Figure 1.

Schematic illustration of the role of DDR1, periostin, Cx43, and CB1 during progression of renal disease. After an initial aggression of the kidney, different factors, cytokines, or signaling pathways upregulate the expression of DDR1, periostin, Cx43, and CB1. Each protein activates downstream receptors and pathways that lead to production of proinflammatory and profibrotic cytokines, inflammation, macrophage activation, energy depletion, apoptosis, and excess matrix production, which cumulatively contribute to renal fibrosis and CKD development. Abbreviations: DDR1, discoidin domain receptor 1; Cx43, connexin 43; CB1, cannabinoid receptor 1; CKD, chronic kidney diseases.