Objectives: Untreated HIV infection was previously associated with IL-32 overexpression in gut epithelial cells (IEC). Here, we explored IL-32 isoform expression in the colon of people living with HIV (PLWH) receiving antiretroviral therapy (ART) and IL-32 triggers/modulators in IEC.
Design: Sigmoid colon biopsies (SCB) and blood were collected from ART-treated PLWH (HIV + ART; n = 17; mean age: 56 years; CD4 counts: 679 cells/μl; time on ART: 72 months) and age-matched HIV-uninfected controls (HIVneg; n = 5). The IEC line HT-29 was used for mechanistic studies.
Methods: Cells from SCB and blood were isolated by enzymatic digestion and/or gradient centrifugation. HT-29 cells were exposed to TLR1-9 agonists, TNF-α, IL-17A, and HIV. IL-32α/β/γ/D/ε/θ and IL-17A mRNA levels were quantified by real-time RT-PCR. IL-32 protein levels were quantified by ELISA.
Results: IL-32β/γ/ε isoform transcripts were detectable in the blood and SCB, with IL-32β mRNA levels being predominantly expressed in both compartments and at significantly higher levels in HIV + ART compared to HIVneg. IL-17A transcripts were only detectable in SCB, with increased IL-17A levels in HIVneg compared to HIV + ART and negatively correlated with IL-32β mRNA levels. IL-32β/γ/ε isoform mRNA were detected in HT-29 cells upon exposure to TNF-α, Poly I:C (TLR3 agonist), Flagellin (TLR-5 agonist) and HIV. IL-17A significantly decreased both IL-32 β/γ/ε mRNA and cell-associated IL-32 protein levels induced upon TNF-α and Poly I:C triggering.
Conclusions: We document IL-32 isoforms abundant in the colon of ART-treated PLWH and reveal the capacity of the Th17 hallmark cytokine IL-17A to attenuate IL-32 overexpression in a model of inflamed IEC.
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