Therapeutic approaches targeting renin-angiotensin system in sepsis and its complications

Dexamethasone inhibited angiotensin II and its receptors to reduce sepsis-induced lung and kidney injury in rats

OBJECTIVES

To investigate the effect of dexamethasone (DXM) on acute lung and kidney injury with sepsis and its possible mechanism.

METHODS

Control (NC), lipopolysaccharide (LPS) and lipopolysaccharide + dexamethasone (LPS+DXM) treated groups were established by random assignment of 72 Wistar rats. The NC rats were injected with physiological saline, while the LPS group was injected with LPS (5 mg/kg) and LPS+DXM group was injected with LPS(5 mg/kg) first and followed by DXM (1 mg/kg). Serum tumor necrosis factor-α (TNF-α) and serum macrophage inflammatory protein 1α (MIP-1α) were measured by ELISA. Lung wet/dry weight ratio, serum creatinine(SCR) and blood urea nitrogen(BUN) were determined at various time points. Hematoxylin Eosin staining (HE) for pathological changes in the lung and kidney. Radioimmunoassay was used to detect the levels of angiotensin II (Ang II) in plasma, lung and kidney tissues. Immunohistochemistry and western blot (WB) were used to detect angiotensin II receptor type 1 (AT1R) protein and angiotensin II receptor type 2 (AT2R) protein in lung and kidney tissues. The level of nitric oxide (NO) in serum, lung and kidney were detected using nitrate reductase method.

RESULTS

Compared with control group, serum TNF-α, MIP-1α, SCR, BUN, lung W/D, Ang II level in plasma, lung and kidney, lung and kidney AT2R protein, NO level in serum, lung and kidney were significantly elevated(P<0.05) and pathological damage of lung and kidney tissues were showed in LPS group rats (P<0.05), whereas DXM down-regulated the above indexes and alleviate pathological damage of lung and kidney tissues. However, the expression of the lung and kidney AT1R protein was opposite to the above results.

CONCLUSIONS

Sepsis can cause acute lung and kidney injury and changes RAAS components in circulating, lung and renal. DXM can improve acute lung and kidney injury in septic rats, and the mechanism may be related to the down-regulation of inflammatory factors, AngII, AT2R, NO and up-regulation of AT1R expression by DXM.

Identification of 18β-glycyrrhetinic acid as an AGT inhibitor against LPS-induced myocardial dysfunction via high throughput screening

Sepsis induced myocardial dysfunction (SIMD) is a serious complication of sepsis. There is increasing evidence that the renin-angiotensin system (RAS) is activated in SIMD. Angiotensinogen (AGT) is a precursor of the RAS, and the inhibition of AGT may have significant cardiovascular benefits. But until now, there have been no reports of small molecule drugs targeting AGT. In this study, we designed a promoter-luciferase based system to screen for novel AGT inhibitors to alleviate SIMD. As a result of high-throughput screening, a total of 5 compounds from 351 medicinal herb-derived natural compounds were found inhibiting AGT. 18β-glycyrrhetinic acid (18βGA) was further identified as a potent suppressor of AGT. In vitro experiments, 18βGA could inhibit the secretion of AGT by HepG2 cells and alleviate the elevated level of mitochondrial oxidative stress in cardiomyocytes co-cultured with HepG2 supernatants. In vivo, 18βGA prolonged the survival rate of SIMD mice, enhanced cardiac function, and inhibited the damage of mitochondrial function and inflammation. In addition, the results showed that 18βGA may reduce AGT transcription by downregulating hepatocyte nuclear factor 4 (HNF4) and that further alleviated SIMD. In conclusion, we provided a more efficient screening strategy for AGT inhibitors and expanded the novel role of 18βGA as a promising lead compound in rescuing cardiovascular disease associated with RAS overactivation.

Extracellular Vesicles Derived from Human Adipose-Derived Mesenchymal Stem Cells Alleviate Sepsis-Induced Acute Lung Injury through a MicroRNA-150-5p-Dependent Mechanism

Extracellular vesicles (EVs) derived from human adipose mesenchymal stem cells (hADSCs) may exert a therapeutic benefit in alleviating sepsis-induced organ dysfunction by delivering cargos that include RNAs and proteins to target cells. The current study aims to explore the protective effect of miR-150-5p delivered by hADSC-EVs on sepsis-induced acute lung injury (ALI). We noted low expression of miR-150-5p in plasma and bronchoalveolar lavage fluid samples from patients with sepsis-induced ALI. The hADSC-EVs were isolated and subsequently cocultured with macrophages. It was established that hADSC-EVs transferred miR-150-5p to macrophages, where miR-150-5p targeted HMGA2 to inhibit its expression and, consequently, inactivated the MAPK pathway. This effect contributed to the promotion of M2 polarization of macrophages and the inhibition of proinflammatory cytokines. Further, mice were made septic by cecal ligation and puncture in vivo and treated with hADSC-EVs to elucidate the effect of hADSC-EVs on sepsis-induced ALI. The in vivo experimental results confirmed a suppressive role of hADSC-EVs in sepsis-induced ALI. Our findings suggest that hADSC-EV-mediated transfer of miR-150-5p may be a novel mechanism underlying the paracrine effects of hADSC-EVs on the M2 polarization of macrophages in sepsis-induced ALI.

Exploring post-SEPSIS and post-COVID-19 syndromes: crossovers from pathophysiology to therapeutic approach

Sepsis, driven by several infections, including COVID-19, can lead to post-sepsis syndrome (PSS) and post-acute sequelae of COVID-19 (PASC). Both these conditions share clinical and pathophysiological similarities, as survivors face persistent multi-organ dysfunctions, including respiratory, cardiovascular, renal, and neurological issues. Moreover, dysregulated immune responses, immunosuppression, and hyperinflammation contribute to these conditions. The lack of clear definitions and diagnostic criteria hampers comprehensive treatment strategies, and a unified therapeutic approach is significantly needed. One potential target might be the renin-angiotensin system (RAS), which plays a significant role in immune modulation. In fact, RAS imbalance can exacerbate these responses. Potential interventions involving RAS include ACE inhibitors, ACE receptor blockers, and recombinant human ACE2 (rhACE2). To address the complexities of PSS and PASC, a multifaceted approach is required, considering shared immunological mechanisms and the role of RAS. Standardization, research funding, and clinical trials are essential for advancing treatment strategies for these conditions.

Sepsis-mediated renal dysfunction: Pathophysiology, biomarkers and role of phytoconstituents in its management

Sepsis has evolved as an enormous health issue amongst critically ill patients. It is a major risk factor that results in multiple organ failure and shock. Acute kidney injury (AKI) is one of the most frequent complications underlying sepsis, which portends a heavy burden of mortality and morbidity. Thus, the present review is aimed to provide an insight into the recent progression in the molecular mechanisms targeting dysregulated immune response and cellular dysfunction involved in the development of sepsis-associated AKI, accentuating the phytoconstituents as eligible candidates for attenuating the onset and progression of sepsis-associated AKI. The pathogenesis of sepsis-mediated AKI entails a complicated mechanism and is likely to involve a distinct constellation of hemodynamic, inflammatory, and immune mechanisms. Novel biomarkers like neutrophil gelatinase-associated lipocalin, soluble triggering receptor expressed on myeloid cells 1, procalcitonin, alpha-1-microglobulin, and presepsin can help in a more sensitive diagnosis of sepsis-associated AKI. Many bioactive compounds like curcumin, resveratrol, baicalin, quercetin, and polydatin are reported to play an important role in the prevention and management of sepsis-associated AKI by decreasing serum creatinine, blood urea nitrogen, cystatin C, lipid peroxidation, oxidative stress, IL-1β, TNF-α, NF-κB, and increasing the activity of antioxidant enzymes and level of PPARγ. The plant bioactive compounds could be developed into a drug-developing candidate in managing sepsis-mediated acute kidney injury after detailed follow-up studies. Lastly, the gut-kidney axis may be a more promising therapeutic target against the onset of septic AKI, but a deeper understanding of the molecular pathways is still required.

Angiotensin-(1-7) ameliorates sepsis-induced cardiomyopathy by alleviating inflammatory response and mitochondrial damage through the NF-κB and MAPK pathways

BACKGROUND

There is no available viable treatment for Sepsis-Induced Cardiomyopathy (SIC), a common sepsis complication with a higher fatality risk. The septic patients showed an abnormal activation of the renin angiotensin (Ang) aldosterone system (RAAS). However, it is not known how the Ang II and Ang-(1-7) affect SIC.

METHODS

Peripheral plasma was collected from the Healthy Control (HC) and septic patients and Ang II and Ang-(1-7) protein concentrations were measured. The in vitro and in vivo models of SIC were developed using Lipopolysaccharide (LPS) to preliminarily explore the relationship between the SIC state, Ang II, and Ang-(1-7) levels, along with the protective function of exogenous Ang-(1-7) on SIC.

RESULTS

Peripheral plasma Ang II and the Ang II/Ang-(1-7) levels in SIC-affected patients were elevated compared to the levels in HC and non-SIC patients, however, the HC showed higher Ang-(1-7) levels. Furthermore, peripheral plasma Ang II, Ang II/Ang-(1-7), and Ang-(1-7) levels in SIC patients were significantly correlated with the degree of myocardial injury. Additionally, exogenous Ang-(1-7) can attenuate inflammatory response, reduce oxidative stress, maintain mitochondrial dynamics homeostasis, and alleviate mitochondrial structural and functional damage by inhibiting nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, thus alleviating SIC.

CONCLUSIONS

Plasma Ang-(1-7), Ang II, and Ang II/Ang-(1-7) levels were regarded as significant SIC biomarkers. In SIC, therapeutic targeting of RAAS, for example with Ang-(1-7), may exert protective roles against myocardial damage.

Losartan attenuates sepsis-induced cardiomyopathy by regulating macrophage polarization via TLR4-mediated NF-κB and MAPK signaling

Sepsis-induced cardiomyopathy (SIC) is a serious complication of sepsis with high mortality but no effective treatment. The renin angiotensin (Ang) aldosterone system (RAAS) is activated in patients with sepsis but it is unclear how the Ang II/Ang II type 1 receptor (AT1R) axis contributes to SIC. This study examined the link between the Ang II/AT1R axis and SIC as well as the protective effect of AT1R blockers (ARBs). The Ang II level in peripheral plasma and AT1R expression on monocytes were significantly higher in patients with SIC compared with those in non-SIC patients and healthy controls and were correlated with the degree of myocardial injury. The ARB losartan reduced the infiltration of neutrophils, monocytes, and macrophages into the heart and spleen of SIC mice. Additionally, losartan regulated macrophage polarization from the M1 to the M2 subtype via nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, thereby maintaining the mitochondrial dynamics balance in cardiomyocytes and reducing oxidative stress and cardiomyocyte apoptosis. In conclusion, the plasma Ang II level and AT1R expression on plasma monocytes are an important biomarker in SIC. Therapeutic targeting of AT1R, for example with losartan, can potentially protect against myocardial injury in SIC.

Olmesartan Ameliorates Organ Injury and Mortality in Rats With Peritonitis-Induced Sepsis

INTRODUCTION

Sepsis and related complications lead to high morbidity and mortality in humans and animals. Olmesartan medoxomil (OLM), a nonpeptide angiotensin II type 1 receptor blocker, has antiinflammatory and antioxidative effects in various experimental animal models. The present study aimed to investigate whether OLM protects against sepsis in a clinically relevant model of polymicrobial sepsis induced by cecal ligation and puncture (CLP).

METHODS

Sepsis was induced by CLP in anesthetized rats. OLM was administered intraperitoneally 3 h after CLP onset. Hemodynamic, biochemical, and inflammatory parameters were analyzed.

RESULTS

The administration of OLM in CLP rats significantly improved their survival rate. Moreover, OLM mitigated CLP-induced hypotension and organ injury (indicated by biochemical parameters), but not tachycardia. OLM significantly reduced the plasma levels of interleukin-6 and nitric oxide.

CONCLUSIONS

OLM markedly attenuated CLP-induced hypotension and organ injury, and hence improved survival by inhibiting the inflammatory response and nitrosative stress in this clinically relevant model of sepsis.

Research Progress on the Mechanism of Sepsis Induced Myocardial Injury

Sepsis is an abnormal condition with multiple organ dysfunctions caused by the uncontrolled infection response and one of the major diseases that seriously hang over global human health. Besides, sepsis is characterized by high morbidity and mortality, especially in intensive care unit (ICU). Among the numerous subsequent organ injuries of sepsis, myocardial injury is one of the most common complications and the main cause of death in septic patients. To better manage septic inpatients, it is necessary to understand the specific mechanisms of sepsis induced myocardial injury (SIMI). Therefore, this review will elucidate the pathophysiology of SIMI from the following certain mechanisms: apoptosis, mitochondrial damage, autophagy, excessive inflammatory response, oxidative stress and pyroptosis, and outline current therapeutic strategies and potential approaches in SIMI.

miR-107 Attenuates Sepsis-Induced Myocardial Injury by Targeting PTEN and Activating the PI3K/AKT Signaling Pathway

Sepsis is a public health problem worldwide. This study investigated the mechanism of miR-107 on sepsis-induced myocardial injury. Sepsis rat models were established by cecal ligation and puncture (CLP), and the cell model was established using lipopolysaccharide (LPS)-induced cardiomyocytes. Cardiac function indexes of rats were measured using echocardiography. Pathological changes in the rat myocardium were observed using histological staining. Expression of miR-107 in the serum of rats and in cardiomyocytes was detected after the treatment with miR-107 mimic and/or pcDNA3.1-PTEN, followed by assessment of cell cycle, proliferation, and apoptosis. Binding sites of miR-107 and PTEN were predicted. PTEN, PI3K, p-PI3K, AKT, and p-AKT levels in LPS-induced cardiomyocytes were measured. miR-107 was significantly downregulated in the serum of CLP rats and LPS-induced cardiomyocytes. miR-107 overexpression remarkably improved cardiac function and histological changes, decreased inflammatory factors, and alleviated the sepsis-induced myocardial injury in rats. In LPS-induced cardiomyocytes, miR-107 overexpression increased cardiomyocyte proliferation, inhibited apoptosis, and enhanced the proportion of cardiomyocytes arrested in S and G2/M phases. miR-107 targeted PTEN. PTEN overexpression partially reversed the inhibition of miR-107 mimic on cardiomyocyte apoptosis. miR-107 overexpression activated the PI3K/AKT pathway by inhibiting PTEN. To conclude, miR-107 activates the PI3K/AKT pathway by inhibiting PTEN, thus attenuating sepsis-induced myocardial injury and LPS-induced cardiomyocyte apoptosis.

Polydatin Improves Sepsis-Associated Encephalopathy by Activating Sirt1 and Reducing p38 Phosphorylation

INTRODUCTION

Our previous study confirmed that polydatin (PD) can alleviate sepsis-induced multiorgan dysfunction (in the vascular endothelium, kidney, and small intestine) by activating Sirt1 and that PD protects against traumatic brain injury in rats via increased Sirt1 and inhibition of the p38-mediated mitogen-activated protein kinase (MAPK) pathway. We aim to investigate whether PD may also attenuate sepsis-associated encephalopathy (SAE).

METHODS

In this study, we constructed an SAE mouse model by cecal ligation and puncture (CLP) and measured Sirt1 protein activity, p38 phosphorylation, brain tissue pathological damage, pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), mitochondrial function (mitochondrial membrane potential, ATP content, and reactive oxygen species), neurological function, and animal survival time. Sirt1 selective inhibitor Ex527 and p38 inhibitor SB203580 were used to explore the possible mechanism of PD in SAE.

RESULTS

We confirmed that PD inhibits neuroinflammation evidenced by reduced proinflammatory cytokines. In addition, PD protects mitochondria as demonstrated by restored mitochondrial membrane potential and adenosine triphosphate (ATP) content, and decreased reactive oxygen species (ROS) level. As we expected, p38 inhibition reduces neuroinflammation and mitochondrial damage. In contrast, Sirt1 inhibition aggravates cerebral cortex mitochondrial damage and neuroinflammation and promotes phosphorylation of p38. Mechanistically, PD treatment suppressed p38 phosphorylation and consequently reduced the neuroinflammatory response, and these effects were blocked by the Sirt selective inhibitor Ex527.

CONCLUSIONS

This study, to the best of our knowledge, is the first to demonstrate that PD alleviates SAE, at least partially, by upregulating Sir1-mediated neuroinflammation inhibition and mitochondrial function protection.

Evaluating the potency of blood long noncoding RNA PVT1 as candidate biomarker reflecting inflammation, multiple organ dysfunction, and mortality risk in sepsis patients

OBJECTIVE

Long noncoding RNA plasmacytoma variant translocation 1 (lnc-PVT1) promotes septic inflammation and organ injuries via multiple ways, while its clinical engagement in sepsis management is indistinct. This study aimed to investigate its relationship with inflammation, multiple organ dysfunction, and mortality risk in sepsis patients.

METHODS

Sepsis patients and age-/gender-matched healthy controls were enrolled; their lnc-PVT1 expression in plasma were detected by RT-qPCR. For sepsis patients only, the inflammatory cytokine levels (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-17A) in plasma were detected by ELISA. According to the survival data during 28-day follow-up, sepsis patients were divided into sepsis survivors and sepsis deaths.

RESULTS

Lnc-PVT1 expression was increased in sepsis patients (N = 157) compared with healthy controls (N = 80) (p < 0.001). In sepsis patients, lnc-PVT1 was linked with higher acute physiology and chronic health evaluation II (APACHEII) score (p = 0.001), total sequential organ failure assessment (SOFA) score, and its most subitems (SOFA-respiratory system, SOFA-coagulation, SOFA-liver, SOFA-cardiovascular system, and SOFA-renal system scores) (all p < 0.01), but not SOFA-nervous system score (p = 0.091); it did not relate to primary infection sites either (p = 0.204). Furthermore, lnc-PVT1 correlated with increased C-reactive protein, TNF-α, IL-1β, and IL-17 in sepsis patients (all p < 0.01). Additionally, lnc-PVT1 expression was higher in sepsis deaths than that in sepsis survivors (p < 0.001), following receiver-operating characteristic curve disclosed that lnc-PVT1 predicted 28-day septic mortality risk (area under the curve: 0.789, 95% confidence interval: 0.702-0.875).

CONCLUSION

Circulating lnc-PVT1 exhibits the potential as a biomarker in sepsis patients to inform inflammation, multiple organ dysfunction, and mortality risk.

Alamandine, a derivative of angiotensin-(1-7), alleviates sepsis-associated renal inflammation and apoptosis by inhibiting the PI3K/Ak and MAPK pathways

Sepsis is a frequent cause of kidney injury. The present study investigated whether Alamandine (Ala) could alleviate sepsis-associated renal injury by reducing inflammation and apoptosis. In addition, we investigated downstream signaling pathways modulated by Ala. Studies were performed in mice treated with lipopolysaccharide (LPS) and in the human proximal tubular epithelial cell line HK-2. The increase in serum creatinine, blood urea nitrogen, cystatin C and Fg, and neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in the kidneys of mice treated with LPS were reduced after administration of Ala. Exposure to LPS increased interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in mice and HK-2 cells, but were reduced after Ala treatment. Furthermore, increased levels of cleaved caspase 3, cleaved caspase 7, cleaved caspase 9, cleaved poly (ADP-ribose) polymerase (PARP) and Bax and reduced levels of Bcl2 in LPS-treated mice and HK-2 cells were reversed after Ala administration. In addition, LPS increased the levels of p-PI3K/PI3K, p-Akt/Akt, p-ERK/ERK, p-JNK/JNK, p-p38/p38 and p-FoxO1 in HK-2 cells, and all were reversed after Ala administration. These results indicate that Ala could improve renal function and inhibit inflammation and apoptosis in LPS induced sepsis mouse models. We demonstrated that Ala attenuated LPS induced sepsis by inhibiting the PI3K/Akt and MAPK signaling pathways.

Dysregulation of the renin-angiotensin system in septic shock: Mechanistic insights and application of angiotensin II in clinical management

Synergistic physiologic mechanisms involving the renin-angiotensin system (RAS), the sympathetic nervous system, and the arginine-vasopressin system play an integral role in blood pressure homeostasis. A subset of patients with sepsis experience septic shock with attendant circulatory, cellular, and metabolic abnormalities. Septic shock is associated with increased mortality because of an inadequacy to maintain mean arterial blood pressure (MAP) despite volume resuscitation and the use of vasopressors. Vasodilatory shock raises the dose of vasopressors required to maintain a MAP of > 65 mm Hg. The diminished response to endogenous angiotensin II in sepsis-induced vasoplegia may be related to the aberrant RAS activation that stimulates a proinflammatory beneficial antibacterial response, increasing the secretion of proinflammatory cytokines that downregulate AT-1 receptors expression. Moreover, excessive systemic upregulation of nitric oxide synthase, stimulation of prostaglandin synthesis, and activation of ATP-sensitive potassium channels followed by reduced vascular entry of calcium ions are putative mechanisms in the reduced responsiveness to vasopressors. However, intravenous angiotensin II in catecholamine-resistant septic shock patients showed substantial evidence of raising the MAP to target hemodynamic levels, thus allowing time to treat underlying conditions. Nevertheless, evidence of catecholamine-sparing effect by adding angiotensin II, aimed at increasing the therapeutic index of vasopressor therapy, does not show an attenuation of end-organ damage. The use of angiotensin II in septic shock has not been evaluated in patients who are not catecholamine resistant. This, in conjunction with an evolving definition of catecholamine resistance, provides an opportunity for further evaluation of exogenous angiotensin II in septic shock.