Protective effect of apelin preconditioning in a rat model of hepatic ischemia reperfusion injury; possible interaction between the apelin/APJ system, Ang II/AT1R system and eNOS

Targeting PI3K/p-Akt/eNOS, Nrf2/HO-1, and NF-κB/p53 signaling pathways by angiotensin 1-7 protects against liver injury induced by ischemia-reperfusion in rats

The liver is an important organ, and hepatic ischemia-reperfusion (IR) injury is a frequent pathophysiological process that can cause significant morbidity and mortality. Thus, our study aimed to investigate the effect of targeting PI3K/p-Akt/eNOS (phosphoinositide 3-kinase/phospho-protein kinase B/endothelial nitric oxide synthase), Nrf2/HO-1 (nuclear factor-erythroid 2-related factor-2/heme oxygenase-1), and NF-κB/p53 (nuclear factor-κB/tumor protein 53) signaling pathways by using angiotensin (1-7) [ang-(1-7)] against hepatic injury induced by IR. Thirty-two male rats were included in sham group, ang-(1-7)-treated group, hepatic IR group, and hepatic IR group treated with ang-(1-7). The levels of hepatic ang-(1-7), angiotensin II (Ang II), angiotensin-converting enzyme 2 (ACE2), HO-1, malondialdehyde (MDA), PI3K, and p-Akt were assessed. The expressions of eNOS and B-cell leukemia/lymphoma-2 (BCL-2) in the liver were determined. Histological assessment and immunohistochemical expression of NF-κB, p53, and Nrf2 were carried out. The levels of reduced glutathione (GSH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in serum were estimated. Results showed that administration of ang-(1-7) to hepatic IR rats led to significant amelioration of hepatic damage through a histological evaluation that was associated with significant upregulation of the expressions of PI3K/p-Akt/eNOS and Nrf2/HO-1 with downregulation of NF-κB/p53 signaling pathways. In conclusion, PI3K/p-Akt/eNOS and Nrf2/HO-1 signaling pathways are involved in the protective effects of ang-(1-7) against hepatic damage induced by IR. Therefore, ang-(1-7) can be used to prevent hepatic IR, which occurs in certain conditions such as liver transplantation, hemorrhagic shock, and severe infection.

Apelin-13: A Protective Role in Vascular Diseases

Vascular disease is a common problem with high mortality all over the world. Apelin-13, a key subtype of apelin, takes part in many physiological and pathological responses via regulating many target genes and target molecules or participating in many signaling pathways. More and more studies have demonstrated that apelin-13 is implicated in the onset and progression of vascular disease in recent years. It has been shown that apelin-13 could ameliorate vascular disease by inhibiting inflammation, restraining apoptosis, suppressing oxidative stress, and facilitating autophagy. In this article, we sum up the progress of apelin-13 in the occurrence and development of vascular disease and offer some insightful views about the treatment and prevention strategies of vascular disease.

Clinical application of regional and intermittent hepatic inflow occlusion in laparoscopic hepatectomy

Aim

The aim of this study is to investigate the advantages and disadvantages of regional and intermittent hepatic inflow occlusion in laparoscopic hepatectomy.

Methods

The clinical data of 180 patients who underwent laparoscopic liver surgery in Taizhou People’s Hospital from 2015 to 2021 were analyzed retrospectively. The patients were divided into the regional occlusion group (n = 74) and the Pringle’s maneuver occlusion group (n = 106) according to the technique used in the intraoperative hepatic inflow occlusion. The pre- and intra-operative indicators, postoperative recovery indicators, and complications of the two groups were compared.

Results

There were no significant differences (p > 0.05) between the groups in terms of sex, age, preoperative alanine aminotransferase (ALT), preoperative aspartate aminotransferase (AST), preoperative albumin, alpha-fetoprotein, liver cirrhosis, hepatitis B, tumor location, gas embolism, intraoperative blood transfusion, postoperative albumin, postoperative total bilirubin (TBIL), postoperative hospital stays, and complications. The preoperative TBIL and operation time were higher in the regional occlusion group than in the Pringle’s maneuver occlusion group, while the amount of intraoperative bleeding, postoperative ALT, and AST in the regional occlusion group were significantly lower than those in the Pringle’s maneuver occlusion group (p < 0.05).

Conclusion

The two occlusion techniques are equally safe and effective, but regional hepatic inflow occlusion is more advantageous in operation continuity, intraoperative bleeding, and postoperative liver function recovery. The long duration and high precision of the regional blood flow occlusion technique demands a more experienced physician with a higher level of operation; therefore, it can be performed by experienced laparoscopic liver surgeons.

New progress in understanding roles of nitric oxide during hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is a major clinical cause of morbidity and mortality in liver surgery and transplantation. Many studies have found that nitric oxide (NO) plays an important role in the HIRI and its increase or decrease can affect the progression and outcome of HIRI. However, the role of NO in HIRI is controversial and complicated. NO derived by endothelial NO synthase (eNOS) shows a protective role in HIRI, while excessive NO derived by inducible NO synthase (iNOS) accelerates inflammation and increases oxidative stress, further aggravating HIRI. Nevertheless, the overexpression of eNOS may exacerbate HIRI and iNOS-derived NO in some cases reduces HIRI. Here we review the new progress in the understanding of the roles of NO during HIRI: (1) NO possesses different roles in HIRI by increasing NO bioavailability, down-regulating leukotriene C4 synthase, inhibiting the activation of the nuclear factorκB (NFκB) pathway, enhancing cell autophagy, and reducing inflammatory cytokines and reactive oxygen species (ROS). And NO has both protective and deleterious effects by regulating apoptotic factors; (2) eNOS promotes NO production and suppresses its own overexpression, exerting a hepatoprotective effect reversely. Its activation is regulated by the PI3K/Akt and KLF2/AMPK pathways; and (3) iNOS derived NO mainly has deteriorating effects on HIRI, while it may have a protective function under some conditions. Their expression should reach a balance to reduce the adverse side and make NO protective in the treatment of HIRI. Thus, it can be inferred that NO modulating drugs may be a new direction in the treatment of HIRI or may be used as an adjunct to mitigate HIRI for the purpose of protecting the liver.

Apelin-13 Attenuates Lipopolysaccharide-Induced Inflammatory Responses and Acute Lung Injury by Regulating PFKFB3-Driven Glycolysis Induced by NOX4-Dependent ROS

Purpose

Acute lung injury (ALI) is a life-threatening condition with limited therapeutic options. Macrophage inflammation plays a key role in the development of ALI. Abnormal glycolysis of macrophages contributes to the inflammatory response. However, the role of macrophage glycolysis in ALI still requires investigation. Apelin-13 has been shown to protect against ALI, whereas the underlying mechanisms remain unclear. In this study, we explored the effect of apelin-13 on lipopolysaccharide (LPS)-induced inflammation and ALI via regulation of glycolysis by modulating redox homeostasis in macrophages.

Methods

Serums from 34 patients with sepsis and 13 healthy volunteers were analyzed. In vivo, the protective effect of apelin-13 against LPS-induced ALI was evaluated using a mouse model of LPS-induced ALI. In vitro, mouse bone marrow macrophages (BMDMs) were pretreated with the antioxidant, NADPH oxidase (NOX) 4 (NOX4) small-interfering RNA (siRNA), the 6-phosphofructo-2 -kinase/fructose- 2,6-biphosphatase 3 (PFKFB3) siRNA, or the PFKFB3 overexpression plasmid before exposure to LPS.

Results

Serum apelin-13 levels were significantly elevated in patients with sepsis and sepsis-associated acute respiratory distress syndrome (ARDS) (P<0.0001). In vivo, apelin-13 suppressed LPS-induced ALI and inflammatory cytokine production (P<0.05). Furthermore, apelin-13 reduced hydrogen peroxide (H₂O₂) content, NOX4 protein levels, and glycolysis. In vitro, LPS stimulation elevated NOX4 protein levels and reactive oxygen species (ROS) production (P<0.05). These changes resulted in the accumulation of glycolysis in BMDMs. Treatment with antioxidant or NOX4 siRNA inhibited LPS-induced glycolysis and inflammatory cytokine production (P<0.05). Moreover, in vitro experiments revealed that PFKFB3 regulates the release of pro-inflammatory cytokines by modulating glycolysis. In contrast, the action of apelin-13 opposed the effects of LPS.

Conclusion

In conclusion, apelin-13 protects against LPS-induced inflammatory responses and ALI by regulating PFKFB3-driven glycolysis induced by NOX4-dependent ROS.

Role of liver sinusoidal endothelial cells in liver diseases

Liver sinusoidal endothelial cells (LSECs) form the wall of the hepatic sinusoids. Unlike other capillaries, they lack an organized basement membrane and have cytoplasm that is penetrated by open fenestrae, making the hepatic microvascular endothelium discontinuous. LSECs have essential roles in the maintenance of hepatic homeostasis, including regulation of the vascular tone, inflammation and thrombosis, and they are essential for control of the hepatic immune response. On a background of acute or chronic liver injury, LSECs modify their phenotype and negatively affect neighbouring cells and liver disease pathophysiology. This Review describes the main functions and phenotypic dysregulations of LSECs in liver diseases, specifically in the context of acute injury (ischaemia-reperfusion injury, drug-induced liver injury and bacterial and viral infection), chronic liver disease (metabolism-associated liver disease, alcoholic steatohepatitis and chronic hepatotoxic injury) and hepatocellular carcinoma, and provides a comprehensive update of the role of LSECs as therapeutic targets for liver disease. Finally, we discuss the open questions in the field of LSEC pathobiology and future avenues of research.

Apelin-13 Protects Dopaminergic Neurons against Rotenone-Induced Neurotoxicity through the AMPK/mTOR/ULK-1 Mediated Autophagy Activation

Parkinson’s disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Several brain–gut peptides are able to exert neuroprotective effects on the nigrostriatal dopaminergic system. Apelin-13 is a neuropeptide, conveying potential neuroprotective activities. However, whether, and how, apelin-13 could antagonize rotenone-induced neurotoxicity has not yet been elucidated. In the present study, rotenone-treated SH-SY5Y cells and rats were used to clarify whether apelin-13 has protective effects on dopaminergic neurons, both in vivo and in vitro. The results showed that apelin-13 could protect SH-SY5Y cells from rotenone-induced injury and apoptosis. Apelin-13 was able to activate autophagy, and restore rotenone induced autophagy impairment in SH-SY5Y cells, which could be blocked by the autophagy inhibitor 3-Methyladenine. Apelin-13 activated AMPK/mTOR/ULK-1 signaling, AMPKα inhibitor compound C, as well as apelin receptor blockage via siRNA, which could block apelin-13-induced signaling activation, autophagy activation, and protective effects, in rotenone-treated SH-SY5Y cells. These results indicated that apelin-13 exerted neuroprotective properties against rotenone by stimulating AMPK/mTOR/ULK-1 signaling-mediated autophagy via the apelin receptor. We also observed that intracerebroventricular injection of apelin-13 could alleviate nigrostriatal dopaminergic neuron degeneration in rotenone-treated rats. Our findings provide new insights into the mechanism by which apelin-13 might attenuate neurotoxicity in PD.

Adipokines, Myokines, and Cardiokines: The Role of Nutritional Interventions

It is now established that adipose tissue, skeletal muscle, and heart are endocrine organs and secrete in normal and in pathological conditions several molecules, called, respectively, adipokines, myokines, and cardiokines. These secretory proteins constitute a closed network that plays a crucial role in obesity and above all in cardiac diseases associated with obesity. In particular, the interaction between adipokines, myokines, and cardiokines is mainly involved in inflammatory and oxidative damage characterized obesity condition. Identifying new therapeutic agents or treatment having a positive action on the expression of these molecules could have a key positive effect on the management of obesity and its cardiac complications. Results from recent studies indicate that several nutritional interventions, including nutraceutical supplements, could represent new therapeutic agents on the adipo-myo-cardiokines network. This review focuses the biological action on the main adipokines, myokines and cardiokines involved in obesity and cardiovascular diseases and describe the principal nutraceutical approaches able to regulate leptin, adiponectin, apelin, irisin, natriuretic peptides, and follistatin-like 1 expression.

Roles for heterodimerization of APJ and B2R in promoting cell proliferation via ERK1/2-eNOS signaling pathway

Apelin receptor (APJ) and bradykinin B2 receptor (B2R) play an important role in many physiological processes and share multiple similar characteristics in distribution and functions in the cardiovascular system. We first identified the endogenous expression of APJ and B2R in human umbilical vein endothelial cells (HUVECs) and their co-localization on human embryonic kidney (HEK) 293 cells membrane. A suite of bioluminescence and fluorescence resonance energy transfer (BRET and FRET), proximity ligation assay (PLA), and co-immunoprecipitation (Co-IP) was exploited to demonstrate formation of functional APJ and B2R heterodimer in HUVECs and transfected cells. Stimulation with apelin-13 and bradykinin (BK) increased the phosphorylation of the endothelial nitric oxide synthase (eNOS) in HUVECs, which could be inhibited by the silencing of APJ or B2R, indicating the APJ-B2R dimer is critical for eNOS phosphorylation in HUVECs. Furthermore, the increase of NOS and extracellular signal regulated kinases1/2 (ERK1/2) phosphorylation mediated by APJ/B2R dimer can be inhibited by U0126 and U73122, respectively, suggesting that the heterodimer might activate the PLC/ERK1/2/eNOS signaling pathway, and finally leading to a significant increase in cell proliferation. Thus, we uncovered for the first time the existence of APJ-B2R heterodimer and provided a promising new target in cardiovascular therapeutics.

BPA disrupts 17‑estradiol‑mediated hepatic protection against ischemia/reperfusion injury in rat liver by upregulating the Ang II/AT1R signaling pathway

Bisphenol A (BPA), a xenoestrogen commonly used in plastics, may act as an endocrine disruptor, which indicates that BPA might be a public health risk. The present study aimed to investigate the effect of BPA on 17β-estradiol (E2)-mediated protection against liver ischemia/reperfusion (I/R) injury, and to identify the underlying mechanisms using a rat model. A total of 56 male Sprague Dawley rats were randomly divided into the following seven groups: i) Sham; ii) I/R; iii) Sham + BPA; iv) I/R + BPA; v) I/R + E2; vi) I/R + E2 + BPA; and vii) I/R + E2 + BPA + losartan [LOS; an angiotensin II (Ang II) type I receptor (ATIR) antagonist]. A rat model of hepatic I/R injury was established by inducing hepatic ischemia for 60 min followed by reperfusion for 24 h. When ischemia was induced, rats were treated with vehicle, E2, BPA or LOS. After 24 h of reperfusion, blood samples and hepatic tissues were collected for histopathological and biochemical examinations. The results suggested that 4 mg/kg BPA did not significantly alter the liver function, or Ang II and AT1R expression levels in the Sham and I/R groups. However, 4 mg/kg BPA inhibited E2-mediated hepatic protection by enhancing hepatic necrosis, and increasing the release of alanine transaminase, alkaline phosphatase and total bilirubin (P<0.05). Moreover, BPA increased serum and hepatic Ang II levels, as well as AT1R protein expression levels in the E2-treated rat model of liver I/R injury (P<0.05). LOS treatment reversed the negative effects of BPA on hepatic necrosis and liver serum marker levels, although it did not reverse BPA-mediated upregulation of serum and hepatic Ang II levels, or hepatic AT1R expression. Therefore, the present study suggested that BPA disrupted E2-mediated hepatic protection following I/R injury, but did not significantly affect healthy or I/R-injured livers; therefore, the mechanism underlying the effects of BPA may be associated with upregulation of the Ang II/AT1R signaling pathway.