EVALUATION OF SERUM TRAIL AND CRP IN CKDU PATIENTS.

Chronic kidney disease of uncertain etiology (CKDu) is a progressive nephropathy of insidious onset, often attributed to repeated nephrotoxin exposure, driving maladaptive cellular responses primarily in metabolically active proximal tubular cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), primarily produced by peripheral blood mononuclear cells (PBMCs), is a key regulator of cell fate (apoptosis, survival, or senescence) that may have a role in modulating stress-induced tubular differentiation in CKDu. Therefore, this study aims to identify the pattern of TRAIL with CKDu disease progression, its association with the dynamics of systemic inflammation (measured with C-reactive protein, CRP), and associated cardiovascular disease (CVD) risk, and evaluate a natural TRAIL modulator as a potential therapeutic intervention.

A cross-sectional study was conducted among 40 clinically diagnosed CKDu patients (55.53±10.44, 85% male), excluding those with acute illness or clinically confirmed comorbidities. Patients were stratified based on eGFR into stage 2 (5, 12.5%), 3A (8, 20.0%), 3B (10, 25.0%), 4 (10, 25.0%), and 5 (7, 17.5%). Serum CRP and TRAIL were estimated using immunoturbidimetry and sandwich ELISA, respectively, and pairwise comparisons were made with healthy control subjects matched for age and gender. CVD risk was assessed based on CRP according to the American Heart Association guideline (<1mg/L: low, 1-3mg/L: moderate, > 3mg/L: high). Subsequently, an in vitro study was conducted using PBMCs isolated from three healthy volunteers, which were treated with the methanolic crude extract of Phyllanthus emblica fruit (PEF) for 24 hours in a controlled environment. TRAIL modulation was assessed by measuring soluble TRAIL protein expression in culture supernatant and mRNA expression in PBMCs.

Serum TRAIL and CRP levels showed a nonlinear trend along with CKDu disease progression, both peaking at stage 3A (median TRAIL: CKDu 362.3 pg/mL vs control 144.6 pg/mL, p=0.021; median CRP: CKDu 1.60 mg/L vs control 0.50 mg/L, p=0.005), followed by a decline in advanced stages. A high proportion of patients in stages 3A (n=7, 87.5%) and 3B (n=9, 90%) had moderate to high CVD risk, with significantly increased odds of elevated risk (3A: OR 21.0, p=0.024, 3B: OR 135, p=0.035) compared to controls. Exposure of PBMCs (106/well) with 500µg/mL hydro-methanolic extract of PEF for 24 hours resulted in a significant decrease in TRAIL mRNA (~40%) and a modest reduction in soluble TRAIL, while cell viability remained unaffected, compared to untreated control.

The observed transient elevation of TRAIL might reflect a phase in which renal proximal tubular cells acquire a senescence-associated secretory phenotype (SASP) due to recurrent sublethal nephrotoxin exposure. The parallel elevation of CRP supports this interpretation, suggesting a transient systemic inflammatory response. Therefore, stage 3A suggests a critical therapeutic window in CKDu and modulation of TRAIL, for example, PEF, could potentially attenuate SASP-driven inflammation, limit progression to irreversible tubulointerstitial fibrosis, and reduce associated CVD risk. However, further in-vitro/ in-vivo mechanistic studies are recommended to validate these findings.