: 309 mOsm). When cells were exposed to HS in addition to different inhibitors: L-NAME (NO synthase inhibitor), nitroguanidine (nNOS inhibitor), and Wortmannin (eNOS inhibitor) cell shrinkage occurred in the absence of NO release, suggesting that HS activates nNOS and eNOS. Consistently, western blot analysis demonstrated that maintaining cardiac myocytes in HS promotes phosphorylation and thus, activation of nNOS and eNOS compared to myocytes maintained in IS. HS-induced nNOS and eNOS activation and NO production were also prevented by AMPK inhibition with Dorsomorphin (DORSO). In addition, the HS-induced negative inotropic effect was exacerbated in the presence of either L-NAME, DORSO, ODQ (guanylate cyclase inhibitor), or KT5823 (PKG inhibitor), suggesting that NO provides contractile support via a cGMP/PKG-dependent mechanism. Our findings suggest a novel mechanism of AMPK-dependent NO release in cardiac myocytes with putative pathophysiological relevance determined, at least in part, by its capability to reduce the extent of contractile dysfunction associated with hyperosmotic stress.