PATHWAYS ASSOCIATED WITH POSITIVE SEPSIS SURVIVAL OUTCOMES IN AFRICAN AMERICAN/BLACK AND NON-HISPANIC WHITE PATIENTS WITH URINARY TRACT INFECTION

Abstract

Urinary tract infections (UTIs) are a common cause of sepsis worldwide. Annually, more than 60,000 US deaths can be attributed to sepsis secondary to UTIs, and African American/Black adults have higher incidence and case-fatality rates than non-Hispanic White adults. Molecular-level factors that may help partially explain differences in sepsis survival outcomes between African American/Black and Non-Hispanic White adults are not clear. In this study, patient samples (N = 166) from the Protocolized Care for Early Septic Shock cohort were analyzed using discovery-based plasma proteomics. Patients had sepsis secondary to UTIs and were stratified according to self-identified racial background and sepsis survival outcomes. Proteomics results suggest patient heterogeneity across mechanisms driving survival from sepsis secondary to UTIs. Differentially expressed proteins (n = 122, false discovery rate-adjusted P < 0.05) in Non-Hispanic White sepsis survivors were primarily in immune system pathways, while differentially expressed proteins (n = 47, false discovery rate-adjusted P < 0.05) in African American/Black patients were mostly in metabolic pathways. However, in all patients, regardless of racial background, there were 16 differentially expressed proteins in sepsis survivors involved in translation initiation and shutdown pathways. These pathways are potential targets for prognostic intervention. Overall, this study provides information about molecular factors that may help explain disparities in sepsis survival outcomes among African American/Black and Non-Hispanic White patients with primary UTIs.

Figure 1.

General (A) sample preparation and (B) data analysis workflow. Plasma samples from sepsis patients with primary urinary tract infection were obtained at hospital admission with survival outcome referring to a patient’s status 90 days post-admission. Sample preparation included tryptic digestion and TMTpro labeling and was partially automated using a Biomek i7 workstation. Fractionated TMTpro batches were analyzed via LC-MS/MS. Normalized TMTpro reporter ion intensities for proteins were analyzed using linear regression models with and without stratification by patients’ racial/ethnic backgrounds (see Materials and Methods). Differentially-expressed proteins are considered as proteins with an FDR-adjusted p < 0.05 and significant fold change values (see Materials and Methods). Figure was created with Biorender.com. Abbreviation: LC-MS/MS = liquid chromatography-tandem mass spectrometry.

Figure 2.

Analysis of data stratified by patients’ racial/ethnic backgrounds. Volcano plot of protein log₂ of averaged TMTpro reporter ion abundances’ ratio of sepsis survivors to non-survivors as a function of FDR-adjusted p-value (N = 1,216 proteins with un-adjusted p < 0.05) in (A) Non-Hispanic White and (B) African American/Black patients. Light grey data points indicate proteins with non-significant FDR-adjusted p-values (adjusted p ≥ 0.05) and/or non-significant fold change values in Non-Hispanic White patients and African American/Black patients. Dashed lines indicate p-value and fold change cutoffs. Example proteins are labeled. (A) Pink data points indicate proteins with both significant FDR-adjusted p-values (adjusted p < 0.05) and fold change values in Non-Hispanic White patients (N = 122 proteins). (B) Blue data points indicate proteins with both significant FDR-adjusted p-values (adjusted p < 0.05) and fold change values in African American/Black patients (N = 47 proteins). (C) Venn Diagram of the overlap of differentially-expressed proteins [pink and blue proteins from (A) and (B)] between survivors and non-survivors in Non-Hispanic White and African American/Black patients. (D) Ingenuity Pathway Analysis of the proteins in (C) (i.e., N = 122 differentially-expressed proteins in Non-Hispanic White sepsis patients and N = 47 differentially-expressed proteins in African American/Black sepsis patients). Canonical pathways were identified from the IPA library using Fisher’s exact test adjusted for multiple hypothesis testing using the Benjamini-Hochberg (B-H) correction. Abbreviations: RPS21 = 40S ribosomal protein S21; RPS3 = 40S ribosomal protein S3; RPL12 = 60S ribosomal protein L12; HNRNPL = heterogeneous nuclear ribonucleoprotein L; KARS1 = lysine-tRNA ligase; XRCC6 = X-ray repair cross-complementing protein 6; INPP1 = inositol polyphosphate 1-phosphatase; IL5RA = interleukin-5 receptor subunit α; AHCTF1 = protein ELYS; IMUP = immortalization up-regulated protein; HRG = histidine-rich glycoprotein; B-H = Benjamini-Hochberg; EIF2 = eukaryotic translation initiation factor 2.

Figure 3.

STRING network of proteins with a significant race-survival outcome interaction term (N = 71). Disconnected nodes are hidden. Node color represents key functions, and line thickness indicates the strength of protein interactions. Blue represents proteins with metabolic functions, red represents proteins involved in translation, and green represents proteins involved in the tumor necrosis factor (TNF) response.

Figure 4.

Box plots of log₁₀ TMTpro intensities of the 16 proteins that change in both Non-Hispanic White and African American/Black survivors are shown. The horizontal line in the box represents the median and X represents the mean. * p < 0.05, ** p < 0.01, and *** p < 0.001, as determined by two-way ANOVAs with replication and Tukey-Kramer post-hoc tests. Purple represents Non-Hispanic White non-survivors, pink represents Non-Hispanic White survivors, dark blue represents African American/Black non-survivors, and light blue represents African American/Black survivors. Abbreviations: THYN1 = thymocyte nuclear protein 1; ACADVL = very long-chain specific acyl-CoA dehydrogenase, mitochondrial; 60S ribosomal protein L12; RO60 = 60 kDa SS-A/Ro ribonucleoprotein; KARS1 = Lysine-tRNA ligase; AHSA1 = activator of 90 kDa heat shock protein ATPase homolog 1; RPS3 = 40S ribosomal protein S3; INPP1 = inositol polyphosphate 1-phosphatase; PITPNA = phosphatidylinositol transfer protein α isoform; HNRNPL = heterogeneous nuclear ribonucleoprotein L; EML4 = echinoderm microtubule-associated protein-like 4; RPS21 = 40S ribosomal protein S21; MAN2C1 = α-mannosidase 2C1; SHFL = shiftless antiviral inhibitor of ribosomal frameshifting protein; XRCC6 = X-ray repair cross-complementing protein 6; FERMT2 = fermitin family homolog 2.

Figure 5.

Ingenuity Pathway Analysis of the differentially-expressed proteins (N = 16) in both Non-Hispanic White and African American/Black sepsis survivors that also have a significant race-survival outcome interaction. Canonical pathways were identified from the IPA library using Fisher’s exact test adjusted for multiple hypothesis testing using the Benjamini-Hochberg correction. Abbreviations: B-H = Benjamini-Hochberg; EIF2 = eukaryotic translation initiation factor 2; DNA = deoxyribonucleic acid; mTOR = mammalian target of rapamycin; eIF4 = eukaryotic translation initiation factor 4F; p70S6K =P70 S6 kinase; tRNA = transfer ribonucleic acid.