Profiling the proteolytic dysfunction in digital dermatitis in cattle and the therapeutic use of a non-antimicrobial matrix metalloproteinase inhibitor

ABSTRACT Digital dermatitis (DD) is a painful inflammatory skin disease affecting the digital regions of cattle feet, linked to pathogenic Treponemes spp. This condition imposes a substantial economic burden on the cattle industry attributable to lameness and subsequent production inefficiencies. Currently, there is an absence of fully effective therapeutics for DD, and the underlying mechanisms governing the skin's inflammatory response remain largely unknown. This study elucidated the proteomic signature in the foot skin of cattle manifesting active DD lesions subjected to topical treatment with a non-antimicrobial metalloprotease inhibitor, CMC2.24 or the routinely used antibiotic treatment, oxytetracycline (OTC). The results demonstrated that active, non-healing ulcerative DD lesions exhibited persistent infiltration of inflammatory leukocytes alongside a proteomic profile characterized by enrichment in neutrophil degranulation-related pathways and elevated activity of matrix metalloproteinases (MMPs), which likely exacerbates cutaneous inflammation and ulceration. Treatment with OTC accelerated the cornification of DD lesions; however, these lesions still exhibited distinct inflammatory characteristics, which included sustained elevated levels of S100A8, a molecule known to promote neutrophil aggregation and reactive oxygen species (ROS) generation. Conversely, the MMP inhibitor CMC2.24 effectively mitigated active DD lesions by attenuating ROS production and keratinization pathways. Furthermore, CMC2.24 inhibited interleukin-1 beta (Il-1β) secretion in both bovine and murine macrophages challenged with DD-associated Treponemas spp. These data indicate a pro-inflammatory proteomic profile in DD lesions, highlighting that a non-antimicrobial MMP inhibitor could effectively reduce foot skin inflammation relative to conventional OTC treatment.