## 2 Pharmacology of Piperine: In Vitro and In Vivo Studies
### Miscellaneous Activity--Kinase, Inflammation, Diabetes  
Piperine inhibits the expression of CD40 and CD86 in bone-marrow-derived dendritic cells (BMDCs), along with inhibiting TNF-\(\alpha\), IL-12, but not IL-6. This eventually suppresses extracellular signal-regulated kinases and c-Jun N-terminal kinases (JNK) activation, but not p38 or NF-kB activation [29]. Piperine activates the JNK, extracellular signal-regulated kinase and p38 MAPK pathways leading to inhibition of cisplatin-induced apoptosis in House Ear Institute-Organ of Corti I (HET-OCI) cells [94]. Piperine reverses down-regulation of adiponectin-AMP-activated protein kinase (AMPK) signaling molecules that facilitate mediating lipogenesis, fatty acid oxidation, and insulin signaling in the livers of mice. Also, it decreases the phosphorylation of insulin receptor substrate-1 (IRS-1) activity in HFD-fed mice [95]. Piperine decreases the activation of the p38-MAPK pathway, which alleviates osteoclast formation [96]. In CTLL-2T lymphocytes, piperine was found to block the IL-2-induced phosphorylation of STAT3 and STAT5 without affecting the phosphorylation of JAK 1 and JAK3, as well as to inhibit phosphorylation of extracellular signal-regulated kinase 1/2 and Akt. The same study showed that piperine also suppresses the expression of cyclin-dependent kinase (Cdk)1, Cdk4, Cdk6, cyclin B, and cyclin D2 [97]. The results of the study of [PERSON] et al. [98] showed that piperine inhibits the phosphoinositide-3 kinase/Akt signaling pathway, HUVEC proliferation and collagen-induced angiogenesis, which plays a vital role in tumor progression. In T-lymphocytes, piperine decreases the expression of cyclin D3, CDK4, and CDK6, inhibits CD25 expression, IL-2, IL-4, and IL-17A and this effect was associated with inhibition of Akt hypophosphorylation [99]. The study on piperine effect to LPS-stimulated human epithelial-like SW480, and HT-29 cells showed that it downregulates the MAPK pathways [100]. Piperine stimulates the p38 MAPK and induces the phosphorylation of AMP-activated protein kinase [101]. The study of [PERSON] et al. [102] found that piperine inhibits TNF-\(\alpha\), intercellular adhesion molecule-1, vascular cell adhesion molecule-1 and E-selectin. Also, by attenuating TNF-\(\alpha\), piperine prevents the phosphorylation and degradation of 1 kB\(\alpha\)[102]. Piperine decreases the vascular smooth muscle cells by increasing the expression of p27 kip1, decreasing cell cycle enzymes (cyclin D, cyclin E, and proliferating cell nuclear antigen), phosphorylation of extracellular signal-regulated kinase (ERK)1/2, and phosphorylation of the p38 MAPK [103]. Also, by down-regulating miR-127, MyB88 expression, NF-kB, and p38 MAPK signaling pathways activation, piperine may act as osteoarthritis therapeutic agent in murine chondrogenic ATDC5 cells [104]. Piperine activates PPARy, leading to inhibition of AKT/GSK3\(\beta\) and reduction of cardiac fibrosis [105]. As piperine phosphorylates AMP-activated protein kinase, facilitates glucose transporter 4 to enter the plasma membrane, increase the intracellular Ca2+ level and activation of Ca2+/calmodulin-dependent protein kinase kinase-beta, it also possesses hyperglycemia-preventing effect [106]. Piperine may act as a novel therapeutic agent for melanoma, as it increases the ratio of Bax and Bcl-2, upregulates the expression of apoptosis-inducing factor, and reduces UVB-induced p-glycoprotein activity in B16F10 mouse melanoma cells [73]. [PERSON] et al. [107] found that in HOS and U2 OS osteosarcoma cells, administration of piperine decreases cyclin B1 and increases phosphorylation of cyclin-dependent kinase-1 and checkpoint kinase 2. Also, inhibited phosphorylation of Akt and activated phosphorylation of c-Jun N-terminal kinase (c-JNK) and p38 MAPK were recorded, pointing to suppression of the metastasis by this natural compound [107]. Piperine was found to be beneficial for tendinopathy, since it inhibits MMP-2, MMP-9, ERK and p38 signaling pathways in collagenase-induced Achilles tendon injury in the rat [108].