TLR4 and diabetes mellitus: In a diabetic retina, hyperglycemia enhances the expression and activation of TLR4 in human endothelial cells that may play an important role in DR [11] Cells exposed to high glucose had an increased expression of downstream factors of TLR4 including myeloid differentiation factor 88, an inflammatory cytokine inducer, and NF-κB [158,159], which may lead to the secretion of more inflammatory cytokines like IL-1β [160].