Angiotensin II enhances bacterial clearance via myeloid signaling in a murine sepsis model.

Sepsis, defined as organ dysfunction caused by a dysregulated host-response to infection, is characterized by immunosuppression. The vasopressor norepinephrine is widely used to treat low blood pressure in sepsis but exacerbates immunosuppression. An alternative vasopressor is angiotensin-II, a peptide hormone of the renin-angiotensin system (RAS), which displays complex immunomodulatory properties that remain unexplored in severe infection. In a murine cecal ligation and puncture (CLP) model of sepsis, we found alterations in the surface levels of RAS proteins on innate leukocytes in peritoneum and spleen. Angiotensin-II treatment induced biphasic, angiotensin-II type 1 receptor (AT1R)-dependent modulation of the systemic inflammatory response and decreased bacterial counts in both the blood and peritoneal compartments, which did not occur with norepinephrine treatment. The effect of angiotensin-II was preserved when treatment was delivered remote from the primary site of infection. At an independent laboratory, angiotensin-II treatment was compared in LysM-Cre AT1aR-/- (Myeloid-AT1a-) mice, which selectively do not express AT1R on myeloid-derived leukocytes, and littermate controls (Myeloid-AT1a+). Angiotensin-II treatment significantly reduced post-CLP bacteremia in Myeloid-AT1a+ mice but not in Myeloid-AT1a- mice, indicating that the AT1R-dependent effect of angiotensin-II on bacterial clearance was mediated through myeloid-lineage cells. Ex vivo, angiotensin-II increased post-CLP monocyte phagocytosis and ROS production after lipopolysaccharide stimulation. These data identify a mechanism by which angiotensin-II enhances the myeloid innate immune response during severe systemic infection and highlight a potential role for angiotensin-II to augment immune responses in sepsis.

Hypertension after multisystem inflammatory syndrome in children (MIS-C).

BACKGROUND: Multisystem inflammatory syndrome in children (MIS-C) is associated with SARS-CoV-2. Long-term consequences of MIS-C remain unknown. The objective was to describe the prevalence and clinical predictors of hypertension (HTN) and elevated blood pressure (BP) following MIS-C. METHODS: A retrospective study of children ≤ 18 years admitted to a tertiary center with MIS-C was performed. HTN and elevated BP were classified as per the 2017 American Academy of Pediatrics Clinical Practice Guidelines and indexed to the 95th percentile. Data included demographics, inpatient clinical measures, and echocardiograms over 1-year follow-up. Data were analyzed using Kruskal-Wallis, chi-square, and logistic regression. RESULTS: Among 63 children hospitalized with MIS-C (mean age 9.7 ± 4.2 years, 58.7% male, body mass index (BMI) z-score 0.59 ± 1.9), 14% had HTN, and 4% had elevated BP > 30 days post-hospitalization. Multivariate linear regression analysis showed that BMI z-score was significantly associated with higher mean systolic (ß = 2.664, CI = 1.307-3.980, p < 0.001) and diastolic (ß = 2.547, CI = 0.605-4.489, p = 0.012) BP index > 30 days post-hospitalization. Acute kidney injury (AKI) (23.8%) (OR = 2.977, CI = 1.778-4.987, p < 0.001), peak inpatient serum creatinine (OR = 2.524, CI = 1.344-4.740, p = 0.004), and maximum CRP (OR = 1.009, CI = 1.002-1.016, p = 0.014) were all associated with increased odds of post-hospitalization HTN. Left ventricular hypertrophy was present in 46% while hospitalized, compared to 10% at last follow-up. All had return of normal systolic function. CONCLUSIONS: Post-hospitalization HTN and elevated BP may be associated with MIS-C. Children with greater BMI or AKI may be at greater risk for developing HTN after MIS-C. MIS-C follow-up requires careful BP monitoring and antihypertensive medication consideration. A higher resolution version of the Graphical abstract is available as Supplementary information.

Impaired angiotensin II type 1 receptor signaling contributes to sepsis-induced acute kidney injury.

In sepsis-induced acute kidney injury, kidney blood flow may increase despite decreased glomerular filtration. Normally, angiotensin-II reduces kidney blood flow to maintain filtration. We hypothesized that sepsis reduces angiotensin type-1 receptor (AT1R) expression to account for this observation and tested this hypothesis in a patient case-control study and studies in mice. Seventy-three mice underwent cecal ligation and puncture (a sepsis model) or sham operation. Additionally, 94 septic mice received losartan (selective AT1R antagonist), angiotensin II without or with losartan, or vehicle. Cumulative urine output, kidney blood flow, blood urea nitrogen, and creatinine were measured. AT1R expression was assessed using ELISA, qPCR, and immunofluorescence. A blinded pathologist evaluated tissue for ischemic injury. AT1R expression was compared in autopsy tissue from seven patients with sepsis to that of the non-involved portion of kidney from ten individuals with kidney cancer and three non-infected but critically ill patients. By six hours post ligation/puncture, kidney blood flow doubled, blood urea nitrogen rose, and urine output fell. Concurrently, AT1R expression significantly fell 2-fold in arterioles and the macula densa. Creatinine significantly rose by 24 hours and sham operation did not alter measurements. Losartan significantly exacerbated ligation/puncture-induced changes in kidney blood flow, blood urea nitrogen, creatinine, and urine output. There was no histologic evidence of cortical ischemia. Significantly, angiotensin II prevented changes in kidney blood flow, creatinine, and urine output compared to vehicle. Co-administering losartan with angiotensin-II reversed this protection. Relative to both controls, patients with sepsis had low AT1R expression in arterioles and macula densa. Thus, murine cecal ligation/puncture and clinical sepsis decrease renal AT1R expression. Angiotensin II prevents functional changes while AT1R-blockade exacerbates them independent of ischemia in mice.