Effect of Da-Cheng-Qi decoction for treatment of acute kidney injury in rats with severe acute pancreatitis

Acute pancreatitis (AP) is commonly a self-limited inflammatory disease caused by abnormally activated pancreatic digestive enzymes [1]. However, approximately 20% of AP cases develop into severe acute pancreatitis (SAP), with high mortality characterized by systemic inflammatory response syndrome (SIRS) and multiple organ injuries and even failure at an early stage [2, 3], including acute respiratory distress syndrome, acute kidney injury (AKI) and acute liver injury. AKI is diagnosed by accumulations of serum creatinine (Scr) and blood urea nitrogen (BUN) or decreased urine output, which reflects a rapid loss of the kidney’s excretory function [4]. AKI is one of the most common complications of SAP increasing the disease mortality [5, 6]. A retrospective and multi-centre study showed that nearly 69.3% of SAP patients developed AKI [5]. Acute renal failure used to be defined as the severe form of AKI [7], which leads to a drastic increase in the mortality of SAP [8‐10]. Therefore, it is essential to ameliorate AKI with SAP as early as possible to decrease the mortality.

The mechanism of SAP resulting in AKI is complex. Available studies revealed that SAP-induced AKI is mainly related to SIRS [9], which involves various cytokines and inflammatory mediators, such as nuclear factor kappa B (NF-B), tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-10, and high mobility group box protein 1(HMGB1) [11]. Endotoxins, reactive oxygen species (ROS), phospholipase A₂ (PLA₂), hypoxemia, as well as a decrease in renal perfusion pressure due to abdominal compartment syndrome and an impairment of renal microcirculation for the release of pancreatic amylase, may also play important roles in the pathophysiology of SAP-induced AKI [12]. The mortality of SAP patients with AKI remains high regardless of the progress in intensive care treatment [9]. Although many worldwide guidelines have been established for AP [13, 14], there is still no exact drug protocol recommended [15] other than renal replacement therapy (RRT) for AKI with SAP [4, 9]. However, the application of RRT remains controversial in many aspects and has many potential complications [16]. A multicentre, multinational, prospective study showed that RRT practice did not align with the best evidence, and variations in practice may be responsible for substantial morbidity [17]. Hence, it is worthwhile to find new interventions for SAP-induced AKI and to explore the potential mechanism.

Da-Cheng-Qi decoction (DCQD), which is composed of Rheum palmatum L. (Dahuang), Magnolia henryi Dunn. (Houpu), Citrus aurantium L. (Zhishi) and Natrii Sulphas (Mangxiao), has been applied to treat AP effectively for decades in China [18]. We hypothesized that the concentration and distribution of the components of the herbal prescription in the target organs were related to its pharmacological effect. Based on this hypothesis, our previous studies have verified that DCQD could alleviate the injuries of the pancreas, lungs, liver and intestines by inhibiting the inflammatory response in rats with AP based on the distribution of its components in target tissues [19‐22]. However, the pharmacological effects of DCQD in the kidney, a target organ, are still unclear. Herein, this study investigates the herbal tissue pharmacology of DCQD in the kidneys of rats with SAP after the administration of different doses of DCQD and explores the underlying mechanisms.

The results demonstrated that major components of DCQD were detected in the kidneys and had protective effects of regulating the inflammatory response. The distributions of major components in kidneys with SAP were similar to those in the serum, pancreas, intestine or liver [20, 22, 25]. However, there were still some differences in the kidney. The component with the highest concentration in the kidney of rats in HDG was rhein, which might be the most bioactive DCQD ingredient, even though it was less abundant than many compounds in DCQD [26], similar to that of plasma and the pancreas, emodin in lung and naringenin in intestine and liver [20, 22]. This finding once again confirms the hypothesis of the tissue pharmacology of the herbs recipe [27] and may be explained by the blood–tissue barriers in different tissues [20]. Our results showed that rhein and naringenin were relatively higher than the other compounds of DCQD in all the treatment groups. However, naringenin was the highest component in the LDG and MDG while rhein was the highest in the HDG. This phenomenon may result from the drug–drug interactions during absorption, distribution, metabolism, and excretion processes or from the procedure of decoction [28]. Zhang et al. [29] verified that Lidanpaidu prescription-a transformation of DCQD-could prevent LPS-induced AKI by restricting the NF-kB signaling pathway. Li et al. [30] proved that Huang-Lian-Jie-Du-decoction and its components had an effect on mitigating LPS-induced AKI by improving the disorder of oxidative stress and energy metabolism, preventing NF-κB and MAPK and activating the Akt/HO-1 pathway in mice. Cell research further confirmed that some single herbs were latently effective for AKI due to their ability to stop the activation of NGAL, HMGB1 and KIM-1 in an invitro AKI-mimicked condition [31]. Herein, Chinese herbs are a potentially effective treatment for AKI and are worth exploration.

AP begins with local inflammation in the pancreas, which often leads to SIRS and multiple organ failure, with high mortality [32]. The inflammatory cytokine response is initiated early and is sustained for several days in the systemic circulation during SAP [33]. The response is blamed for the systemic manifestations of AP and is related to distant organ dysfunction [34]. IL-6 is most credible in the appraisal of the severity of AP for predicting the risk for the occurrence of complications at early stages [35]. TNF-α can exert systemic effects on endothelial cells invivo that cause dystrophic changes to the tubular epithelial cells and cause damage to the peritubular and glomerular capillaries in the kidneys [36]. In contrast, the anti-inflammatory cytokines IL-4 and IL-10 act as potent suppressants to prevent the extracellular killing function of macrophages once activated [37]. IL-10 is likely a primary factor in the negative feedback system that hinders the production of pro-inflammatory cytokines and colony-stimulating factors in various cells [38]. Kusske et al. [39] found that IL-10 could inhibit the activation of macrophages and could alleviate inflammation by reducing the release of inflammatory cytokines and could eventually lower the death rate of SAP in mice.

In our study, we detected the levels of TNF-α, IL-4, IL-6, and IL-10 in kidney tissue to predict the inflammatory response after SAP modelling. The results showed that IL-6 was the highest mediators, and TNF-α was the lowest mediator, among those detected. Our finding echoed that IL-6 was the only significant parameter to predict a complicated AP [35]. After giving DCQD, the levels of pro-inflammatory mediators (TNF-α and IL-6) decreased and the anti-inflammatory mediators (IL-4 and IL-10) increased along with the dose. Moreover, the pathological scores of the kidneys and pancreas showed the same tendency. The highest dose of DCQD had the maximal effects in downregulating the pro-inflammatory mediators, upregulating anti-inflammatory mediators in the kidney and ameliorating pathological damage. The data demonstrated the regulatory effects of DCQD in the inflammatory response to ameliorate AKI with SAP and to eventually attenuate the severity of SAP. Our previous studies revealed a similar effect of DCQD on damage to the lungs, pancreas, intestine and liver [20‐22]. Zhao et al. [21] reported that treatment with DCQD decreased the pathological scores of the lungs; increased the level of IL-10 mRNA and decreased the level of IL-6 mRNA in rats with SAP. Huang et al. [40] found that revised DCQD might reduce lung injury via inhibiting the induction of IL-6 and increasing the expression of HSP70 as well as the concentration of IL-10. With the experimental progress of Chinese herbs, we found that it is essential to study DCQD on the molecular level [22]. As discussed above, rhein and naringenin were relatively higher and might be potentially effective components of DCQD for SAP-induced AKI. Rhein, one major component of Dahuang, bore comparison to the accredited painkiller ibuprofen with its anti-inflammatory effects in adjuvant-induced inflammation by ameliorating oxidative stress significantly [41]. Rhein induces a necrosis-apoptosis switch of damaged pancreatic acinar cells to ameliorate AP in a dose-dependent manner [42] and to prevent an endotoxin-induced AKI by inhibiting NF-κB activities [43]. The naringenin might be another effective component and was reported to alleviate acute inflammation by adjusting the degradation by intracellular cytokines [44] and to reduce kidney damage in diabetic nephropathy through Let-7a/transforming growth factor-β1 receptor (TGFBR1) signalling [45]. Li et al. concluded that emodin had an effect on the lipopolysaccharide-induced AKI by inhibiting the toll-like receptor 2 (TLR2) signalling pathway [46]. Future studies should focus on the relationship between the quantified molecules of DCQD and their pharmacological effects considering their target tissues in SAP.

In 1998, Zhao et al. [47] came to the conclusion that the effects of DCQD on the reduction of acute phase protein levels were dose-dependent in multiple organ disfunction syndrome. Our previous study proved that the concentrations of the ten major components of DCQD increased dose-dependently in the intestine after oral administration [20]. As shown above, the effects of DCQD in the treatment of the AKI with SAP was primarily dose-dependent by regulating the inflammatory response. Therefore, a dose–response for DCQD may exist for the treatment of SAP and needs further study. The HDG accounted for the highest kidney distribution of DCQD and the lowest kidney pathological scores. Therefore, we only detected the levels of Scr and BUN in the SG, MG and HDG. Compared with the MG, the level of Scr in the HDG decreased significantly, with no differences in the BUN. Argyri et al. discovered that BUN and Scr were increased 2–3 days after AKI occurred, when 50% of the renal function was lost, and early diagnosis and intervention reduced mortality [48]. However, we collected the samples nearly one day after successful modelling. This time period might be too short to display significant changes in BUN, which could be the reason for the change in BUN after giving DCQD. Hence, it is necessary to further study and apply more sensitive biomarkers for research and clinical interpretation.

In conclusion, most of the major components of DCQD were absorbed into the kidney of rats with SAP and their concentrations increased dose-dependently. Above all, DCQD ameliorated AKI in rats with SAP by regulating the inflammatory response, and it might be closely related to the intake dose.