Oxidative Stress and Apoptotic Markers in Goats Naturally Infected with Mycobacterium avium subsp. paratuberculosis

Abstract

Paratuberculosis, caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a chronic granulomatous enteritis with significant implications for ruminant health, economic productivity, and potential zoonotic risk. This study investigated the expression of biomarkers of oxidative stress and apoptosis in goats naturally infected with MAP, focusing on three biological matrices: serum, intestinal mucosa, and mesenteric lymph nodes. Twenty MAP-positive goats and ten healthy controls were included. Serum and tissue levels of malondialdehyde (MDA), glutathione S-transferase (GST), glutathione peroxidase (GPX), superoxide dismutase (SOD), glutathione reductase (GSR), and caspase-3 were quantitatively assessed using ELISA tests. Gross and histopathological analyses confirmed MAP infection. Infected animals showed significantly elevated serum levels of MDA and caspase-3 (p < 0.001), along with decreased antioxidant enzyme activities (GSR, GST, GPX, SOD). Tissue analysis revealed increased MDA and caspase-3 levels, particularly in the intestinal mucosa compared to mesenteric lymph nodes, suggesting localized oxidative damage and apoptosis. Conversely, antioxidant enzyme activity was higher in mesenteric lymph nodes, indicating a compensatory response and a pronounced involvement of the intestinal tract. These findings demonstrate that MAP infection induces marked oxidative stress and apoptotic processes, especially in the intestinal mucosa. The imbalance between pro-oxidant and antioxidant systems may play a key role in the pathogenesis and chronic progression of the disease. Caspase-3 and MDA, in particular, have been identified as promising diagnostic or prognostic biomarkers for MAP infection. This study highlights the importance of developing improved diagnostic tools and therapeutic strategies targeting oxidative stress pathways in paratuberculosis.

Keywords: Johne’s disease; Mycobacterium avium subspecies paratuberculosis; antioxidants; apoptosis; oxidative stress.

Figure 1

Gross and histological aspect of MAP-positive goats’ intestines. (A) Intestinal tortuosity (white arrowheads), serous atrophy of the mesenterium (arrowhead), excessive growth of the mesenteric lymph node (arrow). (B) Thickening and tortuosity of the intestinal mucosa (arrowheads). (C) Atrophy and degeneration of intestinal villi (arrowheads), diffuse infiltration of epithelioid histiocytes (white arrowheads), dilatation of villous lacteals (withe arrow), proliferation of mucosal crypt glands (arrows), mononuclear leukocyte infiltrations (stars) associated with edema and fibrosis (hollow stars) in the mucosa and submucosa, scale bar 200 microns, H&E. (D) Degenerative and necrotic changes in villous epithelial cells (arrowheads), proliferation of mucosal crypt glands (arrows), infiltration of epithelioid macrophages in the lamina propria (stars) and mononuclear leukocyte infiltrations (white stars), scale bar 100 microns, H&E. (E) Epithelioid macrophages (white star) and lymphoproliferative foci (star) in mesenteric lymph nodes, scale bar 50 microns, H&E. (F) Acid-fast agents in lamina propria (arrows), scale bar 100 microns, ZN. (G) Acid-fast agents in mediastinal lymph nodes (arrows), scale bar 100 microns, ZN.

Figure 2

Graphical representation of oxidative stress (A–E) and apoptosis biomarker (F) levels in sera of healthy and infected goats. *** p < 0.001.

Figure 3

Graphical representation of oxidative stress and apoptosis biomarker levels in (A–F) mesenteric lymph nodes and (G–L) intestinal mucosa homogenates in healthy and infected goats. *** p < 0.001.

Figure 4

Graphical representation of correlation between (A) intestinal mucosa and mesenteric lymph nodes of GST values (p < 0.05), and (B) serum and mesenteric lymph nodes SOD values. p < 0.05.