Matrix metalloproteinase-9 (MMP-9) is a zinc-dependent endopeptidase that plays a central role in extracellular matrix (ECM) remodeling, angiogenesis, immune cell trafficking, and cytokine activation. Dysregulated MMP-9 activity has been implicated in the pathogenesis of diverse conditions, including atherosclerosis, aneurysm formation, chronic obstructive pulmonary disease (COPD), asthma, neurodegeneration, and malignancy. Although broad-spectrum synthetic MMP inhibitors were initially developed as therapeutic agents, clinical trials failed due to lack of selectivity, poor tolerability, and impairment with physiological tissue repair. This outcome has shifted attention toward indirect pharmacological modulation of MMP-9 using drugs that are already approved for other indications. In this paper, we review the evidence supporting MMP-9 modulation by established therapeutics and adjunctive strategies. Cardiometabolic agents such as statins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), metformin, and pioglitazone reduce MMP-9 expression and enzymatic activity, contributing to vascular protection, improved insulin sensitivity, and attenuation of aneurysm progression. Anti-inflammatory and respiratory drugs, including glucocorticoids, phosphodiesterase-4 (PDE4) inhibitors, macrolide antibiotics, montelukast, and nonsteroidal anti-inflammatory drugs (NSAIDs), suppress MMP-9-driven airway inflammation and pathological tissue remodeling in asthma, COPD, and acute lung injury. Tetracycline derivatives, particularly sub-antimicrobial dose doxycycline, directly inhibit MMP-9 activity and are clinically validated in the treatment of periodontal disease and vascular remodeling. Hormone-related therapies such as rapamycin, estradiol, and tamoxifen exert tissue- and disease-specific effects on MMP-9 within endocrine and oncologic pathways. In parallel, nutritional interventions—most notably omega-3 polyunsaturated fatty acids and antioxidant vitamins—provide adjunctive strategies for mitigating MMP-9 activity in chronic inflammatory states. Taken together, these findings position MMP-9 as a modifiable and clinically relevant therapeutic target. The systematic integration of approved pharmacologic agents with lifestyle and nutritional interventions into disease-specific treatment paradigms may facilitate safer, context-specific modulation of MMP-9 activity and unveil novel opportunities for therapeutic repurposing.

Psoriasis is a chronic immune-mediated inflammatory disease in which cytokine-driven epidermal activation is accompanied by extensive remodeling of the extracellular matrix, basement membrane, and cutaneous microvasculature. Matrix metalloproteinase-9 (MMP-9; gelatinase B) may provide an important link between these structural alterations and several key features of psoriatic inflammation, including neutrophil activation, endothelial dysfunction, vascular hyperpermeability, and leukocyte recruitment. This review critically examines the biological and clinical relevance of MMP-9 across the spectrum of psoriatic disease. Particular focus is given to the cellular sources and regulation of MMP-9, its expression in lesional and non-lesional skin, and its interactions with the IL-23/Th17, IL-17, TNF-α, IL-36, MAPK, and NF-κB signaling pathways. Experimental studies support a functional neutrophil–MMP-9–endothelium axis in which MMP-9 can promote endothelial activation, vasodilation, vascular hyperpermeability, and leukocyte transmigration. However, this mechanistic evidence derives predominantly from experimental systems, whereas human studies mainly demonstrate associations between psoriasis and increased tissue or circulating MMP-9. The interpretation of circulating MMP-9 is further complicated by sample type, enzymatic activation state, assay heterogeneity, treatment exposure, and inflammatory and cardiometabolic confounders. Overall, MMP-9 represents a biologically possible contributor to psoriatic tissue remodeling and vascular inflammation, but its causal importance in human psoriasis remains insufficiently established. Future studies should determine whether MMP-9 can contribute to validated phenotype-specific multimarker models. At present, its clinical utility as either a biomarker or therapeutic target remains exploratory.